Characterizing and modeling hydrogen sulfide production in anaerobic digestion of livestock manure, agro-industrial wastes, and wastewater sludge

Hydrogen sulfide (H2S) is the most undesirable inorganic gas in biogas from anaerobic digestion (AD). However, H2S production in AD is complex and understanding of its processes is still limited. This study performed six controlled batch anaerobic co-digestion experiments to investigate H2S production. Materials were obtained from four field anaerobic digester systems and co-digestion feedstocks from agroindustry. An additional precipitation experiment was conducted to further examine H2S production dynamics. Digesters containing highly soluble, carbohydrate-based wastes had a high H2S final specific production (FSP) value. Additionally, the FSP values were negatively correlated with the initial Fe(II):S ratios in the digester liquid of the batch tests. The precipitation experiment indicated that iron sulfide precipitation was preferred in the presence of an anaerobic community. The H2S production as a time series was successfully modeled using a generalized additive model (R-2>0.82). This study revealed that sulfate, phosphorus, and iron concentrations are important predictors and potential inhibitors of H2S production in AD. Further examination of real-time H2S modeling in AD is warranted.