The conversion of lignocellulosic biomass to bioethanol: pretreatment technology comparison

Abstract

The barrier to realising the potential of lignocellulosic bioethanol is the recalcitrance of cellulosic biomass. Overcoming this biomass recalcitrance is the key challenge to large scale production of lignocellulosic bioethanol. Pretreatment is an important and critical step that enables enzyme hydrolysis of lignocellulose conversion to ethanol. Finding a pretreatment method for reducing the high recalcitrance via cost-effective pretreatment methods would therefore be of great benefit. This study aims at investigating the effect of pretreatment on delignification process of sugarcane bagasse and oil palm trunk. Two methods of pretreatment were compared i.e. alkaline hydrogen peroxide pretreatment (1% and 5% H2O2) and subcritical water pretreatment (170°C, 2.2 MPa) for the effectiveness of reducing the lignin content. Scanning Electron Microscopy (SEM) analysis was also performed to investigate the effect of pretreatment on surface of lignocellulosic biomass. It was observed that alkaline hydrogen peroxide pretreatment gave better results than subcritical water pretreatment based on the lignin content for both lignocellulosic biomass. Pretreated sugarcane bagasse presented lower lignin content than pretreated oil palm trunk. Lignin was successfully removed until 56.99% under the best condition of 5% of alkaline hydrogen peroxide, at 28°C for 72 hours incubation. This study confirmed that alkaline pretreatment was found to have a better method for the conversion of lignocellulosic materials. Furthermore, sugarcane bagasse has a greater potential as basic raw materials used for the bioethanol production than oil palm trunk because it has lower content of lignin with higher content of cellulose.