Fast anaerobic digestion of complex substrates via immobilized biofilms in a novel compartmentalized reactor design

Abstract

Anaerobic digestion of municipal waste is a promising technology for renewable energy production, notably for methane (CH4) production. Existing reactor designs have limitations that prevent efficient conversion and high throughput, especially of substrates high in suspended solids. Here, we introduce a novel compartmentalized reactor design encompassing controlled feed flow over fixed microbial biofilms for high rate CH4 production from enzymatically pre-hydrolyzed municipal solid waste. In a 240 L working volume reactor, the biofilm generation was completed in less than 60 days and CH4 production was minimum ∼700 L day−1 in the ensuing months with a Hydraulic Retention Time (HRT) of 10 days or lower. When the organic load was gradually increased, a reactor productivity of 6 LCH4 Lreactor−1 day−1 was achieved. At this point, the reactor processed 20.8 gCOD Lreactor-1 day−1 at a HRT below 5 days, maintaining above 70% of the maximal Chemical Oxygen Demand (COD) conversion rate. Such fast conversion rates and high yields are far beyond what has been reported for other reactor designs, and are a crucial prerequisite for industrial realization of renewable biogas production from municipal solid waste and other organic waste streams.