Natural gas & bio gas
What is the difference?
What is natural gas?
Natural gas is a fossil fuel mainly consisting of methane gas. When burning, the natural gas produces less emissions of eg. carbon dioxide, than other fossil fuels like coal and oil.
The natural gas was formed many million years ago. The raw material was organic material like animals and plants. The gas was formed when micro organisms fermented the material in an anaerobic (no oxygen) environment. The gas has been stored below the earths surface under high pressure. The gas is extracted by means of drilled gas wells.
The consumption of natural gas is expected to increase rapidly in the future. Sweden is a small actor on the market and has not any natural gas findings of their own. In Sweden gas covers approximately 1% of the energy consumption. The gas network in Sweden starts in Trelleborg in the south, continues along the west coast to Gothenburg and spreads about 150-200 km to the east.
The gas used in Sweden comes from the Danish field ”Tyra” in the North sea. The findings closest to Sweden are situated in Holland, Norway, Great Britain, Denmark and Russia. The European natural gas networks are linked together and expand rapidly.
What is biogas?
Biogas is a renewable fuel and as such it is a part of the natural cycle. Biogas mainly contains methane (approx. 65 %). The rest consists mainly of carbon dioxide (approx 35 %). Small amounts of other gases can be found in the gas. The concentration of methane depends on the raw material used in the biogas production. When burning the methane mainly carbon dioxide and water vapour is formed.
The difference between burning of natural gas and burning of biogas is that the burning of biogas does not give any net contribution of carbon dioxide to the atmosphere.
The carbon dioxide produced when burning the methane is consumed in the cycle of the nature by plants which produce biogas when fermented. Methane is a greenhouse gas and the utilisation of the gas reduces the greenhouse effect of the atmosphere.
In general it is said that there are two types of biogas plants, landfill- and sewage gas plants. Landfill gas is formed during the natural degradation of organic material in a landfill. The degradation (fermentation) in a landfill requires a long period of time. It is generally said that the main part of the organic material is degraded and the main part of the gas is formed after a period of 20 years. Sewage gas is formed during a controlled degradation (fermentation) process and after 20-30 days the main part of the organic material has been degraded. In a biogas plant the produced biogas is separated from the remaining substance after fermentation for further transport to a utilizer.
Except from gas also a nutritious rest product, is produced in a sewage gas plant. This rest product is commonly called bio manure and can after approved quality control be used as manure on fields.