Biofuels: Microbially Generated Methane and Hydrogen

Abstract

The production of methane (CH 4 ) or hydrogen (H 2 ) 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 CH 4 through food chains comprised of fermentative and acetogenic species, which decompose the complex biomass to H 2 , formate and acetate that are further metabolised to CH 4 by methanogens. Methanogens reduce the concentration of products to levels that permit the initial decomposition of biomass by fermentative and acetogenic species. Current H 2 production relies extensively on energy-intensive fossil fuel sources. Photosynthetic and fermentative species offer more efficient routes for H 2 production. Although fermentatives have significantly higher production rates, they have lower yields of H 2 but may be a source of other valuable compounds that are synthesised along with H 2 . Further research must be conducted on obtaining H 2 from reductive pools of NAD(P)H to increase yields and increase economic competitiveness.