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Introduction to Environment
Renewable and Non Renewable resources
Conventional Fuels
Environmental Impacts of Conventional fuels
Modern Fuels and their Environmental Impacts
Methanogenic bacteria and biogas
Microbial Hydrogen Production
Conversion of sugars to ethanol
The gasohol exp ,Solar energy
Converters –Hopes from photosynthetic pigments
Treatment of municipal waste and industrial effluents
ucla genomics
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Methanogens are bacteria that produce
methane gas
They can be used as sources of biogas gas
This would be a renewable source of energy
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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
Methanogens belong to the Archaea group
of the Prokaryotes
Examples
Methanococcus jannaschii
Methanobacterium thermoautotrophicum
The prokaryote kingdom has been split into
several further kingdoms (e.g. Archaea and
Eubacteria) based on the genetics and
biochemistry of microbes
Methanogens are chemoautotrophs
Methanogens use a number of different ways
to produce methane
Using 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
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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
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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
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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.
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
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The amount of
methane release into
the atmosphere will
accelerate.
This in turn will drive
global warming even
further
Peatlands form 2030% of organic C in N.
Hemisphere
UNEP
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Formation
First stage consists into making the waste dissolvable by the enzymes
secreted from micro organisms.
Then, the acid forming bacteria takes action and transforms these
substances into small-structured substances like acetic acid.
After that the methane forming bacteria converts these substances into
biogas.
Hydrolysis stage: Long chained complex carbohydrates proteins oils and
lipids are transmuted into short chained forms. The first step known as
hydrolysis is completed after this transmutation into basic organics.
Acid formation stage: The dissolvable organic materials are transformed
into small-structured materials as acetic acid volatile fatty acids
hydrogen and carbon dioxide.
Methane formation: The stage of acetic acid disintegration or hydrogen
and carbon dioxide synthesis to acquire biogas by bacteria.
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Factors that effect biogas production
The effects of heat: Methanogenic bacteria are inactive at very high or
very low temperatures. That’s why the reactor heat effects the biogas
production or its speed directly.
The effects of PH: The most suitable PH levels for methane producing
bacteria are neutral or have slightly alkali rates.
The effects of toxicity: Antibiotic addition to foods in chicken farming has
a toxicity effect in chicken compost using systems in biogas production.
The effects of organic load speed: Organic load speed is daily organic
material supply amount to bioreactors.
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Advantages of Biogas
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In our country animal and herbal wastes are burned directly
or they are used as compost agricultural soil. But it is more
common to burn wastes for heat production.
Biogas production provides storage or organic wastes under
controllable-suitable conditions. The uncontrolled storage of
farm originated organic wastes-composts pollutes water
earthy and the air.
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Benefits of biogas production
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Biogas is a clean and high heat-capacited energy source.
Wastes do not perish. Instead of that, they become a more
valuable compost.
The weeds in animal compost cannot germinate.
Biogas has especially positive health effects in rural areas.
Smell of animal compost disappears widely after biogas
production. Also, disease agents threatening human health
coming from animal waste become inactive.
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Areas where Biogas is used in
Usage In Heating: acquired biogas is burned by a burner and the gained heat is used in
houses, animal stables, greenhouses and inside the facility. Biogas stoves, hot water
cauldrons or steam cauldrons are generally used in this systems. The biogas purification
before usage is important to eliminate corroding hydrogen sulphur (H2S) and carbon
dioxide.
Usage In Cooking: Biogas can be used in kitchens, as fuel for ovens and stoves using LPG.
Usage In Lighting: Biogas can be used in LPG-using lamps by burning directly and also by
transforming into electricity. The efficiency level is low like 3% when burning.
Preparing Hot Water: We can use biogas to provide hot water at home and industrial need
and also for geyser and other water heater systems.
Usage In Internal Combustion Engine: Biogas can be used in vehicles as an alternative fuel to
common energy sources. Especially in Europe, this kind of applications is encouraged by
several projects.
Electricity Production: Espacially in medium and large facilities, biogas is used in electric
generators. The electric transformation efficiency of biogas is about 22%- 40%.
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