SUPERCRITICAL WATER TREATMENT OF BIOMASS FOR ENERGY AND MATERIAL RECOVERY

TLDR

Supercritical water liquefaction and gasification enable energy recovery from wet biomass and material recovery from biomass species, with cellulose fully dissolving in supercritical water. In supercritical water, dissolved cellulose undergoes rapid hydrolysis and pyrolysis, enzyme‑assisted hydrolysis is possible, lignin is converted to specialty chemicals using a supercritical cresol/water solvent, and the dissolution facilitates efficient biomass gasification. The hydrolysis reaction, limited by mass transfer, is faster than decomposition and allows efficient glucose recovery, while complete gasification produces combustible gases such as hydrogen, carbon monoxide, and methane. Keywords: supercritical water, biomass, cellulose, lignin, liquefaction, gasification, chemicals.

Abstract

ABSTRACT Supercritical water liquefaction and gasification is reviewed with the introduction of some recent findings by the authors. Supercritical water gasification is suitable for recovery of energy from wet biomass while supercritical water liquefaction opens the door to effective treatment of biomass species in terms of material recovery. Cellulose, one of the main components of biomass, is completely dissolved in supercritical water. Once dissolved, reaction of cellulose can take place swiftly by hydrolysis and pyrolysis. The hydrolysis reaction, otherwise slower than pyrolysis due to the mass transfer limitation, is faster than decomposition in supercritical water, and a possibility of efficient glucose recovery has been shown. Once dissolved, super saturation is kept when the solution is cooled down, and swift hydrolysis by enzyme is also possible. Lignin can be also converted into specialty chemicals by using supercritical cresol/water mixture as a solvent. Dissolution of cellulose also enables efficient gasification of biomass. Complete gasification of biomass has been realized with production of combustible gas including hydrogen, carbon monoxide, and methane. Keywords: supercritical waterbiomasscelluloseligninliquefactiongasificationchemicals