In general, biomasses (wood, woody residuals, waste and residue from vegetable or animal origin, but also dedicated agricultural production and parts of organic urban refuse) constitute a well distributed resource and often largely available locally and can be transformed with technologies based on their chemical and physical characteristic into energy and/or fuel.
In particular, biomasses that can go sour can be converted into “biogas“ through a digestive anaerobic process; moreover biogas and syngas can be used in small to medium size cogenerative systems for the production of distributed energy and heat. Biogas can also, if subject to appropriate purification treatments and CO removal, introduced into the natural gas distribution network as “biomethane”.
Biogas is a mix composed mainly by methane, hydrogen, carbon oxide and hydrogen sulfate formed as a consequence of the anaerobic digestion (absence of oxigen) of organic material. The production systems of biogas use the following waste materials:
- Waste products suitable to the fermentation with an high content of biomass such as mud from purification systems, agricultural waste;
- agricultural improvements (effluents, manure);
- plants with an high energy content.
In this way the agricultural improvements and the high energy content plants make up an enormous provision for the production of biogas.
Based on the origin, biogas can be classified also as sewer gas (produced by purification systems), landfill gas (from landfills) or biogas (from biogas plants).
Biogas is a mix of gas obtained by the decomposition of organic substances in an airless condition. It is composed for 50-70% by methane and by carbon monoxide for the remaining 25-40%. Usually it contains other substances such as sulfate hydrogen subtracted at the beginning of the production cycle. From there derives a variety of gas.
Biogas is used in cogeneration groups to produce thermal energy or electricity.
The heat produced can be used to warm up stables, houses, industrial and artisan areas and other places.
As substrate for the production of biogas can be used raw materials as corn and rye or dry or liquid manure.