The effect of organic loading rate on bio-hydrogen production from pre-treated rice straw waste via mesophilic up-flow anaerobic reactor

Effect of organic loading rate (OLR) on the continuous biological H2 production from pretreated rice straw waste using a mesophilic up-flow anaerobic reactor (UAR) was investigated for 140 d. OLR was varied from 7.1 to 26 g COD/l d. H2 yield was significantly increased from 95.5 to 117 mmol/d, when OLR was largely increased from 7.1 to 21.4 g COD/l d, respectively. However, further increase in OLR up to 26 g COD/l d, showed a decreasing trend to 107.1 mmol/d. Likewise, H2 production increased with OLR at the range of 7.1–21.4 g COD/l d, and reached the maximum H2 production of 2.6 l/d. However, the H2 production started to decrease with the further increase of OLR, and dropped to 2.2 l/d at OLR of 26 g COD/l d. The COD and carbohydrate removal efficiency were over 70% and 80% at OLRs of 7.1–21.4 g COD/l d, and decreased thereafter.