Why biogas? A green source of energy with several benefits
What is biogas?
Biogas consists of two gases – methane (Ch4) and carbon dioxide (CO2). Biogas is the result of the biological decomposition that starts when organic material is heated in anaerobic surroundings (oxygen-free). This is normally referred to as the mesophilic process, taking place at 37-42°C or the thermophilic process at 52-56° C. However, it is possible to produce biogas at temperatures from approx. 20° C to 56° C.
The useful part of the biogas is the methane. Methane nearly has the same heat value as natural gas, making it suitable for the same purposes. Biogas can be used as fuel for gas heaters, or motor/generator plants that produce electricity and heat.
Biogas can also be upgraded in an upgrading plant, eliminating the CO2 in the biogas and leaving only the methane. The methane will subsequently be suitable for the existing natural gas grid and used for the same purposes as natural gas.
Biogas is regarded to be CO2 neutral, since it only emits the amount of CO2 provided by plants used for the biogas plant in the form of slurry, energy crops and waste products absorbed during growth. However, by burning and utilising the biogas, methane and nitrous oxide are eliminated and not emitted with the slurry, and these gases are up to 35 times more harmful for the atmosphere than CO2.
Environmental benefits from biogas production
Biogas is a sustainable and CO2 neutral energy form. No fossil carbon is emitted when burning biogas as it is the case with coal, oil and natural gas. The significant greenhouses gases methane and nitrous oxide are further collected and utilised. These gases are formed, when livestock manure is spread on fields without being processed in biogas plants. This makes the production of biogas the cheapest solution for reducing agricultural greenhouse gas emissions.
Another important factor is that degassed livestock manure has higher nitrogen energy efficiency on plants than unprocessed livestock manure, meaning that plants more easily absorb the nutrients in degassed livestock manure. The use of biogas therefore results in reduced nitrogen stripping into our groundwater.
Financial benefits when investing in a biogas plant
Agriculture traditionally produces grain, meat and milk. In Denmark, we have for the past 100 years been leading in producing these goods of high quality by means of environmental responsible processes. However, globalisation has resulted in agriculture being increasingly dependent on the world market and market prices, constituting a huge challenge for most companies.
A biogas plant utilises an existing resource (livestock manure), possible 2nd generation crops (straw, successive crops, beet tops etc.) as well as energy efficient crops, produced on parts of the farmland. This provides agriculture with a wider foundation, since the production includes grain, meat, milk as well as energy.
Since many countries currently subsidize the production of green energy, the energy part is often subject to long-term price assurance.