Exergy Flows in Product Life Cycles

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Analyzing thermodynamic improvement potential of cardboard life cycles

Sarah Herms August 2011

Exergy Flows in Product Life Cycles

Analyzing thermodynamic improvement potential of cardboard life cycles

Sarah Herms August 2011 MSc Thesis of Industrial Ecology

Delft University of Technology, Leiden University

Graduation committee: Dr. R. Heijungs, Leiden University Dr. ir. G. Korevaar, Delft University of Technology

External advisors: ir. W. van Gerwen, Tebodin Consultants & Engineers ir. R. Holland, Tebodin Consultants & Engineers L. de Goeij, Smurfit Kappa

Preface

This research project is carried out as a Master thesis within the Master of Science program in Industrial Ecology (IE) at Delft University of Technology and Leiden University. IE combines knowledge in three areas: analyzing material flows, re-designing technological systems and implementing these in organizations. This research can be found at the interface of analyzing material flows by integrating concepts of the domain of technological re-design.

I want to thank my academic supervisor, Reinout Heijungs and Gijsbert Korevaar, for their constructive feedback and support throughout the research, especially in guiding me through the worlds of LCA and exergy. Further I am very thankful for the helpful and inspiring discussions with Wouter van Gerwen and Reinout Holland on seeing the ‘bigger picture’, value creation and translating technical potential into monetary terms. I also wish to thank Lout de Goeij and Henk Hoven from Smurfit Kappa for fully supporting me in collecting data throughout the company.

Another source of inspiration have been long and sometimes challenging discussions with the group of IE friends and classmates.

Last but not least special thanks go to Philipp, my parents as well as my brothers and sisters that have encouraged and supported me along the way.

Executive Summary

The current industrial system must deal with its sustainability challenges in the production and consumption system. Various tools are available within Industrial Ecology and related disciplines to analyze these sustainability issues and generate solutions. However, so far no clear framework is established to analyze thermodynamic improvement potential in product life cycles and the existing approaches vary considerably among researchers. Consequently only few practical examples and data are structurally available on a life cycle scale.

This research aims at studying product life cycles from a thermodynamic perspective in order to analyze inefficiencies in production chains and propose improvement potential. For this purpose two analytical tools are combined, Exergy Analysis and Life Cycle Assessment (LCA), which allows studying thermodynamic irreversibility and improvement potential on a life cycle scale.

Integration possibilities of these two tools are studied which leads to using exergy consumption as impact category in the established LCA framework. Exergy balances are determined for all unit processes by assigning specific exergy contents to all mass and energy in- and outflows. The exergy contents comprise physical and chemical exergy components. Thereby ‘idealistic’ exergy factors are taken based on the maximum potential work of the specific stream, which is independent of the structural process conditions. This allows including not only the technical inefficiencies of the specific process, but also the structural inefficiencies of the process design. A theoretical improvement potential is obtained that can only be exploited if the process design is changed.

To compare different pathways in a comprehensive way, three indicators are proposed: exergy efficiency, renewable exergy fraction and cycling indicator. In combination with depicting mass, energy and exergy flows along the life cycle, the performance of the life cycle can be evaluated and insights for improvement can be extracted.

The methodology is applied to two cases of cardboard production, one German-based and one Dutch-based chain. It is shown that the power generation within the combined heat and power plant and the board making process are the most exergy consuming steps in the life cycle. The main cumulative exergy input is based on fossil fuels (~95%) and the prevailing exergy loss (~90%) can be traced back to internal irreversibilities. Up to 10% improvement can be achieved by reusing exergy that is currently lost through waste heat and effluents. The exergy consumption can further be reduced by increasing the material efficiency within the board making process: about 20% of cumulative exergy input is lost in ‘scrap’ fibers that are recycled and do not add value to the final product. However to tackle the main losses, structural innovations are needed. Thereby the use of alternative low exergy heat supply, preferably from renewable resources, should be considered. In a best case scenario the cumulative exergy consumption can be reduced by about 40% if solar thermal energy is used for steam generation.

Concluding, the Exergy LCA framework contributes to providing a quantitative structure for designing more sustainable industrial systems according to Industrial Ecology concepts. Applied to the cardboard case it offers insights into thermodynamic improvement potential throughout the life cycle and presents thus a valuable addition to existing initiatives in this industrial branch.

Table of Contents

Preface ...... 3 Executive Summary ...... 4 List of figures ...... 8 List of tables ...... 9

Chapter 1: Introduction and Research Outline ...... 10

1.1. Problem Background ...... 10 1.2. Problem Definition...... 11 1.2.1. Methodology: Exergy Analysis and LCA ...... 11 1.2.2. Case Study: Cardboard Production ...... 12 1.3. Research Questions and Goal Formulation ...... 13 1.3.1. Research Questions ...... 13 1.3.2. Goal Formulation ...... 14 1.4. Scope and System boundaries ...... 15 1.5. Involved Parties ...... 15 1.6. Structure of the Report ...... 16

Chapter 2: Review of Exergy Analysis and LCA ...... 17

2.1. Exergy Analysis ...... 17 2.1.1. Introducing the Concept Exergy ...... 17 2.1.2. Calculating Exergy Contents ...... 18 2.1.3. Types of Exergy Losses...... 19 2.1.4. Review of Application Fields of Exergy Analysis...... 20 2.2. Life Cycle Assessment ...... 22 2.2.1. LCA Framework ...... 22 2.2.2. LCA Applications ...... 24

Chapter 3: Methodological Framework Combining Exergy Analysis and LCA ...... 25

3.1. Review of Exergy LCA Approaches ...... 25 3.1.1. Hybrid Frameworks in Literature ...... 25 3.1.2. Present Integration of Exergy within LCA Databases ...... 29 3.1.3. Exergy based Sustainability Indicators ...... 30 3.2. Evaluation of existing Approaches and Choice of Methodology ...... 34 3.2.1. Evaluation of hybrid Methodologies in Literature ...... 34 3.2.2. Exergy LCA Framework adopted ...... 36 3.2.3. Scope and System Boundaries ...... 38

Chapter 4: The Case of Cardboard Production ...... 41

4.1. Pulp & Paper Industry ...... 41 4.1.1. Market and Value Chain Perspective ...... 41 4.1.2. Technology Perspective ...... 43 4.1.3. Environmental Perspective ...... 45 4.2. Exergy LCA of Cardboard Production ...... 47 4.2.1. Goal and Scope Definition ...... 47 4.2.2. Inventory Analysis ...... 48 4.2.3. Impact Assessment and Interpretation ...... 51

Chapter 5: Conclusions & Discussion ...... 59

5.1. Answering the Research Questions ...... 59 5.1.1. Connecting Exergy Analysis and LCA ...... 59 5.1.2. Applying Exergy LCA to Cardboard Life Cycles ...... 63 5.2. Discussion ...... 66 5.3. Recommendations ...... 68

References ...... 69

Appendices ...... 73

Appendix A: Methodology ...... 73 1) Terms and Symbols used ...... 73 2) Industrial Ecology ...... 74 3) Exergy Analysis within Industrial Ecology Tools ...... 75 4) Literature Review of hybrid Methodologies integrating Exergy Analysis and LCA ...... 77

Appendix B: Pulp & Paper Industry and Case Study ...... 80 1) Functional Use of Paper and Board Grades ...... 80 2) European Pulp and Paper Key Figures ...... 81 3) Sustainability in the Paper and Board Value Chain ...... 83 4) Inventory Template, Example: Board Making ...... 85 5) Assumptions of Calculations used for Case Study...... 86 6) Results of Case Study ...... 91 7) Confirming Mass, Energy and Exergy Balances ...... 93 8) Solar Thermal Energy Calculations ...... 94

Appendix C: Meetings ...... 95 1) Workshop ISPT, January 20th 2011 ...... 95 2) Workshop ISPT, February 15th 2011 ...... 95 3) KCPK Meeting, February 10th 2011 ...... 96 4) KCPK Technology Day, February 17th 2011 ...... 97

List of figures

Figure 1 Problem Definition and Research Questions ...... 14 Figure 2 Components of exergy of matter ...... 18 Figure 3 Applications of Exergy Analysis (adapted from (Liao, Heijungs et al. 2011)) ...... 21 Figure 4 Research projects using Exergy Analysis on different system levels ...... 21 Figure 5 Life Cycle Assessment framework (based on (ISO 1997)) ...... 22 Figure 6 Calculation framework for “cradle to nature” Exergy Analysis (Valero 1998) ...... 26 Figure 7 Contreras Moya, Rosa Dominguez et al. methodology for Exergy LCA ...... 28 Figure 8 Input and output exergies of a system (Gong and Wall 1997) ...... 30 Figure 9 Relation between exergy and sustainability (Rosen, Dincer et al. 2008) ...... 33 Figure 10 Lessons learned from literature review ...... 36 Figure 11 Inventory Template ...... 37 Figure 12 European paper and board consumption and recycling (CEPI 2010) ...... 42 Figure 13 The paper and board production value chain (McKinney 1995; Suh 2009; CEPI 2010) ...... 43 Figure 14 Board production: waste paper collection and web screen of board machine ...... 44 Figure 15 Finishing: external paper layers, printing and recovery of cutting losses ...... 44 Figure 16 System boundary of cardboard case study ...... 47 Figure 17 Mass flows in the Dutch cardboard production chain ...... 52 Figure 18 Energy flows in the Dutch cardboard production chain ...... 53 Figure 19 Exergy flows in the Dutch cardboard production chain ...... 53 Figure 20 Cumulative exergy consumption, exergy sources and exergy losses in the Dutch chain ... 54 Figure 21 Cumulative exergy consumption, exergy sources and exergy losses in the German chain 55 Figure 22 Energy balances including input and output details in NL and DE ...... 56 Figure 23 Exergy balances including input and output details in NL and DE ...... 56 Figure 24 Comparison of material efficiency DE - NL ...... 57 Figure 25 Comparison of exergy flows in the current situation with a best case solar scenario ...... 65 Figure 26 Key figures 2010 of European pulp and paper market (CEPI 2011) ...... 81 Figure 27 Global trade flows of recovered paper in 2009 (CEPI 2011) ...... 82 Figure 28 Developments on the global pulp and paper market (Carlsson, D'Amours et al. 2006)..... 82 Figure 29 Sustainability issues in the paper and board value chain ...... 83 Figure 30 Sustainability initiatives within the paper and board value chain ...... 84 Figure 31 Inventory template of board making ...... 85 Figure 32 Exergy-entropy diagram for dry air (Szargut 1988) ...... 89 Figure 33 Physical exergy of humid air (Szargut 1988) ...... 90 Figure 34 Mass flows in the German cardboard production chain ...... 91 Figure 35 Energy flows in the German cardboard production chain ...... 92 Figure 36 Exergy flows in the German cardboard production chain ...... 92 Figure 37 Mass and energy balances in Dutch and German power plant, board production and board conversion ...... 93 Figure 38 Mass and exergy balances in Dutch and German power plant, board production and board conversion ...... 93

List of tables

Table 1 Literature review of hybrid methodologies integrating Exergy Analysis and LCA ...... 29 Table 2 Sustainability issues and initiatives in the pulp and paper value chain ...... 46 Table 3 Exergy indicators applied to the German and Dutch cardboard chains ...... 58 Table 4 Comparison of exergy indicators in the current situation with a best case solar scenario ... 66 Table 5 Literature review on Exergy Analysis and LCA integration ...... 79 Table 6 Functional use of paper and board grades (EU 2010) ...... 80 Table 7 Area requirements for solar collectors per ton of cardboard ...... 94

Chapter 1

Introduction and Research Outline

With the aim to improve our current industrial system towards a more sustainable one, a multitude of analytical tools have been developed to study its challenges and improvement potential.

This research focuses on combining two of these tools, Exergy Analysis and Life Cycle Assessment, to take advantage of both of their strengths. So far no established framework exists for this hybrid approach leading to little available studies and data. Therefore, in this report integration possibilities are studied and the chosen methodology is applied to a case study – the production of cardboard.

Cardboard is currently produced in a very energy and water intensive manner resulting in a suboptimal sustainable performance. By means of the new hybrid approach, thermodynamic improvement potential is detected along the value chain.

1.1. Problem Background

In the complex domain of sustainability, a multitude of analytical tools are being used individually or in a hybrid form to grasp a productive situation in its complexity.

Life Cycle Assessment (LCA) is a popular analytical tool that aims at compiling and evaluating the environmental impacts of a product from a life cycle perspective. Such a life cycle orientation intends to include direct and indirect supply chain impacts, thus integrating activities from resource extraction, production, distribution and consumption systems to the waste management phase. Introducing the “cradle to grave” idea to the analysis of a certain product pathway allows the identification and prioritization of major environmental issues as well as a complete comparison between different pathways that fulfill the same function (ISO 1997).

The second tool that is crucial to this research is Exergy Analysis. Exergy Analysis is used to study thermodynamic inefficiencies in applications or processes and is thus relevant in revealing improvement potential (Szargut 2005). Exergy indicates the “quality” of energy which is degraded along the production routes. In order to make a process or a system more efficient, this degradation or loss of exergy must be minimized.

Each tool reflects upon a problem from a specific perspective. Whereas LCA focuses on integrating details and environmental impacts of a production system within a life-cycle perspective, Exergy Analysis pays attention to inefficiencies within a process or a system from a thermodynamic perspective. Combining two different perspectives within one combined method has large potential to make use of the strengths while reducing the weaknesses of the individual tools. Thereby the

10 methodological approach for a specific research question can be adapted and improved (Suh 2004). Regarding the combination of LCA and exergy, thematic overlaps can be observed in various areas (Udo de Haes and Heijungs 2007):

1) The environmental impacts of streams studied within a LCA often relate to energy flows and the degradation of exergy throughout an industrial process. However they are not shown as a separate result of the inventory analysis or the impact assessment, but are an integrative part of categories such as depletion of resources and climate change. 2) LCAs can be performed on energy systems in which exergy plays an important role, e.g. by comparing the generation of electricity via different production pathways or by comparing fossil fuels with biofuels. 3) The energetic or exergetic performance within a life cycle of a product can be studied which is the least explored thematic overlap of the ones mentioned here and will be the main connection used in this research project. In the following the challenges of the hybrid approach of LCA and Exergy Analysis are introduced and research questions are deviated.

1.2. Problem Definition

1.2.1. Methodology: Exergy Analysis and LCA Combining the tools LCA and Exergy Analysis generates the advantage of giving a strategic overview of the thermodynamic life cycle performance of a product. Internal and external inefficiencies and improvement potential can be evaluated on a life cycle scale.

However, only few attempts have been made in combining the benefits of both tools and the existing approaches vary considerably among researchers. So far, neither a clear overview of the adopted methods is available, nor are their advantages and disadvantages elaborated upon. Consequently, none of the exploratory approaches can claim to be a validated and accepted methodology.

Given the rather pioneering nature of this hybrid methodology, established structures of the LCA domain have not been expanded considerably into the Exergy Analysis domain and vice versa. For example, traditional life cycle databases such as Ecoinvent do not include data on exergy contents or exergy efficiencies. Also the application range of Exergy Analysis is still focused mainly on the traditional process level. Focusing on only one “piece” of the system conceals the risk that the specific “piece” is optimized while the system as a whole is changed for the worse.

Having no structured exergy data available, e.g. in a database format similar or as integrative part of Ecoinvent, and having only a limited amount of research projects being carried out in the combined area of exergy and systems level approaches, leads to insufficient data availability. Starting new research projects in this hybrid domain requires thus high data gathering activities that are not being effectively shared among the research community yet. Furthermore, the first attempts of combining

11 the exergy and the system level domain need to be evaluated and eventually be confirmed through practical experience.

As a next step, the performance must be evaluated and interpreted from an exergetic life cycle perspective. To achieve this, indicators can be used which present a reasonable approach in communicating performance results to laymen in an objective way. Similar to other analytical tools, such indicators should be defined for this hybrid methodology. Examples of indicator developments within this hybrid domain can already be found in literature, e.g. by (Dewulf and Van Langenhove 2006), (Yang, Hu et al. 2006) and (Connelly and Koshland 2001). These indicator developments are discussed in 3.1.3.

For the above stated reasons researchers such as (Ukidwe and Bakshi 2005), (Dewulf and Van Langenhove 2006), (Gong 2005), (Finnveden and Östlund 1997), (Grubb and Bakshi 2011) call for more practical examples of applying Exergy Analysis on a systems level.

1.2.2. Case Study: Cardboard Production The industrial setting chosen as case study is the pulp and paper industry. Globally it is the fourth largest industrial consumer of energy, consuming 5,9 ExaJoules which represents 6% of the total industrial energy use (IEA 2006).

The high energy intensity puts the industry under pressure from an environmental and from an economic point of view. Although many initiatives and research projects have been aiming at reducing the dependency on fossil fuel input, the industry remains a major energy consumer (Nilsson 1997; Gong 2005).

Moreover, a focus on the paper or board mill can be observed throughout the initiatives and research projects dealing with energy issues in the pulp and paper industry. The Dutch think tank of the paper industry, the Kenniscentrum Papier en Karton, reports many projects aiming at optimizing the energy use of small scale processes and has only recently started to incorporate projects on a supply chain level. It claims that improvement opportunities exist on a broader scale (KCPK 2011).

Another reason for lacking projects that incorporate data of the entire value chain is little data availability. In this highly competitive sector, companies are only rarely willing to share information beyond company borders which increases the difficulty of gathering precise data on a value chain level, e.g. on transport distances and printing services.

1.3. Research Questions and Goal Formulation

1.3.1. Research Questions Based on the challenges described above two main research questions can be defined that are subdivided in further sub questions.

The first research question dealing with the difficulty of integrating the concept of exergy with life cycle thinking is introduced in the following. To answer this rather broad question, sub questions are used to be able to structure the research approach better.

1. How can Exergy Analysis be integrated in a structured way with life cycle thinking? • Which approaches exist in literature to integrate exergy and life cycle assessments? What are their advantages and disadvantages? • How can databases be adapted to be able to integrate exergy balances of production processes? • Which exergy based indicators can be used to facilitate future chain analysis?

The second research question relates to the case study and the sustainability challenges within the paper industry. As specific case the value chain of cardboard production is being used. By means of the case, the methodological questions as posed above can be illustrated in a practical way and the process of data gathering and method validation can be enhanced.

On the other hand, a new perspective is added to the sustainable improvement potential of a value chain that is embedded in the challenging environment of the paper industry.

The second research question is thus phrased as:

2. What are the biggest energy and exergy consuming steps in the cardboard value chain? How can this knowledge be used to improve the life cycle of cardboard production in a sustainable way?

As an overview the problem definition and the respective research questions are summed up in the following figure.

Figure 1 Problem Definition and Research Questions

1.3.2. Goal Formulation The goal of this research is to analyze thermodynamic improvement possibilities in industrial systems from a product life cycle perspective. Integration possibilities of Exergy Analysis and LCA are analyzed and evaluated for that purpose. By applying this hybrid methodology to the energy-intensive cardboard production, inefficiencies and improvement potential are to be detected with the aim to develop towards a more sustainable system.

1.4. Scope and System boundaries

Defining the scope and system boundaries within an industrial ecology research implies to explicitly identify which productive system is to be studied from a spatial and temporal perspective and what elements (processes, flows, actors) are integrated within this productive system.

