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

► Up-flow anaerobic reactor (UAR) is a promising reactor for biohydrogen production from pretreated rice straw. ► Organic loading rate showed significant influence on overall H2 yield, carbohydrate and COD conversion. ► H2 yield was 95.5, 117 and 107.1 mmol/d at OLR of 7.1, 21.4 and 26 g COD/l d, respectively. ► The carbohydrate removal increased from 57.8% to 82% when the OLR was increased from 7.1 to 26 g COD/l d.