Hydrogen production from food wastes and gas post-treatment by CO2 adsorption

The production of H-2 by biological means, although still far from being a commercially viable proposition, offers great promise for the future. Purification of the biogas obtained may lead to the production of highly concentrated H-2 streams appropriate for industrial application. This research work evaluates the dark fermentation of food wastes and assesses the possibility of adsorbing CO2 from the gas stream by means of a low cost biomass-based adsorbent. The reactor used was a completely stirred tank reactor run at different hydraulic retention times (HRTs) while the concentration of solids of the feeding stream was kept constant. The results obtained demonstrate that the H-2 yields from the fermentation of food wastes were affected by modifications in the hydraulic retention time (HRT) due to incomplete hydrolysis. The decrease in the duration of fermentation had a negative effect on the conversion of the substrate into soluble products. This resulted in a lower amount of soluble substrate being available for metabolisation by H-2 producing microflora leading to a reduction in specific H-2 production. Adsorption of CO2 from a gas stream generated from the dark fermentation process was successfully carried out. The data obtained demonstrate that the column filled with biomass-derived activated carbon resulted in a high degree of hydrogen purification. Co-adsorption of H2S onto the activated carbon also took place, there being no evidence of H2S present in the bio-H-2 exiting the column. Nevertheless, the concentration of H2S was very low, and this co-adsorption did not affect the CO2 capture capacity of the activated carbon. (C) 2011 Elsevier Ltd. All rights reserved.