However, while anaerobic digestion for a long time was considered a final stage in the processing of organic by-products and residues, in the eyes of Group Op de Beeck it is an essential intermediate step in efficient nutrient recovery. The digestion process is therefore to be followed by subsequent steps in order to close the entire cycle.

During the anaerobic digestion process part of the carbon (C) present in the organic waste is converted into biogas. The carbon that is not converted into biogas, remains in the digestate (i.e. the digested material) together with the nutrients.

In the next phase the solid fraction of the digestate will be dried at the Op de Beeck NV site until a high-quality organic soil improver is obtained. Finally, the liquid, aqueous fraction is evaporated and fully purified into re-usable or dischargeable water. During this final process all nutrients that are still present are recovered and concentrated into two by-products that can be applied for both agricultural and industrial processes. The purified water is mainly re-used on its own site.

Unlike the conventional treatment techniques, where nutrients such as carbon often end up in the atmosphere and so are lost, because of the successive processing steps all essential elements in the delivered wastes are valorised and recovered as much as possible. As a result the nutrient cycle is fully closed. Furthermore, this way organic waste that can no longer be used for other purposes, such as expired foodstuffs, damaged goods, production residues etc., will still be applied in a useful and sustainable way in the form of green electricity, heat or as a soil improver.