The energy in biogas can be exploited in different ways. For example, it can be used for local heating or remote heating (via district heating networks). Biogas can also be used to generate electricity, thus contributing to an increased proportion of ‘green electricity’ distributed through the grid.
Biogas as vehicle fuel is the area of application increasing the most rapidly. Biogas that has been purified and upgraded to contain a high proportion of methane may with advantage be used as a vehicle fuel. Methane can also be used as a raw material in various manufacturing processes, with diverse final products such as paints, plastics, furniture, animal feeds and lubricant oils. In addition, the biogas process generates a nutrient-rich digestion residue, that can be used as a fertilizer.
In Sweden, biogas has been produced at municipal wastewater treatment plants since the 1960´s. The primary incentive was to reduce sludge volumes. However, the oil crises of the 1970´s changed attitudes, leading to research and development into biogas techniques and the construction of new plants in order to reduce environmental problems and dependency on oil. Industry was first to act; sugar refineries and pulp mills started to use anaerobic digestion for waste water purification in the 1970´s and 1980´s. At this time, several smaller farm-sized plants were also constructed for anaerobic digestion of manure.
During the 1980´s, several landfill plants started to collect and utilize biogas produced in their treatment areas, an activity that expanded quickly during the 1990´s. Several new biogas plants have been constructed since the mid-1990´s to digest food industry and slaughterhouse wastes, and kitchen wastes from households and restaurants.