UUnniivveerrssiittyy ooff SSoouutthh FFlloorriiddaa DDiiggiittaall CCoommmmoonnss @@ UUnniivveerrssiittyy ooff SSoouutthh FFlloorriiddaa USF Tampa Graduate Theses and Dissertations USF Graduate Theses and Dissertations 3-25-2016 SSiizziinngg aann AAnnaaeerroobbiicc DDiiggeesstteerr iinn aa RRuurraall DDeevveellooppiinngg WWoorrlldd CCoommmmuunniittyy:: DDooeess HHoouusseehhoolldd FFuueell DDeemmaanndd MMaattcchh GGrreeeennhhoouussee GGaass PPrroodduuccttiioonn?? Ronald Keelan Greenwade Follow this and additional works at: https://digitalcommons.usf.edu/etd Part of the Environmental Engineering Commons SScchhoollaarr CCoommmmoonnss CCiittaattiioonn Greenwade, Ronald Keelan, "Sizing an Anaerobic Digester in a Rural Developing World Community: Does Household Fuel Demand Match Greenhouse Gas Production?" (2016). USF Tampa Graduate Theses and Dissertations. https://digitalcommons.usf.edu/etd/6090 This Thesis is brought to you for free and open access by the USF Graduate Theses and Dissertations at Digital Commons @ University of South Florida. It has been accepted for inclusion in USF Tampa Graduate Theses and Dissertations by an authorized administrator of Digital Commons @ University of South Florida. For more information, please contact [email protected]. Sizing an Anaerobic Digester in a Rural Developing World Community: Does Household Fuel Demand Match Greenhouse Gas Production? by Ronald K. Greenwade A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering Department of Civil and Environmental Engineering College of Engineering University of South Florida Major Professor: James R. Mihelcic, Ph.D. Sarina J. Ergas, Ph.D. Daniel H. Yeh, Ph.D. Date of Approval: March 17, 2016 Keywords: Biogas, Manure Treatment, Anaerobic Digestion, Climate Change, Carbon, Methane, Cooking Fuels, Sustainable Development Goals, Panamá Copyright © 2016, Ronald K. Greenwade Dedication Por los soldados en la lucha. Acknowledgments I would like to spotlight the people who were essential in the writing of this document. I would have never had the confidence or energy to complete it without their influence and example. Professor James Mihelcic who provided the opportunity for me to study at the University of South Florida and work as a Peace Corps volunteer in Panamá. Without his guidance, expertise and interest in my career I would be lost, without courage and unable to pursue the road less traveled. My parents Susan and Ron Greenwade have always supported my adventures and have never dissuaded me in my endeavors. This research is made possible with support by the National Science Foundation under Grant No. 0965743. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. Table of Contents List of Tables ................................................................................................................................................ iii List of Figures ............................................................................................................................................... iv Abstract ......................................................................................................................................................... v Chapter 1: Introduction ................................................................................................................................ 1 1.1 Problem Statement .................................................................................................................... 1 1.2 Advantages and Disadvantages of Anaerobic Digestion ............................................................ 3 1.3 Focus of Research ...................................................................................................................... 6 Chapter 2: Literature Review ........................................................................................................................ 7 2.1 The State of Rural Energy Consumption .................................................................................... 7 2.2 Microbiology of Anaerobic Digestion ........................................................................................ 7 2.3 Parameters and Process Optimization of a Well Performing Anaerobic Digester .................. 10 2.3.1 Substrate Temperature ............................................................................................ 10 2.3.2 Available Nutrients .................................................................................................. 11 2.3.3 pH Level ................................................................................................................... 11 2.3.4 Nitrogen Inhibition and C/N Ratio ........................................................................... 11 2.3.5 Substrate Solids Content and Agitation ................................................................... 11 2.3.6 Inhibitory Factors ..................................................................................................... 12 2.3.7 Solids Retention Time .............................................................................................. 12 2.4 Rural Anaerobic Digesters ........................................................................................................ 13 2.5 Evaluation of Biodigester Operation and Maintenance .......................................................... 14 Chapter 3: Methods .................................................................................................................................... 18 3.1 Study Location .......................................................................................................................... 18 3.2 Estimating Biogas Production .................................................................................................. 20 3.3 Estimating Household Biogas Demand .................................................................................... 22 Chapter 4: Results and Discussion .............................................................................................................. 29 4.1 Methane Demand .................................................................................................................... 29 4.2 Biogas Supply and Methane Content....................................................................................... 29 4.3 Biogas Production .................................................................................................................... 30 4.4 Appropriate Number of Animals for Household Demand ....................................................... 31 4.5 Assessment of Biogas Supply and Household Demand ........................................................... 33 4.6 Potential Methane, Carbon Dioxide and Carbon Dioxide Equivalence of Excess Biogas per Household ......................................................................................................................... 