Co-inhibition of methanogens for methane mitigation in biodegradable wastes

The inhibition effects and mechanisms of chlorinated methane and acetylene on methanogenesis in the anaerobic digestion process of the biodegradable wastes were investigated. It was found that both chloroform and acetylene could effectively inhibit methanogens while the biodegradability of the wastes was not affected. Acetylene inhibited the activity of methanogens, while chloroform inhibited metabolic process of methanogenesis. A central composite design (CCD) and response surface regression analysis (RSREG) were employed to determine the optimum conditions and interaction effects of chloroform and acetylene in terms of inhibition efficiency, production of volatile fatty acids (VAF) and molar ratio of propionic acid to acetic acid. Chloroform had significant effect on enhancing the production of VFA (F = 121.3; p < 0.01), and acetylene promoted the inhibition efficiency (F = 99.15; p < 0.05) more effectively than chloroform (F = 9.72; p > 0.05). In addition, a maximum molar ratio of propionic acid to acetic acid of 1.208 was estimated under the optimum conditions of chloroform concentration of 9.05 mg/kg and acetylene concentration of 3.6×10−3 (V/V). Hence, methanogens in the wastes can be inhibited while the stabilization process of the biodegradable wastes can still work well, as propionic acid generated during the inhibition process could hardly be utilized by methanogens.