CHAPTER 18:Use of Water and Supercritical Carbon Dioxide in Novel Methodologies for Biomass Processing

Conversion of abundant biomass to bioproducts, biomaterials and bioenergy is essential for accomplishment of the biorefinery concept. The first challenge involved in biorefinery processing is biomass fractionation into individual components. One of the most commonly used methods of biomass deconstruction at industrial level is hydrothermal pre-treatment. However, improvements in this technology by use of low cost and widely available solvents are highly desirable. Supercritical CO2 (scCO2) is a good candidate and its use can result in more efficient biomass processing. The advantage of scCO2 use is that the pre-treated material presents no solvent residues after the pre-treatment and CO2 can be easily recovered and reused. Moreover, CO2 in the presence of water generates an acidic environment that offers several benefits in biomass fractionation and chemical transformations. Therefore, this chapter aims to demonstrate the use of scCO2 and water in biomass pre-treatment, highlighting the effects on hemicellulose and starch hydrolysis, as well as the influence on cellulose hydrolysis and lignin extraction. In addition, the benefits of scCO2 in the conversion of biomass-related monosaccharides (hexoses and pentoses) into value-added products are presented. Finally, the influence of pre-treatments on the enzymatic hydrolysis of pre-treated biomass is discussed.