Biological Hydrogen Production from Biomass

Abstract

This research addressed H2 production from biomass by mixed fermentative cultures,using batch reactors. I studied the effect of heat-treatment of a methanogenic inoculum andacidification of reactor contents to pH 5.5 on H2 production from cattle manure and reed canary grasshay. Hydrogen production from goldenrod and sugarcane was also quantified. The potential forbiological H2 production from nitrogen-deficient substrates was determined using a defined mediumlacking combined N, and a nitrogen-fixing mixed culture. I found that a combination of heattreatment and acidification resulted in the greatest H2 yield from both reed canary grass hay andmanure. All biomass substrates studied readily supported biological H2 production using a heattreatedinoculum with acidification of the reactor contents. However, the H2 yield from manure wasvery low, approximately 1 mL H2/g volatile solids (VS). Sugarcane showed the highest yield, 77 mLH2/g VS with added nutrients. I found that H2 production was possible from a medium lackingcombined N using a nitrogen-fixing mixed culture. The yield of H2 from this medium, up to 240 mLH2/g glucose (1.9 mol H2/mol glucose), was greater than with added NH4Cl. Using the nitrogen-fixingculture, sugarcane showed a relatively high H2 yield of 168 mL H2/g VS, which is similar to yieldsfrom pure carbohydrates from other studies. These results show that H2 can readily be producedfrom a range of biomass materials. However, without substantial improvement, most yields areprobably too low to be practically useful. Sugarcane was an exception, and shows promise as asubstrate for biological H2 production.