Comparison of some new pretreatment methods for second generation bioethanol production from wheat straw and water hyacinth

Pretreatment of lignocellulosic residues like water hyacinth (WH) and wheat straw (WS) using crude glycerol (CG) and ionic liquids (IL) pretreatment was evaluated and compared with conventional dilute acid pretreatment (DAT) in terms of enzymatic hydrolysis yield and fermentation yield of pretreated samples. In the case of WS, 1-butyl-3-methylimidazolium acetate pretreatment was found to be the best method. The hydrolysis yields of glucose and total reducing sugars were 2.1 and 3.3 times respectively higher by IL pretreatment than DAT, while it was 1.4 and 1.9 times respectively higher with CG pretreatment. For WH sample, CG pretreatment was as effective as DAT and more effective than IL pretreatment regarding hydrolysis yield. The fermentation inhibition was not noticeable with both types of pretreatment methods and feedstocks. Besides, CG pretreatment was found as effective as pure glycerol pretreatment for both feedstocks. This opens up an attractive economic route for the utilization of CG.