Detailed scope, spatial and temporal system boundaries of the adopted framework and the case study can be found in 3.2.3. and 4.2.1. respectively.

On a more general level, two limitations need to be discussed. Firstly, it must be considered that the thermodynamic point of view is only one dimension of a multitude of factors influencing the environmental performance of a production chain. Due to time constraints, it is chosen to purposely limit this research project to the thermodynamic dimension. It is clear that other factors, especially those independent of thermodynamic flows such as toxicity or acidification, are not taken into account. Although this might reduce the completeness of the conclusions, various researchers, e.g. (Bakshi and Fiksel 2003) and (Connelly and Koshland 2001), have shown that exergy can be an appropriate measure for sustainability, as will be discussed in greater detail in 3.1.3.. Secondly, it is taken as given that exergy is an appropriate concept to study improvement potential as demonstrated by (Gong and Wall 1997; Rosen, Dincer et al. 2008) or (Sciubba 2005) and that it adds value to a traditional LCA as has discussed by (Arons, Kooi et al. 2004; Grubb and Bakshi 2011). To be able to focus this research on the above stated goal and research questions, these assumptions are not proven at this point but instead it is chosen to reference previous research.

1.5. Involved Parties

The project is carried out with Delft University of Technology and Leiden University as a graduation thesis of the Master in Industrial Ecology. Within Leiden University, the supervising partner is Reinout Heijungs from the Institute of Environmental Sciences and within Delft University of Technology, the supervising partner is Gijsbert Korevaar from the Faculty of Applied Sciences.

Thanks to this combination, expertise in engineering and thermodynamics is joined with knowledge in environmental analysis such as LCAs.

On the practical side, support is given by Tebodin, an engineering consultancy with expertise in the pulp and paper industry. The supervising partner is Wouter van Gerwen, Manager Industrial Projects, and expert in enlarging the engineering perspective on broader system definitions. Thanks to Tebodin’s professional network, input from other institutions such as the Institute for Sustainable Process Technology and the Dutch think tank of the paper industry, the Kenniscentrum Papier en Karton (KCPK) could be integrated.

The case study on cardboard production in Germany and the Netherlands is carried out in cooperation with Smurfit Kappa Specialties Division.

1.6. Structure of the Report

The report is structured in five chapters. The first one presents the research purpose and its design including problem definition, research questions and goal formulation. In the second chapter the theoretical fields of Exergy Analysis and LCA are reviewed independently and calculation methods and application areas are presented. The third chapter reviews and evaluates existing approaches of incorporating Exergy Analysis and LCA, the integration of exergy in LCA databases and the current application of exergy indicators within industrial ecology tools. Based on this literature review, a framework is built which is then applied to the cardboard case study in the following chapter. Chapter four introduces the paper and pulp industry from a multi-dimensional perspective: the market and its value chains, the production process and its technologies and the sustainability issues and current initiatives are presented. Further, the case study is elaborated upon and results of the applied framework are shown.

The final chapter five is dedicated to discussing the methodology and its practical applicability to the case study. Conclusions are drawn to answer the two main research questions and to provide recommendations for future research.

Chapter 2

Review of Exergy Analysis and LCA

2.1. Exergy Analysis

2.1.1. Introducing the Concept Exergy Exergy is a thermodynamic concept routed in the first two laws of thermodynamics. While the first law describes the conservation of energy principle, the second law deals with the non-conversation of entropy principles indicating the direction of reactions and their irreversibility. From this, the concept of “usefulness” or quality of energy and material can be derived, i.e. the concept of exergy. In literature different symbols are used for exergy, e.g. B (Szargut 1989), E (Moran and Shapiro 2004), Ex (Woudstra, Woudstra et al. 2010; Liao, Heijungs et al. 2011). In this report the symbol Ex is used to be consistent with the nomenclature within the university faculties although (Tsatsaronis 2007) argues for using a one-letter symbol to prevent confusion with subscripts. All terms and symbols used throughout the report are listed in appendix A.1. In comparison to energy (nominated here as En ), exergy is only conserved in reversible processes but is destroyed in most real processes as they are irreversible (Gong and Wall 1997). Putting this in terms of input-output balances, the energy balance for a whole process must always be zero while the difference of the exergy balance equals the irreversibility of the process (Valero 1998): (2.1) − = 0 (2.2) − > 0 The difference between the input and output exergy is often referred to as irreversibility of a process which is related to its entropy generation. It can be determined by multiplying the entropy increase,

ΔS , with the temperature, T0. This equation is termed the law of exergy loss or the law of Gouy- Stodola (Szargut 1989): (2.3) − = ∆ = ∆ Exergy is thus defined as the “maximum theoretical useful work obtainable as the system is brought into complete thermodynamic equilibrium with the thermodynamic environment while the system interacts with this environment only” (Connelly and Koshland 2001; Kåberger and Månsson 2001). This means it is the available work obtainable from all flows that are different from the reference flows that are found in their environment. Possible in- and outflows to a system include matter, heat (Q) and work (W). (2.4) = + + A flow of matter can differ from its environment and supply work due to its chemical structure, its temperature or pressure, its velocity or height potential. Thus four components of Ex matter can be distinguished: physical exergy consisting of mechanical and thermal exergy, chemical exergy resulting 17 from the system’s chemical composition, kinetic exergy resulting from the system velocity relative to the environment and potential exergy resulting from system height relative to the environment (Tsatsaronis 2007).

Figure 2 Components of exergy of matter

The exergy of a stream of matter, Ex matter , is the sum of the exergy of its components. (2.5) = + + + Respectively the exergy losses of the studied system, e.g. a factory or a value chain, are equal to the sum of exergy losses of its component parts (Szargut 1988).

2.1.2. Calculating Exergy Contents

Exergy of Work Since exergy is defined as the maximum work potential, a work interaction in energy terms is equivalent in exergy terms. This means that to calculate the exergy content of e.g. electricity, a factor of 1 is used based on its energy content (J.J.C. van Lier and Woudstra 2005). (2.6) =

Exergy of Heat The maximum work potential of a heat stream, Q, is limited by the Carnot factor. Its exergy content,

Ex Q, can therefore be calculated by the Carnot factor multiplied with the energy content of the heat stream (Cornelissen 1997).

(2.7) = 1 −

Exergy of Matter Regarding the calculation process of the exergy of matter, the distinction of exergy components becomes important as different formulas need to be applied. The exergy of matter due to physical disequilibrium with the environment, thus due to temperature and pressure differences is calculated as the difference between the enthalpy, H, and the environmental enthalpy, H0, minus the exergy loss as defined above (Szargut 1988): (2.8) = − − ( − )

The work potential resulting from a substance’s chemical composition is calculated in various steps breaking down the disequilibrium to its environmental reference state and thus its potential work.

The full derivation is explained in detail in Szargut’s article on “Chemical Exergies of the Elements” (Szargut 1989). Standard chemical exergies of compounds can be calculated on a molar basis as: (2.9) = + where G is the standard Gibbs free energy of formation of the compound, nj are molar fractions of the jth chemical element and the index j runs over the elements in the compound (Ayres 1998). For important elements these values can be looked up also in tables calculated by (Szargut 1988). The kinetic exergy is calculated as the difference between the squared speed, w2, of the flow and the speed of its surroundings (J.J.C. van Lier and Woudstra 2005):

(2.10) = − The exergy of matter as a result of its height relative to the environment, the potential exergy is calculated as the difference of the potential energies, Enp, of the matter and its environment (J.J.C. van Lier and Woudstra 2005): (2.11) = , − ,

2.1.3. Types of Exergy Losses Besides the distinction of components of exergy, it is useful to differentiate between types of exergy losses in order to study where irreversibilities occur. Two kinds of exergy losses can be distinguished: internal and external (Szargut 1988). External exergy losses represent the remaining exergy contents of waste and emissions that are dissipated or removed from the production and embody thus unused exergy. Internal exergy losses correspond to the losses of quality due to internal inefficiencies within the process (Valero 1998). These internal irreversibilities may be of technical nature due to technical inefficiencies within the plant, e.g. friction or lack of insulation, or they may be of structural nature. Structural exergy losses are losses determined by the principle and design of the system, e.g. the use of heat for electricity production is structurally limited by the Carnot factor. Whereas technical exergy losses can be reduced through optimization, structural losses can be reduced only by redesigning the system. Internal and external exergy losses depend on each other as a change in process design or optimization influences the exergy content of waste materials and emissions and thus the external exergy losses (Szargut 1988). Whereas internal exergy losses should always be avoided from a sustainability perspective, no general statement can be made on external exergy losses. Here it is essential to define system boundaries that are broad enough to understand the opportunities of this unused exergy. If, for example, the unused exergy can be cascaded further to processes with lower exergy requirements, a reduction of external exergy losses of the first process would increase the total exergy losses and thus the environmental performance of the system as a whole. Whether external or internal losses prevail depends on the studied system and its system boundaries. According to (Szargut 1988) external exergy losses represent the main inefficiency, but (Ayres 1998) claims the opposite.

2.1.4. Review of Application Fields of Exergy Analysis Exergy Analysis is a methodology that uses the exergy concept to determine the most effective way of improving the system under consideration (Rosen, Dincer et al. 2008). Exergy losses and thus inefficiencies in energy processes and systems can be determined and used to increase the exergetic efficiency and optimize the driving forces. The main objective is to use energy in a more economical and physical efficient way (Wang and Feng 2000). Traditionally Exergy Analysis has been applied mainly to single processes or applications to be able to compare alternatives that showed how the exergy embodied in the input resources is partitioned among the products, waste and internal irreversibilities (Dewulf and Van Langenhove 2006). As the analysis method evolved and became more diffused, the application horizon expanded towards whole production chain analysis. With the production chain analysis, a life cycle perspective can be taken starting from natural resources to the final product which allows to calculate a cumulative exergy consumption, thus the total amount of exergy “that has to be extracted from the natural ecosystem in order to deliver the desired product”(Dewulf and Van Langenhove 2006). As exergy presents a relatively objective and unified measure, it has been used as a connection point to economics. A physical-based analysis is added to the traditional monetary-based approach and the economic significance of the second law of thermodynamics is studied as has been done by (Gong and Wall 1997; Ayres 1998; Kåberger and Månsson 2001; Chen, Chen et al. 2006). This connection is used to study industrial societies not only from an economic but also from a physical flow perspective. Thereby Exergy Analysis can be combined with input-output analysis as demonstrated by Ukidwe (2005) who applied a thermodynamic input-output model to study the flows of natural capital through the network of economic sectors and compare their exergy consumption. Only recently, Exergy Analysis has received increasing attention by industrial ecology researchers, in particular by Dewulf and Van Langenhove from the EnVOC Research Group at Ghent University, by Valero from the Center of Research for Energy Resources and Consumption at Universidad de Zaragoza and by Yang et al. from the Center for Industrial Ecology at Tsinghua University, Beijing. Their objective is to quantify the opportunities and benefits of closing material loops at an intercompany level based on the physical measure exergy. The expansion of the traditional Exergy Analysis to production chains, industrial ecology concepts and (resource) economics brings about new questions on how to deal, for example, with the exergy value of natural resources and ecosystems’ services. Here concepts that have been developed in the field of ecosystems, especially by Jørgensen from the Environmental Chemistry Research Group at Copenhagen University, have been integrated and useful analogies have been drawn. The following figures present an overview of the various perspectives and system boundaries that can be combined with Exergy Analysis. Figure 3 depicts the overlaps and embeddedness of the industrial system and ecosystem as well as their respective subsystems that are being studied. Figure 4 shows the same visualization with examples of research projects that have been carried out in combination with Exergy Analysis within the various system boundaries. It must be noted that the research projects mentioned here are only of exemplifying nature and are not intended to serve as complete literature list. As this report focuses on Exergy Analysis within industrial ecology and more specifically with LCA, more examples are mentioned in this area.

Figure 3 Applications of Exergy Analysis (adapted from (Liao, Heijungs et al. 2011))

Figure 4 Research projects using Exergy Analysis on different system levels

2.2. Life Cycle Assessment

As briefly introduced in chapter 1, LCA is an analytical tool used to compile and evaluate the environmental impacts of a product from a life cycle perspective, i.e. including direct and indirect supply chain data. Applying this tool to different production routes of the same product allows comparing production methods from an environmental point of view and evaluating improvement potential. Moreover “hot spots” can be identified within a product life cycle. This can be carried out descriptively or change-oriented (Finnveden and Moberg 2005). The method of LCA is standardized by ISO in the 14040 section which presents a basic framework to objectively evaluate the environmental performance of a product life-cycle. It proposes also the general principle to draw initial system boundaries: “the system should be modeled in such a manner that inputs and outputs at its boundaries are elementary flows” where elementary flows are defined as material of energy flows that are extracted or emitted directly from or to the environment. If inputs or outputs are not traced back to their elementary flows, they are referred to as cut-off (Suh 2004). It must be noted that these guidelines are practically very difficult to follow which leads to extensive discussions among LCA practitioners as addressed in (Suh 2004).

2.2.1. LCA Framework A LCA is carried out in four phases: a goal and scope definition, an inventory analysis, an impact assessment and an interpretation phase.

Figure 5 Life Cycle Assessment framework (based on (ISO 1997))

In the first phase, the goal and scope of the LCA is outlined to explicitly state the questions that are to be answered and the limitations in which this is being done. An important aspect of the goal definition is determining the functional unit and selecting the product alternatives that are taken into consideration. A comparison of alternative pathways is done by normalizing the flows to a functional unit, e.g. 1 ton of produced cardboard that can be produced by means of different production pathways (Suh 2004). The scope definition deals with setting limits to the generalization of the study. Choices relating to the geographical and temporal boundaries as well as regarding the included processes and mechanisms must be made explicitly. The second phase deals with gathering input and output data for each process of the previously defined system. A life cycle consists of a multitude of individual processes for which inputs and outputs can be identified and mass and energy balances can be established. These inputs and outputs are differentiated in two categories according to their source: economic flows and environmental flows. Economic inputs and outputs are flows that are connected to another process within the industrial system whereas environmental inputs and outputs are flows which come from or go to the environment. In order to relate different unit processes to each other, scaling factors are determined between outputs of one process and the inputs of its downward processes. In case that more than one product is generated out of a unit process, i.e. more than one function is present, the inputs have to be allocated to the various functions (Finnveden and Östlund 1997). This can be done, for example, on a mass or energy basis or on a monetary basis. The outcome of the inventory analysis is the inventory table which lists all resources and pollutants that are extracted or emitted along the defined life cycle. Depending on the goal and scope of the research, data can be assessed on an aggregated “cradle-to-grave” level indicating the cumulative amounts of all resources and pollutants or on a unit process level, indicating in- and outflows of each production process. This scope distinction becomes important when incorporating exergy and LCA as will be discussed in chapter 3. The third phase is called impact assessment and has the objective to interpret and aggregate the items in the inventory table. Thereby the concept of impact categories is used. Frequently used ones are climate change, ozone layer depletion, human toxicity, ecotoxicity, acidification, eutrophication and photochemical smog (Pennington, Potting et al. 2004). In a stepwise process, the extractions and emissions from the inventory table are first classified according to the environmental effect to which they contribute. In a second characterization step, it is estimated how much they contribute to the selected environmental problem by means of a characterization factor. In a third and final step, the selected environmental problem is evaluated (Cornelissen 1997). The last step of carrying out a LCA is dedicated to the interpretation of the data and results. Possibilities include breaking down the results among the unit processes, performing sensitivity and uncertainty studies, evaluating the results with respect to the quality of the data and proposing recommendations.

2.2.2. LCA Applications A large number of LCA case studies exist in various industries. Important fields of application include packaging (Levy 2000), energy generation (Cherubini, Bird et al. 2009), building materials (Zabalza Bribián, Aranda Usón et al. 2009), detergents and other cleaning systems (Eide, Homleid et al. 2003), TVs and computer systems (Deng, Babbitt et al. 2011) as well as food production (Roy, Nei et al. 2009).

Chapter 3

Methodological Framework Combining Exergy Analysis and LCA

After describing the general use of Exergy Analysis and LCA independently, its combination is now elaborated upon. This includes a review of integration attempts in literature and a description of the framework used in this report.

3.1. Review of Exergy LCA Approaches

LCA and Exergy Analysis, often nominated as exergetic life-cycle assessment or life-cycle exergy assessment, are combined to study life cycle production chains of a specific product from a thermodynamic perspective. This includes analyzing resource depletion in life-cycle impact assessment, studying improvement potential, estimating environmental impact using exergy as criterion or as part of a multi-criteria study. Moreover, adopting exergy as a common unit in LCAs can be a way to overcome the criticism of different impact categories being aggregated to one unified result. A selection of approaches of applying exergy within LCA and the use of exergy as a measure for sustainability are discussed in the following subchapters.

3.1.1. Hybrid Frameworks in Literature The selection of research projects discussed and evaluated here is based on a literature review of exergy and LCA combined studies and the availability of methodological descriptions among them. This results in the following selection: (Cornelissen 1997) and (Cornelissen and Hirs 2002) from University Twente, (Finnveden and Östlund 1997) from the Swedish Environmental Research Institute, (Valero 1998) from the University of Zaragoza, (Gong and Wall 1997) from Linköping University and Chalmers University of Technology, (Grubb and Bakshi 2011) from The Ohio State University, (Bösch, Hellweg et al. 2007) from ETH Zürich, Radboud University Nijmegen and the Ecoinvent centre, (Contreras Moya, Rosa Dominguez et al. 2007) from Ghent University. Cornelissen uses the combination of exergy within LCA which he calls Exergetic Life Cycle Analysis and Exergetic Life Cycle Assessment, to assess the efficiency of the use of natural resources and to quantify the depletion of resources. He calculates the irreversibility over the life cycle as the sum of exergy losses of all unit process within the system and takes that as a measure of inefficient use of resources and of depletion of non-renewable resources. He adapts the established LCA framework in the phase of inventory analysis and impact assessment. The inventory analysis is extended by including data for exergy calculations such as pressure and 25 temperature. Based on a previous mass and energy balance, an exergy balance per unit process is established. On the other hand, the impact assessment is more limited as life cycle exergy loss is the only criterion: only the exergy of the flows and the exergy losses of the processes are calculated. Based on the total exergy losses throughout the life cycle of the product, the life cycle irreversibility, the improvement analysis is carried out. For multi-functional processes, three allocation methods are proposed: based on the exergy of the flows, based on the exergy destruction in case of separate production of by-products, or based on the distribution of exergy destruction on the basis of changes in the exergy values of the flows. Moreover the Exergy LCA is extended to a “Zero-Exergy LCA” which includes the abatement exergy of emissions, i.e. the exergy used to abate, re-use or dispose emissions in an environmentally friendly way. Finnveden and Östlund also intend to use exergy as a measure for resource depletion but take a more limited approach than Cornelissen. They use exergy as a characterization method within a LCA framework but the exergy contents are calculated only for the elementary input flows, i.e. for minerals and fuels that are extracted directly from the environment. Moreover they limit their research to the chemical exergy of these natural resources. Their cumulative exergy consumption index is therefore the sum of the chemical exergy contents of the natural resources required to produce the product in question. Valero aims at integrating an extended life cycle approach to an exergy analysis in order to study life cycle irreversibilities. Instead of referring to the classical LCA methodology as Cornelissen and Finnveden and Östlund do, he develops a calculation framework for a “cradle to nature” exergy analysis as illustrated in figure 6.

