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More about Biogas

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More about Biogas

Biogas is a by-product of Biodigestion, and consequently, of the Biodigester, as the quantities produced are no more than 2,0 to 4,0 % of the weight of the initial Organic Matter used in the process.

It is a mix of gases, whose composition usually is:

  • Methane (CH4) - 60,0 %
  • Carbonic Gas (CO2) - 38,0 %
  • Sulphide Gas or Acid (H2S)  and other gases - 1,5 % to 2,0 %

As a consequence of it's high methane content, it is a very good gas to generate thermal energy, and even as a combustible for internal combustion engines.

To raise the thermal power of Biogas, and to eliminate its corrosive characteristic because the presence of sulphide gas, it is advisable to treat it.

Thus, sulphide gas can be eliminated by washing Biogas in a solution of potassium hydroxide, and the resulting salt, can be added to biofertilizer to enrich it with sulphur and potassium.

Carbon dioxide can be eliminated by washing the Biogas with water under medium or high pressure. The dissolved carbonic gas, can then be recovered and bottled for use in fire extinguishers.

We can eliminate carbonic gas by washing Biogas with calcium hydroxide, and the resulting salt (calcium carbonate), can be used to correct the pH of acid soils.

After purifying the Biogas, we will have pure methane, a very good flammable gas, that can be used under low pressures in stoves, fireplaces and ovens, and, under high pressures it can be stocked in special cylinders, like those used to stock oxygen or hydrogen.


The digestion has three main stages:

  1. The first, hydrolysis, involves breaking down the large macromolecules to sugars, amino acids, and fatty acids by bacteria under aerobic conditions.
  2. The second stage is acetogenesis, during which acetogenic bacteria convert sugars into short-chain acids, mainly acetic acid.
  3. The third stage is methanogenesis, which is carried out by anaerobic bacteria. Here, the acids are converted into methane.

Text copied from Wikipedia, the free encyclopedia - "Biogas"


last update: 06/12/2016
Biogas is a renewable Energy-Ressource, Biofertilizer Nguvu Taka Mombasa Mombassa NTV