Biogas is generated if organic materials are allowed to rot in closed, airless tanks at suitable temperatures (20-40 degrees C).

Biogas is generated if organic materials are allowed to rot in closed, airless tanks at suitable temperatures (20-40 degrees C). The process that produces it is called "anaerobic digestion". Biogas is a mixture of methane and carbon dioxide (CO2) and is usually when first created contaminated with quantities of hydrogen sulphide (H2S).

The main sources of biogas are plentiful being municipal waste (MSW) landfills that produce landfill gas (LFG); wastewater treatment plants (sewage works), industrial plants, and large scale livestock farms. It can also be produced from cattle manure and community or even individual house toilet waste. In that case each household produces their own biogas by installing a small toilet-attached AD plant, and this is popular in China, India, and many other developing nations.

Anaerobic digestion may either be used to process the source separated fraction of municipal waste, or alternatively combined with mechanical sorting systems, to process residual mixed municipal waste. These facilities are called mechanical biological treatment (MBT) plants.

Biogas, which is also called biomethane is about 20 percent lighter than air. It is an odorless and colorless gas that burns with clear blue flame similar to that of LPG gas. Biogas is a good fuel.

It can be used to fuel an engine for electricity, and afterward the waste heat can be used in a communal heating power plant then producing both power and heat. The heat given off can also be used for heating and drying processes.

Biomethane is a big opportunity because it is being viewed worldwide as an untapped source of energy that, upon recovery and pretreatment, can be used to supply a portion of a nation's natural gas needs. A number of new projects are being sponsored by the U.S. Government for this reason.

It is a regenerative (renewable) fuel with the best production efficiency of all biogenic fuels. Additionally, it need not compete with the production of human food products if the source materials are all wastes.

Biogas consists primarily of methane (CH4), a gas which can be burned to produce heat and electricity. Treated manure can also be transformed into a bio-fertilizer with high agronomic value.

It is most often collected and piped to an engine-generator where it undergoes combustion to produce electricity. However, during energy generation there is a loss of efficiency during transmission which would not occur if the fuel was used directly, where the energy is consumed.

It would be more efficient to use it say in a vehicle at the point at which the energy is consumed. It can be compressed, much like natural gas , and used to power motor vehicles. Both natural gas and biogas can be used in petrol vehicles relatively easily, but some engine adjustments are necessary. For passenger cars, there are purpose-built vehicles that can be fueled with both petrol and compressed natural gas (CNG). But CNG powered transport still only plays a small role within even the most developed German market, (60,000 vehicles to date) although popularity is rising, particularly among local transport authorities.

Biomethane is also used in Sweden as vehicle fuel. It has been reported that at least seven units for upgrading and filling of biogas are in operation at present. It is a renewable energy source because it is extracted from the natural circulation of carbon which has always taken place, and importantly creates no net increase in carbon in the atmosphere.

Biogas is not utilised as vehicle fuel anywhere near as effectively as it could be, and there are almost no biogas upgrading plants available in AD Plants.

There are also no NGV vehicles for use of compressed natural gas (CNG) or biogas available to the public or sold in many countries.

While in the short-term there is potential for biomethane as a fuel, a further significant role also exists which could be played in the mid-term by biomethane-to-liquid by using biomethane as the input for the gas-to-liquid process. This should be noted although we will not have room to discuss it further here.

Biogas being a renewable fuel, attracts renewable energy subsidies in many parts of the world. The fact that biogas could be used much more effectively in the west can be seen from the fact that it already serves more than one million people in Nepal (reported at 4% of the population). The AD sector is also a significant employer and it reportedly provides about 11,000 permanent jobs in the country. If anyone needed to be convinced that 'small scale can be big' then they need look no further that the Nepalese experience!

Anaerobic digestion which produces this gas is basically a simple process carried out in a number of steps that can use almost any organic material as a substrate. It occurs naturally in digestive systems, marshes, rubbish dumps, septic tanks and in the Arctic Tundra.

Most people in the west producing this gas tend to seem to make the process as complicated as possible by trying to improve on nature in complex machines, but a simple approach is also possible, as seen in Nepal, China, South America and India.

The other remaining products, after digestion can also be useful. Further research and implementation of drying digestates from biogas plants would also be useful however it is a totally new field of application to the west. Very similar, manure drying tunnels are not in themselves a novelty, however, up to now they are largely only used for drying poultry manure prior to combustion.

So, all the various methods of producing biomethane need further development, but this can be done quite rapidly, and then biogas has a big chance of being able to reduce our carbon footprints.