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

Abstract

This study aimed to achieve a reliable start-LIP 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, H-2 production decreased below 7.1 mL H-2/g VS (0.10 mol H-2/mol hexose(added)) within 20 days, because the substrate was consumed via non-H-2-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 H-2 yields of 62.6 mL H-2/g VS (0.87 mol H-2/mol hexose(added)). All bacterial species were affiliated with H-2-producing Clostridium spp. at the cases. Base dosage was increased by 11% compared to the un-pretreated condition. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.