Figure 6 Calculation framework for “cradle to nature” Exergy Analysis (Valero 1998)

To complete the cycle, Valero adds the “exergetic cost of replacement of materials”, i.e. the exergy needed to bring the materials back to their initial state. Four phases of calculation are defined: 1) Calculation of exergy of natural resources starting from recognized reference environment. 2) Calculation of exergy throughout the life cycle of a product, including the exergy of all materials and services needed for production, transportation, distribution, use, maintenance and disposal of the product. 3) Calculation of exergy needed to level off all emissions produced throughout a life cycle. 4) Calculation of exergetic costs needed to replace all materials used (recycle, reforestation). This is an extension to Cornelissen’s Zero-exergy LCA idea who considers only the first three steps. In addition, Valero puts the exergy consumed into a monetary perspective and chooses a thermoeconomic approach. Based on Valero’s formulation of calculating the exergy of natural resources and the exergy throughout the life cycle, it is assumed that an integration of exergy on a unit process base is intended. Gong and Wall elaborate upon the importance of a life cycle approach in sustainable engineering and exergy analysis to understand the performance of the entire system and prevent problem shifting. A life cycle approach is briefly conceptualized by distinguishing between three different stages: a construction, an operation and a clean-up phase. In the construction stage exergy is used to build a plant and start-up. Part of this exergy input is stored in the materials used. The exergy input in the operation stage is called direct exergy, whereas the exergy of the other two stages is called indirect exergy. Additionally, exergy is taken as a rational basis for assigning costs. Grubb and Bakshi focus their study on the improvement analysis of LCA and use exergy to identify process improvement opportunities. Similar to Cornelissen (1997), a LCA framework is taken as basis and an exergy balance is calculated for each unit process. The exergy contents of in- and outflows are calculated as a sum of chemical and physical exergy. Furthermore, they extend the scope by using both a unit process and a cradle-to-grave level. As indicator, an ecological cumulative exergy consumption is calculated which is conceptually equal to Finnveden and Östlund’s cumulative exergy consumption indicator (1997). The exergy contents of all natural resources needed for producing a product are aggregated. In contrast to Finnveden and Östlund, Grubb and Bakshi consider not only the chemical exergy but also the physical exergy. Bösch, Hellweg et al. integrate exergy values within the LCA framework as an additional impact category in order to measure resource consumption and exergy removal from nature to produce the product in question. Ecoinvent is used as integration database in which exergy characterization factors are calculated for 2630 products. A cradle-to-grave approach is applied to calculate the cumulative exergy demand which is similar to Finnveden and Östlund’s method (1997). In case of multi-functional processes, exergy is allocated according to revenue or, if this data is not available, according to mass. Very extensive exergy calculations are carried out including chemical, kinetic, hydro-potential, nuclear, solar-radioactive and thermal exergy.

Contreras Moya, Rosa Dominguez et al. also choose the established LCA framework as basis and incorporate exergy as an additional impact assessment. Both, the traditional LCA and the exergetic LCA, are performed as depicted in figure 7. As indicator, the cumulative exergy consumption is calculated based on the cumulative amount of a certain material multiplied by its exergy factor.

Figure 7 Contreras Moya, Rosa Dominguez et al. methodology for Exergy LCA

The described methodologies can be summed up in the following table. An extended version of the table including achievements, conclusions and nomenclature of the respective researchers can be found in appendix A.4. A critical comparison and evaluation of the reviewed methodologies follows in 3.2.1.

Researcher Goal Framework Level of detail System boundary (Cornelissen Assess the efficiency of Exergy as impact Unit process Cradle -to -grave and Hirs the use of natural category in LCA level including 2002) resources and quantify abatement exergy the depletion of of emissions (Cornelissen resources 1997) (Finnveden Use exergy as a Exergy as Cradle -to - Cradle -to -grave and Östlund measure of resource characterization grave level 1997) depletion, calculate factor within a exergy of some natural LCA resources (Valero Use exergy to study life “cradle to cradle” Unit process Cradle -to -nature 1998) cycle irreversibilities calculation level including framework; abatement of Thermo- exergy of emissions economic and replacement of approach materials (Gong and Understand system No clear Not clear Cradle -to -grave Wall 1997) performance at life framework, LCA cycle level; prevent idea presented problem shifting (Grubb and Use exergy to identify LCA framework, Unit process Cradle -to -grave Bakshi 2011) process improvement Exergy as impact and cradle-to- opportunities category assumed grave level (Bösch, Measure resour ce Exergy as Cradle -to - Cradle -to -grave Hellweg et consumption and additional impact grave level al. 2007) exergy removal from category in LCA nature (Contreras Not clear Exergy as Cradle -to - Cradle -to -grave Moya, Rosa additional impact grave level Dominguez category in LCA et al. 2007)

Table 1 Literature review of hybrid methodologies integrating Exergy Analysis and LCA

3.1.2. Present Integration of Exergy within LCA Databases Currently, exergy values are available within LCA databases such as Ecoinvent for a selection of natural resources, e.g. for natural gas or crude oil at the extraction location. (Bösch, Hellweg et al. 2007) have assembled an extensive amount of exergy data including chemical, kinetic, hydro- potential, nuclear, solar-radioactive and thermal exergy for 2630 products. The data is incorporated in Ecoinvent as characterization factor. This allows calculating the exergy input from natural resources at the point of extraction for some products and thus the cumulative exergy consumption of a life cycle as defined by (Bösch, Hellweg et al. 2007) or (Finnveden and Östlund 1997).

3.1.3. Exergy based Sustainability Indicators The discussions above have shown how exergy and exergy losses can be calculated, in which system dimensions they can be and have been applied and how exergy can be integrated in established tools, in particular within the IE domain. In order to communicate the results of these analyses and be able to easily compare, e.g. different production pathways but also different systems between each other, indicators are adopted. They can also provide aggregate information for target groups in question. Within Industrial Ecology, exergy has also been integrated in other analytical tools such as Material Flow Assessment (MFA) and Input Output Analysis (IOA) e.g. by Ukidwe who applied a thermodynamic IOA to an economic-ecological system (Ukidwe 2005) or by Yang, Hu et al. who used Exergy Analysis to study the flows of an Eco-Industrial Park (EIP) (Yang, Hu et al. 2006). An overview of the use of exergy in these two tools can be found in Appendix A.3. Insights from these hybrid approaches can be valuable for the development and choice of indicators. Therefore the review of exergy based indicators is extended to other Industrial Ecology tools.

Review of Exergy based Sustainability Indicators in Literature A selection of indicators that have been developed for hybrid exergy methodologies, e.g. exergy LCA, exergy MFA or exergy IOA is reviewed and evaluated. The standard indicator applied by most researchers is exergy efficiency, a ratio of utilized exergy divided by used exergy. However, both terms can be interpreted in different ways. Utilized exergy can be the total exergy output or only the exergy content of the products or only the exergy of the product excluding the transition exergy. The latter is defined as exergy that is unaffectedly going through the system, i.e. without being used by the process. An example of such transition exergy is the exergy of materials that are transported horizontally. (Gong and Wall 1997) depict the possible interpretations in a graphical way where Exin is the input exergy, Extr is the transition exergy, Expr and Exwaste are the exergies of products and wastes respectively and Exout is the sum of outgoing exergy. Figure 8 Input and output exergies of a system (Gong and Wall 1997)

Based on the chosen interpretation of utilized and used exergy, the exergy efficiency indicator varies in outcome. If all exergy input and all exergy output is considered, the efficiency becomes

∆ (3.1) , = = 1 − This efficiency is also called the ‘simple efficiency’ (Dewulf and Van Langenhove 2006). However, this efficiency can be misleading if the exergy of waste components is not negligible. Therefore, a functional efficiency is often chosen which is the ratio of exergy of products divided by total exergy input:

(3.2) , = = = , − 30

If the transition exergy should be included, it must be subtracted from the input and the output side, leading to the third efficiency definition:

(3.3) , = = Many researchers including (Gong and Wall 1997; Arons, Kooi et al. 2004) favor the second exergy efficiency, ηex,2 , since it gives a more functional interpretation of the process than the first efficiency definition, but avoids the often difficult calculation of transition exergy. Besides exergy efficiency, other indicators have been developed mainly with the objective to assess the sustainability of the determined system. (Dewulf and Van Langenhove 2002) derive indicators from their explanation of a sustainable process which they define as a process using renewable energy resources, having minimum lost exergy and returning all products of the process to their initial state. Based on this definition, three indicators result: - Renewability fraction of exergy input which relates the renewable exergy used to the total exergy input:

, (3.4) = - Exergy efficiency which is equal to the simple efficiency described above:

(3.5) = - Environmental compatibility which is calculated as ratio of exergy input divided by exergy needed to bring all materials to their initial state:

(3.6) =

In their 2006 work, they add two more indicators: non-toxicity which is based on the cumulative degree of degradation and re-use representing the fraction of waste used again as a resource. Additionally, the cumulative exergy consumption is calculated as the total amount of exergy that has to be extracted from the natural ecosystem in order to deliver the desired product. Thus a cradle-to- grave level of detail is applied to their study as discussed in 3.1.1. (Connelly and Koshland 2001) consider three indicators that are very similar to the ones proposed by (Dewulf and Van Langenhove 2002): renewed exergy fraction, exergy efficiency and exergy cycling fraction. The final value that aggregates the results of the three indicators is called the depletion number. Whereas the first two indicators are identical, the exergy cycling fraction aims at determining the cycled fraction of resources relative to the total consumption and is thus similar to Dewulf and Van Langenhove’s re-use indicator. However, Connelly and Koshland additionally weigh the re-used resources in terms of mass by their upgraded exergy content:

∆ [ ] (3.7) = ∗ ∆ = [ ] Where the first term presents the recovered resource fraction in mass (R is the recovered resource, C is the consumed resource) and the second term presents the fraction of upgraded exergy compared to the consumed exergy (Δ εRU measures exergy gain per unit mass). Multiplying both terms, a fraction of exergy returned to the resource, based on total exergy removal from the resource is obtained.

The Chinese research groups (Wang and Feng 2000) and (Yang, Hu et al. 2006) apply an indicator called “environmental negative effect” in their thermodynamic IOA. This indicator weighs a system’s waste by its environmental harm:

(3.8) = where Exi is the physical and chemical exergy of the component i in the system’s wastes; and Bi is the harm coefficient of component i to the environment. To determine the harm coefficient, reference is made to pollution discharge fines for pollutants defined by the Chinese Government. (Wang and Feng 2000) go a step further and deepen the calculations to a “system negative effect” in which they weigh the environmental negative effect and the total exergy loss by an effect coefficient:

(3.9) = + where Exl tot is the total exergy loss and C1 and C2 are the effect coefficients. The effect coefficients are determined according to the economic losses they cause. These two indicators contribute to overcome the difference in impacts of dissipation and discharge exergy and the fact that different systems have different influences on the environment. (Yang, Hu et al. 2006) take a wider approach and assess in addition to the ENE - the Cycling Ratio of Material Exergy (CME) relating the exergy that is recycled in the process to the total exergy consumed:

(3.10) = =

- the process exergy efficiency which is equal to the functional exergy efficiency, ηex,2 (formula 3.2) , proposed by (Gong and Wall 1997) and - the renewable exergy efficiency determining the fraction of renewable exergy used which is equal to (Dewulf and Van Langenhove 2002)’s approach (formula 3.4) . The three indicators are aggregated to an exergy depletion index which is suggested as quantitative indicator to evaluate the sustainability of a system.

Using Exergy as Sustainability Indicator As exergy is increasingly used not only to study energy quality losses in technological applications but also to analyze inefficiencies and unsustainabilities on a system’s level, the arguments for using and avoiding exergy for that purpose are collected. Researchers such as (Connelly and Koshland 2001; Bakshi and Fiksel 2003; Rosen, Dincer et al. 2008) have pointed out the advantage of exergy to serve as a rather simple quantitative indicator and to provide a uniform non-resource specific measure that allows for comparison and evaluation among different processes. In comparison to energy analysis it identifies inefficiencies by taking the quality of energy into account and can thus give ideas for non obvious improvements. Additionally, the theoretical potential for future improvements in a process can be measured with the exergetic efficiency by dividing the exergy output through the total exergy inputs. Given their quantitative uniform nature, exergy assessments can also be compared over time, e.g. in sustainability reports. As economic consideration are always crucial in decision-making, the fact that exergy efficiency is closely related to the costs of operating a system, is another advantage. In the context of sustainability and industrial ecology, researchers have also used these qualities to quantify the benefits of closing resource streams in physical and monetary terms and have applied

Exergy Analysis to provide an indicator for sustainable processes and systems. (Bakshi and Fiksel 2003) mention that “exergy of emissions can be used as proxy for environmental imp act” and (Connelly and Koshland 2001) interpret de stroyed exergy as environmental degradation based on the fact that high exergy sources, such as fossil fuels, have a higher potential to drive processes that impact resources and the environment. Also (Ayres 1998) claims that exergy of waste should be kept as small as possible since its work potential is a general measure of possible environmental disturbance. (Rosen, Dincer et al. 2008) have depicted qualitatively the relation between exergy and environmental impact in a graphical way, showing that increasing exergy efficiency is negatively related to order destruction, resource degradation and waste exergy emissions and thus to environmental impact in general . R eversely, it is positively related to sustainability.

Figure 9 Relation between exergy and sustainability (Rosen, Dincer et al. 2008)

(Valero, Usón et al. 2010) use Exergy Analysis to quantify the benefits of Industrial Ecology which are otherwise difficult to evaluate, but also state that Exergy Analysis is no t sufficient to determine the origin of losses and the potential for savings. They claim that the purpose of the system has to be considered as well and therefore use a thermoeconomic approach in which the objective of the production objective is defined a nd it is differentiated between streams that can be defined as resources and residuals. Despite these examples of using exergy performance as a measure for sustainability, objections against “celebrating” exergy have been raised and must be discussed. In part, the same researchers that interpret exergy performance as a prox y for environmental performance caution about premature conclusions. (Connelly and Koshland 2001) , for example, argue that it is too simple to assume that only the existence of high exergy and thus high driving forces creates environmen tal harm. In addition (Ayres 1998) claims that exergy is not a reliable measure of human or eco -toxicity. According to (Graedel and Allenby 1995) , exergy performance is not only independent of toxicity issues but is often a contradictory objective resu lting in trade-off decisions between toxicity and exergy efficiency. Also (Dewulf and Van Langenhove 2002) maintain that the exergy content of emissions can hardly be related to their environmental impact. (Wang and Feng 2000) criticize two major issues that have to be considered if Exergy Analysis is taken to evaluate the system’s impact on the environment: Firstly, the internal exergy losses within processes, thus the degradation from high quality to low quality exergy thr ough processes can be seen as a waste of resources but does not cause direct environmental pollution except for indirect impacts of resource depletion. On the other hand, the external exergy losses due to waste disposal

33 might be small due to low temperature and pressure but might cause significant and direct environmental impact. Secondly, the different waste compositions of alternative systems have different impacts on the environment. However, the authors offer a constructive approach to these critics by introducing the concepts of “environmental negative effect” and “system negative effect”. As presented above, the exergy value of waste streams is weighted by a harm coefficient and the total exergy loss by an (economic) effect coefficient. The arguments and objections of the above cited researchers are taken into account in the choice of methodology and the final evaluation.

3.2. Evaluation of existing Approaches and Choice of Methodology

3.2.1. Evaluation of hybrid Methodologies in Literature

Evaluation of Frameworks Comparing and evaluating the literature review in 3.1.1, it can be observed that the choice to integrate exergy as an impact category in LCA dominates. However, two “schools” regarding the level of detail can be distinguished: one group including (Finnveden and Östlund 1997); (Bösch, Hellweg et al. 2007); (Contreras Moya, Rosa Dominguez et al. 2007) apply exergy only to elementary flows whereas a second group including (Cornelissen 1997); (Valero 1998); (Grubb and Bakshi 2011) apply exergy balances to all unit processes. The level of detail applied can be related to the goal of the researchers: Whereas the first group intends to use the methodology mainly to assess resource depletion and exergy removal from nature, the second group also includes the study of irreversibilities and improvement potential in their objective. Comparing the two “schools”, the first offers a more limited approach that permits studying only aspects of resource depletion, while the second can additionally be relevant to examine inefficiencies and irreversibilities. It allows for more in-depth improvement analysis since irreversibilities along the life cycle can be broken down to individual unit processes. Information on source and magnitude of inefficiencies can be extracted. The problem is that the two approaches are not explicitly distinguished in literature. This causes ambiguity, which becomes more apparent when comparing various cumulative exergy indicators. The first group refers to this indicator as the sum of exergy of resources extracted from nature to provide a certain product or service. The second group comprehends it as the sum of exergy losses of all production processes needed to provide a certain product or service. Depending on the system boundaries chosen and on the nature of the process the results of the two approaches can diverge significantly. Consequently, they cannot be compared with each other, which asks for a clear nomenclature and definition of indicators. Next to the differentiation regarding the level of detail, a second distinction can be made regarding the chosen system boundary. Cornelissen (1997) and Valero (1998) propose an extension of system boundaries towards a ‘cradle-to-nature’ perspective. Cornelissen includes the abatement exergy of emissions and Valero adds to this the exergetic costs of the replacement of all materials used. 34

Evaluation of Database Integration The currently available data within the Ecoinvent database is a good starting point to integrate exergy into LCA studies. However, it is limited to the very basic fossil and renewable fuels and minerals in their natural extraction status. In theory, the cumulative exergy consumption as the sum of exergy that has to be extracted from the natural ecosystem in order to deliver a desired product could be calculated based on this data (Dewulf and Van Langenhove 2006). In practice, however, a multitude of products of indirect supply chain impacts are cut-off and not traced back to natural elementary flows. This implies that not all exergy inputs are considered and the cumulative exergy calculations are incomplete. Furthermore, some of the exergy input can be transition exergy throughout the whole life cycle if it keeps stored within a material. This exergy input is extracted from the environment at a certain point but not lost as it can be “mined” again from the industrial system at the end of life of the product. Considering only the input side and not a complete exergy balance leaves out this consideration. Moreover, it is not possible to break down the cumulative exergy consumption between the individual production steps within the industrial system. In order to calculate and evaluate the magnitude and source of inefficiencies within production pathways, an exergy balance needs to be done for each unit process and not just over the whole life cycle. The exergy input of natural resources as it is currently being integrated in Ecoinvent has thus only a limited utility. The purpose of this research, as described in chapter 1, is to integrate exergy related data for processes within the industrial system that are not necessarily connected to natural resources and that can serve as basis to analyze improvement potential.

