Pretreatment methods of lignocellulosic wastes into value-added products: recent advances and possibilities

A number of industries currently produce many tons of agroindustrial wastes with significant consequences on the environment and human and animal health. In recent years, increasing emphasis has been placed on reducing this negative impact. This review article aims to investigate the use of pretreatment methods that can be applied as an alternative to the usage of residual biomass. In addition, we seek to highlight the efficiency of the processes as well as possible weaknesses, which are associated with high energy and reagent consumption, low yields, and possible secondary impacts. Generally, the waste chemical composition consists mainly of cellulose, hemicellulose, and lignin; these can be fractionated, extracted, and purified to produce different value-added products, such as biofuels, organic acids, enzymes, biopolymers, and chemical additives. Despite the multiple possibilities to produce different products from lignocellulosic biomass, further research is still required to enhance the efficiency of the methods used nowadays and find new procedures. Graphical abstract Flowchart of pretreatment methods for lignocellulosic residues and some of the possible groups of products obtained with their processing.