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Off-Grid Living Solutions - Biogas
What is biogas?
Biogas is a product of decomposition of organic matter and it takes place naturally in areas such as swamps and landfills. The principal component of biogas is methane. Methane is also happens the main component of natural gas which is used for cooking and electricity generation.
The process that produces gas strictly requires no oxygen - it is called anaerobic process in scientific terms - and it requires bacteria called methanogens. It is estimated that between 590 and 800 million tons of methane is emitted into the atmosphere annually and 90% of this is the natural bio-gradation of organic mass. This creates opportunities and challenges.
Methane is the second most cause of global warming - this greenhouse gas can also be utilized as fuel - and yet we can do better to utilize it in other ways.
It is no surprise then that production and use of biogas is being encouraged by conservationist organizations and donor alike.
Composition of biogas
Biogas behaves like normal gas therefore is has the same properties which govern volume, temperature and pressure. The moisture content affects the amount of heat per unit volume.
- Methane (CH4 ): 40-70%
- Carbon dioxide (CO2): 30-60%
- Others: 1-5%
- Hydrogen (H2): 0-1%
- Hydrogen Sulfide (H2S: 0-3%)
Methane is a fuel and is the main component of both biogas and natural gas. It is found naturally as a fossil fuel such as in oil field or in coal mines - coal-bed methane. The methane in biogas comes from the anaerobic decomposition of organic matter.
Hydrogen sulfide is a highly corrosive compound is the cause of corrosion of the pipe works in biogas plants.
Practical Biogas Production
In general all organic materials can be used to produce biogas, while other materials produce more gas per kg than others, in practice one is limited to what is available.
The following material can all be used to produce biogas:
- Animal products - fat, waste from animal slaughter-houses
- Animal waste - cow dung, chicken litter, human sewage
- Food processing waste from restaurants, cereals such as maize
- Farm waste such as maize stalks, grassy and turf material, leaves and twigs.
- Any other organic matter that would otherwise have gone to waste.
Some material produces more biogas than others - restaurant waste is better than cow dung - in general however it is better to use waste from onsite processing because it requires energy to collect biomass from other areas.
The Anaerobic Process
Use and Application of Biogas
Biogas is essentially methane gas plus a few other components, in all purposes it is similar to natural gas except than natural gas may contain some higher carbon alkanes. Therefore biogas is versatile in its applications.
Cooking is one of the main suitable applications of biogas as a renewable energy source. This is such a crucial application because most renewable energy sources such as solar an wind do not scale enough for cooking in rural areas. Solar is mainly used for low power applications like lighting, TV and mobile device battery charging.
Many people in rural Africa and South East Asia use wood, cow dung and other biomass material for cooking on open fire stoves - there are several problems associated with such a livelihood. The first and most obvious is deforestation. Less visible, but equally critical, are issues to do with health and agricultural fertilizer.
Burning wood or cow dung on an open fire has health consequences from the sooty smoke. Women who cook on open smoking fireplaces are exposed to health hazards that can be mitigated by using biogas.
Cow dung is a good source of organic fertilizer and burning it does will affect food supply. Choosing to burn cow dung for fuel is a desperate move.
Processing cow dung to obtain biogas therefor has several advantages -it automatically eliminates health hazards from smoke and the cow dung is used as both fertilizer and fuel.
Obtaining biogas from cow dung does not affect the fertility of the material - in fact the organic manure will have less odor (will smell less) and will be easy to handle.
Biogas can be used to generate electricity just as natural gas. There are now hybrid engines - using both diesel and biogas - that industry complexes can use to generate onsite electricity.
This opens opportunities for farms that can generate their own power from biomass obtained from their agricultural operations. It is also possible to use biogas for combined heating and generation.
Farmers can use biogas for heating during winter.
Who can produce and use biogas
Anyone, from a small family of 4 - parents plus two kids - to a large city can decide to produce and use natural gas, from each each according to capability to each according to needs.
A small family can have a basic rudimentary plant to produce biogas for cooking on a two plate gas stove. A large industrial scale plant can be located near dairy farms, large city centers - all rich sources of biomass - and can produce electricity to power manufacturing processes.
The following are people who can have interests on use of biogas:
Conservationists - we can argue the cause for renewable energy, we can debate costs.
Small families on tight budget - the off-grid movement. There are small scale solutions for families
Farms - farmers have a natural advantages because a biogas plant serves both as waste management and a source of energy
Donors - those who want to make a difference can sponsor biogas technologies in South East Asia and in Africa.
Waste Treatment Plant Operators - there is so many ways to use waste than just process it.
Biogas can be use to balance the intermittent nature of renewable technologies. One of the problems of renewable technologies is the cyclical nature of the supply. For solar, the sun is up as much time as it is down - even less if you consider daytime cloud cover. Instead of just relying on one source of renewable supply, investors can use more than one technology.