University of Groningen the Sustainability of Producing BTX From

University of Groningen

The sustainability of producing BTX from biomass. Meuwese, Anne

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CIO, Center for Isotope Research IVEM, Center for Energy and Environmental Studies

Master Programme Energy and Environmental Sciences

University of Groningen

The sustainability of producing

BTX from biomass

Anne Meuwese

EES 2013-165 M

Master report of Anne Meuwese Supervised by: Dr. N. Schenk (KNN advies b.v.) Prof.dr. H.C. Moll (IVEM) Prof.dr. A.J.M. Schoot Uiterkamp (IVEM)

University of Groningen CIO, Center for Isotope Research IVEM, Center for Energy and Environmental Studies Nijenborgh 4 9747 AG Groningen The Netherlands http://www.rug.nl/fmns-research/cio http://www.rug.nl/fmns-research/ivem Acknowledgements I would first of all like to thank my supervisor at KNN advies b.v. Dr Niels Schenk for his support throughout the process, his enthusiasm for my research and his confidence inspiring confidence. His no-nonsense mentality combined with optimism and a kind hart have greatly aided the progress of my research.

Secondly, I would like to thank Professor Henk Moll for his insights and advice, without which I would have undoubtedly struggled more with this complex approach to LCA.

I am once again indebted to Professor Ton Schoot Uiterkamp for his determination to make me a better researcher and his passion to inspire those around him to strive for a better world.

Last but not least I would like to thank my colleagues at KNN, especially my boss Dr Cor Kamminga, who provided an energetic workplace with interesting discussions and a pleasant atmosphere that made time fly by.

Summary The dependence of humans on fossil resources is not limited to fuel needs. A significant amount of petroleum feedstock is also used to produce materials, from pharmaceuticals and plastics to asphalt for roads. But just like with fuels, the use of fossil resources for these purposes leads to depletion of resources and greenhouse gas emissions.

Benzene, toluene and the three xylenes (BTX) are bulk chemicals which are vital for the petrochemical industry. Their major downstream products are plastics, but they are also used for solvents, additives and other specialty chemicals. Based on the environmental impacts over the lifecycle of a BTX product, the fossil resource depletion and greenhouse gas emissions make the largest impact on the environment. Because of this and the size of the market for BTX products, it is important to look for more sustainable options for BTX.

One of these options is producing BTX from biomass rather than from fossil resources. A relatively new focus of research, the process is not yet commercial, but it does have the potential to be. Using woody biomass as a feedstock, yields of around 15% are already reached. Woody biomass is preferable, both for product yield but also because using woody biomass is often more sustainable than using starch and oil crops. Compared to the fossil-based process, the fossil resource inputs and

CO 2 emissions are low, so based on those two parameters biomass-based BTX promises to be a sustainable option. The main question of this research was: Is production of BTX from biomass a sustainable use of the resource, considering system efficiency and macro scale effects?

Since the amounts of woody or sustainable biomass available at a certain time are limited, other products from this biomass were also researched, to determine whether the environmental impact of producing BTX was lower than that of other products. Three product categories were chosen, electricity, fuel and materials, to represent a spectrum of products from woody biomass. For fuel products, both ethanol and biomass-based diesel were taken into account. For materials, ethylene, BTX, and two compounds for polyethylene polymer production. The latter two were terephthalic acid (TA, product of BTX) and a sugar based alternative for TA, furandicarboxyllic acid (FDCA), which can be produced well from corn and in theory from wood.

Subsequently, the fossil resource inputs and CO 2 outputs of the biomass- and fossil-based processes for each of these products were calculated. It was concluded that diesel and BTX were more sustainable uses of biomass than ethanol, ethylene and electricity. Comparing the in- and outputs of the production of biomass-based FDCA with the production of biomass-based terephthalic acid (TA, product of BTX), it was concluded that FDCA from corn had lower emissions and fossil resource requirements than TA from wood, but that FDCA from wood performed poorly.

Finally, several macro effects were examined: waste stream use, other renewable resource potential, petrochemical industry trends, recycling- and cascading-potential and scale effects. Biomass-based BTX can use waste streams, does not have another renewable alternative and, will probably be more attractive in the future based on market trends. Since it is a material, there is possibility of recycling and cascading. For the other products concerned, the macro effects were either not positive or less so than for biomass-based BTX.

Therefore, based on fossil resource use, CO 2 emissions and several macro scale effects, it can concluded that producing BTX from biomass is a sustainable use of the resource.

Samenvatting De mensheid is niet alleen voor brandstof afhankelijk van fossiele grondstoffen. Een significant deel van de fossiele grondstoffen wordt gebruikt voor de productie van materialen, van medicijnen tot plastics tot teer. Maar net als bij brandstoffen is er bij het gebruik van fossiele grondstoffen voor deze doeleinden een verband met oprakende reserves en de emissie van broeikasgassen, die op hun beurt weer een verband hebben met klimaatverandering.

Benzeen, tolueen en de drie xylenen (BTX) zijn bulkchemicaliën met een vitale rol in de olie industrie. De belangrijkste producten die uit BTX gemaakt worden zijn plastics, maar BTX wordt ook gebruikt als uitgangsstof voor oplosmiddelen, additieven en andere (fijn)chemicaliën. De belangrijkste milieu effecten van een plastic gemaakt van benzeen over zijn hele levenscyclus zijn het grondstof gebruik en de emissie van broeikasgassen. Gezien de grootte van de markt voor BTX producten, is het relevant om te kijken naar duurzame alternatieven voor de traditionele BTX.

Een van deze alternatieven is het produceren van BTX uit biomassa in plaats van uit fossiele grondstoffen. Dit is een relatief nieuwe technologie die nog niet op commerciële schaal wordt toegepast, terwijl dit wel mogelijk zou zijn. Met hout als grondstof worden al omzettingen van 15% op basis van massa gehaald. Hout is een betere grondstof voor dit soort proces dan olie- of zetmeelgewassen, zowel omdat de opbrengst hoger is en omdat hout vaak milieuvriendelijker wordt geproduceerd dan langbouwgewassen. BTX productie uit hout heeft een lager fossiel grondstof gebruik en minder CO 2 emissies dan BTX productie uit fossiele grondstoffen, en is dus wat dat betreft duurzamer. Het doel van dit onderzoek was uitvinden of BTX uit biomassa duurzaam gebruik van deze grondstof was.

Aangezien er maar een beperkte hoeveelheid duurzame biomassa beschikbaar is per jaar werd in dit onderzoek ook gekeken naar de duurzaamheid van alternatieve producten uit biomassa. Daarmee kon worden bepaald wat de relatieve duurzaamheid van BTX productie is in vergelijking met andere biomassa producten. Er werd gekeken naar drie productgroepen: elektriciteit, brandstof en materialen. Voor brandstof werden bioethanol en biodiesel uit hout bekeken, voor materialen ethyleen uit hout en een suiker-gebaseerd alternatief voor het plastic PET, FDCA. De laatste kan uit zowel hout als mais worden gemaakt.

Voor al deze producten werd voor zowel het fossiele als het biomassa proces de CO 2 emissies en fossiel brandstof gebruik uitgerekend. Gebaseerd op deze berekeningen kon worden geconcludeerd dat BTX en diesel de meest duurzame producten uit hout waren. Het maken van FDCA uit mais had lagere emissies en grondstof gebruik dan het maken van PET uit hout, FDCA uit hout deed het het slechtst. FDCA productie uit mais is echter minder duurzaam, omdat mais ook een belangrijke voedselbron is en dus in de eerste plaats zou moeten worden gebruikt om voedselschaarste tegen te gaan.

Als laatste werd gekeken naar verscheidene macro-effecten: de mogelijkheden om afvalstromen te gebruiken en om te recyclen, trends in de petrochemie, alternatieve hernieuwbare bronnen en opschaalbaarheid. Daar waar een waardeoordeel viel te vormen, kwam BTX altijd het beste uit de analyse.

Op basis van het fossiele grondstof verbruik, de CO2 uitstoot en verscheidene macro-effecten kan worden geconcludeerd dat BTX uit biomassa een duurzaam gebruik van deze grondstof is.

List of abbreviations BTX Benzene, toluene and xylenes FDCA Furandicarboxylic acid HHV Higher heating value HMF hydroxymethylfurfural ILUC Indirect land use change LCA Life cycle analysis PEF Polyethylene furandicarboxylate PET Polyethylene terephthalate PLA Polylactic acid PTA Purified terephthalic acid TA Terephthalic acid

Contents Acknowledgements ...... 1 Summary ...... 3 Samenvatting ...... 4 List of abbreviations ...... 5 1 Introduction ...... 9 1.1 Background ...... 9 1.2 Research aim and questions ...... 11 1.3 Sustainability ...... 12 1.4 Scope ...... 12 1.5 Methods ...... 12 2.0 Fossil-based BTX ...... 13 2.1 introduction ...... 13 2.2 Life cycle analysis of fossil-based BTX ...... 14 2.3 Alternatives to fossil-based BTX ...... 16 3.0 Biomass-based BTX ...... 17 3.1 Research towards biomass-based BTX ...... 17 3.2 Advantages and disadvantage ...... 18 4 Alternative biomass use ...... 19 4.1 Choice of biomass ...... 19 4.2 Uses of lignocellulosic biomass ...... 19 5 LCA and functional units ...... 21 5.1 Set-up of the life cycle analysis ...... 21 5.2 Choice of processes for the functional units ...... 21 5.3 Formulation of the functional unit ...... 22 5.4 System boundaries ...... 23 6 LCA of biomass-based FDCA and TA production ...... 27 6.1 Inventory ...... 27 6.2 Method ...... 27 6.3 Results ...... 27 6.4 Inventory discussion ...... 30 7.0 Biomass versus fossil LCA ...... 31 7.1 Inventory ...... 31 7.2 Methods ...... 32

7.3 Results ...... 33 7.4 Inventory discussion ...... 35 8.0 Discussion LCA results ...... 39 8.1 Outcome of the LCA’s ...... 39 8.2 Correlation in the margins ...... 39 8.3 Electricity differences ...... 39 9.0 Macro scale effects ...... 41 9.1 Using waste streams as feedstock...... 41 9.2 Future trends in the petroleum market ...... 42 9.3 Renewable alternatives ...... 43 9.4 Corn as a feedstock ...... 43 9.5 Cascading and recycling...... 44 9.6 Scale potential ...... 45 9.7 Conclusion ...... 46 10 Discussion ...... 49 10.1 General discussion ...... 49 10.2 Comparison with other research ...... 50 11 Conclusion ...... 53 12 References ...... 55 Appendix A: LCA polystyrene cup ...... 61 Appendix B: inventories ...... 62 Detailed inventory of chapter 6 ...... 62 Detailed inventory chapter 7 ...... 65 Appendix C: Uncertainty determination ...... 71 Appendix D: Sensitivity chapter 6 ...... 73 Appendix E: Sensitivity chapter 7 ...... 75

1 Introduction This research concerns determining the sustainability of producing the chemicals benzene, toluene and the three xylenes (BTX) from biomass instead of fossil resources. BTX is produced on mega ton scale globally, but the non-renewable nature of its feedstocks may pose a problem in the long term. Producing BTX from biomass is attractive, since there is a potential to mitigate carbon emissions on a large scale. However, since the amount of renewable biomass is limited, it is possible that it could be used more efficiently for other purposes than BTX production. Additionally, the production of biomass-based BTX could have a larger impact on the environment than fossil-based BTX production. A comprehensive life cycle analysis was used to determine which BTX production method is most sustainable and what the relative sustainability of biomass-based BTX is compared to other biomass products.

1.1 Background The dependence of industrialized countries on fossil resources is not limited to their fuel needs: a substantial amount of the materials used on a day to day basis is also derived from non-renewable sources (Langeveld, 2010). The petroleum industry and its secondary and tertiary industries produce chemicals ranging from bulk polymers to highly specialized pharmaceuticals. But the emission of CO 2 from the use of fossil carbon sources is associated with climate change, and alternatives will have to be found as supplies of available fossil carbon can run out.

1.1.1 BTX The aromatic compounds benzene, toluene and the xylenes (meta, para and ortho) are often grouped together as BTX (US DOE, 2000). They are part of the six major platform chemicals (along with ethylene, propylene and butadiene), and form the basis for the production of a whole array of bulk chemicals, as shown in figure 1 (Blaauw, 2008).

Figure 1: Major products derived from BTX (after (US DOE, 2012))

In the Netherlands alone, BTX production is about 3,3 Mt annually, accounting for about 3% of global production of BTX. BTX is currently most often produced by the catalytic cracking of the naphtha fraction of crude oil, although production from pyrolysis gas and from coal is also significant (Sweeney, 2008). The demand for the different chemicals within the BTX group is 67:5:28

9 respectively, although no process directly gives this ratio. Therefore, toluene is often converted into benzene and xylene to adjust the ratios.

1.1.2 Negative impacts of BTX BTX has an environmental impact due to the fact that it is produced from fossil resources in an energy intensive process. Although compared to fuel production, chemicals production is a small sector, the non-renewable nature of crude oil will limit its use in the future (Blaauw, 2008). The use of fossil BTX will eventually lead to fossil carbon dioxide ending up in the environment, which is associated with climate change, although the timeframe depends on the application and the waste processing. Aside from these direct emissions, fossil carbon dioxide is also emitted in the production process because of the energy requirements, along with emissions of, for example, NO x and SO x

(Wang, 2008). BTX production accounted for 3.5% of the CO 2 emissions of the chemical industry in Europe in 2009 (Benner, 2012).

1.1.3 Biomass as an alternative for fossil resources One way of decreasing the environmental impact of BTX production is to use biomass as a feedstock instead of crude oil. In general, biomass can be used as a feedstock for a multitude of applications: electricity production, heat production and the production of compounds ranging from combustion fuels to pharmaceuticals. Currently dominant uses of biomass are so called 1 st generation fuels and electricity and heat production. First generation biofuels are mostly made from agricultural crops such as corn and sugar cane but also from oil crops (Naik, 2010). Although they can be processed into ethanol and bio-diesel, the largest drawbacks to these crops are that they are competing with food production and require fertilizers and pesticides in large quantities, which decreases their environmental friendliness. Although second generation fuels are more sustainable since they are based on biomass waste streams, producing higher value products than fuels from biomass is preferable because it makes more efficient use of the limited available renewable biomass. So called “biorefineries” aim to mimic the petrochemical industry and design processes that make a whole range of products from biomass, since process integration will benefit the cost and resource efficiency (Bozell, 2008; Willems, 2009).

