Effect of organic acid pretreatment of water hyacinth on enzymatic hydrolysis and biogas and bioethanol production

Abstract

Due to rapid growth and uncontrolled spreading of water hyacinth in aquatic natural and urban niches, the conversion of this weed to value-added chemicals and biofuels leads to the reduction of pollution and greenhouse effect. The rate-limiting step of the conversion process is hydrolysis reaction of lignocellulosic biomass to sugars, which are subsequently converted to biochemicals and biofuels. To improve the enzymatic hydrolysis efficiency of water hyacinth, the organic acid pretreatments were conducted in this study by using two types of organic acids, including oxalic acid and citric acid. The pretreatment parameters, including pretreatment time, pretreatment temperature, and acid concentration were optimized by using Response Surface Methodology (RSM) based on Box-Behnken design. The highest reducing sugar concentration at 66.92 mg/100 mg-biomass was obtained when using oxalic acid pretreatment. The effects of organic acids on biogas and bioethanol production were observed compared to unpretreated water hyacinth. The biogas and bioethanol yields were increased for 75.61% and 23.26% when using citric acid and oxalic acid pretreatment, respectively. The improvement of biofuel production from water hyacinth by organic acid pretreatment suggested the possibility to applications and solutions in biorefinery industry and environmental situation.