Combination of Technologies for Biomass Pretreatment: A Focus on Extrusion

Lignocellulosic biomasses, mainly forestry and agricultural residues, are inexpensive, available and attractive to reduce the dependence of the world on fossil fuels. However, before their processing in biorefineries, they must undergo a pre-treatment to allow access to the desired compounds of interest (cellulose, hemicellulose, or lignin). However, the pretreatment step significantly reduces and affects the profitability of the biorefinery process. Several pretreatment technologies have been developed so far. However, taken individually, these methods do not make lignocellulosic biomass a fully cost-effective input for biorefineries, hence the current trend to combine technologies. Extrusion is currently one of the most attractive technologies. It is relatively new and has been combined with many other methods to pretreat various types of biomasses with interesting benefits and results. This article provides a critical review of pretreatment combinations involving extrusion and discusses the challenges, solutions, and R&D needs for these combinations.