1.1.4 Production of BTX from biomass BTX is an interesting use of biomass in an economic sense, since there is a large market which can be tapped into by biomass-derived BTX. Unlike new biochemicals, for which a whole new market needs to be created, BTX from biomass can be used as a direct replacement of BTX from fossil sources. The perspective of biomass-based BTX depends thus only on its production cost and the impact/requirements of production. The production of BTX from biomass can follow several routes. A useful feedstock for biochemicals is lignocellulosic biomass, which originates from woody plants. Since part of the molecules therein contain aromatic structures, techniques like liquefaction can extract these aromatic compounds without completely fragmenting them first (Holladay, 2007). Alternatively, the aromatic compounds can be synthesized from other molecules derived from biomass (Williams, 2012). In some cases, like catalytic pyrolysis, the mechanism with which the BTX are formed is not clear, since they can be both formed during the high temperature reaction or simply result from fragmenting larger structures.

1.1.5 Advantages and disadvantages of biomass based BTX Advantages of making BTX from biomass are the renewable nature of biomass, and the fact that polymers made from biomass derived BTX would be a CO 2 sink (Bergsma, 2010). However, the 10 process of making biomass derived BTX is still in its infancy, whilst the fossil derived BTX production is a decade’s old process which has thus been optimized. Therefore, biomass derived BTX production could require more energy and resources than fossil BTX, possibly offsetting its environmental benefits. In order for BTX production from biomass to be sustainable, the benefits must outweigh these costs and also be comparable or better than other uses of the biomass in terms of sustainability.

1.1.6 Life Cycle Analysis Life Cycle Analysis (LCA) is a method to determine what the impacts of producing, using and disposing of a certain product or service is (Finnveden, 2009). Since for this research the impacts of the whole chain are interesting, it is a suitable method of determining the environmental impact. There are two main categories of LCA: attributal or descriptive LCA and consequential or choice based LCA. Attributal LCA is used when a detailed analysis of the physical flows in a single process, while consequential LCA is used to determine which choice between, for example, feedstocks will result in a lower environmental impact.

1.1.7 Larger scale problems Products from biomass usually work well on small scale, but when implemented on large scale can cause more harm than good (Hipolito, 2011). Since BTX is such an important and large scale product nowadays, there is a risk that biomass based BTX could become such a large scale commodity that it outgrows its sustainability, for example when biomass based BTX production competes with food production and biodiversity.

1.2 Research aim and questions This research therefore aims to compare the environmental impact of biomass-based BTX production with several fossil and biomass-based processes to determine which use of biomass would yield the largest environmental gains. Aside from this, the macro effects of production biomass derived BTX will be determined to see if there are significant large scale and long term effects.

Given the research aim, the main research question was:

Is production of BTX from biomass a sustainable use of the resource, considering system efficiency and macro scale effects?

To answer this question, first the functions of BTX in meeting societal needs were determined, to see if those functions can be fulfilled by renewable/more sustainable alternatives. Then the different routes to BTX from biomass were determined. Next, alternative uses of lignocellulose biomass were identified. Since these were very widespread, they were categorized into several utilities. With the BTX route and alternative use routes determined, a functional unit for the life cycle analysis was formed. With these LCA’s, the fossil resource use savings and CO 2 emission savings were determined. Lastly, macro effects of the use of biomass derived BTX and trends in the considered processes were identified, to assess the effect on the sustainability of the systems.

The research is thus divided into the following sub questions:

1) What are the functions of BTX, and what alternatives are there? (chapter 2) 2) What pathways to BTX from biomass are there? (chapter 3) 3) What are other significant uses of lignocellulosic biomass? (chapter 4)

4) What are the environmental impacts of biomass-based BTX compared to fossil-based BTX? (chapter 7) 5) What are the environmental impacts of biomass-based BTX compared to other uses of biomass? (chapter 6 & 7) 6) What are the macro effects of (biomass-based) BTX production? (chapter 9)

1.3 Sustainability In the broadest sense, sustainability is about maintaining a certain status quo, in the environmental sense it is about humanity and nature living in such a harmony that resources are not depleted, the environment is not polluted. A social factor is included by defining sustainability as “meeting the needs of the present without compromising the ability of future generation to meet their own needs” (Brundtland Commission, 1987). In this research, “sustainable” is defined as being the most accommodating to accomplishing the goal of a sustainable society. So a process can be considered sustainable even if it does use a non-renewable feedstock, as long as overall its environmental impact is lower than that of other processes that it can/has to be substituted with. It is assumed that the demand in society for a service is not modifiable, although in practice efficiency increase and reducing demand are options. But in the absence of abstaining from using a product, producing this product with a lower environmental impact is considered sustainable. Aside from looking at “micro”- effects such as the CO 2-emissions of producing one kilogram of product, which give limited information about the overall sustainability of a product, the macro-effects of production are also considered. With both micro- and macro-effects, a general assessment of the sustainability of the products under consideration can be given.

1.4 Scope For the first five research questions, the geographic scope was not defined, although within the inventory phase of the LCA the Netherlands/Europe was used in the process wherever choices had to be made in the inventory phase of the LCA. For the sixth research question, the scale was global, since at this scale the use of biomass has the largest risk of becoming problematic. The time scale for the sixth research question is up until 2030, since that gives some time to develop technology but it is sufficiently near for information and outlooks to be available at that time period.

1.5 Methods The first three sub questions relied on literature research, from scientific journals and where necessary from commercial or government resources. Scientific articles were searched for in the Scopus database.

For the fourth and fifth research questions, LCA schemes were developed based on the results of the first three research questions. Based on these scenarios, a functional unit was defined. The different routes in the scenarios were inventoried using the Ecoinvent v 2.2 database and, where necessary, alternative sources. With the inventory in place, the scenarios were calculated, so a comparison could be made between environmental impacts. These calculations were performed using excel rather than a modelling program like SimaPro, since this was a customized LCA.

For the study of the macro effects, literature and simple models/calculations were used.

2.0 Fossil-based BTX In this chapter the uses, impacts and alternatives to BTX are explored.

2.1 introduction Benzene, toluene and the three xylenes are aromatic hydrocarbons produced in very large volumes worldwide (Sweeney, 2008). Figure 2 shows the molecular structure of the 5 compounds. Although their structure is of importance to their function in chemistry, for this report it is sufficient to note that they are relatively simple structures that are very similar.

Figure 2: molecular structures of a) benzene; b) toluene; c) ortho-xylene; d) meta-xylene; e) para-xylene

Benzene, toluene and xylene are “platform chemicals”: basic chemical compounds that are used as a starting point for a whole range of other compounds. Annual production is around 60 Mt, prices range between 0.52 and 0.86 euro per litre (Sweeney, 2008; ICIS, 2012).

Figure 3 shows the main uses of BTX. Benzene is the highest in demand among BTX. Ethyl benzene and subsequent (poly) styrene production is the major use of benzene. Other important downstream products are phenolic compounds, acetone and nylon-6 (US DOE, 2000). Benzene itself is being phased out as an end stream product (solvent) since it is carcinogenic.

Toluene is used as a solvent and a precursor for polyurethane production. The market for toluene and its products is relatively small. Since toluene is produced in a larger amount than needed during BTX production, a large part of the produced toluene is hydrodealkylated to form benzene (also works with xylene) or disproportionated to form benzene and xylene (Benner, 2012).

Within the xylenes, meta-xylene is used relatively little. Ortho-xylene has some precursor and additive uses, but para-xylene has the largest market, since it is a precursor for polyethylene terephthalate (PET) and high end polymer applications such as aramid fibers (Kroschwitz, 2004).

BTX is produced commercially in three main ways: from reformate, from steam-cracking naphta and by coal pyrolysis. (Sweeney, 2008) Reformate is a mixture of hydrocarbons that has been produced by heating a light fraction of crude oil in the presence of a catalyst, with the goal of producing transport fuel. BTX is part of this reformate, and can be extracted from the mixture. Steam-cracking of naphta is used to produce ethylene (another platform chemical), and has BTX as a by-product. Lastly, pyrolysis of coal also produces BTX, and was in fact the first commercially used process for BTX production. Although it has been out of favour, BTX production from coal is on the rise again with the

13 shrinking resources of crude oil. Aside from these three ways, there are several other processes, for example the catalytic conversion of methanol to BTX. The attractiveness of each route depends on the economic situation of both the feedstock and BTX (products), and production is therefore not constant (Sweeney, 2008).

Figure 3: BTX production chain (from (US DOE, 2000))

Reformate and naphtha cracking are the main sources of BTX globally. Regionally the ratio varies depending on what other industry is present. Since BTX is not only used as a chemical but is also useful as a fuel additive, prices and demand relies partly on the global demand and supply of fuel. Additionally, BTX prices depend on downstream demands and supplies. In 2010, a rise in the price of cotton caused an increased demand in synthetic fibres and therefore in benzene and xylene (PPE, 2011). The dependence of BTX supply and demand on so many factors is a clear sign that it is a vital part of the global economy. Therefore the sustainability of BTX is an important part of the sustainability of society.

2.2 Life cycle analysis of fossil-based BTX As mentioned in the previous paragraph, benzene is a carcinogenic compound, to such an extent that its use is limited to avoid needless exposure. But the production and use of BTX has other impacts, and in order to determine where improvements on the sustainability of BTX could be made, all of them should be mapped.

A previous study looked at the production of polystyrene packaging material (compared to a biomass-based alternative) and showed that among all impacts the impact of carcinogenic substances was the smallest (Zabaniotou & Kassidi, 2003). Other impacts, such as acidification potential and global warming potential were more important.

To expand on those results, a compact life cycle assessment of a polystyrene cup was modelled in SimaPro with the Ecoinvent v2.2 database. It was assumed that cup was made by injection moulding, that the use phase consisted only of transport and that the waste phase was in common domestic waste disposal in the Netherlands. For more details, see appendix A.

Figure 4 shows the normalized impact categories for the life cycle of the polystyrene cup. The first column shows the normalized impacts of the production of the cup, the second the use phase in which the cup is transported 500 km, the last column shows the waste phase. The production of the cup has the largest impact, and this is due to fossil resource depletion and climate change. The use phase has a small impact, although again fossil resource use and climate change are the important impact categories. The waste phase also has some impact; the relevant categories there are climate change (due to the release of fossil carbon from which the polystyrene cup is made) but also human toxicity.

Figure 4: Normalized impact categories LCA polystyrene cup

Again the carcinogenic impact (human toxicity) is shown to be small, although it is the fourth largest impact, the carcinogenetic of benzene is thus not the characteristic cause for the most concern. The largest impacts of the life cycle of the polystyrene cup are due to fossil resource depletion and excess fossil carbon dioxide emissions. Reduction of fossil resource use in the production of polystyrene would benefit the sustainability of polystyrene cups.

Although for other BTX product pathways and lifecycles the impacts are likely to differ somewhat, for the bulk use of BTX (plastics) the impact profile will likely be similar to the one of the polystyrene cup. Aside from efficiency improvements in the process, which can give significant reductions in fossil resource use and in corresponding fossil CO 2 emissions, replacing fossil-based plastics with biomass- based plastics could decrease the impact of plastics production and use.

2.3 Alternatives to fossil-based BTX Biomass-based alternatives can be roughly divided into two groups: replacements for products and replacements for precursors.

Biomass-based plastics that could replace styrene, terephthalic acid and nylon based plastics are already commercially available (Jong, 2012). Poly-lactic acid (PLA), for example, is a well-known example of a biomass based plastic (Cheng, 2011). PLA has two relatively large draw-backs, however; it is based on starch crops and it has slightly different properties than the mass produced fossil-based plastics it is replacing. While some of these properties, such as biodegradability, are seen as positive traits for many (but not all) applications, other properties, such as low viscosity and brittleness, are a negative for nearly all applications (although they also possess some positive traits). Starch crops are also food crops, and production of PLA is therefore in competition with world food supplies. That it is not a perfect replacement of fossil-based polymers is not so much and environmental concern as an economic and technical-potential problem. The implementation rate will be lower, implying that the environmental benefits will only be reaped later. But the physical properties of the alternative (biomass-based) polymers may be so different from the fossil-based polymers, that they cannot be applied to high performance materials. High-performance materials are increasingly important, as they often contribute to a better environment in their own way, such as replacing steel parts in cars and thereby reducing the weight and fuel use of the car (Eleni & Panagiotis, 2006).

Making biomass-based precursors thus has the advantage that the product is usable in the mature market of fossil-based chemicals (Arbogast, 2012). With such “drop in” biomass-based chemicals, a faster transition could be made in that case to a more sustainable society (Harmsen & Hackmann, 2012). An additional advantage is that the simpler the target compound, the more flexible the technology is to the type of feedstock it gets. Instead of high quality starch crops, waste streams and other relatively sustainable renewable feedstocks could be used, thereby taking away the competition with food supplies. And since these drop-in chemicals have the same physical and chemical properties as the fossil-based products they are replacing, there is no resulting loss in quality or performance of the materials made with them.

Because of these two advantages of precursor production, the market readiness and the possibility for using non-food biomass, research into producing BTX itself is making big strides.

3.0 Biomass-based BTX In this chapter a short overview is given into how BTX can be produced from biomass, and what the advantages and disadvantages of doing so could be.

3.1 Research towards biomass-based BTX The production of BTX from biomass was first described in 1983 (Kotasthane, 1983), although the formation of aromatic compounds is normal upon combustion of wood. The reason for this is that about a third of woody biomass consists of lignin, large molecules made up of interconnected aromatic rings (Bozell, 2008). If the lignin is broken down, the individual aromatic compounds can be the product. Although this lignin fragmentation can take place at room temperature, research into aromatics production focus on high temperature fragmentation, since this is more efficient. Interestingly, pure lignin is not the best feedstock for BTX production (Cheng, 2011), it has a lower yield than, for example, wood. Although the exact mechanics are not yet known, the formation of aromatic rings through Diels-Alder reactions probably plays a role.

