Determining the Effect of Ultrasonic Pretreatment on Anaerobic Digestion of Barley Bagasse A Major Qualifying Project Submitted to the faculty of Worcester Polytechnic Institute In partial fulfillment of the requirements for the Degree of Bachelor of Science Submitted to: Professor Michael Timko By: Kerry Muenchow April 24, 2019 Abstract This experiment analyzed the effect of ultrasonic pretreatment on the anaerobic digestion of barley bagasse. Anaerobic digestion is the breakdown of biodegradable substrates by microorganisms in an absence of oxygen, resulting in the production of biogas. Biogas, a combination of hydrogen, methane, and carbon dioxide, can be used to produce electrical, thermal, or mechanical energy. This process can be enhanced with pretreatment methods such as ultrasonic irradiation of the digestible substrate. The experiment determined differences in the anaerobic digestion of untreated and ultrasound-pretreated barley bagasse over 50-days. Differences between the experiments were defined by daily characterizations of the biogas product and the digestate. Characterization of the digestate in the pretreated reactor had variable results due to a change in the biogas collection method. The reactor yielded an average of 164 mL of biogas per day with an average 55% methane composition. Initial energy calculations suggest that sonication parameters must be optimized for the system to be an energy-efficient pretreatment method. The reactor with untreated barley bagasse recently began operation, with full data for a comparison expected in June. i Table of Contents Abstract .......................................................................................................................................................... i 1.0 Introduction ............................................................................................................................................. 1 2.0 Background: ............................................................................................................................................ 3 2.1 Anaerobic Digestion ........................................................................................................................... 3 2.2 Biogas ................................................................................................................................................. 4 2.3 Barley Bagasse .................................................................................................................................... 5 2.4 Anaerobic Digestion of Barley Bagasse ............................................................................................. 5 2.5 Ultrasonic Irradiation .......................................................................................................................... 6 2.6 Ultrasonic Irradiation as a Pretreatment .............................................................................................. 6 2.7 Characterization Techniques ............................................................................................................... 7 2.7.1 Gas Chromatography: .................................................................................................................. 7 2.7.2 pH:................................................................................................................................................ 8 2.7.3 Alkalinity: .................................................................................................................................... 8 2.7.4 Solids: .......................................................................................................................................... 8 2.7.5 COD ............................................................................................................................................. 9 2.7.6 Ammoniacal Nitrogen .................................................................................................................. 9 3.0 Methods and Materials .......................................................................................................................... 10 3.1 Raw Materials ................................................................................................................................... 10 3.2 Sonication Pretreatment .................................................................................................................... 10 3.3 Bioreactor .......................................................................................................................................... 11 3.2.1 Feed Conditions ......................................................................................................................... 12 3.3 Characterization Procedures: ............................................................................................................ 13 3.3.1 Amount of Biogas Produced ...................................................................................................... 13 3.3.2 Gas Chromatography ................................................................................................................. 13 3.3.3 pH Monitoring ........................................................................................................................... 14 3.3.4 Solids: ........................................................................................................................................ 14 3.3.5 Chemical Oxygen Demand: ....................................................................................................... 15 3.3.6 Ammoniacal Nitrogen: ............................................................................................................... 15 3.3.7 Alkalinity: .................................................................................................................................. 15 3.4 Initial Bagasse Substrate Characterization ........................................................................................ 16 4.0 Results ................................................................................................................................................... 17 4.1 Control Reactor Behavior: ................................................................................................................ 17 4.2 Pretreated Bagasse Reactor Behavior: .............................................................................................. 17 4.2.1 Biogas Production ...................................................................................................................... 17 4.2.2 Biogas Composition ................................................................................................................... 18 4.2.3 Ammoniacal Nitrogen ................................................................................................................ 20 4.2.4 Reactor pH and Alkalinity ......................................................................................................... 21 4.2.5 Solids and Chemical Oxygen Demand ...................................................................................... 22 4.2.6 Energy Production Possibilities ................................................................................................. 24 4.3 Expected Comparison Results: ......................................................................................................... 25 4.4 Experimental and Methodology Errors: ............................................................................................ 25 5.0 Conclusions ........................................................................................................................................... 28 6.0 Recommendations ................................................................................................................................. 29 6.1 General Operational Recommendations: ...................................................................................... 29 6.2 Conditional Recommendations: .................................................................................................... 29 7.0 Future Work .......................................................................................................................................... 30 Acknowledgements ..................................................................................................................................... 31 References ................................................................................................................................................... 32 Appendix A: Raw Data for Gas Chromatography ...................................................................................... 35 Appendix B: Raw Data for Biogas Volume ................................................................................................ 36 Appendix C: Raw Data for Solids............................................................................................................... 37 Appendix D: Raw Data for Alkalinity and pH ........................................................................................... 38 Appendix E: Raw Data for Ammoniacal Nitrogen ..................................................................................... 39 Appendix F: Raw Data for COD ................................................................................................................ 40 Appendix G: Raw Data for Energy Production Calculations