Biogas is a wonderfully flexible and renewable form of energy and it can be used as a building block to make not only a wide variety of liquid fuels, but also organic chemicals and even plastics.
The biogas digestion (anaerobic digestion) process can be installed and run at the household level with simple training and support, and it can also be developed in huge projects to anaerobic make community and district anaerobic digestion plants. These can take up to 100,000 tons per year of organic waste and create methane from it.
When the methane produced is cleaned and compressed it is called biomethane, and can be pumped into the district grids which nowadays deliver us natural gas from fossil fuels.
A household biogas plant consists of a tank (at its simplest just an underground brick pit) where manure (human sanitary waste) and other organic materials are mixed with water and allowed to ferment.
A farm biogas plant does the same but in a larger reactor and usually takes the farm animal slurries, but can also in some Scandinavian plants also use silage. The silage is stored for use to feed farm biogas plants during the long cold winters, when other feed organic feed materials may be in short supply. The farm anaerobic digestion (AD) plant can in this way strengthen the ability of farm businesses to withstand bad weather and poor years when crops are poor, and its adoption in large numbers will therefore improve the resilience of the agricultural sector.
Let us not forget either that greater biogas production and the use of it will result in a reduction in greenhouse emissions and sizeable plants can make reductions of the order of 50,000 tonnes of CO2-equivalents annually.
An AD plant always contains two main components: a digester (or fermentation tank) and a gas holder. The digester in the most common types of plant is a rectangular-shaped or cylindrical leakproof vessel with an inlet into which the fermentable mixture is introduced in the form of a liquid slurry.
China is an example of a nation where the government has introduced a biogas program. More and more governments are realizing that biogas production brings benefits not only the ecological system, but it also benefits rural populations. India and Nepal are also well known for their digesters.
The benefits are many and include it being an alternative energy source, methane is very useful for cooking, improving rural sanitation, reducing firewood consumption, relieving the rural women's burden, providing a liquid fertilizer for the fields, and proving a sludge which can improve soil quality, plus more. What is more, each farmer my be able to obtain a cash income from this as well.
The actual results of bio-gas programmes have shown these real benefits improving rural life in so many ways.
In one example the biogas digester attached to toilets provides cooking gas for a 600-student school and vocational-training program the foundation runs. In the past, non-governmental organizations were the only ones offering these ideas but that is rapidly changing as the good word gets around.
After the fermentation has been completed in an AD plant, the biogas leaves from the top of the digester at a low pressure, sufficient to overcome the losses provide enough pressure to push the gas through a gas burner, and similarly through some power generation motors, without any compressor to raise pressure.
The countries in Europe are now beginning to sit up and take stock of successes in China and other nations, and are introducing new legislation to encourage the uptake of AD technology. These laws will be explained and discussed extensively at both the plenary sessions and in the workshops in a surprisingly large number of conferences this year.
Steve Last is an anaerobic digestion expert, and web master. You will find much more about this fascinating subject at his Biogas Digester web site. But for a simple Biogas Calculator follow the link earlier in this sentence.
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