Hydrogen Production from Residual Biomass Via Air-Steam Gasification for a Bioenergy-Based Economy in Sicily

A promising and programmable renewable primary source of hydrogen is biomass. Among the different thermally driven technologies for biomass conversion, gasification is able to provide efficient and sustainable production of hydrogen. Further economic and environmental advantages can be obtained when residual biomasses or wastes are used locally, avoiding long-distance transportation. This work aims at evaluating the potential impact of hydrogen production in Sicily by citrus peel air-steam gasification. According to the technical report of ISPRA, the availability of citrus peel in Sicily is about 33.000 tons per year (solid matter). The thermochemical behavior of such feedstock, i.e. producer gas (syngas) composition and energy conversion efficiencies, were previously evaluated by means of a bench-scale fluidized bed reactor, using different mix of air and steam as gasification medium. A virtual scale-up of the gasification system was developed in order to carry out a preliminary study of the combined hydrogen and power production potential using such feedstock. The downstream processes of syngas, such as hydrogen separation through Pressure Swing Adsorption (PSA) and off-gas combustion, were simulated considering the efficiencies reported in literature and datasheets. The results of this study show that 1280-1850 t/year of hydrogen can be produced by exploiting 100% of available citrus peel in Sicily. The off-gas, obtained after the separation of hydrogen stream in the PSA unit, can be burned in gas engines for combined heat and power production. About 990 to 7800 MWh/year of electricity can be exported to the national grid, while the heat may be used for the citrus peel drying step. The amount of bio-hydrogen that could be produced in the region with such approach can be used for feeding from 500 to 750 electrical hybrid (batteries/fuel cells) minibuses for local public transportation.