Evaluation of Indicators Summing up the literature review of exergy-based indicators, three main groups of indicators can be distinguished: the exergy efficiency indicators, the renewable exergy fraction indicators and the cycling / re-use indicators. These three groups embrace also the aspects proposed by (Connelly and Koshland 2001) to de-link consumption from depletion. In analogy to ecosystem evolution, Connelly and Koshland recommend de-linking consumption from depletion through cascading and cycling, efficiency gains and renewed exergy use. Besides these three indicator groups, Dewulf and Langenhove (2002) extend the system boundary to ‘cradle-to-nature’ and propose an abatement exergy indicator and Wang and Feng (2000) as well as Yang, Hu et al. (2006) weigh the exergetic losses with an environmental harm coefficient. The latter can be a smart way to overcome the critiques of using exergy as a one-dimensional measure for sustainability. On the other hand, it is very challenging to determine the harm and effect coefficients in an objective way within a reasonable time frame. The abatement exergy indicator can be a useful extension to calculate the ‘cradle-to-nature’ exergetic cost of the production of a certain product. This depends, however, on the system boundary drawn.

Figure 10 Lessons learned from literature review

3.2.2. Exergy LCA Framework adopted Keeping in mind the goal of this research and considering the lessons learned from the literature review, a LCA based framework is chosen. The research is carried out in the four phases of LCA with adaptations in the inventory analysis and the impact assessment. Choices made are similar to (Cornelissen 1997)’s and (Grubb and Bakshi 2011)’s approach as similar goals are pursued.

1. Goal and scope definition The goal and scope definition needs to be outlined as in a traditional LCA. Questions to be answered and the scope of the research are determined. Since the goal of this research is to assess thermodynamic inefficiencies and improvement possibilities, a unit process level of detail is chosen. To understand the system and its boundaries, the life cycle network is depicted graphically and the boundaries are outlined explicitly (Valero, Usón et al. 2010). A detailed description of the geographical and temporal boundaries as well as the included processes can be found below in 3.2.3. The functional unit and the production alternatives are described as part of the case study in 4.2..

2. Inventory analysis Similar to the LCA framework, input and output data is collected for each process of the defined system. The collected data is structured according to the following inventory template, which distinguishes economic and environmental inputs and outputs. Additionally to the mass and energy flows, specifications on temperature, pressure and compositions of the flows are needed to calculate the exergy values.

General information Specification (if applicable and available) Comments processflow type flow name product/ amount unit state T unit p unit chemical unit concentration unit waste composition process name economic in Materials (specify moisture content) Chemicals and Additives Goods / Products Transport (incl internal transport) Fuels Water streams

economic out Materials Chemicals and Additives Goods / Products Transport to storage / production Fuels Water streams Output Waste (water content, hazardous?, to incineration / landfill?)

environmental in water from rivers/lakes/ground

environmental out Emissions to air Emissions to water Emissions to soil

Figure 11 Inventory Template

An exemplary overview of the inventory template used for the board making step can be found in appendix B.4.

Once all necessary data is available in the structure of the inventory template, mass and energy balances need to be completed and checked. Based on these balances, an exergy balance per unit process can be established and exergy losses can be calculated. The assumptions used to calculate the exergy contents of each stream are explained in 3.2.3. In case of multi-functional processes, data is allocated by mass of the products. If the products are listed in different units, allocation by physical energy content is used. In order to relate different unit processes to each other and establish a cumulative inventory list, scaling factors are determined by means of the software CMLCA, an established LCA software developed by the Institute for Environmental Sciences of Leiden University. This software is also used to integrate exergy based data in the LCA database Ecoinvent. As laid out in 3.2.1, the current exergy integration in Ecoinvent does not allow assessing improvement potential as Exergy data on the level of unit processes is required for that purpose. This research supplies exergy contents of each stream within the defined boundaries of the case study and integrates these as attributes in the CMLCA software. The integration of case study data in CMLCA is addressed in greater detail in 4.2.

3. Impact assessment The impact assessment of the hybrid Exergy LCA framework is more limited than in a traditional LCA as exergy degradation is the only criterion. The extractions and emissions are classified only by their exergy content and the exergy losses of the processes are calculated. Thereby internal and external exergy losses are taken into account, i.e. irreversibilities that take place within a process and external losses caused by releasing exergy to the environment.

The specific exergy contents are calculated as a relative unit to the unit of the flow in question. For example, a mass flow would have the specific exergy content of xx MJ/kg. This can be interpreted as a characterization factor of the inputs and outputs which is similar to (Finnveden and Östlund 1997)’s approach.

4. Interpretation The last step is dedicated to interpreting the data and results. In this research emphasis is put on breaking down the results among the unit processes to assess the source and magnitude of exergy degradation per production step. Moreover, the exergy loss of a specific process can be related to the life cycle exergy degradation. For this purpose exergy flow diagrams are very useful (Gong and Wall 1997).

In order to be able to compare and analyze the results in a transparent way, indicators are applied that reflect the sustainable performance of the system. As concluded in 3.2.1. the three indicators exergy efficiency, renewable exergy fraction and exergetic cycling provide a good overview and follow (Connelly and Koshland 2001)’s de-coupling strategy. Furthermore, they can be determined with reasonable effort. Regarding exergy efficiency, the simple and the functional exergy efficiency indicators are appropriate to apply. The chosen indicators are thus:

1a) Simple exergy efficiency: (3.1) , =

1b) Functional exergy efficiency: (3.2) , =

2) Renewable exergy fraction: , (3.4) =

3) Exergetic cycling indicator: (3.10) =

Although exergy is the main impact criteria, evaluations can benefit from insights derived from the mass and energy balances as well. Therefore improvement possibilities are discussed based on the mass, energy and exergy streams and by dint of the calculated indicators.

3.2.3. Scope and System Boundaries Two areas need to be outlined in their scope and system boundaries: the life cycle perspective and the exergy calculations.

Life Cycle Boundaries The scope of the life cycle methodology is based on the thermodynamic perspective of a product life cycle, thus the physical flows entering and leaving each production step within the extraction, production, consumption and waste disposal phase. Regarding the challenging questions at which level the processes are to be included and where to set the limits of indirect supply chain impacts, a balance needs to be found between high levels of process detail and the conflicting demand of having broad system definitions in order to include the entire life cycle of a product (Udo de Haes 38 and Heijungs 2007). In this case study, the system is defined within narrow boundaries to allow a high level of detail including thermodynamic specifications for each of the researched production steps. This means that a life cycle approach is taken but indirect supply chain impacts are left out, e.g. impact of the production of trucks to transport the product are not considered. This leads to many cut-off products, e.g. diesel fuel. For some of these cut-off products LCA data has already been compiled in Ecoinvent. In this case, these cut-off products are connected to their respective counterparts, which enlarge the system boundary in terms of a traditional LCA. However, exergy contents are only calculated for the case study data and exergy losses can thus be determined only for the limited system boundary as defined here. As far as the spatial boundaries are concerned, the question is raised what to define as exergy consumption of a material stream. As (Connelly and Koshland 2001) phrase it, the decision should be made explicit whether the exergy consumed is only the exergy content of the fuel input itself or whether the exergy consumed includes the cumulative exergy consumption, thus the exergy used to extract, reﬁne, and deliver the fuel. For this research, narrow boundary conditions are set that only include the direct exergy content of the material streams but not the cumulative exergy consumption. This decision is supported by the spatial boundary of the case study, the production chain of cardboard, for which material and energy data was gathered only for the direct inputs and outputs. Temporal system boundaries are defined over a time period of one year. This implies that data on material and energy streams is gathered and calculated statically for one year. The discussion on integrating exergy data in a life cycle database and on calculating indicators is also based on this temporal boundary.

Exergy Calculations In 2.1. the concept of exergy and its calculation method are introduced. Since exergy is not conserved, the difference between in- and outflows is the exergy loss, which needs to be calculated (law of Gouy-Stodola) . This is done by first establishing mass and energy balances and determining the exergy contents of the known in- and outflows. Possible in- and outflows to a system include matter, heat and work.

Since the exergy of a stream depends on its environment, reference conditions need to be defined. 1 atm and 293 K are chosen for this research as these relate to Szargut’s approach (Szargut 1988).

Calculating exergy of work and heat flows is a standardized procedure: work equals exergy and exergy of heat can be determined by the Carnot factor. Specifying the exergy contents of matter is a more complicated procedure for which assumptions need to be made explicitly.

As introduced in 2.1.1. exergy of matter, Ex matter , is the sum of the exergy of its components: physical, chemical, kinetic and potential exergy. On a life cycle level and specifically in this case study the system velocity and height relative to the environment are not relevant and are thus left out of the exergy calculations. The exergy of matter is thus calculated as the sum of physical and chemical exergy.

= +

This is in line with calculations used by (Cornelissen 1997; Arons, Kooi et al. 2004; Grubb and Bakshi 2011).

The physical exergy of matter depends on the temperature and pressure of the stream and is calculated by means of enthalpy and entropy differences as presented in 2.1.2. However, these values are not available for all streams. For reasons of consistency and given that in this case study pressure differences to the environment are not significant, the Carnot factor is multiplied by the physical energy content to determine the physical exergy content. Thereby the Carnot factor is interpreted as a “quality factor” which determines the “quality”, i.e. the available work potential of the stream. This is in line with (Arons, Kooi et al. 2004)’s approach to calculate a quality factor in a unified consistent way by means of the temperature difference.

= 1 − The standard chemical exergy content for most substances can be looked up in tables by Szargut (1988) and can be taken from other research projects that have specified chemical exergies (Wall 1988; Dincer and Rosen 2007). If high precision is not required, as in this case study, the standard chemical exergy value can be applied for most streams without adaptation (Arons, Kooi et al. 2004).

It must be noted that this method of calculation determines the maximum available work that a flow of work, heat or matter can deliver. The practical available work depends on the systems design and its efficiency. For example, gas is a high exergy fuel but in its role to produce steam the practical efficiency can never use its full chemical potential. It is purposely chosen to use the maximum available work and not the practical efficiencies of the system design, because this way generates not only improvement potential in terms of technical efficiencies but also in terms of structural redesign opportunities.

Chapter 4

The Case of Cardboard Production

4.1. Pulp & Paper Industry

The industrial setting in which the case study takes place is the pulp and paper industry and more specifically the European pulp and paper industry. This traditional industry is an important field in terms of its macroeconomic weight, its extensive physical flows and its environmental impact. The focus of this research is set on the last two aspects, the physical flows and especially its environmental impact. Since all dimensions are interrelated and influence each other, it is important to get a grasp of the market dynamics as well. In the following a brief overview on the market and its value chains, the technologies used and the sustainability issues within the sector are introduced.

A short on note on nomenclature is advisable: Paper is generally used to indicate a wide variety of paper and board grades. Whereas printing paper is a collective term for all printable paper forms with a weight lower than 150 g/m 2, board is classified as thick and stiff paper which is usually heavier than 150 g/m 2 (Luiten 2001). The functional use of paper and board ranges from distributing information to packaging or hygienic use. A complete list of functions and respective paper and board grades can be found in appendix B.1.

4.1.1. Market and Value Chain Perspective

Market Perspective The pulp and paper industry is a capital-intensive industry with strong competition that is mainly based on price and economies of scale. It is characterized by high and long term investments and a trend towards company consolidation, which leads to a decreasing number of pulp and paper mills with increasing production capacity per mill. In the European pulp and paper market the number of companies decreased from 1052 in 1991 to 683 in 2010 (Luiten 2001; EU 2010).

Globally, the pulp and paper business is undergoing structural changes with strongly increasing demand in Asia that cannot be covered by domestic sources and major flows of raw materials coming from Latin America. North America and Western Europe are stagnant or growing slowly besides a recent downturn due to the global economic crisis (Carlsson, D'Amours et al. 2006). Consumption is expected to pick up again due to increasing demand of packaging materials and due to globally improving living standards (EU 2010). An illustration of the trends is attached in appendix B.2. Global revenues amount to 420 billion Euros of which the European market makes up about 81 billion Euros (19%) (CEPI 2011).

Margins are under pressure because of cyclical fluctuations in product prices due to speculation on raw materials, currency exchanges and supply-demand imbalances. Additionally, raw material and 41 fuel prices have been rising and emerging businesses in Asia and Latin America enter the competitive landscape (Luiten 2001). This economic pressure diminishes if the company operates “downstream” the value chain, i.e. closer to the final consumer. Price fluctuations decrease and the added economic value increases along the value chain starting with low added value in the pulp production, remaining still low for most paper and board making processes and increasing for the conversion steps (printing, cutting) (EU 2010; KCPK 2011).

Paper and board can be manufactured from virgin or from recycled pulp. Thanks to EU initiatives and rising pulp prices, the EU recycling rates have risen from 47% in 1995 to 69% in 2010 as shown in figure 12. Virgin and recycled pulp is an internationally traded commodity. 16,5% of the collected recovered paper in the EU is exported with the main destination being China.

Figure 12 European paper and board consumption and recycling (CEPI 2010)

Most of the pulp and paper consumed in the European market is manufactured within the EU. The main pulp producing countries are Sweden and Finland and the main paper producing countries are Germany, Sweden and Finland. In terms of trade balances, the EU is a net importer of pulp, importing 17% of its consumed pulp mainly from Latin America. On the other hand, it is a net exporter of paper and recycled paper, with 18% of produced paper and board being exported in contrast to 5% imported (CEPI 2011). A graphical overview of all pulp and paper related flows within the EU and the global trade flows of recovered paper are shown in appendix B.2.

Value Chain Perspective The value chain within the pulp and paper industry starts with wood harvesting and preparation. Wood chips are then pulped by chemical or mechanical means in order to separate the fibers. Most pulp is produced for further manufacturing of paper and board. Additionally to virgin pulp, about 50% of fibers in Europe come from recovered paper. Often the finished paper or board is converted (printing, cutting, gluing) before being delivered to the end-users. From here, various transportation steps can follow until the paper is collected for recovery, depending on the product and the number of actors (wholesalers, retailers, end consumers) in the chain.

In Europe 64% of paper is recollected for waste paper recovery through household and public collection (Stawicki 2006). The remaining 36% are disposed in municipal waste treatment, composted, or stored on the long term, e.g. in archives or libraries. 42

After recovering the waste paper through sorting, pulping and eventually de-inking, it is ready for re- input into the paper or board production cycle as demonstrated in the following figure.

Figure 13 The paper and board production value chain (McKinney 1995; Suh 2009; CEPI 2010)

4.1.2. Technology Perspective From a market perspective, the industry is highly capital intensive with a high ratio of capital to labor. To continuously achieve economies of scale, large scale operations are favored and technologies play an important role (EU 2010).

From a technological perspective the paper making process is distinguished in three areas of activities: pulp preparation, paper making within the paper machine and finishing operations.

In the pulp preparation, wood logs that have been first debarked and chipped into small pieces are separated into individual fibers by chemical or mechanical means. Mechanical pulping implies grinding the wood using silicon carbide or aluminum oxide to separate the fibers. Chemical pulping involves cooking the wood chips at high heat with added chemicals to chemically remove the fiber bonds. Wood is the main raw material used to produce virgin pulp. Alternatives to wood such as straw, hemp, grass or cotton are rarely used in Europe. An alternative to virgin pulp is recovered paper pulp which already accounts for more than half of the raw material input in the paper and board industry.

After screening, cleaning and often bleaching (or de -inking in case of recovered paper pulp) , the fibers are mixed with water, chemicals and additives. This mixture is called furnish and has a dry weight percentage (dw%) of about 1%.

This furnish is spread onto a moving web screen which moves through the paper or board machine as illustrated in figure 14. Water is removed from the mixture in three sections: in the forming section through draining and suctioning which increases the dw% to up to 20%; the pressing section in which water is removed mechanically by pass ing the paper sheet through press nips (result ing in up to 40 dw%); the drying section in which the remaining water is thermally removed through evaporation. The paper should have a dryness of 90 -95%. The thermal drying section requires the largest amount of energy per kilogram water removed and is often focus of energy efficiency projects.

Figure 14 Board production: waste paper collection and web screen of board machine

In the finishing operations, a series of rollers , called calendar stacks, are applied to smooth en and finish the final paperboard. In case board is produced, external paper layers are sometimes glued on top of the board (figure 15) or a coating layer is applied. Finally, the paper or board is cut according to c ustomers’ requirements and delivered to the printing and conversion step or directly to the industrial user (Luiten 2001; EU 2010) .

Once the paper has reached its end of life, it is either collected as waste paper or disposed of in other waste treatments (landfill, incineration, composting). In theory, a maximum of 81% of consumed paper and b oard can be collected and recycled. 19% is estimated to get lost in long term st orage (libraries, archives) or is uncollectable such as sanitary paper. The more the threshold of 81% is approached, the less benefit s can be achieved, since smaller niche batc hes imply longer transportation and less economies of scale (CEPI 2010).

Figure 15 Finishing: external paper layers, prin ting and recovery of cutting losses

4.1.3. Environmental Perspective Although the pulp and paper industry has improved its environmental footprint significantly since the 1990s, there are still many challenges that need to be addressed.

Table 2 summarizes the sustainability issues and its respective initiatives per value chain step. Thereby, reference is made to the steps and respective colors used in the value chain description above. Graphics that illustrate the issues and initiatives similar to the value chain graphic above are attached in appendix B.3.

The sustainability issues and respective initiatives are classified according to the aspects energy, water and others. The latter category includes mainly materials and emissions related subjects. Energy consumption is a key issue from an environmental and economic perspective: on average 16% of the production costs are related to energy consumption (EU 2010). The use of chemical additives and contaminants play a role on the input side but also on the output side as they end up in waste streams and emissions to water, air and soil. From a material perspective, recycling of waste paper has improved by about 20% in the last 15 years as discussed above. However, waste paper pulping deals with water pollution and chemicals used to remove ink and other contaminants. In addition, it must be noted that fibers can be recycled only a limited number of times due to decreasing fiber length and contamination.

Regarding the environmental performance along the value chain, it can be said that most issues and initiatives are located in the first half of the value chain, i.e. in wood harvesting, in pulping as well as in the paper and board production. In the last two decades progress has been achieved especially in the field of chlorine substitution, reduced water pollution and energy efficiency. In addition, a vast number of programs aiming at sustainable raw material management have been launched, e.g. the Forest Stewardship Council, the Program for the Endorsement of Forest Certification or the Legal Logging Code of Conduct for the Paper Industry.

Comparing this environmental value chain performance with the economic one from above, an inverse relation becomes evident. Whereas the added value increases along the production steps along the value chain, the environmental issues decrease. A shift from material to immaterial value creation is a major driver of this relation which can be observed in many other sectors as well (Ukidwe and Bakshi 2005).

Table 2 Sustainability issues and initiatives in the pulp and paper value chain

4.2. Exergy LCA of Cardboard Production

To illustrate the hybrid Exergy LCA methodology on a practical case and to be able to answer the second research question, a production chain within the paper and board industry is selected. By cooperating with Smurfit Kappa, an international cardboard producer that incorporates many production steps internally, data on the production processes could be collected.

4.2.1. Goal and Scope Definition The goal of applying the Exergy LCA methodology to this case study is twofold: testing the practical applicability of the discussed framework and answering the second research question, i.e.:

What are the biggest energy and exergy consuming steps in the cardboard value chain? How can this knowledge be used to improve the life cycle of cardboard production in a sustainable way?

The Exergy LCA methodology is applied to two production pathways that deliver the same product – cardboard as packaging material. The two production pathways are very similar in terms of processes and technologies but are carried out in different regional contexts as clarified in the following. The functional unit is defined as 1 ton of converted cardboard.

