Biogas is a renewable energy that can replace natural gas. It is produced by anaerobic digestion of organic material. Manure, sewage sludge and other organic waste types from industries and households are suitable feedstocks. Biogas production is thus a combined energy production and a waste treatment technology. When manure is used for biogas production, the emission of greenhouse gasses from handling and storage of slurry is reduced. A by-product from biogas production is high quality natural fertilizer.
Biogas production in Denmark
The production of biogas in Denmark is rapidly increasing. The total production is expected to more than triple from 2012 to 2020, reaching a total annual production of 15 PJ. To date the majority of the produced biogas is used in electricity production. In the future it is expected that a greater share of the produced biogas will be upgraded and delivered to the natural gas grid. The Figure below shows the historical and expected future biogas production and its use in Denmark from 2012 to 2020.
Historical and expected future biogas production and its use in Denmark 2012-2020.
Biogas production in Denmark is spread throughout the country. The majority of biogas plants are manure-based agricultural plants located near the farms. Other biogas plants are part of waste water treatment plants located in or near bigger cities. A smaller number of biogas plants are industrial- or landfill plants treating organic wastes from these sites.
Biogas is promoted through public subsidies
Biogas is promoted through public subsidies according to its use. The different support schemes for biogas include the following uses:
- Production of electricity
- Upgraded biogas delivered to the natural gas grid or cleaned biogas delivered to a town gas grid
- Use of biogas for process purposes in the industry
- Use of biogas as a transport fuel
- Use of biogas for heating purposes
The Danish Energy Agency is responsible for the rules and regulations regarding the different support schemes. The Danish Energy Agency is administrating the payment of subsidies mainly as feed-in tariffs.
Energy crops in biogas production
Manure represents more than three quarters of the total feedstock input on agricultural biogas plants. Energy crops such as corn and beets can be used in biogas production to increase the organic matter and thus the total production of biogas. However, when using energy crops in biogas production, the benefits for climate and environment are reduced.
The Danish Energy Agency regulates the amount of energy crops in the production of biogas. To be eligible for subsidies the biogas production cannot exceed 25 pct. energy crops in the input feedstocks. By 2018 the acceptable level of energy crop in biogas production is lowered to 12 pct. The beneficiary is responsible to provide an annual documentation to The Danish Energy Agency of the feedstock used for the biogas production.
Biogas used for transport cannot receive subsidy as a transport fuel if food crops (corn, maize, sugar beets and jerusalem artichokes) have been used in the production of biogas.