High rate biomethanation using spent biomass as bacterial support

Abstract

Methanogenic bacteria were found strongly adhered to several green biomass feedstocks digested in a solid-phase stratified bed (SSB) biogas fermenter, and hence these digested feedstocks were examined for their potential for use as methanogen support for a high-rate biogas fermenter, A 1.1 l experimental down flow fixed bed (DFFB) fermenter was operated at 35 degrees C using synthesized liquid waste, This gave gas production levels up to 6.5 l/l/d, Methanogenic activities measured on such biomass support material exhibited a potential to achieve much higher biogas production, Short-duration thermal and feed shocks were tolerated without their exhibiting typical methanogen washout characteristics. The DFFB fermenter functioned well even at 21 +/- 1 degrees C, with gas production rates up to 3 l/l/d, and thus appeared to have potential for producing biogas at small scales and at high rates from various combinations of liquid and solid biomass wastes.