37 Chapter 5: Conclusions and Recommendations for Future Research ........................................................ 42 5.1 Conclusions .............................................................................................................................. 42 5.2 Recommendations for Future Research .................................................................................. 44 i References .................................................................................................................................................. 46 Appendix A: Calculation of the Household Cooking Energy Demand of Rice/ Beans................................. 50 Appendix B: Calculation of Methane to Cook 0.5 kg of Rice/ Beans .......................................................... 57 Appendix C: Model Inputs and Results for the Design of a Small-Scale Anaerobic Digester for Application in Rural Developing Countries ........................................................................................... 59 Appendix D: Personal Daily Methane Requirement for a Panamanian Living in Study Location ............... 61 Appendix E: Appropriate Amount of Animals for a Household in Study Location ..................................... 62 Appendix F: Calculations for Methane, Carbon Dioxide and Carbon Dioxide Equivalence of Excess Biogas Production at Standard Pressure .............................................................................................. 63 Appendix G: Permission Statement to Use Figure 2-1 in This Work........................................................... 67 Appendix H: Permission Statement from The World Factbook to Use Figure 3-1 in This Work ................ 68 Appendix I: Permission from Laurel E. Rowse to Use Figure 3-2 in This Work ........................................... 69 ii List of Tables Table 1-1 Advantages and disadvantages of anaerobic treatment..............................................................5 Table 2-1 Inhibitory chemicals commonly found in anaerobic digesters and the concentration that may result ininhibition...……...…..........................................................................................12 Table 2-2 Break-even points for each biofuel considered by Bruun et al (2014) in which the percentage of methane lost in a reactor due to fugitive gas emission would translate into the same global warming potential.………….……………………………………………….………….……....14 Table 3-1 Literature reported values of biogas required to cook 0.5 kg of rice and 0.5 kg of beans on a dry basis....................................................................................................................24 Table 3-2 Daily intake of principle food groups for Panamanians in 1992 adapted from the Food and Agricultural Organization of the United Nations (1999)……….……..............................26 Table 3-3 Census data from a rural town in the Darien Provence of Panamá of households which owned swine...…………......................................................................................................27 Table 4-1 Number of swine or dairy cows each household would need to cover cooking energy demands with a biogas of 40% methane....................................................................................32 Table 4-2 Number of swine or dairy cows each household would need to cover cooking energy demands with a biogas of 70% methane....................................................................................32 Table 4-3 Swine ownership, methane supply, and methane demand emissions for a biogas with a methane of 40% ..………………….……………………………………………….…..……………………………..35 Table 4-4 Swine ownership, methane supply, and methane demand emissions for a biogas with a methane of 70%..……………………………..……………………….………………..….………………………..………..36 Table 4-5 Potential methane, carbon dioxide and carbon dioxide equivalence of excess biogas per household with a biogas methane content of 40%…………….……………………….…………………..39 Table 4-6 Potential methane, carbon dioxide and carbon dioxide equivalence of excess biogas per household with a biogas methane content of 70%……………………………….…………..…..………..40 iii List of Figures Figure 2-1 The energy ladder, showing how fuel type can change as a household’s social and economic status increases…………………………………………………………………………….…………….…........8 Figure 2-2 Anaerobic digestion process flow chart…………………………………………………………………………..………9 Figure 3-1 Location of town where the author served 15 months as a Peace Corps Volunteer………………19 Figure 3-2 Anaerobic digester design tool flowchart used to estimate gas production.............................21 Figure C-1 Model inputs from mathematical model ………………………………………………………………………………59 Figure C-2 Outputs from mathematical model……………………………………………………………………………………….60 iv Abstract Anaerobic digestion is the process by which organic carbon is converted into biogas in the form of carbon dioxide (𝐶𝑂 ) and methane (𝐶𝐻 ). Both of these products are greenhouse gases that 2 4 contribute to global warming. Therefore if anaerobic reactors are improperly maintained and biogas is leaked or intentionally released into the atmosphere because biogas production exceeds household demand, these reactors may become generators of greenhouse gas emissions instead of sustainable energy producers. The objective of this research was to develop a framework to assess if the demand for biogas by a rural adopter of an anaerobic digester matched with the associated local gas production. A literature review of the energy required to prepare commonly consumed food of rice and beans was conducted to establish required household biogas volumes. This review determined that 0.06 𝑚3 of methane was required to prepare a half a kg of rice (on a dry weight basis) and 0.06 𝑚3 of methane was required to prepare a half a kg of beans (on a dry weight basis). Furthermore an analysis of occupants of a rural Panamanian town was performed along with a design model for rural anaerobic reactor gas production to determine if an overproduction of biogas would occur if anaerobic reactors were built for families who owned swine. It was determined using this approach that all of the fifteen household would experience an overproduction of biogas based on household demand of methane and therefore would risk the release of greenhouse gases. Household size ranged from one to seven occupants and swine ownership ranged from one to fifteen per household. The differences of biogas supply with respect to demand from these fifteen situations ranged from 0.09 to 0.35 𝑚3 of a biogas with 40% methane and 0.27 to 6.17 𝑚3 of excess biogas with a methane content of 70% per household per day. An average of 0.45 𝑚3 of a biogas with 40% methane per household per day was calculated and 0.87𝑚3 for 70% methane for all fifteen households, excluding one outlier. However, because this research uses v a model based on plug flow reactor mechanics, results may produce varied results from other studies concerning small scale anaerobic digestion. vi