Assessment of microbial community in the startup process of a pilot biogas plant

Abstract The production of biogas as a strategy for biotransforming large volumes of waste into bioenergy is one of the alternatives for reducing greenhouse gases. Metabarcoding analysis aims to understand the role of microbiota from the beginning of the process in the success of biogas production. This study compared microbial diversity and metabolic prediction in a pilot plant producing biogas for vehicular use, utilizing organic solid waste and customs-seized organic products, across the stationary phase (SP), initial phase (IP), and batch phase (BP). In 14 days of operation (IP), the daily production was 126 Nm 3 /day. In the BP, it reached 207 Nm³/day, with 65% methane recovery. The phyla Bacteroidota and Firmicutes predominated (47% in the BP) and were associated with hydrolysis and acidogenesis. DMER64 prevailed along with hydrogenotrophic archaea, Methanosarcina , and Candidatus Methanofastidiosum . Genes related to hydrogenotrophic metabolism and the reduction of CO 2 to CH 4 stood out during the initial period of operation. Factors such as the feeding regime and substrate composition may have influenced the bacterial community and the selection of specific archaeal genera, affecting the process. Understanding microbial communities in relation to physicochemical parameters can contribute to controlling the operation and efficiency of renewable energy production.