Hydrolysis of Biopolymers in Near-Critical and Subcritical Water

Near-critical and subcritical waters have been known as green solvents that can be applied in many different fields of applications. In recent years, they have been proposed as solvents media to recover waste substances from plant biomass. Near-critical and subcritical water treatment is a powerful technique and one of the most effective methods for this, because water at around its critical point behaves as a reaction medium with unique properties. Water at around its critical point was able to promote various reactions such as oxidation, hydrolysis, and dehydration. Hence, near-critical and subcritical water can be used for the conversion of plant biomass composed of three major biopolymers (i.e., cellulose, hemicellulose, and lignin) to value-added chemical compounds, as well as for oxidizing hazardous waste into CO₂ or harmless compounds. This chapter presents the concepts of near-critical and subcritical water and their application in degradation of plant biomass components at temperatures of 100-400°C.