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Biogas

Almost every biologically decomposable waste is suitable for biogas production. Biogas is currently produced out of biological waste from communal and agricultural dumps. This gas is produced by disintegration of organic matter with the help of so-called “methane germs” (present in muck, green plants and mud from water cleaning facilities). The process of disintegration takes place within enclosed tanks without oxygen. Mostly used materials from agriculture are: liquid manure, straw muck, straws, corn silage. There are also other materials, that can be processed this way, but the process is significantly longer. The biomass is being heated within biogas station to maintain operation temperature within airtight reactor. Usual temperature for mesophilic germs is at the level from 37 to 43 degrees of Celsius, for thermophilic germs at the level from 50 to 60 degrees of Celsius. Biogas quality is determined mainly by the ratio of methane (CH4) to carbon dioxide (CO2) within the gas. Heat value depends directly on the amount of methane. Biogas facility produces also a waste, so-called “sludge dry residue”. This matter is a suitable fertiliser for agricultural purposes.

The source for heat/power cogeneration is a cogeneration unit, which works with efficiency at the level from 80 to 85%. Part of produced heat is utilised to heat fermentation tanks and facility itself, as well as to produce DHW for the needs of the facility. There is always a problem during summer period to utilise so much heat. Annual heat utilisation number of this source reaches as much as 8000 hours p.a., what means, that this source is SOLID (compared to photovoltaic or wind power plants).

Due to legislation valid in Slovakia, only those biogas facilities are being built here that have maximum electric power at the level of 1MW. Real payback period of such a facility is approximately from 7 to 8 years.
Heat value of biogas based on the amount of methane:



Normal methane amount at nominal operation conditions is approximately at the level from 55 to 60% within biogas facilities.