Effects of base-pretreatment on continuous enriched culture for hydrogen production from food waste

This study aimed to achieve a reliable start-up method for continuous enriched culture for hydrogen production from food waste. When ground and diluted food waste (volatile solids (VS) 4.4 ± 0.2% containing 27 g carbohydrate-chemical oxygen demand/L) was fed, H2 production decreased below 7.1 mL H2/g VS (0.10 mol H2/mol hexoseadded) within 20 days, because the substrate was consumed via non-H2-producing acidogenesis. To suppress the unintended microbial reactions, three methods were examined: lowering H2 content by continuous CO2 sparging, acid-pretreatment of food waste at pH 2.0 for 1 day, and base-pretreatment of food waste at pH 12.5 for 1 day. The base-pretreatment reduced indigenous anaerobic bacteria in food waste by 4.9 log and enabled a stable long-term operation over 90 days with the H2 yields of 62.6 mL H2/g VS (0.87 mol H2/mol hexoseadded). All bacterial species were affiliated with H2-producing Clostridium spp. at the cases. Base dosage was increased by 11% compared to the un-pretreated condition.