Modeling volatile organic sulfur compounds in mesophilic and thermophilic anaerobic digestion of methionine

Processes involved in volatile organic sulfur compound (VOSC) generation and degradation in mesophilic and thermophilic digestion of methionine were identified, kinetically studied and a mathematical model was established. MM was found to be the only VOSC directly generated from methionine degradation. MM was methylated to form DMS and both MM and DMS were subsequently degraded to H2S. Mixed-second order kinetics were found to best fit the VOSC generation and conversion processes. The kinetic constants (average values) for MM generation and methylation and MM and DMS degradation were estimated to be 0.0032, 0.0047, 0.027, and 0.013 l g−1 h−1 respectively at 35 °C and 0.0069, 0.0012, 0.0083, 0.005 l g−1 h−1 respectively at 55 °C. More rapid MM release and slower VOSC decline at thermophilic temperature implied that VOSC could be more problematic at thermophilic temperatures as compared to mesophilic conditions.

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► Identified VOSC conversion processes in anaerobic digestion of methionine.
► Established a mathematical model for methionine degradation at 35 and 55 °C.
► Digestion at 55 °C may cause more serious odor problems than at 35 °C.