For an easier comprehension of the system and its boundaries, the studied life cycle network is depicted graphically.

Figure 16 System boundary of cardboard case study

The scope of the case study is outlined around the direct resource inputs and direct waste outputs of each unit process within the outlined system. Recovered paper is the main input material which leads to a fairly closed loop system although it needs to be considered that other (initially virgin) paper sources enter the system through the disposal phase of other paper and board chains. 47

The case study can be seen as a “zoom” into an exemplary value chain within the board making industry in which pulp is prepared from waste paper. In the following steps, cardboard is produced and eventually converted (printed, cut, glued) and transported to customers as packaging material. At that point it enters the use phase in which it is filled or packed and transported further to other destinations such as retailers and end consumers. The amount of steps between the packing steps and the end consumer can vary because of different structures with big and small wholesalers. For this research project, the transportation steps are assumed to be as shown in figure 16. In each step of the use phase a certain percentage of waste board is produced that is either sent to a waste paper recovery facility or to other end-of-life destinations, e.g. to incineration, landfill, composting or to long term storages. The collected waste paper is recovered and passed on to a new pulp preparation phase of either board production or other production chains.

The nature of the cardboard case allows taking a closed loop life cycle chain perspective, leaving out indirect supply chain effects. For example, diesel is taken as input for the transportation steps but the life cycle steps of diesel production are not accounted for. This decision is crucial when it comes to determining the cumulative exergy consumption.

At this point, it must be said that this system boundary approach does not fulfill the formal ISO 14040 requirements of an LCA as stated in 2.2. However, by connecting the case study to materials for which data is available in Ecoinvent, the requirement is fulfilled for the most input streams. Some material streams that did not have a respective background process available in Ecoinvent are being left “cut-off” and thus cannot be traced back to elementary flows. Exergy related data is only collected for the outlined system.

From a spatial perspective, two production chains have been chosen for comparison that are mainly based in two countries – Germany and the Netherlands. Imports and exports are included only by considering higher transport distances. As the two analyzed production chains are very similar in terms of life cycle processes and differ mainly in regional peculiarities, it is straightforward to draw equal system boundaries around both cases, an issue that can be quite challenging if the production routes differ greatly from each other.

Temporal system boundaries for both value chains are defined to be one year with data of 2010 being used.

4.2.2. Inventory Analysis Input and output data is collected for each unit process of both production pathways, the German and the Dutch, within the above defined system. Data is gathered from the Smurfit Kappa’s sourcing, production and sales activities by means of the inventory template presented in chapter 3.2.2. Interviews with operational managers and engineers as well as site visits are organized to underline and improve the detail and quality of the data. In case data cannot be supplied at the required detail level or specifications on temperature, pressure and compositions of the flows are not available, back-up data from literature is taken or reasonable assumptions are made in consultation with experts from the company and scientific institutions.

Looking at figure 16, most information related to waste paper recovery, pulp preparation & board production and converting as well as the transportation steps in between is provided by company

48 internal data. For the use phase, colored in green in figure 16, and their intermediate transportation steps information from public sources and literature is pulled together.

Compiling Mass, Energy and Exergy Balances As a first step, mass and energy balances are compiled for each unit process of the system. Regarding the mass balance of the pulp preparation and board production process, special attention must be given to a consistent distinction between the wet and dry mass content of the materials.

To complete the energy balance, all possible in- and outflows need to be considered, i.e. work, heat and matter. Whereas the first two are already provided in energy units, the energy contents of matter flows need to be determined. The energy content, interpreted here as enthalpy, h, is composed of a physical and a chemical component (Szargut 1988), which is analogous to the considered exergy contents as delineated in 3.2.3.

(4.1) ℎ = ℎ + ℎ

The physical enthalpy, hph , is determined by the temperature difference of the flow in question and the reference environment, multiplied by the respective heat capacity, cp. This is in line with the approach of (Wall 1988; Hellström and Kärrman 1997). The chemical enthalpy, hch , can be calculated as the enthalpy of devaluation, D° , which has been tabulated for common inorganic and organic substances by (Szargut 1988). If the substance in question contains only the elements C, H, O or N, the enthalpy of devaluation is equal to the net calorific value (lower heating value).

The energy content of a flow of matter can thus be determined as:

(4.2) ℎ = ( − ) + °

Once the mass and energy balances are completed and checked for all unit processes, the exergy balances can be established and exergy losses can be calculated according to the method described in 3.2.3. The complete exergy balance can be summed as:

(4.3) ( + + + ) − ( + + + ) = ∆ Detailed derivations of calculations and required assumptions used to compile mass, energy and exergy balances are described in appendix B.5.

Since this research aims also at providing practical improvement suggestions based on the results of the applied Exergy LCA, a “practical” calculation approach is added to the “complete” calculation approach. The complete version includes all physical and chemical energy and exergy contents of all streams, independent of the stream’s purpose. The “practical” calculation approach contains all physical energy and exergy values but considers the chemical energy and exergy only of those flows that are introduced to the process for their chemical potential. This means that the chemical component of “transition” materials such as fibers, chemicals and water is left out. These materials

49 are not employed for their thermodynamic value but for other property reasons and are not changed in their chemical composition throughout the process. Both approaches are valuable in their coexistence. The complete approach provides a comprehensive analysis but the practical approach enables a clearer picture of the energy and exergy transformations throughout the pathways. The latter method is also suggested by (Arons, Kooi et al. 2004); (Gong and Wall 1997).

Connecting Life-Cycle Data in CMLCA In order to connect the mass, energy and exergy balances of the individual unit processes to a life- cycle assessment, scaling factors need to be specified. Furthermore, the knowledge and data acquired in this study should be made structurally available to future researchers. To do so, the software CMLCA is used, in which the databases of Ecoinvent have been imported. First, the mass balances that have been calculated for each unit process are entered via specifying products and elementary flows (here called ‘extensions’) flowing in and out. In case an input or output does not have a related mass stream, it is entered with its energy content, in MJ.

A product can be classified as good or as waste. This depends on whether the disposal of the stream needs to be paid for or not. Therefore, rejects that are transported to a waste disposal site and waste water that is going to the public sewage are defined as waste. Waste water that is treated and cycled internally is not defined as waste.

Once all mass balances have been filled in, the energy and exergy balances are completed. This is done through attributes which can be interpreted as characterization factors. Attributes can be defined for each product and each extension. Four attributes are specified in this project: physical energy, chemical energy, physical exergy and chemical exergy.

An attribute is a specific factor that relates to the initial unit of the product. That means a stream of matter that is entered with a mass unit of ton would have an energy attribute with the unit MJ/ton. For a heat flow that is entered with an energy unit of MJ the physical energy attribute would have the factor 1 MJ/MJ. The physical exergy attribute would be calculated by the Carnot factor. For work or electricity flows, both the physical energy and the physical exergy attribute would be 1 MJ/MJ.

The exergy attributes take the meaning of “quality factors” that provide information on available work per unit of mass or unit of energy. This relates to the quality factor approach addressed by (Arons, Kooi et al. 2004).

In case a unit process has more than one good as output and is thus a multi-functional process, an allocation mechanism needs to be specified. This is the case for the board production, the power plant and the conversion step. For the board production and conversion all outcomes are stated in mass units and data can be allocated on a mass basis. The outputs of the power plant step are listed in energy and in mass units which makes an allocation based on the physical energy content necessary. Here the common attribute ‘physical energy content’ is selected as allocation principle. After defining allocation principles for the multi-functional processes, the system can be solved for the functional unit, 1 ton of converted cardboard. The outcome is a cumulative inventory list of all products and extensions that have entered and left the system up to this point.

The same procedure is applied to both alternatives, the German and the Dutch production pathway, which can be compared in the following impact assessment.

4.2.3. Impact Assessment and Interpretation As discussed in 3.2.2, the impact assessment of the adopted Exergy LCA framework focuses on assessing the exergy consumption. Interesting points to look at regard the cumulative exergy degradation as well as the source and destination of exergy inputs and outputs for each process step. Since mass and energy balances need to be compiled in order to calculate the exergy degradation, it is useful to integrate insights also from mass and energy flows.

The following three figures present an overview of the mass, energy and exergy flows in the Dutch production chain. The figures are composed in analogy to the general system description in 4.1.1 and 4.2.1. Similar illustrations for the German chain are enclosed in appendix B.6. An overview of energy combined with mass flows and of exergy combined with mass flows for both cases studies is shown in appendix B.7. This overview also demonstrates the completeness of the mass and energy balances that have been compiled before determining the exergy balances.

Figure 17 depicts the mass flow in the Dutch cardboard production chain scaled to the functional unit of 1 ton of converted cardboard. The main flow is related to fibers that transit all production steps, starting from recovered paper that is used to produce board which is then converted and utilized in different use phases until it is partially recovered back as fiber input. In this illustration only the fibers that are related to the conversion of 1 ton of board are included, i.e. cardboard that is delivered from the board production to other customers is not shown. In the Dutch chain about half of the input of converted board comes from external sources whereas the German converter is supplied mainly by the co-located board producer. In the Dutch as well as in the German use phase (packer, retailer, end consumer) approximately 26% of the fibers leave the cycle to other end-of-life destinations such as incineration, composting and long-term storage. The average collection rate of waste paper for both chains is thus 74%.

Figure 17 Mass flows in the Dutch cardboard production chain

An interesting difference between the two cases is the fiber recycling within the board production and board conversion step that points out that the Dutch case recycles about 30% less than the German counterpart. This revelation becomes important when considering the cumulative energy and exergy consumption.

Figure 18 and 19 illustrate the energy and exergy flows in the Dutch case study related to the production of 1 ton of converted cardboard. Here the “practical” calculation approach is chosen to allow a clearer overview, i.e. the energy / exergy of fibers and other materials is considered as transition energy / exergy and is not included. It appears clearly that the main energy and exergy input and losses arise in the power plant and board production. This is the case for both the Dutch and the German chain. Comparing the energy and the exergy flows it can be seen that the main input energy, the stream of fossil fuels colored in brown, has a similar exergy content compared to the energy content, i.e. it is a high quality energy source. The arrow of exergy losses, portrayed in light gray, demonstrate where the exergy content deviates from the respective energy stream and thus where the exergy degradation occurs.

Figure 18 Energy flows in the Dutch cardboard production chain

Figure 19 Exergy flows in the Dutch cardboard production chain

To compare the exergy consumption throughout the German and the Dutch chain in a distinct way, the cumulative exergy consumption split among all studied processes is presented in figure 20 and 21. Also here it can be clearly observed that the power plant and the board making step represent the biggest contributors to the overall exergy consumption in both chains. Further it can be seen that part of the exergy introduced in the power plant is cascaded to the board making step and, in case of the German chain, also to the conversion step. This is possible as the conversion process of the German chain is co-located with the power plant and the board making whereas in the Dutch chain, only the board making and the power plant process are geographically close. Consequently, the exergy input for the transportation step “to converter” is higher for the Dutch chain than for the German chain.

Figure 20 and 21 also indicate where the cumulative exergy input comes from (exergy sources) and where it is lost (type of losses). For both chains a similar picture is present: the main exergy source is fossil fuel (95% in Dutch chain, 93% in German chain) with the main fuel being natural gas used for combined heat and power generation. The main type of loss is of internal nature, i.e. internal irreversibilities caused largely by the energy conversion from natural gas to steam and by the degradation of steam to low temperature heat. It accounts for 86% in the Dutch chain and for 91% in the German chain which implies that about 10% of the cumulative exergy input is wasted by emitting it unused through waste, effluents and useful heat.

Overall the Dutch chain consumes less exergy per ton of converted board produced than the German chain with 6,8 GJ of exergy consumed compared to 8,5 GJ exergy consumed.

Figure 20 Cumulative exergy consumption, exergy sources and exergy losses in the Dutch chain

Figure 21 Cumulative exergy consumption, exergy sources and exergy losses in the German chain

To study the exergy sources and type of losses in greater detail, a closer look is taken at the main exergy degrading steps: the power plant and the board production. Figure 22 and 23 put the energy and exergy flows within the Dutch and German power plant and board making steps side by side. For completion, the conversion steps are also shown.

The main energy input in the German and Dutch chain takes place in the power plant in which more than 90% of the energy input is attributable to natural gas used for combined heat and power generation. The negative heat and water input in the German chain results from the chosen reference conditions of 20°C. Water at a temperature lower than this reference condition is inserted which leads to a negative energy value. In the Dutch chain, this negative energy value is compensated by recycled condensate water that has a higher temperature. In the Dutch chain, 76% of the energy input is cascaded to the board making. The remaining 24% are emitted as heat to the air. In the German chain 90% is cascaded to further processes: 96% of this is supplied to the board production and 4% to the conversion step. In contrast to the Dutch chain, the unused energy (10%) is emitted not only as heat to the air but partially also through the effluent cooling water. This can be traced back to the fact that the studied Dutch system has a closer water system in which water is reused more often. Consequently, less uptakes and discharges from and to the environment are necessary. However this leads to higher pollution values.

Besides the cascaded energy, about 0,4 GJ additional energy is supplied to both board making steps which represents 10% of the Dutch board making energy and 8% of the German board making energy. On the output side, most of the energy is emitted as unused heat to the air.

As mentioned above, in the German chain a part (0,2 GJ) of the power plant output is cascaded to the conversion step which is enabled through regional vicinity. In the Dutch chain, the conversion step is energetically independent and utilizes for the most part natural gas as energy source. The German conversion step is fueled mostly by electricity and heat.

Figure 22 Energy balances including input and output details in NL and DE

Figure 23 Exergy balances including input and output details in NL and DE

Based solely on the energy graphs, only limited conclusions and recommendations for improvement can be drawn. Figure 23 demonstrates the exergy flows within the power plant, board production and conversion steps. As mentioned above, the input flows to the power plant steps consist of high quality energy sources. The output side, on the other hand, shows that the cascaded heat has a lower exergy than energy content and that the unused heat flows emitted in the power plant and board making steps have only little exergy content. Of all three steps, 74% of output exergy is reused in the Dutch case and 80% in the German case. In absolute terms, the highest improvement potential for reusing external exergy losses is given in the board production. 0,5 GJ/ton in the Dutch board production and 0,4 GJ/ton in the German board production is lost.

As indicated above, it is interesting to relate the exergy consumption with the mass flows. The presented figures demonstrate that the main exer gy is inserted in the power plant and then cascaded to the board production as steam and electricity. Steam is mainly used for drying purposes. Connecting this insight to the fiber recycling flows gives th e following picture.

Figure 24 Comparison of material efficiency DE - NL

In order to produce 1 ton of cardboard (not converted yet), 7,1 GJ of exergy are inserted within the system boundaries of the German case study (5,8 GJ in the Dutch case). Of this around 60% is already lost when it enters the board production, mainly due to internal irreversibilities in the power plant related to natural gas to steam conversion. Summing up all the mass flows of fiber that are lost in the screening, pressing, drying, laminating and cutting sections, a total of 260 kg accumulate per ton of cardboard produced (200 kg in the Dutch case). From an exergy perspective, the fibers that are lost after the drying section are more important since they have passed already the main exergy consuming step . Interestingly, the majority of fibers is lost after that point, i.e. in the laminating and cutting section. 20% in the German case and 12% in the Dutch case are lost after the drying section and are reinserted as new fiber in the beginning of the board p roduction process. This means that 1,4 GJ of exergy per ton of cardboard (0,7 GJ in the Dutch case) are supplied to the process without adding value to the production chain.

An additional instrument for comparison that has been suggested by (Gong and Wall 1997) , (Dewulf and Van Langenhove 2002), (Connelly and Koshland 2001) among others, is the use of indicators. In 3.2.2. three indicators are chosen that provide a good overview on the sustainability of the studied system: exergy efficiency, renewable exergy fraction and exer getic cycling indicator . Two types of exergy efficiencies are determined: the simple and the fu nctional efficiency that relates the exergy of the product to the exergy input. The following table summarizes the three indicators for the German and the Dutch production chain for the practical and the complete calculation approach. The indicators calculated with the practical application approach follow (Gong and Wall 1997) ´s suggestion to exclude the transition exergy. 57

NL DE practical complete practical complete Exergy efficiency - simple - 34% - 94% - 30% - 93% - functional - 24% - 69% - 22% - 64% Renewable exergy 0% 0% 0% 0% fraction Exergetic cycling 24% 69% 22% 64% indicator

Table 3 Exergy indicators applied to the German and Dutch cardboard chains

Table 3 shows a similar picture for both case studies with the Dutch case study performing slightly better in exergy efficiency and exergetic cycling. If the exergy efficiency is determined by the simple ratio for the practical approach, about one third of the input exergy is converted into useful output exergy throughout all studied processes. If only the used output exergy is considered, the efficiency is lower with 22% for the German and 24% for the Dutch chain. Concerning the complete approach, the results appear very positive with a simple efficiency of over 90%. The high efficiency can be traced back to the fact that the exergy content of input and output fibers represents a very high portion of the overall exergy input and output. The exergy of fibers is a transiting exergy flow that is hardly changed throughout the process which distorts the overall efficiency results. This indicates the importance of applying the practical approach for comparison. The difference between the simple and the functional efficiency is larger for the complete approach because the exergy content of lost fibers is subtracted from the output exergy. This difference can thus be interpreted as an indicator for material efficiency from an exergy perspective. The fact that the difference is smaller in the Dutch case (94-69=25) than in the German case (93-64=29) confirms the results on material efficiency shown in figure 23. Regarding the renewable exergy fraction, both case studies and both calculation approaches bring about the same result: no renewable exergy is used. The exergetic cycling indicator fulfills in both of these case studies the same role as the functional exergy efficiency indicator. It shows the percentage of exergy that is cycled and thus reused. Given that the system is studied within life-cycle boundaries, the sum of reused exergy throughout the life cycle is equal to the sum of utilized exergy as defined for the functional exergy efficiency.

Concluding it can be said, that both case studies show similar results with regard to mass, energy and exergy flows. The prevailing exergy input is related to fossil fuel usage and the main exergy loss is caused by internal irreversibilities with the major exergy consuming processes being the power plant and the board production. Overall the Dutch case study performs better than the German counterpart with a lower cumulative exergy consumption per ton of converted board and a slightly better sustainability performance according to the applied indicators. The higher material efficiency and the closed water system within the Dutch board making step contribute positively to the Dutch performance.

In the following chapter, the research questions are being answered and discussed based on the experience of applying the Exergy LCA methodology to the cardboard case study. Furthermore recommendations for future research are proposed.

Chapter 5

Conclusions & Discussion

The goal of this research is to analyze thermodynamic improvement potential in product life cycles. For that purpose integration possibilities of Exergy Analysis and LCA have been studied; a hybrid methodology for which there is no established framework available yet. An accepted framework would to apply the methodology to practical studies and to form exergy data sets.

This research contributes to create a better understanding on the opportunities and challenges of a hybrid methodology by evaluating how exergy analysis can be integrated in a structured way with life cycle thinking (1 st research question).

