Enhancement of Biogas Production from Bundled Rice Straw Solid-State Fermentation by Adding Microbial Agents

Abstract

Two contrasting garage-type solid-state fermentation experiments were designed at pilot scale to reveal the intensification process and effects of adding compound inoculants. Bundled rice straw and fresh pig manure were used as feedstock with a total solids concentration (w/w) of 20% under ambient temperatures of 26 to 35 oC. The characteristics of biogas production and variations in bacterial community composition were investigated. The results indicated that using microorganisms shortened the start time of anaerobic solid-state fermentation. The target methane content in the biogas production reached 30% 7 days before the control group. A target of 50% was reached 8 days before the control group. Throughout the fermentation cycle, the cumulative gas production of the experimental group was 1340 m3, which was 20.5% higher than the control group. Cumulative methane production increased by 45%. Clustering and principal coordinates analysis suggested that the addition of compound bacteria increased the diversity of the microbial community and stabilized its structure, thus improving gas production efficiency and methane purity. These findings can assist future bioaugmentation research pertaining to the application of composite microbial agents.