Although the first article on this subject appeared in 1983, it was not until the 2000’s that research in this field intensified. Most research is directed towards catalytic pyrolysis, which is degradation of the biomass under high temperature in the absence of oxygen. The catalyst is added to drive the reaction towards specific products (Mihalick, 2012). Without a catalyst, the resulting pyrolysis oil is a mixture of (oxygenated) hydrocarbons, which is used as fuel (Zhong, 2010).

Aside from pyrolysis, there are also several gasification reaction used to produce BTX, through thermal degradation in the presence of some oxygen at higher temperature (Link, 2012). But because of the higher temperature, the lignin is degraded to a larger extent, destroying the aromatic rings.

Some research is also directed at upgrading of pyrolysis oil and ethanol into BTX, although one can imagine that the direct conversion of wood to aromatics without this step should theoretically be more efficient (Valle, 2010; Inaba, 2005).

Reaction temperatures between 450 and 600 oC give the best BTX yields. Of the catalysts used, the H- ZSM-5 doped with Gallium works best; although un-doped or doped with other elements also give satisfactory BTX yields (Cheng, 2011).

Although research into and optimization of the process is on-going, some authors report quite high yields already, like Mihalick et al. (2012) who achieve an energy efficiency for BTX production from oak of 29% HHV.

The ratio of benzene, toluene and xylene resulting from the reaction varies strongly. The oak based reaction by Mihalick et al. yields mostly para-xylene, whilst the reaction of Cheng et al. (2012) yields mostly benzene. As mentioned in chapter 2, in the fossil-based BTX production process conversion of the BTX ratio obtained to the one aimed for is standard practice. It will therefore be a balancing act to find a biomass-based BTX process that optimizes the total yield with the efficiency of conversion to the intended yield.

3.2 Advantages and disadvantage The advantages of biomass-based BTX production are:

- The possibility of using non-food crops and waste biomass as a feedstock. Since agricultural land is a limited resource, it should ideally be reserved for food production as food is an essential human need. The use of waste streams is also beneficial, since this is making value out of something that was less valuable before. - The production of a precursor/”drop-in” chemical. “Drop-in” chemicals are chemicals of an alternative source (in this case biomass) that are identical to the fossil-based chemicals, and can thus be used in existing processes. This both shortens the transition to this alternative source, and saves the cost of building new infrastructure and market. - It has a relatively high value (see section 9.5) - It has a relatively high chain efficiency compared to other biomass based processes (see section 7.1)

The largest drawback to BTX production from biomass is that it requires biomass, which is only available in a limited amount at a time, and there are more processes/uses that require it (Bergsma, 2010). Given this limitation, the advantages gained by replacing fossil-based processes with biomass- based processes should be optimized by choosing the right processes to be replaced. This research therefore compares environmental gains of the production of BTX from biomass to the gains from alternative uses of biomass.

4 Alternative biomass use In this chapter alternative uses of biomass are expanded upon.

4.1 Choice of biomass As mentioned in the previous chapter, not all biomass feedstocks are considered sustainable. Part of the reason is that many high yielding crops only grow well on agricultural land and thus compete with food production (Bergsma, 2010). Another reason why a biomass feedstock could be considered non-sustainable is that it requires too much energy and material to grow. Intensive crop production requires fertilizers, pesticides and water, which all require energy to either produce or distribute.

This energy, when fossil-based, not only utilizes a non-renewable feedstock but also results in CO 2 emissions.

So sustainable biomass is either a waste stream of food/crop production or can be cultivated in relatively minimal conditions. Biomass that falls within this category is for example straw, corn stover, waste wood or cultivated wood. Incidentally, these feedstocks are also a good feedstock for BTX production. However, this lignocellulosic biomass can be used in other processes as well.

4.2 Uses of lignocellulosic biomass

4.2.1 Raw material Woody biomass has been used as a raw material for thousands of years; timber to build, hemp for rope, and more recently for making paper. Although the sustainability of these uses is important, they are unlikely to show much change in the near future. Since this research is focused on a choice for new uses of biomass, the raw material functions are not considered further.

4.2.2 Electricity and heat Burning woody biomass for heat production is also an age old use. But this is mostly done on a domestic scale in furnaces and stoves, not on an industrial scale. On an industrial scale, the co-firing of power plants with biomass is a growing technology (Bergsma, 2010). Electricity production is one of the main uses of fossil fuels, and accounts for a large share of anthropogenic CO 2 emissions. Although (partly) replacing fossil fuels in power plants with biomass could reduce these emissions, it is a destructive use of biomass that may not get the most value out of the limited supply. Additionally, electricity can also be generated by other renewable resources like wind, water and solar energy. But, since electricity production is so predominant, it will be used in the comparison in this research.

4.2.3 Fuel Transport fuel, unlike electricity, is harder to make from alternative renewable resources (Ladanai & Vinterbäck, 2009). Although hydrogen powered and electric vehicles are under development (or even produced), biomass based fuels are still a sought after technology. Ethanol from sugar reed is used on a very large scale in Brazil; many other countries have a targeted percentage they wish to achieve. One of the problems with biomass-based fuels is that some compete with food supplies and others have drastically low or even negative energy efficiencies, and are thus not very sustainable. The so- called second generation fuels, however, are made from sustainable biomass and could have a positive contribution to decreasing the impact of transportation. Ethanol can also be made from woody biomass, although it is newer technology than the starch-crop based ethanol. Other pathways

19 are conversion to pyrolysis oil, or gasification to syngas with subsequent synthesis of Fischer-Tropsch diesel.

4.2.4 Chemicals Since chemistry is at a level where nearly any compound can be made from very basic starting materials, virtually any chemical can be made from lignocellulosic biomass (Jong, 2012). Within biomass-based chemicals, there are also certain obvious products from certain feedstocks (like ethanol from corn), but in the future integrated bio-refineries could produce a large range of chemicals (and heat and electricity) relatively independent of the feedstock. The more important point is the efficiency with which compounds can be made of a feedstock. But even efficient conversions should be placed in a context, like the sustainability of crop production and the degree of environmental impact of the fossil compound it is replacing.

4.2.5 Other renewables Figure 5 shows a diagram of the basic services that fossil carbon resources provide: heat and materials, which in turn can then also be used for electricity and transport. On the right hand side, various renewable resources and the services they provide are shown. Wind and water power can only provide electricity and transport. Geothermal power can only provide heat. Solar power can provide heat and electricity. Only biomass can provide materials; it is the only renewable source of carbon.

Figure 5: Services from fossil and renewable sources

5 LCA and functional units In this chapter the set-up for the life cycle analysis of biomass-based BTX is described. With this, the functional units can be chosen as well as the production chains for arriving at the functional unit. The next two chapters, six and seven, presents the inventories and results of the life cycle assessments.

5.1 Set-up of the life cycle analysis The goal of this research is to identify the sustainability of biomass-based BTX production. Life cycle analysis, LCA, is a tool that is used to determine the in- and outputs of a product over the chosen life cycle (Finnveden, 2009). Life cycle does not necessarily mean from resource mining to the disposal of the product, an LCA can also be performed from resource mining to the finished product, or just the use phase of an item. The chosen system boundaries should be such that all the relevant stages are taken into account. A proper definition of the functional unit, the product or process under study, is therefore necessary.

As mentioned before (section 3.2), given the limited supply of sustainable biomass, a straightforward comparison between biomass-based and fossil-based BTX would not give any information on whether biomass-based BTX production is the optimal use of sustainable biomass. So aside from an LCA of biomass-based BTX, other biomass-based processes will be considered as well. For each biomass-based process, the fossil-based process will also be analysed, so the savings that a replacement by biomass would give can be calculated. The biomass-based process that would give the biggest savings would be the preferential one, from and environmental point of view.

Although LCA often considers a very large number of impacts, in this research, only fossil resource use, CO 2 emissions and land/biomass use are considered for simplicity sake. But since fossil resource use and CO 2 emissions are the most significant impacts of BTX (see section 2.1) the results are still very relevant. Limiting the impact categories is done more often when larger numbers of processes are considered (Cherubini 2009).

Indirect land use change, CO 2 emissions associated with having to cut down forest to accommodate increased use of cultivated land, is not considered here for simplicity reason. But since the biomass considered is mostly wood, which has a small indirect land use change (ILUC) and nearly all processes would have the same ILUC, this is less relevant (Sanchez, 2012; Cherubini, 2009).

5.2 Choice of processes for the functional units BTX is part of a functional unit, but for the other uses of biomass, choices had to be made. As mentioned in the previous chapter, the choice is limited to products/services that can be made from lignocellulosic biomass, for reasons of sustainability and because this is the obvious choice for BTX production.

From (lignocellulosic) biomass, one can either make energy (either electricity or heat), fuel or materials. In this research, the choice was made to have at least one option from each of those categories in the LCA, so that no value judgement would have to be made between them. It should be noted though that materials are considered more valuable than fuel, and fuel more valuable than energy. But in terms of demand, the fuel sector is the largest, and in terms of readiness level, energy is the most common use of lignocellulosic biomass (Bergsma, 2010).

Within energy, electricity was chosen over heat since electricity is used for a wider range of services and is generated centrally more often. For fuel, diesel was chosen, because the production of diesel from wood (so-called Fischer-Tropsch diesel produced via gasification) is very promising and the fossil-based counterpart is also common. Within BTX, the product ratio should be as is currently the demand, i.e. 67:5:28 (Sweeney, 2008).

For other materials, research into the options from lignocellulosic biomass was performed. Research into biomaterials from lignocellulose is relatively new, because the lignin component is relatively inhomogeneous compared to cellulose or lipids in other biomass (Holladay, 2007). Research is mostly focused still on analysing the product mixtures of treatment steps, rather than on producing single market products. Products and processes can be divided into three groups: those that separate the cellulose and use it as a feedstock, those that separate lignin and use it as a feedstock and those that use lignocellulose as a feedstock (Ma, 2012). Products from cellulose range from PLA and ethanol to furans. From lignin, polymer enhancers are made (keeping the molecule relatively intact) and all sorts of aromatics and cyclical derivatives. From lignocellulose, separate products from the above could also be isolated after, for example, pyrolysis, but another option is also to reduce all starting materials to CO and H 2 (syngas) and use that as a feedstock/starting point for more advanced molecules.

The choice was made to have furandicarboxylic acid (FDCA) as the other material option from lignocellulose. FDCA is a possible replacement of para-xylene in PET (making PEF as an end product), and is currently being commercially developed for biomass-based plastics production (Eerhart, 2012). FDCA is produced from the cellulose component of biomass, through enzymatic and mild acid treatment. Using PEF instead of fossil-based PET could save up to 51% fossil fuel use and up to 54%

CO 2 emissions (Eerhart, 2012).

Aside from FDCA, ethanol from lignocellulose was also considered. Ethanol is also at the base of a range of other chemicals, among them polymers and thus fossil BTX replacements. However, biomass based ethanol is currently mostly used as a fuel, and the fossil-route to ethanol goes via ethylene. Ethylene is used more commonly as a materials precursor. Therefore both ethanol and ethylene were modelled, so as to give a more complete picture.

5.3 Formulation of the functional unit So the chosen processes are:

- Electricity production - Diesel production - Ethanol production - Ethylene production - BTX production - FDCA production

The problem with FDCA production is that though it may be possible to synthesize fossil-based FDCA, but that is probably a far more elaborate process than the biomass based route. At the very least, there exists a fossil-based alternative: para-xylene based terephthalic acid (TA). Thus the choice was made to make a separate comparison between biomass-based FDCA production and biomass-based

22 terephthalic acid production. Since they are stoichiometrically interchangeable for PET/PEF production, the functional unit was 1 mole of FDCA or 1 mole of TA.

The other processes can be based both on biomass and on fossil resources. Although at first the production volume in the functional unit was chosen arbitrarily (e.g. 1 kg ethanol or 1 MJ ethanol from either fossil or biomass resources), a more correct comparison could be made using the biomass processes as a basis for the functional unit. Since the question is what process would give the largest (fossil resource and CO 2 emission) savings for a given amount of biomass, the amount each process could produce from 1 kg of biomass was chosen as the functional units. An earlier example of such savings per unit of biomass LCA is research by Gustavsson et al. (1995). Table 1 shows the result of the output per kilogram of wood calculations.

Table 1: Biomass efficiency and products from 1 kg (higher heating value of 18.5 MJ/kg) of wood (based on own calculations)

biomass efficiency MJ produced kg p roduced electrici ty 0.206 3.814 diesel 0.341 6.309 0.143 ethanol 0.231 4.27 0.144 BTX 0.269 4.98 0.118 ethylene 0.253 4.68 0.098

5.4 System boundaries With the functional units defined both in quantity and quality of products, the life cycle stages that are to be taken into account were defined. Two separate LCA systems were designed, since the comparison between biomass-based BTX and biomass-based FDCA had to be considered separately from the other functional units because FDCA did not have a fossil-based route. As mentioned in the previous paragraph, for this first system the functional unit was one mole of FDCA or one mole of TA production. The unit of mole was chosen because this is a more fair comparison than a weight unit. Having one plastic bottle as the functional unit would also have been a good comparison, but the amount of PEF or PET needed for one bottle is subject to higher uncertainty than the amount of FDCA or TA needed for one mole (which is exact). Only the production phase was considered because the use and waste phase were assumed to be identical for FDCA and TA, since PEF and PET have roughly similar properties. The first LCA system schematically represented in figure 6, and is the subject of chapter 6.

Figure 6: LCA scheme FDCA versus TA

The other LCA system concerns the functional units described in table 1. Initially, only the production phase was considered. But, since electricity produced from fossil fuels is based on the combustion of those fuels and subsequent release of carbon dioxide, there was a bias towards replacing this process. The processes that produce fuel or materials do not emit the contained fossil CO 2 until the use and waste phases. Therefore, for all processes, the use and waste phase were also considered.

The assumption was made, though, that the use and waste phases would be the same for biomass and fossil sourced products. The only item considered different was the fossil CO 2 contained and at some point emitted from the fossil sourced products. So not considered were, for example, transport and distribution of the products, energy needs for the use of them or the impact of the waste phase processing.

