Enhancement of volatile fatty acids production from rice straw via anaerobic digestion with chemical pretreatment

Rice straw is one of the most abundant renewable biomass sources and was selected as the feedstock for the production of volatile fatty acids (VFAs) from which microbial biodiesel can be produced. Two kinds of chemical pretreatments involving nitric acid and sodium hydroxide were investigated at 150 °C with 20 min of reaction time. The nitric acid pretreatment generated the most hemicellulose hydrolyzate, while significant reduction of the lignin occurred with sodium hydroxide pretreatment. Anaerobic digestion of 20 g/L rice straw yielded 6.00 and 7.09 g VFAs/L with 0.5 % HNO₃ and 2 % NaOH, respectively. The VFAs yield with 2 % NaOH was 0.35 g/g.