To test the methodology and start generating exergy data for foreground processes the case of cardboard production is chosen as practical application. Thereby the call of various researchers such as (Ukidwe and Bakshi 2005), (Dewulf and Van Langenhove 2006), (Gong 2005), (Finnveden and Östlund 1997), (Grubb and Bakshi 2011) has been followed to study more practical examples of applying Exergy Analysis on a systems level (2 nd research question).

The answers to both research questions are discussed in the following.

5.1. Answering the Research Questions

5.1.1. Connecting Exergy Analysis and LCA To answer the first research question on how Exergy Analysis can be integrated with life cycle thinking, the three sub-questions are first dealt with separately.

• Which approaches exist in literature to integrate exergy and life cycle assessments? What are their advantages and disadvantages? The dominating approach in literature to combine Exergy Analysis and LCA is to integrate exergy consumption as an additional impact category in LCA. However, the exergy consumption in a life cycle perspective is interpreted and calculated in different ways among the researchers. Thereby two main groups can be distinguished: the first group including (Finnveden and Östlund 1997), (Bösch, Hellweg et al. 2007), (Contreras Moya, Rosa Dominguez et al. 2007) aims at using exergy consumption as a measure for resource depletion and calculates the cumulative exergy consumption as the sum of exergy contents of all natural resources (elementary flows) that are needed to produce a certain product. Thereby only the cumulative exergy inputs are considered and no real exergy balance is applied. The second group including (Cornelissen 1997), (Valero 1998), (Grubb and Bakshi

2011) broadens the scope and uses exergy to also study irreversibilities and improvement potential within a product life cycle. To achieve this, exergy balances need to be established on the level of unit processes. Cornelissen and Valero go even further and extend the system boundaries towards a ‘cradle-to-nature’ perspective. Cornelissen includes the abatement exergy of emissions and Valero adds the exergetic costs of the replacement of all materials used.

Comparing the two groups, the first takes an easier but also more limited approach that permits studying only aspects of resource depletion. (Bösch, Hellweg et al. 2007) have contributed greatly to this group by integrating exergy characterization factors for 2630 products in the Ecoinvent database, but considering only the input of natural resources. The second group allows for more in depth improvement analysis since irreversibilities along the life cycle can be broken down to individual unit processes. Information on source and magnitude of inefficiencies can be extracted. In this approach, data needs to be specified in more detail in the inventory analysis and exergy balances need to be calculated for each unit process. The first attempts are very valuable but the determined exergy factors have not been communicated in a structured way in order for them to be usable by the research community.

• How can databases be adapted to be able to integrate exergy balances of production processes? Currently exergy data is integrated in databases such as Ecoinvent only for elementary flows, i.e. natural resources. This allows determining the cumulative exergy consumption of a product following the limited approach of the first group (Finnveden and Östlund 1997), (Bösch, Hellweg et al. 2007), (Contreras Moya, Rosa Dominguez et al. 2007), as discussed above.

Nonetheless, this is often a non complete calculation of the cumulative exergy consumption as a multitude of products of indirect supply chain impacts are cut-off and not traced back to natural elementary flows. This implies that not all exergy inputs are considered and the cumulative exergy calculations are incomplete. Furthermore, some of the exergy input can be transition exergy throughout the whole life cycle if it is kept stored within a material. This exergy input is extracted from the environment at a certain point but not lost as it can be “mined” again from the industrial system at the end of the product life. Considering only the input side and not a complete exergy balance leaves out this consideration.

But more importantly for this research is the fact that this approach does not enable studying improvement potential on a unit process level. In order to calculate and evaluate the magnitude and source of inefficiencies within production pathways, an exergy balance needs to be compiled for each unit process and not just over the whole life cycle.

For this purpose additional specifications are needed. Specific exergy contents are calculated for all mass, heat and work flows (in MJ/kg for mass flows or in MJ ex /MJ en for heat and work flows) according to the approach presented in 3.2.3. Based on the mass and energy balances, the exergy balance of a unit process can then be determined.

With the aim to provide the calculation results to the research community, the established structure of LCA databases can be used. Here specific exergy contents can be ‘attached’ to all mass and energy flows as characterization factor. In this research the software CMLCA is used in which all unit 60 processes with their respective mass and energy balances have been integrated. The specific exergy content is ‘attached’ to each mass and energy in- and outflow by defining it as attribute to all products and environmental extensions (elementary flows). In total, energy and exergy factors are specified for 156 products and 53 extensions as part of this research. As discussed in 3.2.3., a distinction is made between physical and chemical components of exergy and energy. In total, four attributes are thus defined to each flow: physical energy, chemical energy, physical exergy and chemical exergy. If a flow is already specified in energy terms, for example heat, then the specific physical energy content has a factor of 1 MJ en /MJ e and the specific exergy content would be equivalent to its Carnot factor in MJ ex /MJ en . The chemical energy and exergy contents would be zero for a heat stream.

The exergy attributes take the meaning of “quality factors” that provide information on available work per unit of mass or unit of energy. As mentioned above, these “quality factors” need to be interpreted as idealistic factors that show the total theoretical potential that a specific flow could provide. They are not adapted to the specific process design of a unit process.

• Which exergy based indicators can be used to facilitate future chain analysis? This sub question aims at identifying a set of exergy based indicators that can be used to study and compare production chains in order to be able to choose the most sustainable solution.

Before identifying this set of indicators, a brief conclusion is given to the question whether exergy is a valuable indicator for sustainability. In 3.1.3. the use of exergy as sustainability indicator has been reviewed and opinions of various researchers have been compiled. Concluding, it can be summed that exergy is a very useful and rather impartial indicator while evaluating energy and material quality degradation, resource depletion and partially for environmental emissions. It helps quantifying and structuring the concept of sustainability, but this quantification often entails a trade- off between completeness and sustainability. It should be kept in mind that exergy alone cannot account for all unsustainabilities. A pure focus on thermal inefficiencies cannot provide a whole picture as toxicity, acidification, land use, biological impacts of emissions to air, water and land, or other environmental measures are not included. An analysis based only on exergy could, for example, result in a positive performance of cycling of toxic substances whereas a more extensive analysis would show that a safe disposal of the toxic substance would have been a better option.

As suggested in other environmental strategies, a preventive approach is recommended. Reducing exergy degradation and thus resource depletion and emissions through closed cycles eliminates a significant driver of environmental damage. Developing thermodynamically mature industrial systems does not solve one specific and isolated environmental problem but helps avoiding driving factors that can cause unpredictable changes and consequences in the global ecosystem.

Indicators best to be used to assess the sustainability of production chain from a thermodynamic perspective can be distinguished in three main groups in analogy to (Connelly and Koshland 2001)’s de-coupling strategy: the exergy efficiency indicators that relate different exergy outputs to the exergy input; the renewable exergy fraction indicators that aim at evaluating the percentage of renewable exergy input compared to the total exergy input; and the cycling / re-use indicators that assess the percentage of exergy that is re-used or recycled.

Besides these, Dewulf and Langenhove propose an abatement exergy indicator that relates the rate of exergy returned to the environment (recovered resources) to the rate of exergy removed from the environment. Wang and Feng as well as Yang, Hu et al. introduce an environemental negative effect index that is calculated by weighing the exergetic losses with an environmental harm coefficient.

Dewulf and Langenhove’s indicator is proposed within extended ‘cradle-to-nature’ system boundaries and can be a useful addition to calculate the ‘cradle-to-nature’ exergetic costs of the production of a certain product. This depends, however, on the system boundary drawn. Within the traditional LCA boundaries, as outlined in this research, it is not applicable. The environmental negative effect index can be a smart way to overcome the critiques of using exergy as a one- dimensional measure for sustainability. On the other hand, it is very challenging to determine the harm and effect coefficients in an objective way and within a reasonable time frame. With the aim to assess and compare the thermodynamic sustainability of product life cycles in a comprehensive way and within reasonable efforts, (Connelly and Koshland 2001)’s de-coupling strategy is taken as reference point. Their proposal to de-link consumption from depletion through cascading and cycling, efficiency gains and renewed exergy use is represented by the three main indicator groups as discussed above. Therefore the simple and functional exergy efficiency, the renewable exergy fraction and the exergetic cycling indicators are chosen. While testing them by means of the case study, it results that the indicators confirm insights gained through extensive assessment. However, it must be noted that the exergetic cycling indicator fulfills the same role as the functional exergy efficiency indicator. It shows the percentage of exergy that is cycled and thus reused. Given that the system is studied within life-cycle boundaries, the sum of reused exergy throughout the life cycle is equal to the sum of utilized exergy as defined for the functional exergy efficiency.

1. How can Exergy Analysis be integrated in a structured way with life cycle thinking? Based on the answers of the three sub questions, it can be summed up that Exergy Analysis and LCA can be integrated best by including exergy consumption as additional impact category in the established LCA framework. If the goal is to study thermodynamic improvement potential, exergy consumption must be assessed on a unit process level and not only based on natural resources inputs. This can be done by establishing mass and energy balances for each unit process and then assigning specific exergy contents to all mass, heat and work in- and outflows within the defined system boundaries. This way, exergy balances can be obtained for all unit processes and exergy losses can be calculated. The exergy contents comprise physical and chemical exergy components. Thereby ‘idealistic’ exergy factors are taken based on the maximum potential work of the specific stream which is independent of the structural process conditions. This allows including not only the technical inefficiencies of the specific process but also the structural inefficiencies of the process design. A theoretical improvement potential is obtained that can only be exploited if the process design is changed, for example by using gas in a gas steam cycle the full exergy potential of gas can never be reached but the efficiency is determined by the temperature differences of combustion and cooling. A discussion on this issue follows in 5.2.

These specific exergy contents can be attached as characterization factor to flows (products and extensions) that are already listed in established LCA databases such as Ecoinvent.

To compare the exergetic performance of production chains and get an overview from different perspectives, three types of indicators are valuable to use: exergy efficiency, renewable exergy fraction and cycling / re-use indicators.

5.1.2. Applying Exergy LCA to Cardboard Life Cycles The Exergy LCA is applied to the life cycle of cardboard production which is put under pressure from an environmental and economic perspective because of its energy and water intensive production methods. Two case studies are assessed and compared: a German and a Dutch cardboard production chain.

After completing mass and energy balances for all unit processes within the system boundaries, exergy balances are calculated based on the specific exergy contents of mass and energy streams. All three balances provide valuable insights and are taken into account in the interpretation phase.

Results Both case studies show similar results with regard to mass, energy and exergy flows. On a cumulative life cycle level, the prevailing exergy inputs are related to fossil fuel usage in both cases (95% in Dutch chain, 93% in German chain). Natural gas is the main exergy source in the production steps and diesel is the main exergy source in transportation steps. On the output side, a distinction is made between internal and external exergy losses, i.e. between “quality” that is degraded within a process due to technical or structural inefficiencies and “quality” that is lost with unused materials, effluents and emissions. For both case studies the internal losses dominate (86% in the Dutch chain, 91% in the German chain).

On a unit process level, two steps can be clearly identified as main exergy consumer: the power plant and the board making process. In both chains they account for 82% of the cumulative exergy consumption.

Combining the insights of energy and exergy flows with the mass flows, it can be observed that a significant portion of the exergy input is “wasted” in producing scrap board. 12% of fibers in the Dutch chain and 20% of fibers in the German chain are recycled after having already received the main exergy consuming treatments. By this 0,7 GJ of exergy per ton of cardboard in the Dutch case and 1,4 GJ in the German case are supplied to the process without adding value to the final product.

Applying the three groups of indicators generates similar results for both case studies with the Dutch case performing slightly better for exergy efficiency and exergetic cycling. The simple exergy efficiency varies between 30% for the German and 34% for the Dutch case and the renewable exergy fraction is 0% for both cases. The exergetic cycling and the functional exergy efficiency fulfill the same role as discussed above and amount to 22% for the German and 24% for the Dutch case.

Overall the Dutch case study performs better than the German counterpart with a lower cumulative exergy consumption per ton of converted board, a higher material efficiency and a slightly better sustainability performance according to the applied indicators.

Conclusions on Improvement Potential The results of the Exergy LCA applied to the cardboard production chains provide insights in possibilities of improvement.

The dominance of fossil fuel input and the non-existence of renewable exergies show a large demand for improvement. Looking at the application of those fossil fuels in greater detail, it is observed that most fossil fuel usage is related to natural gas used for combined heat and power production (CHP). Even though CHP entails higher efficiencies than producing steam and electricity separately it is still not an optimal process from an exergy perspective. Especially when considering the exergy needs in board production. Here the main exergy is demanded by the drying section of the board machine which utilizes heat of a medium temperature range (170-180°C). Thus, high quality energy is used to meet low quality needs. To reduce unsustainabilities in the system, large differences between the exergy supplied and demanded by the system should be avoided. If high quality fuels are used to cover heat demands, the exergy efficiency becomes low. Alternatives in reducing the exergy input and thus increasing the exergy efficiency include e.g. decreasing exergy needs in the drying section by employing lower temperatures or increasing the material efficiency. The results of the case studies show that 12-20% of cumulative input exergy is consumed by material losses without adding value to the final product. The importance of material efficiency for exergy efficiency can also be extended on the whole life cycle: using less material per functional unit in the converting and use phase (packer, retailer, end consumer) reduces the cumulative exergy needs. Moreover, it is valuable to consider the use of alternative, low exergy fuels. Since only heat of a medium temperature range is needed to thermally remove water, thermal heat sources with lower exergy content than natural gas, preferably from renewable sources, present a sound alternative. Solar or geothermal heat could, for example, deliver a base heat and could then be supported with natural gas supply to achieve the desired temperature. Thereby the objective of raising the renewable exergy fraction could be satisfied. Less dependence on natural gas supply and its price developments would be an additional positive side-effect. A scenario in which solar thermal energy replaces natural gas for steam generation is presented below.

On the output side, the results demonstrate that about 90% of exergy is lost due to internal inefficiencies and 10% is lost by means of outflowing streams. This indicates that up to 10% improvement can be achieved by reusing emitted exergy. However, the closer one comes to the maximum reuse potential, the more difficult it becomes to extract the improvement potential in terms of exergy needs and monetary investment (law of diminishing marginal returns (Paul A. Samuelson and Nordhaus 2001)). Greater improvement potential seems to be realizable by tackling the internal exergy losses. These losses are largely determined by structural losses of the energy conversion processes within the CHP plant and by degradation of medium temperature steam to low temperature heat emissions. To reduce these structural losses, the current process design needs to be innovated. Whereas the reuse of external losses has been the most commonly followed option to collect the ‘low hanging fruits’, more structural changes such as diversifying the energy input towards lower exergy sources provide higher and long-term improvement potential.

To complete the picture, a discussion on the results of the cycling indicator is valuable. 22-24% of the input exergy is re-cycled or cascaded to other processes which can mostly be attributed to the cascade of steam and electricity from the power plant to the board making process. The external exergy losses show that there is 10% room for improvement to cycle or cascade output energy further. The cascade indicator is especially important in a life-cycle perspective. For example, 64 additional exergy input can sometimes be beneficial if the output exergy can be cascaded further in a thorough manner, even outside the traditional company borders. Re-using waste heat for residential heating is one example for decreasing external exergy losses and increase the exergetic cycling performance. If only the simple exergy efficiency was taken into account, this consideration would be left out.

Solar scenario To reduce the difference between exergy supply and demand in the power plant and board making steps, the use of solar thermal energy can be considered as alternative. To obtain an idea on possible improvements that are realizable by using solar thermal energy, a calculation example is presented as indication.

If the heat demand for the board production was fully supplied by solar thermal energy, a cumulative exergy reduction of 38% in the Dutch case or 41% in the German case could be achieved. Line focus or point focus collectors such as the parabolic trough are able to heat up synthetic oil up to 390°C which is then converted to steam via a heat exchanger (Boyle 2004).

The exergy flows in the power plant and board production would change in the following way:

Figure 25 Comparison of exergy flows in the current situation with a best case solar scenario

The high exergy input of natural gas in the power plant would be substituted by solar energy, which is interpreted as “free exergy”. It generates the amount of exergy that is needed in the board production and cascades the exergy in form of steam to the board making step. The exergy demand in the board production is fulfilled to the same extent as in the base case without the need for gas to steam conversion, which implies high internal exergy losses.

This scenario would change the sustainability performance according to the three indicator groups, exergy efficiency, renewable exergy fraction and exergetic cycling indicator as shown in the following

65 table. The exergy efficiencies would increase as the same exergy output relates to a reduced exergy input. In addition, the solar energy input would make up 20% in the Dutch case and 25% in the German case increasing thereby the renewable exergy fraction. The exergetic cycling indicator also improves because of the reduced exergy input.

NL DE NOW SOLAR NOW SOLAR Exergy efficiency - simple - 34% - 53% - 30% - 49% - functional - 24% - 39% - 22% - 37% Renewable exergy 0% 20% 0% 25% fraction Exergetic cycling 24% 39% 22% 37% indicator

Table 4 Comparison of exergy indicators in the current situation with a best case solar scenario

However, a complete substitution of gas by solar thermal energy supply implies that an extensive area is available and sufficient energy storage is feasible. Given these limitations, this improvement possibility should be interpreted as a best case scenario. The underlying assumptions and calculation details are enclosed in appendix B.8.

5.2. Discussion

The Exergy LCA framework chosen is based on an extensive review of existing methodologies in literature while keeping in mind the goal of this research: to study thermodynamic improvement potential in product life cycles. The results of applying the framework to the cardboard case studies confirm that the goal has been reached: thermodynamic improvement potential is elaborated and first solution approaches towards a more sustainable system are proposed.

Compared to a traditional LCA, this framework allows elaborating specifically on thermodynamic losses and improvement solutions. Furthermore, it helps overcoming the challenge of LCAs to compare and weigh results of different environmental effects. On the other hand, it must be noted that this reduced complexity implicates the risk of missing sustainability issues that are not related to thermodynamic flows such as toxicity or acidification. Exergy is a valuable quantitative concept to analyze and communicate sustainability issues, but does not account for all unsustainabilities. The practical utility of the framework as well as the limitations as sustainability indicator are confirmed by the case studies: the thermodynamic insights obtained by applying the framework could not have been achieved by means of a traditional LCA study. As shown above, these insights enable a detailed understanding of the source and magnitude of inefficiencies and can serve as basis for designing more sustainable systems. On the other hand, the case studies have also shown that the thermodynamic perspective does not provide a complete overview on sustainability issues. The Dutch case has a closer water cycle than the German counterpart which permits reusing the waste heat within the effluents and reduces the overall exergy consumption. The trade-off is a higher water pollution level. Nonetheless, reducing exergy consumption helps avoiding drivers of environmental 66 damages and is thus recommended as a preventive environmental strategy. For a complete picture to be obtained, it is recommended to apply Exergy LCA as part of a multi-criteria study.

Compared to a traditional Exergy Analysis, the framework facilitates to put the exergy consumption of one unit process in relation to the consumption of the defined life cycle. Further, the path dependency of exergy flows and exergy losses and their impacts throughout the life cycle can be observed, e.g. the impact of an energy transformation on its downstream processes. According to (Arons, Kooi et al. 2004) the degradation of exergy should be delayed as long as possible since high losses in the beginning of the chain limit all following process steps in their value creation. This rule facilitates choosing the most sustainable production route and the most favorable exergy sources.

