Biohydrogen production by anaerobic digestion of corn cob and stem of faba bean hydrolysates

Biomass waste for hydrogen production is an important goal for the Hydrogen Economy. In this paper is reported the research of corn cob and stem of faba bean agricultural waste by hydrolysis for sugar production. Acid hydrolysis was performed in 1 g of dried raw material per 15 mL of different H3PO4 acid solutions heated at 100°C and 130°C during 2 h. The sugar yield was determined by dinitro salicylic acid technique. The maximum sugar recovery calculated in g of sugar per g of raw material were 0.43 and 0.17 for corncob and faba bean stalk respectively. For fermentation, hydrolysates were mixed in sealed vials with culture medium in anoxic atmosphere, an inoculum of 0.05 mL of Clostridium butyricum and 0.05 mL of Enterobacter cloacae was used, the vials were incubated at 37°C, two samples were taken every 2 h. The cell growing was monitored using a Petroff-Hausser counting chamber, hydrogen production was determined by gas chromatography and pH was also determined for each sample. In both substrates the cell growing lag time was 4 hours and after 11 hours hydrogen production was detected. The saccharide-biohydrogen production yields for sugars obtained from the hydrolysates were calculated according to the 2.75 mol H2 per mol glucose reported experimentally in mexican fruits and vegetable waste. They were 18.9% and 12% for corncob and faba bean stem respectively.