Methane Production By Bacteria Fermentation As A Source of Fuel

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The biological process of microbial methanogenesis can occur where organic matter accumulates, such as in animal digestive tracts and in river sediments, under anaerobic conditions (Chynoweth 1996). Wastewater treatment has used methanogenesis, producing methane CH4, for over 150 years in the digestion of biosolids (Rittmann 2008). Interest in methane production by bacterial fermentation as a source of fuel has progressed since the issues of oil security in the 1970s (Logan 2004, Benemann, Weissman, Koopman and Oswald 1977).

Sources and Supply of Substrate

Yadvika and colleagues, in a review quoted by Antoni, Zverlov and Schwarz (2007) state the choice of substrate as organic household or industrial waste, commercial energy plant life and plant biomass. Specific substrates include household food waste and garden waste, municipal solid waste, sewage sludge and wastewater, industrial recycling of paper, agricultural and food production waste including fats from abattoirs and factories and manure from horses, pigs, cows and chickens. Energy crops considered suitable for adding purely or mixing with organic waste to produce biogas are clover, grass, young poplar and willow trees and maize (Antoni et al. 2007) although there are arguments against growing new biomass when waste plant materials is available.
Appropriate substrate for bacterial fermentation to produce methane is available and accessible. A general point is that quality control procedures will be required to ensure, what Antoni calls “a homogenous quality of substrate” entering bacterial fermentation processes. The lack of a substrate quality control system will limit the effectiveness and efficiency of methane production towards fuel.

Biofuels as a Source of Transportation Fuel

Organic waste as a commodity will grow proportionate to the increasing global population. Earlier this year, Kunzig asserted that the current 7 billion people in the world are projected to reach a global population of 9 billion by 2045. Consumption of energy worldwide in 2004 was reported by Goldemberg and Johasson cited by Rittmann, as 13 terrawatts (1TW = 1012W) with approximately 80% of that energy derived from fossil fuels. Figures from EIA published in 2006 are cited by Antoni et al. (2007) that transportation uses 27% of primary energy worldwide and is the fastest growing sector.
Against this demand, the potential of methane to contribute to producing a biofuel is considerable as only a small number of energy-rich chemicals compounds can be produced by microbes (Madigan, Martinko, Dunlap and Clark 2009) and still have the capacity to make safe fit for purpose fuel that can be stored and have a high energy efficiency in combustion engines and capability to power a vehicle (Antoni et al. 2007).

References

Antoni D, Zverlov VV, Schwarz WH. Biofuels from microbes. Applied Microbiology and Biotechnology. 2007; 77:23-35
Benemann JR, Weissman JC, Koopman BL, Oswald WJ. Energy production by microbial photosynthesis. Nature. 1977; 268 (5615): 19-23.
Chynoweth DP. Environmental impact of biomethanogenesis. Environmental Monitoring and Assessment. 1996; 42: 3-18.
Kunzig R. Population 7 Billion. [homepage on the Internet] National Geographic; 2011 [updated January 2011; cited 2011 Jul 20]. Available
Logan BE. Extracting Hydrogen and Electricity from Renewable Sources. Environmental Science and Technology. 2004; 160A-167A
Madigan MT, Martinko JM, Dunlap PV, Clark DP. Brock Biology of Microorganisms. 12th ed. San Francisco (USA): Pearson Benjamin Cummings; 2009.
Rittmann B. Opportunities for Renewable Bioenergy using Microorganisms. Biotechnology and Bioengineering. 2008; 100 (2): 203-212.