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Depending on the type of feedstock, biogas
is basically free. Utilizing biogas solves
two environmental problems in one stroke.
Since it is mainly produced from
waste products biogas helps taking care of
the waste issue and at the same time
contributing to cleaner air, because
biogas does not add to the CO2 greenhouse
effect. This clean fuel can be produced from a wide
variety of available organic materials, including animal manure,
food waste,
crop residues, and many other organic
waste sources. Anaerobic
digestion is the treatment of organic
waste in an oxygen free environment to
produce biogas. The result is a methane
gas which can be used to produce
electricity and thermal energy.
One good example is manure, a valuable
source for energy. Farm animals are
responsible for almost a fifth of the
pollution causing global warming according
to the UN report “LLS”, and methane released from manure
is 21 times more harmful to the ozone
layer than CO2. However, processed
correctly, manure also represents a huge
potential for sustainable energy and
fertilizer production, while at the same
time, reducing greenhouse gas emissions up
to 85%.
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Advanced biogas
production technology results in a
fuel that is
efficient and environmentally
friendly. A mixture of methane
(CH4) and carbon dioxide (CO2)
provides sufficient
calorific value
to operate biogas cogeneration
plants. A clean and economical
alternative to fossil fuels.
Biogas is efficiently converted
into electrical and thermal energy
to be used locally. Excess energy
can be fed into the public
electricity grid.
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Some
biogas plant operators decide not
to digest manure alone but to mix
other organic substances,
so-called coferments as well.
Typical coferments are fats,
market wastes, organic residues
from food industry waste and many
similar substances. Doing so, the
operator of the cofermentation
biogas plant increases his
earnings in two ways: first, just
by adding coferments disposed for
a fee, and second, through a higher
biogas production output.
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An anaerobic digestion
system typically comprises
of the following
components:
A solids removal process
to remove suspended solids
and other indigestible or
dangerous materials in the
waste which is usually
achieved using one or more
of the following
technologies: a screw
press, belt press,
centrifuge, lamella
separator or dissolved air
flotation system.
The pre-treatment tank
which corrects the pH of
the waste and acts as a
buffer tank to continuous
process reactor tanks.
The reactor tank which
digests the organic
material in the waste in
four stages: hydrolysis,
acidogenesis, acetogenesis
and methanogenesis which
converts the complex
organic molecules to
methane, carbon dioxide
and water.
A post treatment stage to
remove sludge produced in
the anaerobic tank or to
further polish the organic
strength of the waste.
The biogas produced is
then stored is a suitable
vessel and consumed in a
2G® cogeneration CHP power
plant.
There are a wide range of
anaerobic technologies
available to digest waste,
from simple lagoons to
upflow anaerobic sludge
blanket and expanded bed
reactor systems. Simple
technologies tend to
require higher hydraulic
retention times, which
require more space for
larger reactor tanks.
However the advantages
include that they are more
robust and less expensive.
The most suitable
technology is dependent on
the composition and volume
of the waste to be treated
and space restriction on
site. The volume and
methane content of the gas
produced is dependent on
the digestibility of the
waste and the reactor used
to digest the waste. The
digestibility and levels
of methane produced can be
determined through
laboratory testing with
various suitable
technologies.
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Cogeneration CHP
Technologies
are recommended by the
U.S. Department of
Energy. |
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