Biogas: its origin

ENERGY

Biogas: its origin

Biogas is a gaseous biofuel generated from the degradation of organic matter produced during “anaerobic digestion”.

Anaerobic digestion is a biological process in which a group of bacteria degrade organic matter in the absence of oxygen, thus generating organic matter:

A gaseous stream called:

Biogas composed mainly of 60% CH4, 40% CO2 and other gases in minority concentrations(H2, H2S, etc.). This biogas can be used to produce:

Directly electricity or in cogeneration systems (electricity + heat).
Or biomethane after a purification process (upgrading). This biomethane has the same characteristics as fossil methane and can be injected into the natural gas grid.

A liquid stream called:

Digestate, which is characterized by its high content of macro and micronutrients(N, P, K, Mg, Ca and S).

Digestate can be applied to the soil (directly or after different physical-chemical treatments) as an organic amendment, biofertilizer or biostimulant.

In this way, its use reduces the consumption of mineral fertilizers whose manufacture requires fossil fuels.

ANAEROBIC DIGESTION

Phases of anaerobic digestion

Hydrolysis

Acidogenesis

Acetogenesis

Methanogenesis

Breakdown by enzymatic action of the most complex molecules (carbohydrates, fats and proteins) into simpler and easily metabolizable intermediate compounds (sugars, fatty acids and amino acids).

Transformation of intermediate compounds into volatile fatty acids (VFA) (acetic, propionic, butyric acids…).

Transformation of VFA into acetic acid, H2 and CO2.

Transformation of acetic acid and H2 into CH4 and CO2.