To fit the exergy concept into the static LCA framework and to integrate exergy data in LCA databases, exergy values are determined using general formulas without restrictions for the process design. Practical efficiencies cannot be accounted for in LCA structures as they differ between process designs and process purposes. Therefore, specific exergy contents are calculated that are relative to a material or energy stream and not to process configurations. This leads to using idealistic exergy factors, i.e. using the maximum theoretical potential of a given material of energy flow and not the practical efficiency of a certain process. By using these idealistic factors, not only the technical inefficiencies of the specific case, but also the structural inefficiencies of the process configuration are included, which results in theoretical improvement potential that can only be fully exploited if the process is innovated.

Depending on the goal of the analysis, idealistic exergy factors are not necessarily disadvantageous. Maximum improvement potential can be assessed and structural inefficiencies become apparent, which might trigger interests in process innovations. Indicators based on these idealistic factors can also be an integrative part of a long-term energy strategy within companies. On the other hand, it is more difficult to extract information on purely technical efficiency improvement potential. In any case, the exergy calculations must be explicitly stated and interpreted as idealistic.

It must be considered that the general exergy values are in part approximations based on the assumptions delineated in 3.2.3. However, the extenuated precision hardly influences the magnitude of exergy consumptions and its relation among different unit processes and consequently does not distort the overall results.

To sum up, the Exergy LCA framework contributes to providing a quantitative structure for designing more sustainable industrial systems according to Industrial Ecology concepts. Applied to the cardboard case it offers insights into thermodynamic improvement potential throughout the life cycle and presents a valuable extension to existing initiatives in this industrial branch.

5.3. Recommendations

Recommendations are given in two areas: the first concerns the Exergy LCA framework itself and the second concerns the extension of the framework towards other disciplines.

Regarding the Exergy LCA framework, it is recommended to formalize and standardize the methodology as has been done for the traditional LCA. It is expected that this stimulates more practical case studies, which allows to extent and develop the exergy database further. Thanks to the quantitative and unifying nature of exergy, a comparison between a wide variety of life cycles is possible. As part of this formalization process, clear calculation rules and nomenclature must be established. As discussed in 3.2.1., there is ambiguity about what to consider as cumulative exergy consumption. Two calculation approaches are used: one based on the sum of exergy of resources extracted and one on the sum of exergy losses of all unit processes. Since they are not explicitly distinguished in literature, it becomes difficult to compare them. Based on the insights of this research, it is recommended to refer to the second option as cumulative exergy consumption, i.e. to the sum of exergy losses of all unit processes.

A second area of recommendation is the possible connection of Exergy LCA to social and economic disciplines. In order to implement the technically assessed improvement potential, the economic feasibility of solution approaches should be explored. In combination with the exergy concept, it can be determined how much investment is needed per unit of saved exergy and how this ratio varies among different solution approaches.

In order to explore the feasibility of proposals that aim at extending exergy reuse flows beyond company borders aspects from social science would be valuable to be taken into account. Especially if the studied structure develops from a chain towards a network, Social Network Analysis can be a insightful addition. This tool maps and analyzes relationships and flows between people, groups and organizations and has previously been suggested by (Faße, Grote et al. 2009) in the context of environmental value chain analysis.

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Appendices

Appendix A: Methodology

1) Terms and Symbols used

Terms

CHP: Combined Heat and Power GHG: greenhouse gas

CME: Cycling Ratio of Material Exergy IOA: Input Output Analysis

CMLCA: LCA software of the environmental KCPK: Kenniscentrum Papier en Karton institute CML LCA: Life Cycle Assessment EIP: Eco-Industrial Park MFA: Material Flow Analysis ENE: environmental negative effect SNE: system negative effect EU ETS: European Union Emission Trading System

Symbols

Bi: harm coefficient of component i Ex abatement : abatement exergy needed to bring all materials back to their initial state C°: calorific value

Ex ch : chemical exergy of matter C1: effect coefficient

Ex fuel : exergy of a fuel cp: specific heat at constant pressure

Ex in : ingoing exergy D°: enthalpy of devaluation

Ex in, renewable : renewable exergy input dw%: dry weight percentage

Ex matter : exergy of matter En: energy

Ex ph : physical exergy of matter En p: potential energy

Ex k: kinetic exergy of matter En ph : physical energy

Ex out : outgoing exergy Ex: exergy

Ex : potential exergy of matter : mass flow of consumed resources p

Ex pr : exergy of products ηex : exergy efficiency

Ex Q: exergy of heat Q: heat

Ex tr : transition exergy R: gas constant

Ex W: exergy of work S: entropy

Ex waste : exergy of waste T: temperature

G: Gibbs free energy w: speed

H: enthalpy W: work h: specific enthalpy xH2O : percentage of moisture in fuel

RU hph : physical specific enthalpy Δε : exergy gain per unit mass

C hch : chemical specific enthalpy Δε : exergy consumption per unit mass

HHV: Higher Heating Value ΔdH° : standard normal enthalpy change

LHV: Lower Heating Value Δh evap, H2O : heat of vaporization of moisture

: mass flow of recovered resources φ0: relative humidity of the atmospheric air

2) Industrial Ecology This research is carried out as a Master thesis within the Master of Science program in Industrial Ecology (IE) at Delft University of Technology and Leiden University. IE is an interdisciplinary program with the objective to re-design industrial systems by optimally circulating materials and energy, thereby reducing resource consumption and avoiding waste. Knowledge in three areas is developed: analyzing material flows, re-designing technological systems and implementing these in organizations.

This research can be found at the interface of analyzing material flows by integrating concepts of the domain of technological re-design.

3) Exergy Analysis within Industrial Ecology Tools Besides the ability of using exergy to examine the magnitude and origin of inefficiencies, it can serve as a unifying measure across disciplines as, e.g. the quality of a resource can be expressed in Joules instead of in monetary terms. In the interdisciplinary environment of IE, this opens the opportunity of “impartial” comparisons. For example, technologies can be compared without referring to its present monetary value but with reference to their environmental performance. It also allows for a comparison over time as exergy is a time-independent measure.

To carry out such comparisons, established tools like LCA, MFA or IOA are available within which exergy can be integrated which will be discussed in the following.

Depending on the scope of analysis and its complexity, different analytical methods can be combined with Exergy Analysis. As can be seen in figure 3, the scope of Exergy Analysis ranges from single technological applications or processes to whole industrial societies. With increasing numbers of actors and processes, the complexity of the analysis increases rapidly and different analytical methods are required to account for and deal with these circumstances.

Furthermore, it must be decided which physical and / or monetary streams to focus on. The following examples demonstrate that a research can concentrate on energy, material or monetary flows or a combination of them. Thermoeconomics combines, for example, physical exergy flows with production costs to study the process of cost formation of products based on the second law of thermodynamics. With this approach the marginal costs of exergies can be calculated and exergy improvements that are best paid off in the system can be identified as shown by (Silveira and Tuna 2003) and (Valero 1998). Another combination is proposed by (Sciubba 2005) who aggregates exergy values of physical flows with exergy flows equivalent to capital, labor and environmental remediation costs.

As tool within the Industrial Ecology research field, Exergy Analysis and its combination with established methodologies such as LCA, MFA or (environmental) IOA helps in designing industrial systems according to Industrial Ecology design concepts and contributes in quantifying the benefits of them, which are otherwise difficult to evaluate quantitatively (Dincer and Rosen 2007). Within Industrial Ecology Exergy Analysis is most commonly applied to the production chain level or to the regional level, either on (eco-) industrial parks or other regional dimensions such as cities or nations.

In the following a brief introduction to the combination of Exergy Analysis with MFA and IOA is given. A detailed discussion on the integration in LCA is carried out in chapter 3.

Material Flow Analysis MFA is a family of different methods studying material throughputs in (parts of) the industrial systems, mostly between the societal and the supply chain level. Material and energy inputs and outputs are accounted for sectors, regions or nations in units of mass (Finnveden and Moberg 2005). Thereby the focus is on the technical processes with their inputs and outputs in the studied region. The analysis is usually static for one year but can be extended to a dynamic model.

In combination with a thermodynamic approach, exergy and emergy analysis have been used next to material and energy flow analysis, e.g. by (Michaelis and Jackson 2000) who calculated the cumulative exergy consumption of the UK steel sector.

Input-Output Analysis IOA is a well-established tool within economics to describe trade dimensions between industries in a specific region, mainly expressed in monetary terms (Finnveden and Moberg 2005). It has also been extended to other research fields such as environmental IOA or thermodynamic IOA by including environmental impacts or exergy contents. Thermodynamic IOA is the least developed among the exergy related IE tools, however a few attempts have been made. To mention are (Ukidwe and Bakshi 2005) from Ohio State University who applied a thermodynamic IOA to calculate exergy consumption throughout various economic sectors and compared the exergy consumption, which they related to environmental degradation, to the economic value-added of the respective sectors. An extensive theoretical review of the methods used can also be found within the Handbook of Input-Output Economics in Industrial Ecology, edited by (Suh 2009).

Also Valero’s research group at the Center for Research of Energy Resources and Consumption at the University of Zaragoza has moved forward to combine thermodynamic studies with Industrial Ecology tools and thermodynamic input-output analysis in particular. After an initial exploration of exergy within energy-ecology analysis (Valero 1998) their approach was developed further and applied to industrial symbiosis and eco-industrial park concepts (Valero, Usón et al. 2010). Here the thermodynamic perspective of energy and material flows has also been combined with economic cost consideration into a thermo-economic study.

On a macro-economic level (Chen, Chen et al. 2006) approached a resource economics study by calculating the exergy inputs and outputs for the Chinese economy in order to illustrate improvement possibilities of different conversion sectors.

Next to thermodynamic IOA, (Sciubba 2005) has developed extended exergy accounting to calculate the exergetic cost of a product in which he includes next to physical exergy streams also exergy flows equivalent to capital, labor and environmental remediation costs to calculate the cost of a product.

4) Literature Review of hybrid Methodologies integrating Exergy Analysis and LCA

Researc Nomenclat Goal of Framework Achievements Conclusions her ure using Exergy within LCA (Corneli Exergetic Use ELCA to As framework for the Exergy LCA, Cornelissen uses Irreversibility of the Finally, it is ssen Life Cycle assess the a similar framework as is used for LCAs: the goal life cycle of a concluded that and Hirs Analysis, efficiency of and scope definition remain the same whereas the product is a exergy LCA is a 2002) Exergetic the use of inventory analysis is more extensive since complete measure of valuable Life Cycle natural mass and energy flows have to be compiled for inefficient use of extension of (Corneli Assessment resources each production step. Here the black box approach resources. LCA. It can ssen (ELCA) and of considering only the in- and outflows can be It is also a measure totally replace it 1997) quantify the resumed. The impact assessment is more limited for the depletion of in case the Irreversibili depletion of that in a LCA as life cycle exergy loss is the only non-renewable process in ty of life resources criterion: only the exergy of the flows and the resources. question is a cycle is the exergy losses of the processes are calculated. For renewable zero-exergy sum of Based on the total exergy losses throughout the life resources, a emission exergy cycle of the product, the life cycle irreversibility, distinction needs to process. losses of all the improvement analysis is carried out. Besides be made. processes presenting possibilities to reduce this irreversibility, throughout the improvement analysis can be extended with an the life exergo-economic analysis which considers also the = cycle. monetary costs. For multi-functional processes, three allocation − method are proposed: based on the exergy of the flows, based on the exergy destruction in case of Suggest a new separate production of by-products, or based on criterion for the the distribution of exergy destruction on basis of depletion of natural changes in the exergy values of the flows. resources based on the work potential Moreover the Exergy LCA is extended to a so called of materials, thus “Zero-Exergy LCA” which includes the abatement on their exergy. exergy of emissions, i.e. the exergy used to abate, This is supposed to re-use or dispose emissions in an environmentally replace the abiotic friendly way. resource depletion indicator used in LCA (Finnved Cumulative Focus is on Calculate the chemical exergy of some natural Presents exergetic Suggest to use en and exergy exergies of resources according to the method proposed by characterization exergy Östlund consumptio natural (Szargut 1989). factors for a consumption as 1997) n is resources: they calculate the exergy used to produce one selection of a calculated Use exergy kilogram of product but do not take the exergy minerals and fossil characterization by as a destruction throughout the life cycle but the exergy fuels. method in LCA. summing measure of contents of the ores needed to produce the the exergy resource products. contents of depletion in the the Cumulative exergy consumption is calculated by required characterisa summing the exergy contents of the required ores ores for the tion of an for the production of the products. Prudence is production LCA, suggested in the definition of system boundaries. of the calculate Here LCA system boundaries are assumed with products. exergy of elementary flows as input. some natural (Note: They do not make an exergy balance but resources include only input exergy of natural resources. This has a limited utility as discussed in the present application of exergy in LCA databases) 77

(Valero Exergetic Extend the To complete the life cycle calculation approach, Develops a Exergy Analysis 1998) analysis of life cycle also the “exergetic costs of replacement of calculation is a valuable the life approach materials” needs to be added, e.g. exergy to purify framework for tool to find cycle from water to its original state, to recycle materials or to cradle to cradle inefficiencies (ExLCA) “cradle to reforest woods. exergy analysis. and grave” Therefore 4 phases of calculation are defined: irreversibilities towards a - Calculation of exergy of natural resources starting but should be cyclical from recognized reference environment accompanied by approach - Calculation of exergy throughout the life cycle of a broader analysis that product, including the exergy of all materials and that include our imitates services needed for production, transport, values and nature, thus distribution, use, maintenance and disposal of the quality from product perception. “cradle to - Calculation of exergy needed to level off all cradle” emissions produced throughout a life cycle - Calculation of exergetic costs of the replacement of all materials used (recycle, reforestation)

Valero puts the exergy consumed also into a monetary perspective and chooses a thermoeconomic approach. (Gong Life Cycle Introduce Distinguish between three different stages of a Argue that a life and Exergy and clarify system: construction, operation and clean-up. In cycle Wall Analysis important the first stage, exergy is used to build a plant and perspective of 1997) (LCEA) concepts of start-up. Part of this exergy input is stored in the exergy analysis sustainable materials used. is very valuable engineering, The exergy input in the operation stage is called to understand among direct exergy, whereas the exergy of the other two the them being stages is called indirect exergy. performance of LCEA and the entire thermo- system and economic prevent accounting. problem shifting. Use exergy as a rational basis for assigning costs. (Grubb Ecological Focus more Combine LCA, energy analysis and exergy analysis. Apply Exergy analysis and Cumulative on Use both a process level (gate to gate) and a life thermodynamic provides Bakshi Exergy improveme cycle level (cradle to gate) analysis to the same innovative 2011) Consumpti nt analysis Complete first energy balance over each process or system at two insights for on (ECEC) is of LCA and unit operation involved in the production pathway. different scales: the identifying defined as use exergy To extend the energy balances to exergy balances, traditional improvement the to identify information on pressures, temperatures and engineering scale of potential on a cumulative process composition of streams are needed. a local process and life cycle basis. amount of improveme The unit operations with the greatest energy life cycle scale. exergy nt and/or exergy losses are defined to have the The insight for required to opportuniti greatest improvement potential. improvement that produce es They state that established frameworks are both scales provide the major followed but do not mention which one. I assume is compared. inputs to the most common life cycle assessments are being the followed. production Exergy is calculated as the sum of physical and process. chemical exergy. The exergy analysis at the life cycle scale consists of quantifying the chemical exergy of all raw materials needed for the main inputs of the production process in question. (Bösch, Cumulative Use exergy Chemical, kinetic, hydro-potential, nuclear, solar- Integrate exergy CExD is found to Hellweg Exergy as measure radiative and thermal exergies are applied to the data in Ecoinvent to be a good et al. Demand for resource resources contained in the Ecoinvent database. provide an indicator to (CExD) is requiremen additional impact assess energy 78

2007) understood ts and to Integrate exergy data in Ecoinvent through category indicator. and resource as total assess total characterization factors and calculating CExD for Make a large source demand. It exergy exergy 2630 products. of exergy values integrates also removal removal available to the the quality of from from nature CExD is specified in MJ-equivalents to emphasize it research energy and non- nature to in order to being an impact assessment indicator and not an community. energetic provide a produce a inventory elementary flow. resources. It is product or product. not a sufficient service, In case of multi-functional ores, i.e. that deliver indicator for the calculated Integrate more than one metal, exergy is allocated based on quality of as a sum of exergy in revenue whenever Ecoinvent provides this materials. exergy of Ecoinvent to information. If no revenue data is available, all required provide an allocation by mass is applied. resources. additional impact category indicator. Make a large source of exergy values available to the research community. (Contrer Exergetic Apply LCA methodology according to ISO 14040: LCA can be as Life Cycle Goal and Scope Definition, Inventory Analysis, complemented Moya, Assessment Impact Assessment, Interpretation. However the with the ELCA Rosa (ELCA) impact assessment is split in two parts: the to obtain more Doming traditional LCA impact assessment to study the solid uez et Cumulative environmental performance of a product and an conclusions on al. 2007) Exergy exergetic analysis to obtain exergy consumption the Consumpti indexes. environmental on is performance understand To calculate the Cumulative Exergy Consumption, as measure the cumulative amount of a certain material is to quantify multiplied by its exergy factor. The sum of all the use of cumulative input materials times their respective exergy of exergy factor adds up to the Cumulative Exergy resource Consumption. during the complete product life cycle

Table 5 Literature review on Exergy Analysis and LCA integration

Appendix B: Pulp & Paper Industry and Case Study

1) Functional Use of Paper and Board Grades

Table 6 Functional use of paper and board grades (EU 2010)

2) European Pulp and Paper Key Figures

Figure 26 Key figures 2010 of European pulp and paper market (CEPI 2011)

Figure 27 Global trade flows of recovered paper in 2009 (CEPI 2011)

Figure 28 Developments on the global pulp and paper market (Carlsson, D'Amours et al. 2006)

3) Sustainability in the Paper and Board Value Chain

Figure 29 Sustainability issues in the paper and board value chain

Figure 30 Sustainability initiatives within the paper and board value chain

4) Inventory Template, Example: Board Making Comments g/l g/l g/l g/l g/l g/l unit concentration unit chemical composition Specification (if applicable and available) K K K KKKKKKK Pa Pa K Pa K Pa Pa K Pa Pa K K KKKKKKK Pa Pa K Pa K Pa Pa K Pa Pa K unit pressure unit temperature state (solid / liquid / gas) ation / landfill?) kg kg kg km km km kg kg kg m³ g g g km km km General General information amount unit price unit product/ waste Recovered paper paper Recovered kg Chemicals and Additives Goods / Products Goods Transport (incl Transport internal transport) by truck by ship by train Fuels electricity level) (indicate voltage coal (specify calorific value)gas (specify calorific value) oil (specify calorific value)biomass (specify) kJ heat (specify) (specify)other kJ Water streams kJ waterCooling Process water kJ kJ Chemicals and Additives kJ kJ m³ m³ Goods / Products Goods Solidboard Emissions to water Emissions to soil Emissions Transport to storageTransport / production by truck by ship by train Fuels electricity level) (indicate voltage coal (specify)gas (specify) oil (specify)biomass (specify) kJ heat (specify) (specify)other Water streams cooling waste water waste watereffluent WasteOutput (water content, hazardous?, to inciner kJ kJ kJ kJ kJ kJ m³ m³ economic in Materials moisture (specify content) economic out Materials environmental in water from rivers/lakes/ground environmental out to air Emissions process name process process type flow name flow Figure 31 Inventory template of board making

5) Assumptions of Calculations used for Case Study

Mass Balance - Data in Herzberg in given as wet content, in Coevoerden as dry content. Same dry weight percentage is applied for similar materials for consistency.

