Meyer, C. Monohan, J. Green, R. Von Weddle. Feedstock and Microbial Community Analysis for a Mesophilic Co-fermentation Anaerobic Digestion Facility. California State University, Chico. Spring 2017.
Eight substrates comprising 90% of the feedstock from a two-stage, mesophilic anaerobic digestion biogas plant located in Oroville, CA were evaluated at lab scale for their total solids/volatile solids content, biomethane potential, and micro/macronutrient concentrations in order to determine their biomethane potential in anaerobic digestion. Specific biomethane potentials from 20-day trials for eight types of substrate were trap grease (735 ml/g TS) cheese whey (452 ml/g TS), potatoes (328 ml/g TS), apple waste (460 ml/g TS), olive waste (626 ml/g TS), salami waste (709 ml/g TS), cow manure (191 ml/g TS) and food waste (579 ml/gram TS). Substrates representative of four different macronutrient groups including lipids (trap grease), proteins (cheese whey), carbohydrates (potatoes), and simple sugars (apple waste) were tested in biogas potential trials with samples collected at five time points over a 10-day period. DNA was extracted and sequenced from each sample using Ion Torrent PGM to determine if the community structure of bacteria and archaea changed in response to a change of feedstock composition. No significant changes in the bacterial community and only minor changes in the archaea community were observed suggesting that microbial communities stemming from mixed substrate co-fermentation biogas reactors are well suited to a wide variety of substrates. Further, these microbial communities appear slow to respond to a sudden shift in feedstock type. This result contrasted with other feedstock related community studies which saw large community shifts in inoculum stemming from a single substrate inoculum source. This implies the co-fermentation facilities which operate on substrates stemming from different macronutrient types may contain microbial communities which are more resilient to changes in feedstock composition.
While an undergraduate, David completed an internship with the Bay Area based biotechnology company CytoCulture International. During his internship David utilized industrial microbiology techniques to analyze groundwater samples to assist in the bioremediation of hydrocarbon contaminated groundwater. After completing his undergraduate degree, David continued his work with CytoCulture International in its partnership with Biogas Energy to write a California Energy Commission grant focused on optimizing energy production from locally produced organic wastes using anaerobic digestion. David used this research opportunity to continue his education and completed his M.S. in Environmental Science from CSU Chico in spring of 2017. David completed his research on the California Energy Commission grant in the summer of 2017 and now works as the process control manager for the anaerobic digestion facility located at North State Rendering in Oroville California. David continues to be involved in bioremediation work and is active in the Bioresource Lab which is part of the Center for Water and the Environment at CSU Chico.