The second LCA system is schematically represented in figure 7, and is the subject of chapter 7.

Figure 7: LCA scheme fossil versus biomass

5.5 Production chains from fossil fuel Fossil to BTX: Since production of fossil-based BTX is performed by two relevant ways, reformate (72%) and pyrolysis gas (24%), and global trade is prevalent, a weighted average of the average (so not marginal) impacts and inputs/outputs of the two routes is used (Sweeney, 2008).

(Reforming) From crude oil, a mixture of hydrocarbons with a boiling point in the range of 70-190 oC is obtained by fractioning. This mixture is hydro treated to remove impurities, which are removed by distillation. The feed is then concentrated to limit it to C6-C8 hydrocarbons. After this it is fed to the reformer, which works at high temperature and pressure and with a platinum-rhenium catalyst (Sweeney, 2008). Presumably, a distillation process then separates the products.

(Pyrolysis) In this process, BTX is a by-product of the production of other hydrocarbons, mainly ethylene (Sweeney, 2008).

In this research, data were taken from an average of several European plants.

Fossil to ethylene: Ethylene is produced by cracking the naphta (light hydrocarbon) fraction of crude oil (Korschwitz, 2004).

Fossil to ethanol: Although large amounts of global ethanol are produced through biomass fermentation when destined for consumption, industrial ethanol production proceeds through the hydration of ethylene (catalytically in the vapour phase) (Logsdon, 2004).

Fossil to electricity: There are numerous ways of producing electricity from fossil sources. There is no global trade in electricity but (at least in Europe) there is a regional trade. For the LCA calculations, the average of the Dutch production mix was used.

Fossil to fuel: Since the transport fuel from biomass will be Fischer-Tropsch diesel, diesel will also be used as the fossil-based fuel. Diesel is made of a blend of fractions from crude oil, and requires the additions of additives to give optimal performance (Hochhauser, 2004).

5.6 Production chains from biomass In all the routes below the starting point is wood chips, which also need to be produced themselves. An appropriate type of woodchip was selected from the ecoinvent database.

Biomass to BTX: The most effective way of obtaining BTX from biomass is through catalysed pyrolysis, as demonstrated by Mihalick et al. (2012) and Cheng et al. (2011). Production of BTX from biomass is still at lab/pilot plant scale. It is likely that if it were produced on a large scale, the process and process parameters are different, but for the sake of having a starting point the lab/pilot plant parameters will be used. The woodchips are first torrefied (roasted) to remove moisture and then ground, which requires less energy due to the torrefaction step (Phanphanich & Mani, 2011). After these preparation steps, the ground wood is fed to the catalytic pyrolysis reactor in a continuous feed. Along with the woodchips a catalyst and hot sand go through the reactor. The product gas is removed in vapour form, the sand and char are collected at the end of the screw (Zhong, 2010). The BTX is purified and separated through distillation, and the excess toluene and xylene are hydrodealkylated into benzene, to yield the 67:5:28 ratio that is the current demand (Sweeney, 2008).

Biomass to ethanol: As mentioned above, producing ethanol from biomass is very common. However, ethanol production from wood is less common, since the standard fermentation method does not work with the majority of components in woody biomass without some processing steps (Gnansounou and Dauriat, 2010). The general process of obtaining ethanol from wood contains the following steps: pre-treatment in dilute acid, hydrolysis (which yields cellulose and glucose), fermentation (sometimes in combination with the hydrolysis step) and then concentration of the produced ethanol. Lignin is a solid waste product in the process, since only the cellulose and hemi- cellulose components can be hydrolysed to sugars (Ko, 2012; Treasure, 2012).

Biomass to ethylene: Ethylene production from biomass is already performed commercially in Brazil (Braskem 2012). The feedstock used in that process is sugarcane (via ethanol), in this research the basis will be the ethanol produced from wood, which is then dehydrogenated to ethylene.

Biomass to electricity: Producing electricity from biomass can simply be achieved by burning the biomass in a steam turbine power plant (Patzek & Pimentel, 2005).

Biomass to fuel: Although there is a large array of fuels possible using biomass as a feedstock, FT- diesel is the most energy efficient from woody biomass (Patzek & Pimentel, 2005). FT-diesel is produced in the Fischer-Tropsch process, where a mixture of CO and H 2 is reacted exothermally to produce hydrocarbons. Syngas can be obtained from dry biomass by gasification and subsequent removal of contaminants (Langeveld, 2010).

Biomass to FDCA: Eerhart et al. (2012) have researched the process of producing FDCA from corn. The corn is first processed into fructose, which is then converted to HMF, and subsequently oxygenized to FDCA. Aside from this corn based process, a poplar based process that produces HMF is also considered.

6 LCA of biomass-based FDCA and TA production In this LCA, the production of biomass-based PEF and biomass-based PET is compared. PEF and PET differ only in that PEF is made with the monomer furandicarboxylic acid (FDCA) and PET with the monomer terephthalic acid (TA, or PTA when purified).

6.1 Inventory

Because of the relatively complex LCA model, only the land and fossil resource inputs and the CO 2 outputs are considered, rather than a complete assessment of all the possible emissions and impacts of life cycles. Additionally, although for most processes these data are available in the Ecoinvent database that was used for them, for some of the biomass based processes only limited data is available. Table 2 below gives a summary of the inventory. For a more detailed inventory, see appendix B.

Table 2: Inventory FDCA and TA LCA

Fossil renewable land CO 2 energy energy biomass use emissions Process unit (MJ) (MJ) (MJ (m 2) (kg) ter ephtha lic acid from wood 1 mol e 3,16 0,09 14,98 0, 55 0,17 FDCA from corn 1 mole 2,31 0,00 ? 0,30 0,13 FDCA from poplar 1 mole 3,48 0,00 29,32 1, 07 0,21

6.2 Method For this LCA comparison the functional unit was producing 1 mol of FDCA or 1 mole of TA, and comparing the in- and outputs of the processes (Finnveden, 2009). Mole is a unit that describes amount of chemical substance. 1 mol was chosen rather than 1 kg, because FDCA has a lower mass than TA, whilst on a stoichiometric basis equal amounts are needed to produce one mole of PEF/PET. Using mole as a basis for comparison thus makes sense on a chemical level.

The uncertainty of the data was defined using the pedigree matrix for uncertainty, which gives separate uncertainties for different factors, which are then combined to a single uncertainty factor. These factors were then used to calculate higher and lower values for the calculations (Frischknecht & Jungbluth, 2007).

The sensitivity analysis was performed by calculating what the effect on the end-results was of an increase in certain inputs.

6.3 Results Figure 8 shows the fossil resource use per mole for the different processes. As is evident from the graph, FDCA from corn shows the lowest fossil resource needs, and FDCA from polar the highest. However, within the uncertainty FDCA from poplar could also be the lowest, and FDCA from corn the highest in fossil resource use. For the biomass-based TA process, the production of xylene only accounts for slightly over 1/3 of the emissions and fossil resource use. The oxidation of xylene to terephthalic acid has a far bigger impact, since it is an energy intensive process (see appendix B).

Fossil resource use in MJ in use resource Fossil 0 Teraphtallic FDCA from FDCA from acid from corn poplar wood

Figure 8: Fossil resource use in MJ per mole

Figure 9 shows the CO 2 emissions per mole of the different processes, again showing corn based FDCA to perform the best and poplar FDCA to perform the poorest. Again, within the uncertainty margin, the order of performance could be entirely the reverse. As with the fossil resource use, the oxidation of xylene accounts for more than half of the impact/emissions.

0,35

0,3

0,25

0,2

0,15

CO2 emissions CO2 0,1

0,05

0 Teraphtallic FDCA from FDCA from acid from corn poplar wood

Figure 9: CO 2 emissions per mole of product

Figure 10 shows the land use per mole of the different processes, again showing FDCA from corn performing the best and FDCA from poplar the worst. Here, the uncertainty is smaller, so even near the extremes FDCA from poplar still has the most land use and FDCA from corn the least.

1,8 1,6 1,4 1,2 1 0,8 0,6 land use in m2 in use land 0,4 0,2 0 Teraphtallic FDCA from FDCA from acid from corn poplar wood

Figure 10: Land use per mole of product

The reason FDCA from poplar performs poorly is that the HMF yield from poplar is very low. The process thus requires a lot of biomass input, with its associated energy requirements and CO 2 emissions.

It is important to note, though, that the biomass-based BTX process could also use waste streams as a feedstock. This would mean that the land use is virtually non-existent, which is a distinct advantages over processes that require quite specific feedstocks, like the FDCA process.

The results of the sensitivity analysis are shown in appendix D. In summary the results are:

- The FDCA process, which uses only direct in- and output data for the whole process, is entirely dependent on these data (as expected)

- For the CO 2 emissions of TA production, the TA process (oxidation of xylene) is most important - For the land use of TA production, the amount of biomass needed for BTX production is most important - For the fossil resource use of TA production, again the TA process is the most important

- For the CO 2 emissions of FDCA from poplar production, the emissions of the oxidation of HMF and the emissions of extracting the HMF are the most important. - For the land use of FDCA from poplar production, the amount of HMF obtainable from wood is most important - For the fossil resource use of FDCA from poplar production, the resource use of the oxidation of HMF and the resource use of extracting the HMF are the most important.

So improvements in the TA process would be most beneficial for the sustainability of TA production, and improvements in the oxidation of HMF and the extraction of HMF from wood would be most beneficial for the sustainability of the FDCA from poplar process.

6.4 Inventory discussion For TA from wood and FDCA from poplar, it was assumed that the higher heating value of the used biomass is 18.5 MJ/kg, in practice there is variation in the HHV of woody biomass.

6.4.1 Terephthalic acid from wood The discussion points for biomass-based BTX production also apply to this process.

A xylene isomerisation step is not included here because of the specific data on BTX yields used in the inventory; the conditions used by Mihalick et al. yield para-xylene almost exclusively.

The whole production process from biomass pyrolysis to terephthalic acid production combined will probably give more opportunity for heat management, reducing the amount of fossil resources needed and CO 2 emitted.

6.4.2 FDCA from corn

The energy needs and CO 2 emissions associated with corn production and milling into glucose used in the source are on the low side. Although part of this is due to the combustion of waste streams for process energy, offsetting some of the fossil resource need and CO 2 emissions, the data used in the source article are lower compared to other data found in Ecoinvent for starch from corn in Germany.

CO 2 emissions associated with indirect land use change (ILUC) were not taken into account here, since the ILUC emissions were not given for the other feedstocks either. However, in the source material (Eerhart et al, 2012) it was calculated that ILUC can add up to 0.7 kg of CO 2 per kg of PEF produced. This translates to 0.81 kg CO 2 per kg of FDCA (the ILUC is associated with just FDCA production, not the rest of the PEF production; per kg PEF 0.86 kg FDCA is needed). Per mole of

FDCA, the functional unit of the LCA, this doubles the value from 0.13 to 0.26 kg CO 2 per kg CO 2 produced, which is significantly higher than the CO2 emissions of biomass-based TA production. Although the production of woody biomass for this TA production can also add some ILUC emissions, these are generally lower than the corn ILUC emissions. So taking ILUC into account it is likely that production of FDCA from corn would have higher CO 2 emissions than TA from wood.

6.4.3 FDCA from poplar The data used for the HMF yield from poplar were on a preliminary research paper (Yang, 2012), in the future HMF yields from poplar can probably be optimized. However, the value used in the calculations for the energy requirements of the production of HMF from poplar are possibly an order of magnitude too low, since they were based on the mass of the product rather than the mass of the input. Since part of the process is acid-hydrolysis of the biomass, the energy requirement is significant.

7.0 Biomass versus fossil LCA In this LCA, several the biomass-based and fossil-based processes of several functional units are modelled. The goal was to compare the savings in fossil resource use and CO 2 emissions that the replacement with a biomass-based process could achieve, in order to assess which use of biomass would be the most sustainable. The functional units under consideration are electricity, diesel, ethanol, BTX and ethylene. The volume of each product to be produced in the functional unit is dependent on the efficiency of biomass conversion of the process (see paragraph 5.3).

7.1 Inventory

Because of the relatively complex LCA model, only the land and fossil resource inputs and the CO 2 outputs are considered, rather than a complete assessment of all the possible emissions and impacts of life cycles. Additionally, although for most processes these data are available in the Ecoinvent database that was used for them, for some of the biomass based processes only limited data is available. Table 3 shows the inventory of the production phase used for the calculations. The source of the data and assumptions behind them are further expanded upon in appendix B.

Table 3: inventory of the LCA

Product/process IN OUT Efficiency

2 value unit fossil resources renewable (biomass) land CO emissions Energy product Energy efficiency Biomass efficiency MJ MJ MJ m2 kg MJ Fossil electricity 1 MJ 2.13 0.13 1 0.46 Fossil diesel 1 kg 50 .3 0.1 0.05 0.44 45 .7 0.90 Fossil ethanol 1 kg 44 .4 0.3 0.09 1.06 29 .8 0.67 Fossil BTX (67:5:28) 1 kg 62 .8 0.2 1.40 41 .8 0.66 fossil ethylene 1 kg 60 .7 1.10 48 0.79

Biomass electricity 1 MJ 0.50 0.04 4.85 0.17 0.04 1 0.19 0.21 Biomass FT -diesel 1 kg 6.30 134 4.77 0.38 45 .7 0.33 0.34 Biomass ethanol 1 kg 6.33 106 3.78 0.39 29 .8 0.26 0.28 Biomass BTX 1 kg 11.0 0 155.4 5.69 0.72 41 .8 0.25 0.27 Biomass ethylene 1 kg 21.6 189 6.74 1.42 48 0.25 0.27

Table 4 shows the fossil CO 2 emissions in the use and waste phase. As mentioned in chapter 5, because the biomass-based and fossil-based products are assumed to be identical in how they are used and disposed of, only the fossil emissions due to combustion of the product are relevant.

Diesel and ethanol, used as fuel, are combusted in their use phase, producing fossil CO 2. Biomass- based ethanol and FT-diesel only emit biogenic CO 2 in the use phase. It is assumed that BTX and ethylene are used to produce plastics, and that the use phase does not differ for biomass-based and fossil based BTX and ethylene plastics. However, when they are incinerated in the waste phase, fossil based BTX and ethylene plastics will result in fossil CO 2 emissions.

