Influence of the Sludge Ratio on the High-solids Thermophilic Methane Fermentation of the Organic Fraction of Municipal Solid Waste and Bio-sludge
Yoshio Okuno*, Yu-You Li*, Hiroshi Sasaki**, Koji Seki* and Ikuo Kamigochi**Abstract
The influence of the sludge ratio on the high-solids thermophilic methane fermentation of the organic fraction of municipal solid waste(MSW)and bio-sludge was investigated by using a semi-continuous flow completely mixed reactor. The methane fermentation experiments were conducted at a constant influent total solid(TS)concentration of 12-13% and a constant retention time of 15 days by altering the sludge ratio from 0% to 50% under thermophilic condition(55C[Celsius degree]). As the sludge ratio in the influent TS increased from 0% to 50%, the degradation efficiency of volatile solid decreased from 78% to 49%, while the biogas production yield decreased from 0.8 to 0.5L/g-VS. For maintaining high rate stable methane fermentation, addition of minerals to the feed was necessary for the MSW-rich cases when the sludge ratio in the influent TS was lower than 10%, while successful operation was possible without mineral addition when the sludge ratio was higher than 25%. The energy production in an integrated biogas system of thermophilic methane fermentation and power generation using biogas was calculated based on the experimental results obtained from this study.
Key words: methane fermentation, high-solids co-digestion, thermophilic, organic fraction of municipal solid waste, power generation