1. Methanization or anaerobic digestion

1.1 Biological process

Methanization is a natural phenomenon occurring in various biotopes (sediments, rice paddies, landfills, etc.) in the absence of oxygen. It involves the bioconversion of organic or volatile matter (OM or VOM) by an ecosystem made up of numerous anaerobic bacteria. Depending on temperature conditions, these ecosystems are made up of psychrophilic (below 20°C), mesophilic (between 20 and 45°C) or thermophilic (above 45°C) micro-organisms. Anaerobic digestion is accompanied by the release of biogas produced by methanogenic micro-organisms.

This natural tendency of sludge to ferment can be domesticated in a bioreactor, which maintains optimal conditions of anaerobiosis, mixing and temperature. Sludge digestion comprises four fermentation phases...