Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis

This study aims at using Emergy Theory to investigate the sustainability hydrogen production from corn stalks by supercritical water gasification, all the inputs including renewable resources, non-renewable resources, purchased inputs in the whole life cycle of hydrogen have been incorporated and transformed into emergy. The emergy indices with respect to this technology can be summarized as follows: the transformity is 5.5323E + 13 sej/kg, the emergy yield ratio (EYR) which is a measure of the ability of the system to exploit and make local resources available by investing in outside resources is 1.0117, the environmental load ratio (ELR) which indicates the load on the environment by the system is 5.0684, the environmental investment ratio (EIR) which can measure the utilization level of the invested emergy is 85.8303 and the emergy index of sustainability (ESI) which is a measure of the sustainability of a product, a process or a service is 0.1996. Therefore, it is not sustainable in the long term perspective for hydrogen production from corn stalks by supercritical water gasification in the current situation of Huaibei city in China. According to the results of sensitivity analysis, two implications are obtained for enhancing the sustainability of hydrogen from corn stalks: one is developing innovative agricultural system to reduce the consumption of nitrogenous fertilizer and phosphate, and another is to improve the yield and utilization efficiency of corn stalks.