Table 4: Use and waste phase CO 2 emissions in kg and electricity that can be generated in the waste phase in MJ. Both are per kg of wood input. (based on own calculations)

MJ produced Use phase Waste phase Electricity emissions (kg) emissions (kg) generated (MJ) electricity 3.81 - - diesel 6.31 0.452 - ethanol 4.27 0.275 - BTX 4.98 - 0.399 0.585 ethylene 4.68 - 0.370 0.479

Table 5 shows the value per MJ of the different products. This is different from the value of the processes, because the BTX and ethylene processes in their lifetime also produce electricity during waste incineration. The amount of electricity produced is based on the amount of product, which by the waste phase is assumed to have a combustion energy of 20.5 MJ/kg (HHV of PET, which both xylene and ethylene are part of) and the incinerator is assumed to have an energy efficiency of 24% (calculation by KNN advies b.v.).

Table 5: value of the products per MJ in 2012 euros (calculated from ICIS (2012) and Agentschap NL (2012))

value (euro/MJ) electricity 0,0 19 diesel 0,017 ethanol 0,019 BTX 0,019 ethylene 0,021

7.2 Methods

In this LCA, the best use for biomass is determined by comparing the fossil resource and CO 2 emissions savings that can be achieved by using 1 kg of wood (HHV= 18.5MJ/kg) different ways. Table 4 shows the biomass efficiency (HHV product/HHV wood), and how much is therefore produced per process. The fossil resource needs and CO 2 emissions associated with producing these amounts of product via the biomass-based route are then subtracted from the fossil resource needs and CO 2 emissions associated with producing the same amount from biomass.

For example, electricity can be produced from wood with 20.6% energy efficiency (higher heating value), thus 1 kg of wood yields 3.81 MJ electricity. Producing 3.81 MJ electricity from biomass is associated with 0.15 kg CO 2 emissions, whilst producing 3.81 MJ from fossil resources is associated with 0.5 kg CO 2 emissions. So by spending 1 kg of wood on electricity production, 0.35 kg of CO 2 emissions can be avoided.

The sensitivity analysis was performed by calculating what the effect on the end-results was of an increase in certain inputs.

7.3 Results Unlike in the previous chapter, where the graphs represented emissions and land a fossil resource use, the main results in this chapter are represented in savings achieved by replacing fossil processes with biomass-based processes. So while in the previous chapter small numbers/bars were considered good (since they represent smaller resource uses and emissions), in this chapter larger bars/numbers are better since they represent larger savings.

Table 6 shows the fossil resources and CO 2 emissions saved by producing each functional unit from biomass instead of fossil resources.

Table 6: fossil and CO 2 savings resulting from producing the functional unit from biomass

MJ produced Fossil resources saved CO 2 emissions saved in MJ in kg electricity 3.81 6.22 0.351 diesel 6.31 6.31 0.461 ethanol 4.27 5.48 0.371 BTX 4.98 6.17 0.481 ethylene 4.68 5.17 0.364

Figure 10 shows the fossil resource savings resulting from replacing the fossil resource based processes with biomass-based processes. As is evident from the graph, ethanol and ethylene show the smallest savings, and from a fossil resource conserving point of view should be the last processes to be replaced by biomass. Biomass-based FT-diesel results in the greatest saving, although electricity, diesel and BTX all give virtually the same savings.

However, the error margins for all functional units except ethylene are large. This is mainly due to uncertainty in the biomass-based processes, but the uncertainty of the fossil-based processes also contributes, especially for BTX. BTX has a large positive error margin, and since the process is far from optimized it is more likely to achieve greater savings than calculated here.

6 in MJ 4

0 Fossil Fossil resource savings per kg woof input

Figure 10: Fossil resource savings per kg of wood input

Figure 11 shows the CO 2 emission savings resulting from replacing the fossil resource based processes with biomass-based processes. Here, the biomass-based BTX gives the greatest savings, with biomass-based FT-diesel close behind. Biomass-based electricity, ethanol and ethylene show lower savings. So from a CO 2 limiting point of view, BTX should be the first process to be replaced with biomass.

The error margins are also large with these results, but since the differences between the savings achieved is bigger, it is likely that the calculated order of largest savings will remain as it is. The difference in ratios between the CO 2 emission savings and the fossil resource savings is due to the fact that fossil diesel and BTX production have a relatively high CO 2 output per unit of product compared to the fossil resource input. A reason for this could be a higher use of coal in the process.

0,8 0,7 0,6 0,5 0,4

in kg in 0,3 0,2 0,1 CO2 saving per kg wood input wood kg per saving CO2 0

Figure 11: CO 2 savings per kg of wood input

Figure 12 shows the value that can be generated from a kilogram of wood. For BTX and ethylene, this includes value from generating electricity during waste incineration. The BTX process generates the largest amount of value per kg of wood, but the ethylene and FT-diesel processes generate about the same. Ethanol production from biomass generates the least value per kg of wood.

Figuur 12: value generated per process per kg of wood

The results of the sensitivity analysis are shown in appendix E. In summary they are:

- For all biomass-based processes, the amount of biomass needed to produce a given amount of product is very important for the resulting savings. This is due to the fact that the biomass efficiency determines the volume of the functional unit, and if this volume is larger the inputs and emissions of the fossil-based routes in the system also increases, and those in-puts and outputs are important for the result.

- For the fossil-based processes, the fossil-resource use of the electricity and ethylene routes

are relatively important, as are the CO 2 emissions of the electricity, ethanol and ethylene routes for the achieved savings.

- The individual process steps of the biomass-based BTX process have a small contribution.

So increasing the conversion efficiency of the biomass-based processes is very important for their sustainability.

7.4 Inventory discussion For all biomass-based processes, it was assumed that the higher heating value of the used biomass is 18.5 MJ/kg, in reality there is variation in the HHV of woody biomass.

7.4.1 Fossil-based electricity The data used are based on average Dutch electricity production, even though marginal data are formally more appropriate here, since this is choice based LCA. However, biomass-based electricity would be base load electricity rather than peak load, the latter is used for marginal data.

Rather than data of the Dutch electricity production, average European electricity could have been used, to widen the region on which the results are applicable. Indeed, most of the processes in the inventory are based on European or Swiss data.

7.4.2 Biomass-based electricity The used data are from a Swiss plant using softwood pellets, there is probably some variation if other wood is used or a different type of plant. There could possibly be some improvement in efficiency as the technology matures.

7.4.3 Fossil-based diesel Since this is very mature technology, the data is assumed to have a high degree of certainty, although there is probably also a very slight variation based on region and feedstock.

7.4.4 Biomass-based FT-diesel As mentioned in the inventory, the Fischer-Tropsch step is modelled minimally as only an energy conversion step. On the one hand, there are probably fossil resource needs and CO 2 emissions related to process steps and plant construction/catalyst production. On the other hand, the heat generated during the process is not taken into account; this could lead to efficiency improvements of the whole production chain.

Additionally, while the assumption is made here that Fischer-Tropsch diesel has the same higher heating value as commercial petroleum diesel, in practice there are some differences (<10%) (Sunde, 2011).

7.4.5 Fossil based ethanol Whilst the data for the production process are assumed to be very certain, the use of fossil produced ethanol as fuel is rare.

7.4.6 Biomass-based ethanol The Ecoinvent dataset uses the average ethanol yield from wood reported in literature, rather than the maximum, which is about 7 percentage points higher in efficiency.

7.4.7 Fossil based BTX Since this is very mature technology, the data is assumed to have high certainty, although there is probably also a very slight variation based on region and feedstock.

7.4.8 Biomass-based BTX The loss of mass and increase in HHV of the resulting biomass during torrefaction is not taken into account.

The ratio between products and yield of BTX depends on the type of wood used. Lower yields resulting from a different feedstock would invariably mean that BTX performs less well, although it should be noted that all the biomass-based processes have this problem. The ratio differences will have an influence on how much processing after the pyrolysis step is necessary, as mentioned before all five products are already commercially transformed into one another depending at different plants.

The power supply during pyrolysis is based on the data used for “fossil based electricity”, which, as mentioned there, may not be the correct choice.

The CO 2 emissions associated with the fossil energy requirement of the BTX distillation and hydrodealkylation are assumed to be equal to combustion of an equal amount of diesel. In industrial

36 processes, coal or other fossil fuels are also used to power processes, leading to a different CO 2 emission factor.

The hydrodealkylation step produces methane, which could be used to provide process energy. For the production of 1 kg of BTX, this could be 6 MJ, about 60% of the fossil energy requirement.

In this inventory the wood feedstock was chipped, then torrefied, then ground. It has not been determined what the optimal feedstock is or whether torrefaction would negatively impact the BTX yield. However, the sensitivity analysis shows that these processes are of little impact on the results, so there is leeway for a different feedstock preparation process.

7.4.9 Fossil based ethylene Since this is very mature technology, the data is assumed to have a high degree of certainty, although there is probably also a very slight variation based on region and feedstock.

7.4.10 Biomass based ethylene Although the lowest estimate of energy requirement needed for dehydration of ethanol was used, it is still relatively high energy requirement compared to the fossil energy requirement of ethanol production itself. But it is comparable to values found in literature for the dehydration of ethanol to ethylene (Liptow & Tillman, 2009).

The dehydration of ethanol costs energy and the hydrogenation of ethylene releases energy. The fossil based ethylene process, which cracks ethylene directly, has a lower process CO 2 emissions than the biomass-based ethylene process, that requires the ethanol dehydrogenation step. However, since the lifetime CO 2 emissions and fossil resource requirements are higher, the overall environmental impact of fossil-based ethylene is higher than that of biomass-based ethylene.

8.0 Discussion LCA results In this chapter the results of the two LCA’s are discussed, following which in chapter 9, the macro- effects that could influence the outcome are presented.

8.1 Outcome of the LCA’s The first LCA, which compared the production of terephthalic acid and furandicarboxylic acid from biomass, showed that the TA route from biomass performed slightly worse on all accounts than the FDCA route from corn, but better on all accounts than FDCA from poplar. Since TA production is a major product of BTX, this is important for assessing the sustainability of biomass based BTX production. However, since FDCA production requires a starch rich feedstock, which is usually less sustainable than wood or waste streams, TA production is probably more favourable on a big scale. The oxidation of xylene to terephthalic acid has the largest impact, bigger than all the steps of biomass-based xylene production, and research into lowering this impact is therefore also an important step towards sustainability.

The second LCA, which compared the fossil resource use and CO 2 emission savings of replacing several fossil-based processes with biomass-based processes, was favourable for biomass-based BTX on all accounts. However, biomass-based diesel performed about equally well, and the error margins were large enough and the savings of each route close enough together such that the calculations may perhaps not be properly reflecting the actual situation.

So overall the production of biomass-based BTX is relatively sustainable, compared to other uses of land/biomass. But since the uncertainty margins are rather large and some other uses of the biomass uses perform (slightly) better than BTX, an analysis of which direction of the margins will go most likely is necessary.

8.2 Correlation in the margins Although the margins are large, they are correlated to some extent. First of all, between electricity and biomass-based BTX production are directly related, since biomass-based BTX production has an electricity input. So if electricity production were to become more sustainable, the savings that biomass-based electricity would yield are smaller, whilst the biomass-based BTX production would give larger savings compared to fossil-based BTX production. It is safe to assume, though, that most processes in the LCA even the fossil-based processes use some to a significant amount of electricity.

There is also probably correlation between the yields of products from biomass, with all of the biomass-based processes having some potential for improvement. However, for the newer technologies (BTX, ethanol/ethylene and FT-diesel) this potential is probably higher than for electricity production.

Finally, there is correlation due to the fact that the uncertainty margins were determined by the author using the Pedigree matrix. While this method gives a good backbone for determining uncertainty, it is still subject to some judgement, and therefore there is a correlation due to the harshness of this judgement.

8.3 Electricity differences Among the fossil based processes, electricity production is most likely to change or be an inaccurate representation. Since electricity production originate from so many sources, it differs greatly in

39 emissions and resource needs per country (Dones, 2004). Whilst in some European countries there are a lot of inefficient coal fired power plants, in others electricity production is almost entirely based on renewable resources. Therefore the choice of region in the LCA is quite important, especially since this is also an important factor in the outcome of the second LCA. There is also a trend towards sustainability in electricity production in Europe, as wind and solar energy are becoming more popular with the consumer (Kitzing, 2012). So whilst at the moment electricity production in some parts of Europe may be less sustainable than the current Dutch electricity production, in the long term electricity production it is likely to be more sustainable in general, making the substitution with biomass-based electricity less favourable.

However, the biomass-based BTX process would become more favourable if electricity were more sustainable, since in this research the electricity need of the BTX process was met by the fossil-based electricity. Since the fossil-based electricity actually reflects the Dutch productivity mix, a change in its in- and outputs would correspond to a change in the in- and outputs of the biomass-based BTX process.

9.0 Macro scale effects In this chapter, the various macro scale effects are assessed, as well as their influence on the outcome of the LCA’s is.

9.1 Using waste streams as feedstock This paragraph deals with the possibility of using waste streams rather than virgin material as a feedstock.

9.1.1 Advantages of using waste streams The advantages of using waste streams as a feedstocks are two-fold: it saves the resources needed for producing virgin material, and it generates value from an otherwise invaluable stream (Campbell & Block, 2010).

For biomass-based processes, this means that the land requirement is negligible, which lowers competition with food-crop production. Aside from land, the water, energy and materials/fertilizer needed for production are also avoided. Usually, the processing of waste streams into feedstock also requires some resources, but for plenty of waste streams this resource input is smaller than the resources needed to produce virgin feedstocks. So using waste streams may make processes more sustainable.

The generation of value from waste streams is not so much an environmental advantage as it is an economic advantage. Although biomass waste is usually already used in some capacity, it is mostly in low value products. New technologies such as BTX production could increase the value gained, and a higher value also gives the opportunity to use harder to process waste streams that would otherwise be too expensive to use. But since waste streams are low in value and sometimes a burden to dispose of, there is a push-effect from the waste producer to engage in new technology. This could be an incentive to introduce biomass-based processes faster, resulting in environmental benefits, provided the biomass-based route is more sustainable than the alternative fossil-based route.

