Supercritical water gasification of biomass model compounds: A review

In recent decades, conversion of bio-renewable resources to biofuels or bio-based chemicals has received a great deal of attention, owing to the resource exhaustion, environmental concerns, and socio-economic issues of fossil fuels. One of the promising biomass conversion routes is the supercritical water gasification (SCWG) of biomass for producing H2 or combustible gases. SCWG is an effective conversion technology, particularly for high water-containing feedstocks, because of its unique advantage by avoiding the costly feedstock de-watering/drying process. To improve gasification performance, it is necessary to have a deeper understanding of the basic chemistry and kinetics of biomass SCWG. Therefore, this review focuses on the performance (chemistry and kinetics) of SCWG of biomass model compounds (cellulose, hemicellulose, lignin, lipid, and protein), and more importantly the binary or multi-component systems to elucidate the interaction effects induced by two or more biomass components in supercritical water (SCW). In addition, the advantages and technical challenges for using SCW as the reaction medium are discussed. Finally, the future R&D directions are presented.