Life Cycle Analysis of an Integrated Biogas-Based Agriculture Energy System by Siduo Zhang B. Sc., Nankai University, 2010 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in The Faculty of Graduate Studies (Chemical and Biological Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) February, 2013 © Siduo Zhang, 2013 i ABSTRACT Large quantity of manure is generated in the livestock industry in British Columbia (BC) and natural gas is being consumed intensively in BC’s agriculture sector. We proposed to integrate the livestock farms and the greenhouses to promote waste-to-energy and waste-to-material exchanges following the principles of Industrial Ecology (IE). Natural gas consumptions on farms are replaced by renewable biogas generated from anaerobic digestion (AD) of farm wastes (mainly livestock manure). CO2 for plant enrichment in greenhouses is supplied by biogas combustion flue gases and the residues (digestate) from digesters are used as animal bedding materials, plant growing media, and liquid fertilizers. An integrated dairy farm and greenhouse was first modeled. Co-digestion of manure with a variety of organic farm wastes was further evaluated with an aim to enhance the biogas production. To address the problems of too much digestate surplus and high CO2 demand for greenhouse CO2 enrichment, the mushroom farm was further introduced into the integrated system. In this way, the digestate surplus can be used as a growing media for growing mushrooms and the CO2–rich ventilation air from the mushroom can be directed to the greenhouse for CO2 enrichment. A Life Cycle Analysis (LCA) was conducted to quantify the environmental impacts of each of the proposed cases in comparison to the conventional agriculture practices. The LCA results showed that the integrated dairy farm-greenhouse system reduces non-renewable energy consumption, climate change, acidification, respiratory effects from organic emissions, and human toxicity by more than 50% compared to conventional operations; among which the reductions in non-renewable energy consumption, climate change, and human toxicity are the most significant. If the digestate surplus is treated as a waste, the integrated system has a ~20% increase in eutrophication and respiratory effects from inorganic emissions. When other organic wastes are co- digested with dairy manure, all the impacts can be further reduced in all cases. If a mushroom farm is introduced to form an integrated dairy farm-greenhouse-mushroom farm system, a large greenhouse can be facilitated and the digestate can be largely reused; thus all the analyzed impacts are significantly reduced compared to the base scenario. ii PREFACE Some preliminary results of Chapter 2 were published on page 1 to 12 of supplement of Journal of Yunnan Normal University (Natural Science Edition) in 2011 under the title of ―A Life Cycle Assessment Case Study on a Farm Scale Biogas Plant in British Columbia‖. The co-author of this article is Xiaotao Bi. Also part of the content in Chapter 2 was presented in a poster in the Symposium on Industrial Ecology for Young Professionals (SIEYP II) on June 11th, 2011 at Berkeley under the title of ―A case study on an integrated animal farm-greenhouse Eco-Industrial system in British Columbia‖. The co-authors are Xiaotao Bi and Roland Clift. The method used in the preliminary studies was generally the same as in Chapter 2. But the system boundary, scenarios, and results were later modified and updated in Chapter 2. Parts of the content in Chapters 2 and 4 were orally presented in the 62nd Canadian Chemical Engineering Conference on October 15th, 2012 at Vancouver under the title of ―A Biogas Based Agriculture Eco-Industrial Park in British Columbia‖. The scenarios and results were again modified and updated in this thesis. Lastly, Appendix E, an article titled “Life Cycle Costing of an integrated animal farm-greenhouse Eco-Industrial system in British Columbia‖ was published on page 20 to 28 of Life Cycle Assessment XI Conference (Chicago 2011) Proceedings. The co-authors of this article are Xiaotao Bi, Anthony Lau, and Roland Clift. iii TABLE OF CONTENTS Abstract .................................................................................................................................................. ii Preface ...................................................................................................................................................iii Table of Contents .................................................................................................................................. iv List of Tables ........................................................................................................................................ vi List of Figures ....................................................................................................................................... ix List of Abbreviations ............................................................................................................................. x Acknowledgement ................................................................................................................................ xi Dedication ............................................................................................................................................ xii 1. Introduction ........................................................................................................................................ 1 1.1 Problems and Opportunities ......................................................................................................... 1 1.2 Industrial Ecology for System Integration ................................................................................... 4 1.3 Life Cycle Analysis for Impact Assessments ............................................................................... 6 1.4 Objectives and Proposed Approaches .......................................................................................... 8 1.4.1 Objectives and Research Goals ............................................................................................. 8 1.4.2 Proposed Approaches .......................................................................................................... 10 1.5 Structure of Thesis ..................................................................................................................... 12 2. LCA of An Integrated Dairy Farm and Greenhouse ........................................................................ 14 2.1 Introduction ................................................................................................................................ 14 2.2 Framing of LCA Study ............................................................................................................... 14 2.2.1 Functional Unit .................................................................................................................... 14 2.2.2 System Boundary ................................................................................................................ 15 2.2.3 Scenarios ............................................................................................................................. 16 2.3 Description of Inventory Model ................................................................................................. 17 2.3.1 Inventory for Energy ........................................................................................................... 18 2.3.2 Inventory for Materials ........................................................................................................ 19 2.3.3 Inventory for System Operations ........................................................................................ 21 2.4 Results and Discussions ............................................................................................................. 25 2.4.1 Life Cycle Inventory Data ................................................................................................... 25 2.4.2 Life Cycle Impact Assessment ............................................................................................ 35 2.4.3 Normalization Analysis ....................................................................................................... 43 2.4.4 Uncertainty Analysis ........................................................................................................... 46 iv 2.5 Conclusions ................................................................................................................................ 47 3. LCA of An Integrated Dairy Farm and Greenhouse with Co-digestion .......................................... 49 3.1 Introduction ................................................................................................................................ 49 3.2 Framing of LCA Study ............................................................................................................... 49 3.2.1 Functional Unit .................................................................................................................... 49 3.2.2 System Boundary ................................................................................................................ 50 3.2.3 Scenarios ............................................................................................................................. 50 3.3 Description