Methanization, also known as anaerobic digestion, is a technique used to recover organic waste from agriculture (animal excrement, grain residues, plant waste) and cities (organic household waste, urban sludge).
The digester is the central element of the process. It is in the digester that the degradation of organic matter by micro-organisms takes place in the absence of oxygen (anaerobic), unlike composting, which takes place in the presence of oxygen (aerobic).
After about forty days of heating and stirring, the outputs are "biogas" and the "digestate", which is a sludge rich in organic matter. These two by-products of anaerobic digestion are used as follows:
- Biogas, composed of 70% methane, is used as fuel to produce electricity, heating or fuel for natural gas vehicles (NGV). It can also be injected into the urban gas network.
- The digestate is used as fertilizer in the fields.
Methanization reduces the amount of waste sent to incinerators and sends locally produced energy and fertilizer to cities and farms.