9.1.2 Processes with feedstock flexibility Not all biomass-based processes are flexible in the type of feedstock the can use. Processes that use certain inherent structures in the biomass, such as sugars or oils, need the feedstock to be high enough in those structures in order to be profitable (Campbell & Block, 2010) The processes considered in this research that could use waste streams are the biomass-based electricity, FT-diesel and BTX/TA-processes. The electricity process can use any dried biomass, since it is combusted and only the heat of that process is used to generate electricity, the structure of the biomass is unimportant. The FT-diesel process uses gasification to first reduce the biomass to CO and H 2 (and other gasses). Whilst there is some variation in the quantity and ratio of the product gasses depending on the structure of the feedstock, the process is relatively flexible. The BTX process is also relatively flexible, even though the lignin content of the feedstock may be important to the yield. However, biomass waste streams tend to be high in lignin content, since this is the biomass component that is least useful for other processes such as food and oils.

The ethanol/ethylene and FDCA processes are less flexible to the feedstock. These processes are heavily dependent on the sugar/cellulose content of the feedstock. For the FDCA process, this is because the final product is derived from a sugar molecule. For the ethanol/ethylene process, the ethanol is produced by fermentation of sugar. As mentioned before, waste streams tend to be high

41 in lignin and are usually low in sugar content, making them unsuitable for such processes. Additionally, because these processes use bacteria, enzymes and yeasts, the feedstock has to be such that it does not kill or deactivate the organisms and enzymes.

It should be noted, that the fossil based processes considered in this report are currently not adapted to waste streams, except for electricity production. The latter will be explored further on in this chapter.

So the FT-diesel, electricity and BTX/TA process have the potential to become more sustainable through the use of waste streams, whilst the ethanol/ethylene process and FDCA production are limited to high starch-content feedstocks.

9.2 Future trends in the petroleum market In this paragraph, the future trends in the petroleum market and their effect on the results of this report are explored. This is only a short overview; an upcoming report by KNN advies b.v. will look further into the economic outlook of BTX on the market.

With fossil resources declining, prices of petroleum products increase, although not always linearly (Cherubini, 2010). For BTX production, the price-trend is complicated by the fact that toluene and xylene can also be mixed with transport fuel, which occurs more when fuel prices are high (or indeed the demand for BTX is low) (PPE, 2012). But in general, it can be said that increases in the price of fossil resource will be an incentive to use biomass-based processes. Either through a direct increase in the price of the product, or because of an indirect price change because of a lowered demand in the process that the product is a by-stream of.

Aside from this economic change, there can also be a change in the environmental impact of the fossil-based resources. Some products could be made from coal rather than oil. Since coal has a higher carbon content than the other fossil resources, the carbon emissions from those processes (over their lifetime) will be higher than for oil and gas based processes (Brandt & Farrel, 2007). This effect is enhanced by the fact that coal has to be mined, which is more damaging to the environment (and humans) than extracting oil and gas from the land. This means that the savings of using a biomass-based process would be even greater. Coal is already used to produce electricity and BTX, although production of diesel and ethylene from coal is also technically possible.

Another transition within the petroleum industry is the (partial) transition to shale gas (ICIS, 2012). Shale gas is natural gas trapped in shale, a mud-type layer. It is expected that shale gas use will rapidly increase in the coming decades, since conventional natural gas resources are depleting. Whilst some products are expected to become cheaper, such as electricity and ethylene (and thus also ethanol), the prices of BTX and other refinery products are not likely to become lower. This is because part of the crackers that produce BTX are expected to shut down with the rise of shale gas (ICIS, 2012).

So future trends in fossil resources may increase interest in all biomass-based processes. But BTX is affected both by the transition to coal and the transition to shale gas, while ethanol/ethylene is expected to undergo the least change.

9.3 Renewable alternatives As mentioned in chapter 2, for some of the fossil-based processes/products there is a variety of renewable alternatives (McKinney, 2007). Figure 13 shows, once again, a schematic overview of the fossil-based products and their renewable alternatives.

Figure 13: services from biomass and fossil resources

In this research, six products were considered: electricity, diesel, ethanol, ethylene, FDCA and BTX. If diesel and ethanol are considered purely as transport, than electricity, diesel and ethanol also have other renewable options. Ethylene, FDCA and BTX, being materials, need either fossil or biomass feedstocks to provide the carbon sequestered in them.

With only a limited amount of renewable biomass available, it makes sense to utilize it for products that have no renewable alternatives. The amount of solar energy received on earth is theoretically abundant to provide all the energy humans use. In practice, there are logistic, economic, and cultural restraints to switching entirely to solar energy. But the long term plan should be to focus biomass resources on materials use as long as this is not less sustainable than using it for other processes. In this research, it was concluded that using it for materials is a relatively good choice, although the processes could benefit from improvement. The next question is whether the renewable alternatives for the processes that are not biomass-based are sustainable. The overall answer is yes (McKinney, 2007).

9.4 Corn as a feedstock As mentioned before, using corn as a feedstock for non-food processes is a threat to global food resources (Pimentel, 2003). High yield food crops, such as corn, require fertile soil. Whilst with irrigation and fertilizer and other auxiliaries the amount of agricultural land can be expanded somewhat, new agricultural land is largely made by cutting down (rain) forest. Since this may lead to an increase greenhouse gas emissions and a decrease in biodiversity it is considered unsustainable. Although globally there is enough food per capita, for a variety of reasons, in practice there still a substantial incidence of famine (McKinney, 2007). This is only expected to increase in the coming decades due to population increases and droughts, despite the also anticipated increases in some agricultural yields. It would therefore be unethical to strive to increase substantially the share of non- food uses of agricultural land.

The impact of this on the production of FDCA from corn is that while on a small scale it is relatively sustainable; on a large scale it is undesirable due to food shortages and environmental reasons.

9.5 Cascading and recycling Figure 14 shows the value pyramid for utilities used in society. At the top are pharmaceuticals, followed by specialty chemicals, followed by food, followed by materials (such as clothing, timber, plastic bags) followed by fuel, with electricity and heat at the bottom (Bergsma, 2010).

pharmaceuticals chemicals food materials fuel electricity heat

Figure 14: value pyramid utilities

While the value is highest at the top, the volume of production is largest at the bottom. Producing medicines is relatively difficult, producing heat is easy. In paragraph 9.3 it was mentioned that manufacturing products from the upper part of the pyramid is a good use of biomass since it is the only renewable source of carbon. Making products from the top of the pyramid is also useful because of “cascading”, in which biomass (or another resource) is first used to make products for which high quality or a specific feedstock is needed, and then using waste streams of that process to generate products lower in the pyramid.

For example, although this is quite a specifically excellent example, from a taxus tree one could first extract the specific structures in the plant that make cancer medication, then use the rest of the tree in a pyrolysis process to produce chemicals and plastics (Yazdani, 2005). When those plastics are collected, they could then be used in building materials such as for insolation purposes. If this is then disposed of, the waste could be incinerated to generate electricity and heat. With such a process, almost the entire value pyramid is catered to. Whilst if electricity was directly produced, other resources would have to be employed to produce other parts of the pyramid.

Aside from cascading, recycling is also a way to get more out of a resource (McKinney, 2007). Recycling of chemicals and materials is increasingly used as a way to limit resource use and environmental burdens. Although recycling requires a well-functioning logistics network to separate and reprocess materials and chemicals, it is often worth the effort. And even though, for example, recycling plastics is a difficult process because not all plastics can easily be reprocessed, there is still more potential than for recycling fuel, heat and electricity. Once the latter three are used, they cannot be recovered since they are simply spent.

So producing ethylene, FDCA and BTX/TA from biomass has a distinct advantage over producing fuel and electricity, since the former can be part of a cascading or recycling chain, making the most of the resources.

9.6 Scale potential In this paragraph the potential of the different biomass-based processes is calculated, based on the amount of available sustainable biomass in 2020-2030. Whether or not all of this biomass is suitable as a feedstock is at first not considered, the assessment is only based on the conversion efficiency.

The sustainable biomass potential is a point of discussion, since it is partly based on assumptions and not all researches take the same constraints into account. Assumptions have to be made on how yield increases will develop and how much land will be used. Constraints on how much land is needed for food crop production are also not universally accepted. Therefore, a high and a low estimate are used. The conservative estimate for the global sustainable biomass potential in 2020- 2030 is 33 EJ, the optimistic 100 EJ (Bergsma, 2010).

Table 7 shows the resulting possible amounts of product that can be produced from this biomass. Obviously, not all the renewable biomass resources will ever be used for a single process, but these calculations do give an estimate of scale. Aside from the production potential, the current use of the products is given, which for most products is currently based on fossil resources (except for ethanol).

Table 7: production potential based on available sustainable biomass

Product conversion low estimate high estimate current use efficiency (EJ) (EJ) (EJ) electricity 20.6% 6.8 20.6 70.9 diesel 34.1% 11.3 34.1 25.2 ethanol 23.1% 7.6 23.1 2.4 ethylene 25.3% 8.4 25.3 5.2 BTX 26.9% 8.9 26.9 4.6

As is evident from the table, the world demand for ethanol, ethylene and BTX could theoretically be made met by biomass, although it would require a significant amount when the lower estimate is correct. Diesel demand could be met, if the renewable biomass volume is higher than the average estimated potential. Electricity demand is too great to be met by biomass, with even the high estimate case being less than a third of the demand.

What direction the ratio of biomass use will go cannot directly be predicted by these figures. However, looking at a combination of the value and the demand, an estimate is made here nonetheless.

Although electricity is a low value use of biomass, see figure 14, the demand is so high that a large share of biomass will probably go to electricity production, especially since biomass can be used as a back-up or co-firing feedstock for coal and waste incineration plants.

Ethanol is also a relatively low value use of biomass, but is currently one of the larger shares, because it is relatively straightforward to produce, and the changes required in the transport system to accommodate ethanol are relatively small (Campbell & Block, 2010). But since it has a relatively

45 lower value and its sustainability is under discussion, it is not expected that ethanol production from biomass will grow a lot.

FT-diesel from biomass, on the other hand, is expected to grow quite a lot, since research shows that, when made from sustainable biomass, it is one of the most sustainable fuels available.(Swain, 2011) It is also high in value and demand, although there would probably be some logistic barriers to be overcome.

Ethylene and BTX are both relatively high value uses of biomass with a sizeable demand, they could therefore potentially form an important part of biomass use, especially when fossil resources dwindle. But since their market are relatively small in size (compared to fuel and electricity), it is unlikely that they will form a major part of biomass use, unless fossil alternatives would be non- existent. For smaller scale production BTX has an advantage over ethylene production, because BTX (liquids) are easier to store and handle than ethylene (gas).

Although it is hard to predict how the biomass-based market will develop, it can be concluded that in a cautiously optimistic scenario, BTX, ethylene and ethanol could all be made from sustainable biomass, but electricity and electricity will probably become the major uses.

9.7 Conclusion Table 8 shows a summary of this chapter, for each biomass-based process. The second column shows whether or not waste streams can be used for the process; the third column shows whether the trends in the petroleum market are beneficial for the future of the biomass-based process or not; the fourth column shows whether or not there are renewable alternatives; the fifth column shows whether the process needs a food crop as a feedstock; the sixth column shows whether the process has cascading or recycling potential; the seventh column shows whether a significant amount of the global demand could be met in the future using sustainable biomass resources.

Table 8: Summary of this chapter

can use petroleum renewable corn/food cascading/ demand waste market alternatives crop recycling steams trends feedstock potential electricity yes beneficial yes no no high diesel yes beneficial indirect no no moderate ethanol no neutral indirect sometimes no low ethylene no neutral no sometimes yes low BTX/TA yes very no no yes low beneficial FDCA no very no yes yes - beneficial

In order to show this more clearly, the entries in the previous table were converted to scores, with a poor quality (such as the inability to use waste streams) being scored a -1, a good quality (such as the ability to be recycled) a +1, and neutral or ambiguous ones scored a 0. The results are shown in table 9, along with the total of the score. The demand is considered neutral, “0”, for all, since it is not considered a positive or negative macro effect.

Table 9: Numerical summary of this chapter, the demand column is not used in the total

can use petroleum renewable corn/food cascading/ demand TOTAL waste market alternatives crop recycling steams trends feedstock potential electricity 1 1 -1 1 -1 0 1 diesel 1 1 0 1 -1 0 2 ethanol -1 0 0 0 -1 0 -2 ethylene -1 0 1 0 1 0 1 BTX/TA 1 1 1 1 1 0 5 FDCA -1 1 1 -1 1 0 1

This is of course a simplification of the conclusions drawn above, and not all the different qualities should count the same. But we can conclude that the production of BTX from biomass has many attractive qualities, whilst the production of ethanol is not that attractive. Diesel production scores second best, whilst electricity, ethylene and FDCA score somewhere in-between. There are probably more large scale trends and effects that affect these processes, in this analysis, biomass-based BTX production seems very promising in this analysis.

10 Discussion The first paragraph discusses the research in general; the second compares the results of this research with the results by other authors.

10.1 General discussion In this general discussion the overall approach to the research is discussed, as well as a summarized discussion of the LCA’s and macro effects. The aim of this research was to assess whether or not production of biomass-based BTX is sustainable. The research questions (section 1.2) were all answered to some extent.

In chapter two, the choice was made to model the impact of fossil based BTX by modelling a polystyrene cup, since polystyrene is one of the major products made with BTX. But since polystyrene is only one of a very large range of possible end-products, this is not entirely representative of the whole spectrum. Choosing a pharmaceutical or longer life material or even a fuel derived from BTX, the impacts would probably be different. However, since there was such a clear indication that fossil resource use and greenhouse gas emissions were the most important impacts that the author deems it likely that this will be the trend for most BTX products. Furthermore, while polymers are not the only product from BTX, they are the main product and the target product for biomass-based BTX and are therefore the most obvious choice to study. Therefore, the choice of modelling a polystyrene cup as a representative of BTX products was reasonable.

