Supercritical water gasification of biomass in diamond anvil cells and fluidized beds

With the shift in interest towards renewable energy, hydrogen as an alternative gaseous fuel seems to attract much attention. Waste biomass is an ideal option for the synthesis of biofuels due to its abundance and no net CO 2 emissions. Hydrogen can be produced through supercritical water gasification of waste biomass. Hydrogen is an attractive energy carrier which can be used as a direct fuel or in fuel cells to generate electricity and in other energy‐producing processes. Gasification of biomass in supercritical water can be performed for hydrogen generation in both batch and continuous modes with/without the application of catalysts. In spite of the progress made in various gasification technologies, diamond anvil cells and fluidized beds as the new‐generation batch and continuous reactors, respectively, are not fully recognized. The current review is focused on understanding the design, application and limitations of these two new reactor configurations to help motivate their wide‐scale utilization. The review also discusses the potential of diamond anvil cells in studying the involved chemical reactions, thermodynamics, and phase behavior of biomass components during gasification. Nonetheless, the caliber of fluidized beds in continuously gasifying biomass for hydrogen production in supercritical water is also documented.