An application of ultrasonication in lignocellulosic biomass valorisation into bio-energy and bio-based products

The industrial revolution has caused a tremendous impact on our modern way of life. It shapes the economic, social and culture of many modern societies around the world. However, the world's heavy dependence on fossil fuels has exacerbated the effect of modernisation, causing a detrimental effect to the world climate. Recently, the scientific community has shifted their focus to the valorisation of lignocellulosic biomass as a renewable and clean source of energy. Lignocellulosic biomass is a potential substitute for fossil fuel as it could be transformed to various bio-energy and bio-based products by biorefineries. However, the recalcitrant nature of lignocellulosic biomass hinders the commercialisation at large scale due to the processing difficulties and economically not viable. Hence, ultrasound has been utilised as an auxiliary energy to intensify pretreatments as well as biorefinery processes in the productions of bio-fuels and fine chemicals. In this review, the background information of lignocellulosic biomass and ultrasound is provided. Furthermore, the applications of ultrasound as a complement to existing pretreatments and bioprocessing technologies are discussed by highlighting the importance of mechanoacoustic and sonochemical effect produced by the ultrasound. Lastly, technoeconomic analysis and socioeconomic impact of utilising ultrasound in the biomass processing are elaborated to provide a holistic view on the novel and environmentally friendly green technique.