Hydrogen and methane production from untreated rice straw and raw sewage sludge under thermophilic anaerobic conditions

摘要

Bioenergy produced from co-digestion of sewage sludge (SS) and rice straw (RS) as raw materials, without pretreatment and additional nutrients, was compared for the one-stage system for producing methane (CH_4) and the two-stage system for combined production of hydrogen (H_2) and CH_4 in batch experiments under thermophilic conditions. In the first stage H_2 fermentation process using untreated RS with raw SS, we obtained a high H_2 yield (21 ml/g-VS) and stable H_2 content (60.9%). Direct utilization of post-H_2 fermentation residues readily produced biogas, and significantly enhanced the CH_4 yield (266 ml/g-VS) with stable CH_4 content (75-80%) during the second stage CH_4 fermentation process. Overall, volatile solids removal (60.4%) and total bioenergy yield (8804 J/g-VS) for the two-stage system were 37.9% and 59.6% higher, respectively, than the one-stage system. The efficient production of bioenergy is believed to be due to a synergistically improved second stage process exploiting the well-digested post-H_2 generation residues over the one-stage system.