For the discussion into what alternative uses of woody biomass there are, the choice was made to limit the categories and products under consideration, for simplicity sake. There are likely to be other important uses of woody biomass, but the products under consideration all had high volume fossil counterparts (except for FDCA), and were therefore relevant to study. Secondly, products within the same categories and with similar biomass conversion efficiencies probably give similar results, since in this research the results are even relatively close between different categories.

For the choice of which biomass-based routes were included in the LCA’s, choices were partly based on what information was available. Since the Ecoinvent database is convenient and relatively reliable and consistent, where possible it was employed, although this might mean that in some cases the data were more specific to a single plant rather than the general trend. Additionally, other choices were also slightly arbitrary, choosing diesel over gasoline and the choice of Dutch electricity production over European electricity production.

In the inventory, a higher heating value of 18.5 MJ/kg was used for all woody biomass, whilst in practice there is some variation depending on the type of wood and whether or not it has been dried. Although this would alter the results somewhat, overall it would create little relative changes between the savings of the biomass-based process, since they would all change by about the same amount.

In this research, the only impacts considered were fossil resource use and CO 2 emissions, and for the

FDCA/TA LCA, land. The other impacts, such as acidification potential, toxicity or indeed non-CO 2 greenhouse gas emissions were not taken into account, to keep the LCA’s simple. Including the other impacts could very well change the relative performances of the biomass-based processes.

The data used in this research were average rather than marginal data; this was mainly done because average data are more widely available than marginal data. But because the aim of the research was on the impact of large scale application of the processes under consideration rather than of a single plant, using average data was the appropriate choice either way.

The error margins of the LCA’s were rather large, which could be due to being too strict in determining uncertainty. Using a Monte Carlo to determine the statistically relevant uncertainty would probably have narrowed the margins.

The general approach to the question of the sustainability of biomass-based BTX is considered appropriate. As pointed out above, there is room to improve the details and data sourcing.

10.2 Comparison with other research Eerhart et al. (2012) show in their LCA of biobased PEF that it is more sustainable than fossil-based PET and more sustainable than biobased PLA, PHA and PE, although the latter two are also more sustainable than petrochemical alternatives.

Tijmensen et al. (2002) explore the options for producing FT liquids to replace various fuels, showing that they are already cost effective, which would be very beneficial for their breakthrough into the market, thus competing with BTX from biomass.

An LCA of platform chemicals from lignocellulosic biomass in a biorefinery showed that greenhouse gas emission reductions of 37-48% could be achieved and a fossil fuel use reduction of up to 80%. Compared to this research, the GHG reductions are on the low side, but the fossil resource use reductions are comparable. (Hipolito 2011)

Willems (2009) sheds a light on the obstacles facing biomass-based chemicals, the largest being transport difficulties and the enormous gap between lab scale and commercial production. The latter problem is less of an issue for biomass-based platform chemicals such as BTX, since they are drop-in chemicals. But the transport issue is important, since for biomass-based BTX the feedstock is also spread out, and conversion plants are most likely more profitable when they are centralised. Therefore there is a need for further research into the effects of transport on the economic and environmental impacts of biomass-based BTX production.

Ragauskas et al. (2006) give a strong argument for the biorefinery: an integrated plant that makes the most out of sustainable biomass to produce the services that humans need. This is in line with the argument made in this paper that cascading and recycling are important, as are the use of waste streams.

A 2006 report by CE (Croezen, 2006) looked at the current options for replacing petrochemical processes with bio-based processes and concluded that the price and relative obscurity of biomass- based chemicals are a problem, and that for some processes the land use and process energy are rather high. It also comments on the unequal playing field created by the stimulus of green electricity and fuels, which makes it hard for biochemical to break through onto the market. While these conclusions complement or agree with the results of this research, it should be noted that in the report most processes relied on non-sustainable biomass.

A DOE research (Holladay, 2007) on opportunities for lignin usage concluded that while lignin has a potential high impact, technologically speaking only power, fuel and syngas are short-term opportunities, with aromatics production a long term goal. While this research agrees that lignin has a high impact, it does not agree that aromatics production from lignin is a long term goal, since the BTX yield from lignocellulosic biomass is already high enough to be commercially viable. But that could be due to the five years between the researches, a period during which the field has progressed quite significantly. It should be mentioned that pure lignin is not the ideal feedstock for the biomass-based BTX process, although in a biorefinery framework the lignin is a waste stream which is suitable for little other products.

A 2010 report by CE (Bergsma, 2010) concludes, like this research, that for the Netherlands producing chemicals from biomass is an excellent use of biomass, and that agricultural crops should not be used for fuel production. Biomass-based electricity is also considered good use even in the long term, but this is probably in light of the decision to build more coal fired power plants in the Netherlands.

So overall this research is in agreement with other reports on the subject, but because there are so many options for biomass use and parameters to consider, there is some differentiation.

11 Conclusion The question addressed in this research was whether the production of BTX from biomass was a sustainable use of the resource. The environmental impacts of fossil-based BTX were examined, from which it was concluded that the fossil resource depletion and greenhouse gas emissions were the major impacts. Biomass-based BTX has the potential to become a large use of woody biomass. And though it is a new process, advances made in the field are such that yields are comparable to other biomass-based routes. Five other uses of biomass (ethanol, ethylene, FT-diesel, electricity and FDCA) were also examined, chosen to represent the different kind of products from biomass. The life cycle assessment of the fossil resource inputs and CO 2 outputs of all these systems revealed that per kilogram of wood input, biomass-based BTX production gave the biggest improvement compared to the fossil-based route. Biomass-based diesel also performed well. Comparing FDCA with biomass- based TA showed that FDCA from corn had lower fossil resource input and CO 2 output, but wood based FDCA performed worse. Since corn is however also a food crop, it is not an entirely sustainable feedstock. Other macro effects that were not included in the LCA were the possibility of using waste streams, renewable alternatives, the possibility of cascading and recycling, the trends in the petroleum market and the scale potential. Aside from the scale potential, which is neutral either way, the other four macro effects gave a positive outlook to the production of biomass-BTX, while some of the other products under consideration were negatively or not as positively affected.

So overall, from this research, it can be concluded that:

- Biomass-based BTX production is more sustainable than fossil-based BTX production - Compared to other uses of lignocellulosic biomass, BTX production performs equally or even better. However, within the LCA system the differences were rather small and the error margins large, which means that the individual parameters are relevant. - In the study of the macro effects, it was shown that trends in the petrochemical industry, the possibility to use waste streams and other factors would benefit biomass-based BTX production more than the other biomass-based products.

Further research should focus on performing an LCA on other impact categories as well, since this may clarify the differences between the processes. Furthermore, the effect of logistic difficulties such as transport from the biomass production site to industrial sites should be researched, as well as the effect of the specific technologies and feedstocks used for the biomass-based BTX process. Practical research into streamlining the production process so that fuel use and emissions could be further minimized and waste stream usage optimized would also benefit biomass-based BTX production, although the outlook is very good already.

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Appendix A: LCA polystyrene cup The polystyrene cup was modelled in SimaPro using the Ecoinvent v2.2 database.

Table 10 shows the inventory for the model, consisting of expandable polystyrene, injection moulding of said styrene, transport and curb side collection.

Table 10: inventory PS cup LCA

Phase process/product value unit production Polystyrene, expandable, at plant/RER S 0.1 kg production injection moulding/RER S 0.1 kg use Transport, lorry, 16 -32t, EURO3/RER S 0.0001 tkm Waste Curb side collection/RER S 0.1 kg

Figure 15 shows the network for the single score impact of the life cycle stages, showing that the polystyrene production has the largest impact, followed by the injection moulding and incineration/waste phase.

Figure 15: Network overview of single score impac polystyrene cup LCA

Appendix B: inventories For the inputs of biomass, coal, gas and oil higher heating values were used to convert them from the units in Ecoinvent/other sources to MJ. For data from Ecoinvent, both “coal, brown, in ground” and “coal, hard, unspecified” are combined as “coal”; “gas, natural, in the ground” is “gas”; “oil, crude, in the ground” is oil. For use in the model and for calculating energy efficiencies, the higher heating values of coal (22.7 MJ/kg, average of values in Key Energy Statistics 2007), natural gas (38.7 MJ/m3, average of values in Key energy statistics 2007) and crude oil (42.9 MJ/kg, average of values in Key Energy Statistics 2007) are used to convert the given units into energy units. The higher heating value of wood is assumed to be 18.5 MJ/kg

Detailed inventory of chapter 6

FDCA from corn The data for FDCA production were obtained from Eerhart 2012, using an average of the six cases they calculated. The land use is based on 0.23 ha needed per t of PEF; per t of PEF 0.85 t FDCA is needed.

Table 11

Source Eerhart 2012 Includes cradle-to-gate IN OUT 14.8 MJ fossil resources 1 kg FDCA 2 0.97 m land 0.85 kg CO 2 Per mole of product, the in-and outputs are the following:

Table 12

Source Eerhart 2012 Includes cradle-to-gate IN OUT 2.31 MJ fossil resources 1 mole FDCA 2 0.3 m land 0.13 kg CO 2

Biomass-based purified terephthalic acid The data for biomass-based TA production were based on biomass-based xylene production as described on page. Economic allocation was used to determine the in- and outputs of biomass-based xylene production.

Using economic allocation, the emissions per kg of xylene are

Table 13

Source calculations Includes cradle to distilled xylene IN OUT 8.28 MJ fossil resources 1 kg xylene

136 MJ biomass 0.53 kg CO 2 5.58 m2 land To determine the in- and outputs of the rest of the TA production process, the datasets for fossil terephthalic acid and fossil xylene were used. Per kg of TA, 0.66kg of xylene is needed. Thus, the in-

62 and outputs of 0.66 kg xylene production were subtracted from the in- and outputs of 1 kg of fossil TA production.

The in-and outputs of the purified terephthalic acid process are:

Table 14

Source ecoinvent v 2.2 Includes cradle-to-gate IN OUT 56.7 MJ fossil resources 1 kg PTA

0.69 MJ renewable energy 1.5 kg CO 2

The in-and outputs of the fossil-based xylene process process are:

Table 15

Source Ecoinvent v2.2 “xylene, at plant, RER/S” Includes Cradle-to-gate IN OUT 56 g coal 1 Kg xylene 3 679 dm natural gas 1.3 kg CO 2 803 g oil 0.2 MJ Renewable energy The in-and outputs of the purified terephthalic acid minus the in- and outputs of the fossil xylene process process are:

Table 16

Source calculation Includes TA process-0.66 kg xylene process IN OUT 13.6 MJ fossil resources 1 kg PTA-xylene

0.56 MJ renewable energy 0.677 kg CO 2 For the total in- and outputs of biomass-based TA production, the in- and outputs of 0.66 kg biomass- based xylene production were added to the “TA-fossil xylene” in- and outputs.

Table 17

Source calculation Includes TA process+0.66 kg biomass-based xylene process IN OUT 19.1 MJ fossil resources 1 kg biomass-based PTA

0.56 MJ renewable energy 0.68 kg CO 2 90.2 MJ biomass Per mole of product this is:

Table 18

Source calculation Includes TA process+0.66 kg biomass-based xylene process IN OUT 3.16 MJ fossil resources 1 mole biomass-based PTA

0.09 MJ renewable energy 0.17 kg CO 2 15 MJ biomass

FDCA from poplar The data for production of FDCA from poplar were obtained from Eerhart 2012, Yang 2012 and Ecoinvent. Yang (2012) describes the production of HMF from poplar, yielding 0.082 g of HMF per g of poplar. The molecular weight of HMF is 126g/mol.

Table 19

Source Yang 2012 Includes poplar to HMF IN OUT 1 kg poplar 0.082 kg HMF From ecoinvent v2.2 “woodchips, softwood, at forest” was used to model the in- and outputs of poplar.

Table 20

Source Ecoinvent v2.2 “woodchips, softwood, at forest” Includes biomass production IN OUT 4.1 g coal 1 kg woodchips 3 1.27 dm natural gas 0.030 kg CO 2 6.9 g oil 19.1 MJ Biomass 0.70 m2 land It was assumed that the production process of HMF from poplar was similar to that of fructose production from corn, which is probably an underestimation. The in- and outputs of HMF oxidation are provided by Eerhart 2012.

Table 21

Source Eerhart 2012 Includes HMF oxidation IN OUT 1 kg HMF 1.24 kg FDCA

11.8 MJ fossil resources 0.68 kg CO 2 The in- and outputs of the HMF production from corn are:

Table 22

Source Eerhart 2012 Includes fructose from corn IN OUT 10.5 MJ fossil resources 1 kg fructose

0.63 kg CO 2 Combining the datasets above, the in- and outputs per kg of FDCA from poplar are:

Table 23

Source calculations Includes cradle-to-gate IN OUT 188 MJ biomass 1 kg FDCA

22.33 MJ fossil resources 1.35 kg CO 2 And per mole of product:

Table 24

Source calculations Includes cradle-to-gate IN OUT 29.3 MJ biomass 1 mole FDCA

3.48 MJ fossil resources 0.21 kg CO 2

Detailed inventory chapter 7

Fossil electricity The data for fossil electricity were obtained from data by Agentschap NL on electricity production in the Netherlands in 2010 for fossil resource use and CO 2 emissions of average electricity production in the Netherlands. Their system only considers the power plant itself and not mining, transport etc., which they estimate accounts for an additional 5.26% of emissions and resources. Therefore, their data were multiplied by 1.0526 to obtain cradle to grave emissions and resource needs.

Table 15

Source Harmelink 2012 Includes Plant in- and outputs IN OUT 2.02 MJ Fossil resources 1 MJ electricity

0.124 kg CO 2

Table 26

Source Harmelink 2012/0.95 Includes Cradle-to-gate IN OUT 2.13 MJ Fossil resources 1 MJ electricity

0.130 kg CO 2

Fossil diesel The data for fossil diesel production were obtained from Ecoinvent v 2.0, using the input “Diesel, at refinery, RER/S”. The Ecoinvent data encompasses cradle-to-gate in- and outputs.

