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Lisenko T., Chala K.
Nayional University of Food Technologies, Kiev, Ukraine
What
is biogas
Biogas typically refers
to a gas produced by the biological breakdown
of organic matter in the absence of oxygen. Biogas
originates from biogenic material and is a type of biofuel.
One type of biogas is produced by anaerobic digestion
or fermentation of biodegradable materials such as biomass,
manure or sewage, municipal waste, and energy crops. This type
of biogas comprises primarily methane and carbon dioxide.
The other principal type of biogas is wood gas which is created
by gasification of wood or other biomass. This type
of biogas is comprised primarily of nitrogen, hydrogen,
and carbon monoxide, with trace amounts of methane.
The gases methane, hydrogen and carbon
monoxide can be combusted or oxidized with oxygen.
Air contains 21% oxygen. This energy release allows biogas
to be used as a fuel. Biogas can be used
as a low-cost fuel in any country for any heating
purpose, such as cooking. It can also be utilized
in modern waste management facilities where it can be used
to run any type of heat engine, to generate either
mechanical or electrical power. Biogas is a renewable fuel
and electricity produced from it can be used
to attract renewable energy subsidies in some parts
of the world.
Production
Depending on where
it is produced, biogas can also be called swamp, marsh,
landfill or digester gas. A biogas plant is the name often
given to an anaerobic digester that treats farm wastes or energy
crops. Biogas can be produced utilizing anaerobic digesters. These
plants can be fed with energy crops such as maize silage
or biodegradable wastes including sewage sludge and food waste.
Landfill gas is produced
by organic waste decomposing under anaerobic conditions
in a landfill. The waste is covered and compressed
mechanically and by the weight of the material that is deposited
from above. This material prevents oxygen from accessing the waste
and anaerobic microbes thrive. This gas builds
up and is slowly released into the atmosphere
if the landfill site has not been engineered
to capture the gas. Landfill gas is hazardous
for three key reasons. Landfill gas becomes explosive when
it escapes from the landfill and mixes with oxygen within lower
and higher explosive limits. The methane in biogas forms
explosive mixtures in air. The lower explosive limit is 5%
methane and the upper explosive limit is 15% methane.[1]
The methane contained within biogas is 20 times more potent
as a greenhouse gas than carbon dioxide. Therefore uncontained
landfill gas which escapes into the atmosphere may significantly
contribute to the effects of global warming. In addition
to this volatile organic compounds (VOCs) contained within landfill
gas contribute to the formation of photochemical smog.
Applications
Biogas can be utilized
for electricity production, cooking, space heating, water heating and process
heating. If compressed, it can replace compressed natural
gas for use in vehicles, where it can fuel
an internal combustion engine or fuel cells.
Methane within biogas
can be concentrated to the same standards as natural
gas, when it is, it is called biomethane. If the local
gas network permits it the producer of the biogas
may be able to utilize the local gas distribution
networks. Gas must be very clean to reach pipeline quality,
and must be of the correct composition
for the local distribution network to accept. Carbon dioxide,
Water, hydrogen sulfide and particulates must be removed
if present. If concentrated and compressed it can also
be used in vehicle transportation. Compressed biogas is becoming
widely used in Sweden, Switzerland and Germany. A biogas-powered
train has been in service in Sweden since 2005.
Bates' and his biogas car were
the subject of a short documentary film called 'Sweet
as a Nut' in 1974, at which point
he had run his car for 17 years
on gas he had produced by processing pig manure.
Bates, an inventor, lived in Devon,
UK and in the film talks through the simple process
and benefits of running a car on biogas.
The conversion was simply made with an adapter attached
to any combustion engine.
Biogas in developing nations
In India biogas produced from the anaerobic
digestion of manure in small-scale digestion facilities
is called Gober gas. In India biogas is generated
at an estimated 2 million+ household facilities. The digester
is an airtight circular pit made of concrete with
a pipe connection. The manure is directed to the pit,
usually directly from the cattle shed. The pit is then
filled with a required quantity of wastewater. The gas pipe
is connected to the kitchen fire place through control valves.
The combustion of this biogas has very little odour
or smoke. Owing to simplicity in implementation
and use of cheap raw materials in villages,
it is one of the most environmentally sound energy
sources for rural needs.
Biogas is used extensively throughout rural
China and where wastewater treatment and industry coincide.
The Biogas Support Program in Nepal
has installed over 100,000 biogas plants in rural areas.
Vietnam's Biogas Programme for Animal
Husbandry Sector has led to the installation of over
20,000 plants throughout that country.
Biogas is also
in use in rural Costa Rica.
In Colombia experiments with diesel
engines-generator sets partially fuelled by biogas demonstrated that
biogas could be used for power generation, reducing elecricity costs
by 40% compared with purchase from the regional utility.
1. https://en.wikipedia.org/wiki/Biogas
2.
http://www.biogasinfo.ru/
3. Alternative Energy Sources Authors: Michaelides,
Efstathios E. Stathis ,2012,