If you’re looking for a different, educational. and ecologically sound project look no further than a domestic Biogas plant. Bio methanisation can convert all domestic waste into a hygienic cooking fuel with minimal investment.. Biogas payback time is typically no more than two years.
The gas is produced by feeding easily degradable waste material (including wastewater) through an inlet chamber into the plant. Anaerobic bacteria convert the waste into gas. The main component of Biogas is methane which is a renewable source of energy.
At the outset however we would point out that for practical purposes and unless you live on a farm Biogas is unlikely to go anywhere near to satisfying the energy needs of a household. The amount of waste that an urban family will produce is likely to be sufficient to power a single burner stove for perhaps 90 minutes a day.
Biogas is however well worth considering if you have an off grid holiday retreat or would like to promote a community or home based educational project for young people. Alternatively you may also have a community facility which produces the appropriate waste products on a significant scale and which can be converted into Biogas for use in that facility. Or perhaps you have stables which produce manure.
Biogas school project
Most amateur urban community Biogas schemes however will exist partly at least for their intrinsic educational or curiosity interest rather than for the value of the energy they produce.
What is Biogas
Biogas is being promoted seriously in the third world, and not merely for the value of the fuel itself. It also helps discourage the tendency in some communities to throw waste materials into the roads and other public places. Biogas production is particularly suited to the third world locations for other reasons. The locations are usually hotter, (the digestion process works better at consistently warm temperatures), and the necessary raw materials to produce the Biogas are more readily available in rural communities.
Domestic Biogas Production in India
Anaerobic digestion is the process of biologically degrading biomass in an oxygen-free environment. When there is no oxygen present anaerobic bacteria ferments biomass into Biogas, a mixture comprising methane, carbon dioxide, hydrogen sulphide and a small amount of hydrogen. The Biogas arises solely from the bacterial action. The process itself generates heat, but further heat is required to maintain the ideal generator temperature of 35°c or more.
The methane content of Biogas can vary considerably but typically it will be around 50-60% compared with 80% with Natural Gas. Biogas is generated naturally at the bottom of swaps lakes and stagnated ponds, and in the digestive system of animals, including humans. We expel it regularly.
Although Biogas isn’t really a single alternative energy source for most homes it can be produced commercially and can be burnt in power stations or upgraded to Natural Gas calorific standards and used accordingly. It can even power buses. Upgrading Biogas to a product comparable with natural gas (‘green gas’) is achieved by removing carbon dioxide, ammonia, of H2S, and some of the hydrocarbons.
Animal dung or sewage, can be converted into slurry and fed into an anaerobic digester. So Biogas is practical proposition for a farm.
A small Biogas installation consists of the following parts:
Basic Biogas Unit
- Manure and waste collection
- The anaerobic digester unit which optimizes the development of the naturally occurring anaerobic bacteria
- Storage unit for the effluent. The anaerobic digestion process produces Biogas and effluent. The effluent itself is an organic product that also has value as a fertilizer so waste storage facilities to store the effluent are needed
- Gas handling parts, a gas pump, pressure regulator, condensate drain, gas meter, piping etc
Benefits of Biogas
Lower Carbon Dioxide Emissions
The Carbon Dioxide from Biogas originates from recently living matter and so is part of the Carbon Dioxide Cycle. The large amounts of Carbon Dioxide emitted by coal and natural gas are not. The Carbon Dioxide emitted by fossil fuels is new to the present earth atmosphere, it having been stored for millions of years and would not have been introduced into the atmosphere at all were it not for human intervention
Lower Methane Emissions
Animal manures release methane into the atmosphere but methane is a more potent greenhouse gas than Carbon Dioxide is so it’s better environmentally to burn it instead of releasing it.. It’s better for organic waste to be used in an anaerobic digester with Biogas as the end project rather than trying to collect methane from landfill sites. It would also save more energy if organic waste, was recycled domestically rather than put into landfill and would prevent contaminants leaching into the ground
Reduced use of resources
Biogas doesn’t require transmission pipes to deliver it. Neither does it need to be liquefied and shipped.
Animal slurry and sewage sludge often finishes up as fertiliser but it’s better to extract Biogas from it first leaving the fertiliser still available at the end. Biogas also fills a gap for those seriously trying to use renewable energy only in the home. Solar and wind power generates electricity for lighting etc but do not so easily satisfy cooking needs. Biogas can provide the relatively small proportion of the household energy requirement needed for cooking without heating the entire property unnecessarily with fires in the Summer.
The Biogas digester is the part where the organic wastes are introduced, usually in slurry form with water, to be broken down. The storage container is used to hold the gas until it’s piped for use. A facility is required to dry the spent effluent ready for use as a fertiliser.
There is nothing particularly unsafe about Biogas but it is a flammable substance and should be treated as such. Its lower methane content makes Biogas somewhat less dangerous that other types of hydrocarbon carbon fuels but it should still be noted that it is still potentially explosive. The area surrounding the Biogas generating digester must be ventilated. However any of the usual safety standards which apply to hydrocarbon fuels will be more than sufficient to satisfy Biogas safety standards.
However the significant safety consideration which Biogas does not share with other forms of energy is the hygiene requirement associated with the nature of the raw material itself. Excrement and rotting matter will contain significant toxins. Care should be taken to ensure that excellent hygiene standards are observed.
KCS will be returning to the subject of building the Biogas Generator itself soon. In the meantime if you have any questions which need answering concerning Biogas or are embarking on a generating project please let us know