Characteristics and mechanisms of H2S production in anaerobic digestion of food waste

Abstract

The biogas produced in food waste anaerobic digestion (FWAD) contains H2S which can lead to corrosion, bad smell and poisoning accident. To control H2S pollution, the characteristics and mechanisms of H2S production in FWAD should be known. In this study, a lab-scale FWAD batch test was applied for 20 days under 35 °C. The production potential and average concentration of H2S were 765 ± 163 g/t (TS) and 1065 ± 267 ppm, respectively. 76% of total H2S was produced within 6 h on the first day of fermentation, acidification and gas production were key reasons for high H2S production at this time. Compared to H2S peak production time, that of methane was long (4 days) and after that of H2S. Sulfides were found to be the dominant form of sulfur (accounting for 20–70% of total sulfur) in the mixed fermentation liquor in fermentation batch. These sulfides were from protein, which could be decomposed slowly to sulfide by protein-using bacteria and methanogen at the time of methane production peak, and sulfate, which could be converted to sulfide by Sulfate reducing bacteria (SRB) during the first two days of fermentation. Protein would be the main contributor to sulfide/H2S for the continuous feeding FWAD system in long term operation, due to its presence as the main form of sulfur in food waste.