The usage of bio gas
Natural gas has been used for many years and most applications and equipment are designed for the usage of natural gas and thereby its heat value. The possibilities of usage are therefore many and a continuous development of these takes place. The situation for the usage of biogas is different. The lower heat value and the content of carbon dioxide make the equipment and components designed for natural gas difficult to use. The usage of landfill gas is especially difficult since this gas also contains nitrogen The heat value of landfill gas is low even in comparison to sewage gas. The utilisation of biogas is therefore often conditioned either by a modification of components and equipment or the gas being upgraded to a better quality.
The usage to generate electricity and heat.
The most common way to use the gas is to use the gas directly as fuel to produce process- or district heat. In some countries the tax regulations makes it advantageous to produce electricity with biogas as fuel. These two areas of utilization are the simplest since they only demand components to be chosen for a gas with a lower heating value. They do not demand cleaning and/or upgrading of the gas.
Upgrading plants.
To allow bio gas either as fuel for vehicles or to be feed into the natural gas grid it has to be purified to reach the quality of natural gas. This is done in an upgrading plant in which impurities and unwanted components like particles, water and carbon dioxide are removed. By removing the carbon dioxide the methane gas content as well as the heat value is raised. There are several ways to upgrade biogas to natural gas quality such as processes called pressurised water, chemical absorption and PSA (Pressure Swing Absorption). If the mentioned processes shouldn’t upgrade the gas to natural gas quality propane gas can be added as a final step in the process. Landfill gas can not be treated as described to reach natural gas quality. The reason being its content of nitrogen gas which in comparison to carbon dioxide is relatively difficult to separate from methane gas
Alternative for natural gas
Biogas upgraded to natural gas quality can be transported in the natural gas grid and be used as natural gas. This is a positive thing from an environment point of view since biogas is a renewable- and natural gas a fossil fuel.
Fuel for vehicles
Bio gas is an efficient fuel for vehicles both from an economic and from an environmental perspective. When changing from a fossil fuel like petrol or diesel to biogas the contribution to reduce emissions such as the greenhouse gas carbon dioxide but also hydrocarbons, nitrogen oxide etc. is very important. Vehicles using gas as fuel are as safe as other vehicles.