Keywords: biogas, dry digestion, leachate recirculation, one-stage systems, batch process, batch anaerobic digestion, solid substrates, volatile fatty acids, water circulation, hydrolysis, biomass moisture content
Effect of various leachate recirculation strategies on batch anaerobic digestion of solid substrates
Various leachate recirculation strategies were applied to a batch-wise operated solid-phase digestion system in laboratory-scale tests. Comparative experiments with both continuous and intermittent leachate recirculation revealed no advantages of a continuous flow. Results suggest that leachate recirculation should not be carried out continuously during process initialisation when methanogenesis is the rate-limiting step. Continuous watering resulted in the accumulation of Volatile Fatty Acids (VFA) during process start-up. In addition, no need for continuous water circulation was found for the following digestion process when hydrolysis was rate-limiting. Even in the absence of liquid recirculation, degradation was only slightly retarded when the biomass moisture content was adjusted.