Technical and economic evaluation of hydrogen production by biomass gasification in supercritical water and in air-steam media

Technical and economic conditions of hydrogen production by biomass gasification in supercritical water and in air-steam media have been evaluated. Reaction mechanism, technological process, product gas composition and operation costs of two processes were compared. Results indicate that biomass gasification in supercritical water has much more advantages than in air-steam medium, such as easier operation process, smaller machine area, high gasification efficiency, and less pollution, etc. There are no needs of biomass pretreatment and post-processing for product gas in supercritical water. Moreover, the proportions of hydrogen, carbon dioxide, methane are high, so these kinds of product gas all can be utilized. However, the cost of producing 1Nm³hydrogen in supercritical water is $0.6537, which is a little higher than $0.4228 in air-steam media. With the construction of more supercritical water unit and accumulation of more experience, hydrogen production by biomass gasification in supercritical water will have a more bright future.