Energy Balance - Energy content calculations: A similar distinction as done for the exergy contents described in chapter 2 is made for the energy contents: Of the six forms of energy (Chemical, Electrical, Radiant, Mechanical, Nuclear and Thermal), radiant and nuclear are not relevant in this study. Electrical energy can be completely used for doing work and has thus an exergy factor of 1. As a life cycle approach is used considering only inputs and outputs and mechanical energy is rather important within a process step, it is not considered relevant for this study on an input/output level.

Energy contents that need to be calculated are thus thermal (physical) and a chemical energy: (A.1) ℎ = ℎ + ℎ

The physical enthalpy, hph , is determined by the temperature difference of the flow in question and the reference environment, multiplied by the respective heat capacity. This is in line with the approach of (Wall 1988; Hellström and Kärrman 1997).

(A.2) ℎ = ( − ) This calculation is used for all streams except for steam where the enthalpy of steam is taken from the Mollier diagram. For consistency reasons, the enthalpy of steam in the reference conditions (293K, 1 atm) is subtracted from the enthalpy of the steam flow in question as done also by (Wall 1988).

(A.3) (ℎ − ℎ) = ( − ) According to (Szargut 1988), the chemical energy can be calculated as the enthalpy of devaluation, D° , which is based on the “reaction of devaluation” and the standard normal

enthalpy change of this reaction, ΔdH° . The enthalpy of devaluation represents the practical value of the chemical energy that can be obtained when the element interacts with common components of the environment. (Szargut 1988) has tabulated enthalpy of devaluation for common inorganic and organic substances.

(A.4) ° = −∆° Combining this equation with the one above results in:

(A.5) ℎ = ℎ + °

If the substance in question contains only the elements C, H, O or N, the enthalpy of devaluation is equal to the net calorific value.

(A.6) ° = ° Calorific values of common fuels are listed in literature. The net calorific value (or lower heating value, LHV) is more commonly used in Europe than HHV and has been applied also in the Ecoinvent database.

Energy contents of mass flows are determined based on the flow’s dry content.

- Transport energy calculations: Assumptions of power efficiencies: o Diesel motor of trucks: 40% according to (Huppertz 2011) o Gasoline motor of cars: 35% according to (Huppertz 2011)

Combustion equation in an engine is: Hydrocarbon + O 2 (g) CO 2 (g) + H 2O (l) If the combustion takes place using air as the oxygen source, the nitrogen can be added to the equation, although it does not react, to show the composition of the flue gas:

CxHy + (x+y/4) O 2 + 3,76 (x+y/4) N 2 x CO 2 + (y/4) H 2O + 3,76 (x+y/4) N 2

Average diesel fuel is C 12 H23 Thus:

1mol C 12 H23 + 17,75 mol O2 + 66,56 mol N 2 = 12 mol CO 2 + 11,5 mol H 2O + 66,56 mol N 2

Multiplying by molar mass:

1 kg C 12 H23 + 3,39 kg O 2 + 11,14 kg N 2 = 3,16 kg CO 2 + 1,24 kg H 2O + 11,14 kg N 2

Since O 2 in and H 2O out don't have an impact from an environmental nor from an exergetic point of view, they are left out in the transport analysis (similar reasoning why they are not included in ecoinvent).

- Heat emissions: Since the Exergy LCA methodology deals with entire production steps rather than single, devices, work produced ends up in low temperature heat at the output side of the complete process energy balance. However, it should be differentiated from heat dissipated due to internal irreversibilities (second law of thermodynamics). Thus heat emitted from produced work is labeled differently than heat emitted as inefficiency. It is assumed that heat of produced work is emitted at 70°C and exhaust gas of transport is emitted at 250°C.

Exergy Balance In general the exergy balance is calculated as

(A.7) ( + + + ) − ( + + + ) = ∆

Where the exergy of heat, Ex Q, is calculated as a product of the Carnot factor times the energy content of heat; the exergy of work, Ex W, is equal the energy of work; the exergy of matter is composed in two components, the physical exergy, Ex ph , and the chemical exergy, Ex ch .

The physical exergy is mostly determined by multiplying the physical energy of the matter times the Carnot factor and the chemical exergy is mostly taken from standard chemical exergy tables as compiled by (Szargut 1988).

Some exceptions are:

- Fuels: Since the exact composition of complex fuels are very difficult to know, (Woudstra, Woudstra et al. 2010) propose an approximation to calculate the exergy of a fuels:

For solid fuels: (A.8) = + ∗ ∆ℎ, Where LHV fuel is the lower heating value of the fuel, xH2O is the percentage of moisture in the fuel, Δh evap, H2O is the heat of vaporization of the moisture.

For liquid fuels with more than one carbon atom in the molecule: (A.9) = 0,975 ∗ For gas forming fuels with more than one carbon atom in the molecule: (A.10) = 0,950 ∗ Where HHV fuel is the Higher Heating Value of the fuel

- Liquid water and steam: According to (Szargut 1988), the standard chemical exergy cannot be taken as approximation for liquid water and steam because their chemical exergies depend on the temperature and humidity of atmospheric air. The chemical exergy is given by: (A.11) = Where φ0 is the relative humidity of the atmospheric air. For the Netherlands and Northern Germany, the two regions in which the case study takes

place, the relative humidity is on average φ0=0,79 which gives a chemical exergy of Ex ch =31,87 kJ/kg.

- Dry and humid air: According to (Szargut 1988), the chemical exergy of air can be neglected if the moisture content is similar to that of the environment. The chemical exergy content of dry air is thus neglected and the chemical exergy content of humid air is looked up in Szargut’s tables.

Regarding the physical exergy content of air, the value can be looked up in the exergy- entropy diagram of Baehr shown below in figure 32. The physical exergy of humid air can be looked up in the diagrams illustrated in figure 33.

Figure 32 Exergy-entropy diagram for dry air (Szargut 1988)

Figure 33 Physical exergy of humid air (Szargut 1988)

Complete versus practical approach Once all mass, energy and exergy balances have been compiled, a “complete” overview of thermodynamic flows is available. However, many of the materials inserted in the processes are not employed for their thermodynamic value but for other property reasons. In thermodynamic terms, they are interpreted as “transition materials” that do not change their chemical composition. In order to get a clearer picture of the thermodynamic pathways, it is suggested by (Arons, Kooi et al. 2004) to include only those thermodynamic streams that are relevant to understand the system. In this case study this implies including all physical energy and exergy values but considering the chemical energy and exergy values only of those flows that are introduced for their chemical potential. This means that the chemical component is taken only for the used fuels (gas, diesel, coal). This latter approach is called the “practical calculation approach”. In the enclosed excel file, an overview of both approaches can be found. The tabs are called “NL all”, “DE all” and “NL prac”, “DE prac” respectively.

6) Results of Case Study In the following the mass, energy and exergy flows for the German chain are presented. The figures are composed in analogy to the illustrations of the Dutch chain shown in 4.2.3.

Figure 34 Mass flows in the German cardboard production chain

Figure 35 Energy flows in the German cardboard production chain

Figure 36 Exergy flows in the German cardboard production chain

7) Confirming Mass, Energy and Exergy Balances

The following figure shows the mass and energy flows and balances for the three major processes in the cardboard life cycle: the power plant, the board production and the board conversion steps. The two case studies, the Dutch and the German chain are presented in parallel. Further figure 38 shows the same picture, but focusing on mass and exergy flows.

These representations demonstrate the fulfillment of the mass and energy balances that have been completed before determining the exergy balances and consequently the exergy losses.

Figure 37 Mass and energy balances in Dutch and German power plant, board production and board conversion

Figure 38 Mass and exergy balances in Dutch and German power plant, board production and board conversion

8) Solar Thermal Energy Calculations

To determine the solar thermal energy availability and possible contribution to a cardboard production process, regional solar characteristics and different types of solar thermal collectors need to be addressed.

Solar radiation in Northern Europe is assumed to be 1000 kWh/m² per year which is an average of the whole year. In July a radiation of 4,5-5 kWh/m² per day and in January of 0,5 kWh/m² per day are estimated according to (Boyle 2004).

Two main categories of using solar thermal energy can be distinguished: solar collectors for the generation of hot water, e.g. unglazed panels, flat plate water collectors or flat plate air collectors. These collectors can increase the water temperature only to a limited extent (up to 85°C). The second category includes collectors that bundle the solar energy in order to achieve medium to high temperature, e.g. evacuated tube collectors, line focus collectors and point focus collectors.

The line focus and point focus collectors are used to generate steam for electricity production. In this case synthetic oil is often used as heating fluid which can be heated up to 390°C. Via a heat exchanger steam is produced (Boyle 2004). These solar thermal engines can also be coupled to a gas or coal fired power plant, which can help to increase the temperature of the steam and which allows to have a steady energy flow independent of weather conditions.

Regarding the energy output, different values can be found in literature. For the simple solar collectors such as flat plat water collectors, values range from 390 kWh/m² per year (EnergyMatters 2011) to 750 kWh/m² per year (SolarServer 2011). Assuming an average obtainable temperature of 70°C this results in exergy values of 57 kWh and 109 kWh respectively.

For the focus collectors, e.g. parabolic trough collectors, (Fraunhofer 2004) states that the efficiency of obtaining thermal energy from incoming solar radiation is 37%. Assuming a radiation of 1000 kWh/m² per year, an output of 370 kWh/m² is calculated. These collectors generate much higher temperatures resulting in higher exergy values. With a conservatively estimated 350°C, an exergy value of 196 kWh/m² can be achieved.

Based on these efficiencies and assuming that the same exergy demand needs to be fulfilled with the solar energy supply, the following area requirements results for one ton of cardboard:

Dutch case German case

Simple solar collectors, 57 kWh ex /m² 5,06 m² 7,22 m²

Simple solar collectors,109 kWh ex /m² 2,65 m² 3,78 m²

Focus collectors, 196 kWh ex /m² 1,48 m² 2,11 m²

Table 7 Area requirements for solar collectors per ton of cardboard

The solar scenario as presented in chapter 5.1.2. is based on the assumption that the electricity is also generated from renewable sources and that the solar exergy is equal to the exergy demand of the process. For a detailed discussion on how to consider exergy from renewable sources, it is referred to (Dewulf and Van Langenhove 2006).

Appendix C: Meetings

1) Workshop ISPT, January 20th 2011

Chairman: Andreas ten Cate; Specialist: Maarten Oudshoorn; Facilitator: Wouter van Gerwen

In this workshop the aim was to brain-storm ideas on how to improve the sustainability of value chains. After a first round of idea generation we ended up with a number of categories: avoid waste (e.g. hygiene of materials (avoid value loss), closing cycles, assess value in waste streams); geographical symbiosis (think and optimize over the fence); the trend from global to local (in operation, production and consumption); required redesign due to increasing complexity of close collaborations; and cultural change needed in society (consequences of a circular economy).

One point of discussion was the transition process towards an increasing collaboration between industries. Driving forces were identified: awareness of each other’s excellence; ownership and the impact of a strong problem owners in the product cycle; one team – one goal; a yardstick to measure sustainability and value; sharing knowledge and benefits; focus on benefits and representation of - economic and non economic - value. Barriers were identified: legislation; dependency; (lack of) mutual trust; secrecy and confidentiality; knowledge ownership; sharing costs and benefits in a balanced way.

To start with concrete examples, value chains that are relevant to the participants were selected: paint; food; medicine; construction materials; transport; metals; and energy. As an example, the “paint” value chain was looked at based on the categories defined previously. As a conclusion, the topic energy was proposed as a first subject to study how to avoid most of the identified roadblocks.

2) Workshop ISPT, February 15th 2011 This workshop is a follow-up of a workshop held in January in which the main outcome was brain- stormed ideas about how to increase the sustainability of value chains. In this workshop the participants helped identifying concrete and strategically relevant issues that need to be addressed to create more sustainable value chains.

In a first session, two value chains were depicted for two exemplary products, a box of pampers and a can of peeled tomatoes. With the objective to close loops around the chosen product, use bio- based materials and design the product in a way to facilitate the separation of components, the strong and weak points to be dealt with were identified. Thereby out-of-the-box thinking and conventional re-design opportunities were discussed in an inter-disciplinary group. Social acceptance of proposed changes and their impact on up-stream and down-stream processes and industries resulted in a complex and diverse issue framework.

After exchanging ideas with other parallel sessions, the brainstorm session of the previous workshop and the lessons learned from the two exemplary value chain re-designs were combined to generate

95 ideas for an ISPT roadmap. With changing partners, the issues were organized in the previously defined categories: avoid waste, symbiosis, from global to local, society and Redesign / Complexity.

In the end both a generic strategic problem definition and a more defined action plan were identified in order to grasp the bigger picture in its complexity but at the same time to be able to start the challenge today.

3) KCPK Meeting, February 10th 2011 Participants: Arie Hooimeijer (KCPK), Tom de Haan (KCPK), Wouter van Gerwen (Tebodin), Annerieke Aarsen (Wereld van Papier), Sarah Herms

The objective of the meeting was to get to know the projects of KCPK and to discuss informal cooperation and information exchange possibilities. KCPK is active in the energy transition program of the VNP, the Koninklijke Vereniging van Nederlandse Papier- en kartonfabrieken. The program consitsts of five sub-programs: Energy Management, Energy Neutral Paper, Supply Chain of the Future, Bio-refinery and Without Water.

The subject of this research has some overlap with the third program, the Supply Chain of the Future, in which Tom de Haan is active.

This programs intends to address the energy and material losses throughout the paper supply chain which are much higher than the losses in the production due to the fact that many conversion steps (printing, refining) are done in many different locations across Europe and in every conversion steps energy and material losses occur. Furthermore, the transport is not organized in an efficient way, e.g. folded empty boxes are transported resulting in high space requirements.

Especially in high end applications, e.g. parfum boxes, high losses can be observed as high value is added in the conversion steps reducing the pressure on material and energy efficiencies. Smurfit Kappa is dealing with the low added value part of the supply chain as can be seen by the prices of solid board versus the price of a final box: the solid board of a perfume box is worth 2ct whereas the final box is worth 25 ct.

According to KCPK, higher energy and material gains can be achieved in the conversion process than in the milling process.

The whole supply chain is much broader than just the pulping – production – conversion steps as the collection and sorting activities of recovered paper play a big role. Recovered paper is not always used locally, as an example from the Groningen area shows where recovered paper is shipped to Berlin.

The Waardeketten-project of KCPK focuses therefore on integrating the production and conversion steps better and on designing the product in a way that can be cut more efficiently.

One actor to look at is Paper Recycling Nederland . To ensure the business case of recovered paper, a guarantee system is established that “jumps in” if the price for recovered paper is too low.

Escaboard is the biggest competitor of Smurfit Kappa but it focuses more on graphical paper. Solidpack has the same strategic focus as Smurfit Kappa but is a lot smaller.

4) KCPK Technology Day, February 17th 2011 The KCPK technology day is organized by the Kenniscentrum to share innovations, research and ideas among the actors of the paper industry. The day was divided in two main topics: energy efficiency and material efficiency. Next to classical optimization ideas, a new discussion could be observed. The paper industry in unsustainable and in crisis which brings up new functional questions, such as “do we actually need white paper? What do the customers really need? Do we actually need glue? What are other possibilities? etc”

Drying energy represents 50% of the energy need in the paper industry and attracts thus a lot of research attention.

Specifc process optimizations were presented:

• Eska Graphic Board: reducing drying energy through reduction of water content in the glue • Smurfit Kappa Roermond Papier: the effects of using different types of starch on paper quality and energy needs • Wageningen Research: alternatives that have the potential to reduce water consumption and thus also drying need: uncleaned starch, lignin, furan resins, modified starch, waterglas, sodium silicate (waterglas). Attention was given to the effects that these alternatives have on the viscosity of paper (which has to < 30% for the paper to be stable). To maintain viscosity, additives are added (best additive is clay which is similar to PVA glue in terms of contact and viscosity). Higher temperature usually results in less viscosity. Through higher drying potential of starch, 10- 15% of energy can be saved, e.g. by using sodium silicate. However, the production of sodium silicate is also energy intensive. Thus the life cyle of this new process should be assessed as well as the reuse and recycle potential.

Paper needs heat but produces also heat which provides integration possibilities. An overview of waste heat use possibilities was given by Jobien Laurijssen from KCPK: • Less steam demand: • less water use: higher initial water temperature to increase drying efficiency, warm air • higher drying efficiency • don’t use gas to produce steam to warm up water -> high exergy losses • Internal use of waste heat • Direct: heat up inlet air, heat rooms, heat process water • Upgrade: heat pump (use waste heat of 70°C to convert to 160°C), mechanical steam compression • Conversion: to electricity (thermo acoustic power (done in Nieuweschans), Organic Rankine Cycle), to cold • Separation of water and air flows: Membrane technology, Sorption technology • Waste heat supply

• Sappi Maastricht: best practice of using waste heat in residential area • Difficulty is not technical or economic but organizational because there is a lack of “pulling” organizations. Who takes the risk, the responsibility? Back-up needed? More commitment from communities? • VNP is connected with the heat network • Sustainable heat production • From incineration of rejects, biomass, biogas • From the ground: geothermal, but need 5-6 km depth to get 150°

Heat initiatives in the Netherlands: Warmtenet, Warmtebonus in SDE, Oprichting NEW, IWB subsidie Studies: Roland Berger on energy prices, Spoelstra (2007) on Dutch energy consumption per industry and fuel use showing that heat use makes a big portion.

A new waste paper sorting technique was presented by Norske Skog Parenco. The new technique allows a better quality and homogeneity of recovered paper and thus a higher recycling factor. With higher quality recovered paper, less energy and chemicals need to be used. The project is financed by the EU.

The second part of the day was dedicated to material efficiency.

Material savings means also energy savings (10% material efficiency > 10% energy efficiency)

Next to internal process material optimization, the paper industry tries to look “outside its box” and evaluate alternative feedstocks next to wood and possibilities to use and upgrade its waste streams. A multi-product-mill is envisioned where by-products / waste streams can serve as feedstock for biofuels or bio-chemicals. In order to obtain more concentrated high added value by-products, the primary process might need to be adapted.

According to SCA Packaging De Hoop there are many valuable components in the process water that are needed by other industries, e.g. fatty acids. However they occur in very small concentrations which require research in separation technologies. Procede has researched several possibilities for separation: liquid extraction is very energy intensive for low concentrations, adsorption can be used to increase the concentration in the water. Millvision also presents possibilities to isolate valuable polymers from process water and KCPK presents a project about using sludge for bioplastics that has been carried out with Crown van Gelder, Purac and Bumaga.

Another topic is the optimization of cellulose cascading. Wageningen Research is developing a cellulose matrix showing which feedstocks are available for which then feasibility studies are carried out , for example by Smurfit Kappa Group (Organosolv: sulfur-free pulping process).