A kinetic model for methanogenesis of acetic acid in a multireactor system

Bioconversion of acetic acid to methane by a crude culture of methanogens in a continuous multireactor system was investigated. Culture of methanogens was drawn from an active cow-dung digester (12 days) and was grown in a semisynthetic medium (pH 6.3, 37 degrees C) with acetic acid as the sole carbon source. The solubilities of CO(2), HCO(3) (-), and CO(3) (2-) increased with the rise in pH and exercised considerable influence on the gas composition. Various mechanisms for methanogenesis of acetic acid based on the available pathways were considered. Experimental data were compared with these mechanisms, the best fit was determined, and the corresponding rate expression was identified. This mechanism predicted that, of the total methane produced, 72%;comes from acetic acid directly and 28%;via the CO(2) reduction route.