|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
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.