Enhanced H_2 fermentation of organic waste by CO_2 sparging

摘要

This study aimed to improve the productivity of dark fermentative hydrogen production from organic waste. An anaerobic sequencing batch reactor was used for hydrogen fermentation and it was fed with food waste (VS 4.4 ± 0.2% containing 27 g carbohydrate-COD/L) at various CO_2 sparging rates (40-120 L/L/d), hydraulic retention times (HRTs; 18 -42 h), and solid retention times (SRTs; 18-160 h). CO_2 sparging increased the H_2 productivity by 5-36% at all the examined conditions, confirming the benefit of the replacement of headspace gas by CO_2. The maximum H_2 production was obtained by CO_2 sparging at 80 L/L/d, resulting in the H_2 productivity of 3.18 L H_2L/d and the H_2 yield of 97.3 mL H_2/g VS_(added)- Increase of n-butyrate and isopropanol yields were concurrent with the enhanced H_2 yield by CO_2 sparging. Acidogenic efficiency, the sum of H_2. organic acid, and alcohol, in the CO_2-sparged reactor ranged from 47.9 to 56.0%, which was comparable to conventional acidogenesis. Thermodynamic analysis confirmed that both CO_2 sparging and CO_2 removal were beneficial for H_2-producing reactions, but CO_2 sparing has more profound effect than CO_2 removal on inhibiting H_2-consuming reactions.