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Anaerobic co-digestion is a popular option to increase biogas production, thus increasing recapture potential, with grease trap waste, or FOG (fats, oils, and greases), showing the highest methane production potential. In order to ensure reactor stability and optimal performance, the correct microbiome composition is essential. However, it is currently unknown what microbiome compositions are optimal or how to create them. This work monitored nineteen full-scale anaerobic digesters, at six separate facilities, monthly for one year to link operational characteristics with microbiome composition. Of the nineteen digesters studied, three perform FOG co-digestion, four perform co-digestion with biodiesel wash water, one is fed only TWAS (thickened waste activated sludge), and the remaining eleven are fed primary sludge and TWAS. Microbiome composition was analyzed using 16S rRNA amplicon sequencing. Operational data from each of the full-scale facilities was examined to determine their influence on microbiome compositions.

Batch sensitivity assays were created to link microbiome structure with digester functionality in response to organic overloads. Eleven full-scale anaerobic digesters were selected for these assays including three FOG co-digesters, two biodiesel co-digesters, one TWAS only digester, and 5 municipal digesters. Each set of twenty-five 100mL batch anaerobic digesters were seeded with 80mL of digestate and up to 20mL of canola oil (volume differences were made up with digestate supernatant). Five batch anaerobic digesters were ran as digestate-only controls, and the remaining twenty were fed 1 mL, 5 mL, 10 mL, and 20 mL of canola oil (in quintuplets). Total methane produced, methane production rates, and methane content of the biogas were used to calculate the functional sensitivity of each full-scale anaerobic digester. The batch sensitivity assays were performed in winter and summer to account for seasonal variations in full-scale plant operation and microbiome compositions.

This project presenter is available for live video chat on Sept. 1, 2020 from 10:15 a.m. - 12:00 p.m. PDT.