Biogas Ireland, Biogas Dublin, NGV - Natural Gas Vehicles Dublin, CNG Ireland, NGV Ireland, NGT

BIOGAS

Biogas is a mixture of methane and other gases produced from the decomposition of organic materials. It is produced naturally in landfills, and from the processing of animal waste, sewage, crop waste, and cellulosic and non-cellulosic crops.

Biomethane is a pipeline-quality natural gas-substitute produced by purifying biogas.

Landfills, animal waste “lagoons,” and sewage processing plants are major sources of biogas, a major component of which is methane.

Methane is a significant greenhouse gas -- estimated to be 21 times as intense a greenhouse gas as carbon dioxide.

This biogas can be captured and “flared,” which reduces the methane to carbon dioxide. But, in doing so, its energy value is wasted.

An energy-wise and greenhouse gas-wise alternative is to capture the biogas from these renewable waste sources, convert that biogas to biomethane, and use the biomethane to displace petroleum or other fossil fuels in transportation or other energy applications.

A 1998 U.S. Department of Energy study1 concluded that a feasible biomethane potential from these sources would be 10 billion gasoline-gallon-equivalent per year.

If all this biomethane were used in vehicles, it is estimated that this would reduce greenhouse gases by 500 million metric tons of CO2 per year – or removing the emissions equivalent to 90 million light-duty gasoline vehicles off the road.

This is a form of methane sequestration, with energy savings as a bonus.

When we take into consideration its amount, methane takes second place after carbon dioxide as a greenhouse gas produced through human activities. However, because carbon dioxide takes part in photosynthesis, when oxygen is produced by plants, methane is considered to be twenty times more harmful than carbon dioxide. The only way to decrease emission of methane is to store it and then use it as fuel with preserving the highest efficiency of machines.

The prevention of methane emission contributes to the realisation of goals set on Kyoto conference, which concern decrease in gas emission and to the realisation of commitments made by the countries of European Union in this field. Landfills, places where plant waste is kept and farms emit the biggest amount of methane. What causes this is uncontrolled process of decomposition which results not only in emission of methane to the atmosphere but also in odour, emission of carbon dioxide and combustion of oxygen. This unfavourable process can be controlled by building installations to recover biogas. Biogas is a gas containing about 55% up to 96% methane. Thanks to modern equipment and a process of methane decomposition which is skilfully carried out in biogas-works, gas can be stored and used in internal combustion engine as a high octane fuel.

As Ireland is a country of 365 - day grass vegetation, we can consider grass silage as a main material supplied to small biogas-works placed next to CNG filling stations. Decomposition is a self-contained process in which oxygen does not take part and factors such as pH value, temperature, continuity of silage supply or kind of equipment are preserved. Temperature depends on kind of bacteria used in the process (psychofile, mezofile, termofile). Mezofile installations are widely used and optimal temperature is 32°C to 45° C. PH value in the process of decomposition with one strain has to be between 6.8 and 7.5. Continuity of silage supply is also crucial. The location of Ireland gives possibility of continuous grass supplies, and also straw, leaves, animal waste and sewage can be used when needed. Also, the selection of silage is important. Any harmful waste can spoil the production of biogas and even destroy bacteria and finally stop the process. Preparation for the next process takes about one week.

Another important factor for the continuity of the process is equipment of biogas-works such as strains, stirring equipment (biomass has to be stirred to equalize the concentration of bacteria in silage), biogas store, pumps, feeders, equipment filtering and drying gas, stores of compost created in biogas production, drivers, sensors. Taking health & safety into consideration it is important to train workers to pay attention to safety regulations.

Using alternative fuels instead of diesel gas provides several environmental and health benefits, including improved air quality, decreased ground level ozone, and decreased respiratory problems. According to INFORM, a non-profit environmental research organization, CNG buses emit 95 percent fewer particulates than diesel buses, and they also emit lower levels of Volatile Organic Compounds and Nitrogen Oxides, both precursors to ground level ozone. Replacing a conventional diesel bus with a CNG bus is equal to removing the soot from 20 to 30 cars. Furthermore, over the typical 12 to 15-year life of a single bus, using one powered by alternative fuels will save more than 190,000 gallons of diesel fuel.