methanogens and Biogas
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Transcript of methanogens and Biogas
METHANOGENS AND BIOGAS
ucla genomics
Methanogens
Methanogens are bacteria that produce methane gas
They can be used as sources of biogas gas This would be a renewable source of energy
© 2008 Paul Billiet ODWS
Ecology Methanogens require anaerobic conditions In the digestive systems of herbivores, marshes or
lake bottoms. Many require warm conditions to work best. They are associated with a source of organic
matter (e.g. plant remains or sewage) and with heterotrophic bacteria
The heterotrophs break down this organic matter to release compounds such as ethanoic acid (aka acetic acid or vinegar) and hydrogen
The ethanoate ions are a substrate for the methanogens
© 2008 Paul Billiet ODWS
ClassificationMethanogens belong to the Archaea group of the ProkaryotesExamples Methanococcus jannaschiiMethanobacterium thermoautotrophicum
The prokaryote kingdom has been split into several further kingdoms (e.g. Archaea and Eubacteria) based on the genetics and biochemistry of microbes
© 2008 Paul Billiet ODWS
Biochemistry Methanogens are chemoautotrophs Methanogens use a number of different ways
to produce methaneUsing ethanoate (acetate) that may be derived
from the decomposition of cellulose:
CH3COO+ + H- CH4 + CO2 +36 kJ mol-1
Or using hydrogen and carbon dioxide produced by the decomposers:
4 H2 + CO2 CH4 + 2 H2O +130.4 kJ mol-1
© 2008 Paul Billiet ODWS
Biogas production
From the decomposition of wastes in farming sewage treatment
A bi-product of the cleaning up of waste water
Biogas consists of about 40% CO2 and 60% CH4
BEA Dithmarschen
© 2008 Paul Billiet ODWS
Requirements a fermenter, which is supplied with an innoculum of
bacteria (methanogens and decomposers) anaerobic conditions an optimum temperature of 35°C an optimum pH of 6.5 to 8
This needs to be monitored as the decomposers produce acids and they work faster than the methanogens consume the acids
organic waste (biomass) e.g. sewage, wood pulp
© 2008 Paul Billiet ODWS
Methanogens and the greenhouse effect
Half of the methane produced by methanogens is used up as an energy source by other bacteria
Half is lost to the atmosphere (600 M tonnes y-1) where it acts as an important greenhouse gas
As more land is converted to rice paddy fields and pasture for grazing animals more methane will be produced
DAF Shiga Pref.
© 2008 Paul Billiet ODWS
Warming up the brew
As global warming progresses the permafrost with thaw in the regions covered by tundra
Tundra contains extensive reserves of frozen peat
As the peat warms and melts, it will provide a source of material for methanogens
© 2008 Paul Billiet ODWS
The knock on effect
The amount of methane release into the atmosphere will accelerate.
This in turn will drive global warming even further
Peatlands form 20-30% of organic C in N. Hemisphere
UNEP
© 2008 Paul Billiet ODWS