Biogas

Germany Russian Federation

Biogas is produced from organic wastes by concerted action of various groups of anaerobic (without air access) bacteria and is a mixture of methane and other gases in the following proportions:

Gas
Chemical formula Volume ratio
Methane
CH4
40 - 70%
Carbon dioxide
CO2
30 - 60%
Other gases
 
1 - 5%
Hydrogen
H2
0 - 1%
Hydrogen sulphide
Н2S
0 - 3%
 

Biogas composition

 
Calorific capacity of 1 cubic meter biogas equals according to the methane content 20-25 mega joules and is equivalent to of burning of 0,6 – 0,8 liter gasoline, 1.3 – 1.7 kg firewood or using 5 -7 kW of electrical energy.
Тhe technology of biogas production can be described in such way. The biomass (waste products or herbage) are supplied through the pump station or charging machine into the reactor. The reactor is a heated and heat-insulated storage tank, equipped with mixers.
As construction materials for industrial storage tank serve most often reinforced concrete or coated steel. The composite materials are sometimes used in the small plants. In reactor live beneficial bacteria, which feed on biomass.
Biogas is a product of life of such bacteria. Bacteria life sustaining requires food, warming up to the 35-38 °С and periodical mixing. The appeared biogas is collected in the gas storage (gas holder), than passes through the gas purification system and is supplied to the consumers (boiler or electric generator). The reactor works without air access, is airproof and non-hazardous.
A special two-stage technology is required for fermentation of some raw material types. For example, bird dung and distillery stillage can’t be recycled into the biogas in the usual reactor. The additional hydrolytic reactor is required for recycling of such raw materials.
Such reactor allows controlling the acidity level, so bacteria don’t die because of increased acid or alkali content. The recycling of these substrates is possible according to the single-stage technology, but including the co-fermentation (mixing) with other raw material types, for example, with the dung or silage.
There are also industrial and domestic plants. Industrial plants differ from domestic plants in having mechanization, heating systems, homogenization, automation. The most common industrial method is anaerobic fermentation in the methane tanks.

 

Volume ratio