Biofuels: Microbially Generated Methane and Hydrogen

The production of methane (CH4) or hydrogen (H2) from renewable biomass by microorganisms growing anaerobically has the potential for contribution to independence from fossil fuels. Anaerobes function in Nature by converting biomass to CH4 through food chains comprised of fermentative and acetogenic species, which decompose the complex biomass to H2, formate and acetate that are further metabolised to CH4 by methanogens. Methanogens reduce the concentration of products to levels that permit the initial decomposition of biomass by fermentative and acetogenic species. Current H2 production relies extensively on energy-intensive fossil fuel sources. Photosynthetic and fermentative species offer more efficient routes for H2 production. Although fermentatives have significantly higher production rates, they have lower yields of H2 but may be a source of other valuable compounds that are synthesised along with H2. Further research must be conducted on obtaining H2 from reductive pools of NAD(P)H to increase yields and increase economic competitiveness.