Effect of chemical pretreatment using sulfuric acid on biogas production from water hyacinth and kinetics

Abstract

Abstract The effect of chemical pretreatment on biogas production from water hyacinth (WH) was investigated. In pretreatment process, H2SO4 concentration was varied to be 0, 1, 2, 3, 4, 5 %v/v and residence time was varied to be 0, 30, 45, 60, 75, 90 min. Effluents of pretreatment were used as biogas feedstock. The results showed that pretreatment changed not only the cellulose content but also the glucose, COD (Chemical Oxygen Demand) and COD/N (COD/Nitrogen) ratio. Cellulose degradation occurred to follow first-order reaction based on the power law model. The best pretreatment condition was H2SO4 concentration of 5%v/v with residence time of 60 min because the slurry pretreated at that condition contained COD/N of 388.2. Anaerobic digestion of the slurry produced the biggest total biogas (424.30 mL) with the highest methane content (64.38%). The pretreatment increased total biogas 131.45% compared to without pretreatment. The measured total biogas for 90 days was fitted by using modified Gompertz, Cone, First Order model in which they resulted fitting error of 0.271–9.789%, 0.032–8.743%, 3.491–5.681% respectively. In prediction using Ratkowsky and Phenomenogical model, the slurry containing optimum COD/N of 393 (total biogas 434.64 mL) was obtained with pretreatment of H2SO4 5%v/v for 65 min.