Table 27

Source Ecoinvent v2.2 Includes Cradle-to-gate IN OUT 47 g coal 1 Kg Diesel 3 55 dm natural gas 0.436 kg CO 2 1100 g oil 0.1 MJ Renewable energy

Fossil ethanol The data for fossil ethanol production were obtained from Econinvent v 2.0, using the input “ethanol from ethylene, at plant, RER/S”. The Ecoinvent data encompasses cradle-to-gate in- and outputs.

Table 28

Source Ecoinvent v2.2 Includes Cradle-to-gate IN OUT 80 g coal 1 Kg ethanol 3 436 dm natural gas 1.060 kg CO 2 609 g oil 0.3 MJ Renewable energy

Fossil BTX The data for fossil BTX production were obtained from Ecoinvent v 2.0, using the inputs “benzene, at plant, RER/S”, “toluene, liquid, at plant, RER/S”, “xylene, at plant, RER/S”.

Table 29

Source Ecoinvent v2.2 “benzene, at plant, RER/S” Includes Cradle-to-gate IN OUT 57 g coal 1 Kg benzene 3 631 dm natural gas 1.5 kg CO 2 877 g oil 0.19 MJ Renewable energy

Table 30

Source Ecoinvent v2.2 “toluene, liquid, at plant, RER/S” Includes Cradle-to-gate IN OUT 41 g coal 1 Kg toluene 3 666 dm natural gas 1.2 kg CO 2 776 g oil 0.14 MJ Renewable energy

Table 31

Source Ecoinvent v2.2 “xylene, at plant, RER/S” Includes Cradle-to-gate IN OUT 56 g coal 1 Kg xylene 3 679 dm natural gas 1.3 kg CO 2 803 g oil 0.2 MJ Renewable energy Using the demand ratio given by Sweeney (2007), 67:5:28, the weighted average in- and outputs for BTX according to the demand ratio were calculated. So (inputs BTX)=0.67x(inputs benzene)+0.05x(inputs toluene)+0.28x(inputs xylene). The Ecoinvent data encompasses cradle-to- gate in- and outputs.

Table 32

Source BTX 67:5:28 ratio Includes Cradle-to-gate IN OUT 55.9 g coal 1 Kg BTX 3 646 dm natural gas 1.4 kg CO 2 851 g oil 0.9 MJ Renewable energy

Fossil ethylene The data for fossil ethylene production were obtained from the technical report of the Ecoinvent v 2.2 database “plastics”, using the ethylene production data. The Ecoinvent data encompasses cradle- to-gate in- and outputs.

Table 33

Source technical document ethylene by ecoinvent v2.2 Includes Cradle-to-gate IN OUT 4.2 g coal 1 Kg ethylene 3 537 dm natural gas 1.1 kg CO 2 927 g oil 0.16 MJ Renewable energy

Biomass electricity The data for biomass electricity production were obtained from Ecoinvent v 2.2, using the input “wood pellets electricity CH/S”.

Table 34

Source Ecoinvent v2.2 “wood pellets electricity CH/S” Includes Cradle?-to-gate IN OUT 16 g coal 1 MJ electricity 3 3.2 dm natural gas 0.037 kg CO 2 3.7 g oil 4.85 MJ Biomass 38 MJ other renewable energy

Biomass diesel The data for biomass diesel production were obtained from Ecoinvent v 2.2, using the input “syngas from wood, fluidized bed reactor, CH/S” for the in- and outputs of syngas production, and 71% energy efficiency for the conversion of syngas to liquid fuel (Swain). It is assumed that the exothermic Fischer-Tropsch synthesis of diesel from syngas does not require additional inputs and has no emissions. The obtained value for CO 2 emissions (380g/kg diesel) is in the same range as values found in literature: Roedl 402 g/kg diesel and Searcy 237-792 g/kg diesel.

Table 35

Source Ecoinvent v2.2 “syngas from wood, fluidized bed reactor, CH/S” Includes Cradle-to-syngas IN OUT 7.6 g coal 1 m3 syngas 3 2.7 dm natural gas 0.033 kg CO 2 6.44 g oil 11.2 MJ Biomass 0.5 MJ other renewable energy Syngas has a higher heating value of 5.4 MJ/m 3. Converion of syngas to diesel has an energy efficiency of 71%. So for the production of 1 kg diesel (HHV 44 MJ/kg) 11.5 m 3 of syngas is needed

Table 36

Source Ecoinvent v2.2 “wood pellets electricity CH/S”, Swain Includes Cradle-to-gate IN OUT 86 g coal 1 kg diesel 3 31 dm natural gas 0.377 kg CO 2 74 g oil 128 MJ Biomass 5.7 MJ other renewable energy

Biomass ethanol The data for biomass ethanol production were obtained from Econinvent v2.2, using partly the input “ethanol from wood, CH/s” and partly the technical document on that dataset. The fossil resource needs and CO 2 emissions of wood ethanol production were obtained from the dataset, whilst the biomass required was obtained from the technical document, since there was a significant discrepancy between biomass requirements found in literature and the biomass input into the dataset.

Table 37

Source technical document ethanol from wood Ecoinvent v2.2 Includes ethanol process IN OUT 6.94 kg wood 1 kg ethanol This 6.94 kg input/kg ethanol is the average value of several studies.

Table 38

Source Ecoinvent v2.2 “ethanol from wood” Includes Cradle-to-gate, without biomass input IN OUT 29.91 g coal 1 kg ethanol 3 56.8 dm natural gas 0.389 kg CO 2 81.7 g oil Combining the two datasets above, the inputs and emissions for one kg of ethanol are:

Table 39

Source Ecoinvent v2.2 “ethanol from wood” and its technical document Includes Cradle-to-gate IN OUT 29.91 g coal 1 kg ethanol 3 56.8 dm natural gas 0.389 kg CO 2 81.7 g oil 129 MJ Biomass

Biomass BTX The data for biomass BTX production were obtained from several sources. For the biomass feedstock, from Ecoinvent v2.2 “woodchips, softwood, at forest” was used.

Table 40

Source Ecoinvent v2.2 “woodchips, softwood, at forest” Includes biomass production IN OUT 4.1 g coal 1 kg woodchips 3 1.27 dm natural gas 0.030 kg CO 2 6.9 g oil 19.1 MJ Biomass

Table 41

Source Phanphanich 2011 Includes torrefaction and grinding IN OUT 1 kg woodchips 1 kg wood powder

0.09 MJ fossil resources 0.01 kg CO 2 For the pyrolysis process, including recycling of waste biomass for heat production and purification of the product, data from (achtergrond artikel ZHong) was used. For the BTX yield from the process, Mihalick (2011?) was used, which also provided a ratio of BTX yield for hardwood. Electricity in and outputs are assumed to be the same as for the process chain “fossil electricity”

Table 42

Source Peacocke 2004, Mihalick 2011 Includes biomass pysolysis to BTX mix (29.1:22.6:48.3) IN OUT 139.3 MJ biomass 1 kg BTX mix 2.2 MJ electricity

For the separation of BTX into the individual chemicals, data from (pygas upgrading) was used. CO 2 emissions based on emissions of burning 0.79MJ diesel to power distillation process

Table 43

Source GTC technology Includes distillation of BTX IN OUT 1 kg BTX mix 0.291 kg benzene 0.79 MJ fossil resources 0.226 kg toluene 0.483 kg xylene2.6

0.06 kg CO 2 Since the pyrolysis process yielded a different ration of BTX than demanded, data from US DOE (2000) were used to determine the in- and outputs of xylene and toluene dehydroalkylation into benzene. For the separation and dehydroalkylation steps, the CO 2 emissions associated with the energy input were assumed to be the same as emissions from combustion of an equal amount of diesel.

Table 44

Source EERE Includes hydrodealkylation process IN OUT 0.188 kg toluene 0.324 kg benzene

0.224 kg xylene 0.01 kg CO 2 Because the total BTX yield is now 7.5% too low (the high xylene fraction means the mole yield is relatively low), the whole process needs to be multiplied by 1.08, giving:

Table 45

Source calculations Includes cradle-to-gate IN OUT 10.97 MJ fossil resources 1 kg BTX demand ratio

155.36 MJ biomass 0.72 kg CO 2

Biomass ethylene The data for biomass ethylene production were obtained from the same sources as biomass ethanol production. For the dehydration of ethanol data from (Hishier 2007) were used.

Table 46

Source Capello 2009 Includes dehydration including purification etc. IN OUT 1 kg ethanol 0.68 kg ethylene

8.26 MJ fossil resources 0.58 kg CO 2 The ethylene yield is only 0.68 kg per kg ethanol input, since a water molecule is lost in the process. Combining therefore 1.47 times the dataset of biomass-based ethanol production and 1.47 times the dehydration process, the following data are obtained for biomass-based ethylene production:

Table 47

Source calculations Includes cradle-to-gate IN OUT 21.46 MJ fossil resources 1 kg ethylene

189 MJ biomass 1.4 kg CO 2

Appendix C: Uncertainty determination The table below shows the uncertainty factors for each of the inventory items in the appendixes above.

The table number 48 shows to which table/item the entry refers, in case the description is unclear. Rows 3-9 show the individual factors for each of the items in the Pedigree matrix of uncertainty (Frischknecht & Jungbluth, 2007). This matrix is a tool with which to determine the uncertainty in LCI, further described in the reference. The letters correspond to the following factors:

R: Reliability (how accurate are the data measurements) C: Completeness (was the general scope large enough?) T: Temporal (how recent is the data?) G: Geographic (is the data from the right region?) F: Further technological correlation (is the used data of the very technology being studied?) S: Sample size B: Basic indicator

When all these individual factors have been assigned, the total uncertainty factor (or square geometric standard deviation) is calculated by means of the formula (Frischknecht & Jungbluth, 2007):

With U1-U6 being the uncertainty factors mentioned above.

The basic indicator was 1 in most cases, but in some cases it was larger than 1. For fossil-based electricity, the basic uncertainty is 1.1, to account for the choice of using average rather than marginal data. For the efficiency of the conversion of syngas to fossil diesel the basic uncertainty factor is 1.2, since only the basic energy efficiency of conversion was used, not process energy and emissions as well. For the amount of ethanol obtainable from wood, the basic uncertainty factor is 1.22, a figure derived from the deviation from the average as deduced from the source of the data (Jungbluth, 2007). For woodchip production there was a basic uncertainty factor of 1.1, since woodchips are but one of many possible inputs of wood into the biomass-based BTX system. Finally, FDCA from corn had an additional uncertainty in fossil resource use that is not expressed in the uncertainty factor but is taken into account in the error margin, which is 3.9 MJ/kg. This figure was based on using a different feedstock (corn from Germany rather than corn from the US).

With the total factor of each input table known, the uncertainty margins were based on a calculation of the highest and lowest values for each process.

Table 28: uncertainty factors inventory

What Table R C T G F S B Total Fossil electricity 25 1 1 1 1.02 1 1 1.1 1,102 Fossil diesel 27 1 1 1 1 1 1.05 1.05 Fossil ethanol 28 1 1 1 1 1 1.05 1.05 Fossil benzene 29 1 1 1 1 1.2 1.05 1.207 Fossil xylene 30 1 1 1 1 1.2 1.05 1.207 Fossil toluene 31 1 1 1 1 1.2 1.05 1.207 Fossil BTX 32 1.207 Fossil ethylene 33 1 1 1 1 1 1.05 1.05 Biomass electricity 34 1.05 1.1 1 1.02 1 1.1 1.155 Biomass syngas 35 1 1.1 1 1.02 1 1.1 1.14 Biomass FT Swain 36 1.2 Biomass diesel 1.25 Biomass ethanol from 37 1 1 1 1 1 1 1.22 1.22 wood Biomass ethanol process 38 1 1.1 1 1.02 1 1.1 1.145 Biomass woodchip 40 1 1.1 1 1.02 1 1.1 1.1 1.18 production Biomass grinding 41 1.05 1 1 1 1 1.1 1.11 Biomass pyrolysis 42 1 1.05 1 1 1.2 1.1 1.23 Biomass distillation 43 1 1 1 1 1 1.1 1.1 Biomass hydrodealkylation 44 1 1.1 1 1 1 1.1 1.144 Biomass ethylene 46 1 1 1 1 1.2 1.1 1.228 FDCA from corn 12 1.05 1 1 1.1 1 1.1 * 1.15 Biomass PTA process 16 1 1 1 1 1 1.05 1.05 FDCA from poplar 19 1 1 1 1 1.2 1.1 1.23 HMF oxidation 21 1 1 1 1 1.2 1.2 1.29 Fructose production 22 1 1 1 1 1.5 1 1.5 process

Appendix D: Sensitivity chapter 6 The sensitivity of the results towards the input data was calculated by increasing the value of the input data (amount required, fossil resource use and CO 2 emissions) by a certain amount. The change in the results divided by the change in the input values is the sensitivity. A very sensitive parameter will give a greater change in the results when altered than a not so sensitive parameter. The figures below (16-18) show the sensitivity of the different input parameters of the three processes of the LCA in chapter 6.

Figure 16 sensitivity of TA production inventory

Figure 17: sensitivity of FDCA from corn production

60% 40% 20% 0% -20% Fossil resource use -40% land use -60% CO2 emissions -80% -100% -120% woodchips HMF HMF from HMF from production poplar oxidation softwood

Figure 18: sensitivity of FDCA from poplar production

Appendix E: Sensitivity chapter 7 The sensitivity of the results towards the input data was calculated by increasing the value of the

input data (amount required, fossil resource use and CO 2 emissions) by a certain amount. The change in the results divided by the change in the input values is the sensitivity. A very sensitive parameter will give a greater change in the results when altered than a not so sensitive parameter. The figures below (19 & 20) show the sensitivity of the different input parameters of the three processes of the LCA in chapter 7.

190,00% 160,00% 130,00% 100,00% 70,00% 40,00% 10,00% Fossil resource use -20,00% -50,00% CO2 emissions -80,00% -110,00% diesel diesel diesel ethanol ethanol ethanol ethylene ethylene ethylene electricity electricity electricity biomass needed Biomass fosres en co2 Fossil fos res en co2

Figure 19: sensitivity of input parameters

110,00% 90,00% 70,00% 50,00% 30,00% 10,00% -10,00% -30,00% fossil resource use -50,00% CO2 emissions -70,00% -90,00% -110,00%

Figure 20: sensitivity of input parameters BTX