Supercritical water gasification of biomass for hydrogen production – Review

The paper summarizes the recent developments in the field of supercritical water gasification (SCWG) of biomass. Chemical and chemical engineering studies are introduced and sorted into categories, which are the main factors influencing the chemical reaction pathways of SCWG. These are: the components of biomass (carbohydrates, lignin, ash, proteins and lipids), reaction conditions e.g. concentration and the possible addition of heterogeneous catalysts. Most studies focus on model compounds, here the interference of the components in mixtures give a deeper understanding in view of the conversion of real biomass. Also studies with biomass are reported; here in most cases the effect of salts, catalyzing hydrogen formation, is dominating. The progress in knowledge is evaluated in view of the hurdles to overcome for a wide industrial application. Recent paper hints to a future of hydrothermal gasification as part of a bio-refinery and with an internal use of hydrogen produced.