Biogas is a by-product of Biodigestion, and consequently, of the Biodigester, and 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 average composition is:

Methane (CH4) - 60,0 %
Carbonic Gas (CO2) - 38,0 %
Sulfide 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 sufide gas, it is advisable to treat it.

Thus, sulfide 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 resultig 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 cilinders, like those used to stock Oxygen or Hydrogen.