5. Digestate recovery

During the anaerobic digestion process, the physical and chemical nature of the substrates is altered. While some of the organic carbon in the substrates is converted into biogas, the nitrogen, phosphorus and potassium, as well as the inorganic or bio-refractory compounds (plastic, woody compounds, etc.) initially present, are concentrated in the liquid or solid fractions of the digestate, depending on their affinity for one or other of these matrices. The digestate, mainly composed of water (70 to 98% depending on the process), also contains anaerobic micro-organisms.

Post-treatment of the digestate can be applied according to local needs for use and management of the fertilizing elements it contains. In surplus areas, it may be necessary to export certain elements to other territories. Post-treatment to concentrate and separate the fertilizing elements can be...