Recovering critical fertilisers such as phosphorus from sludge treatment
The Acqua&Sole company recovers organic matter and nutrients by regenerating resources from food industry waste.
Since 2016 their plant processes sludge and other organic waste from agri-food industry via thermophilic co-digestion. Anaerobic digestion and simultaneous extraction of ammonia produces at the end of the process:
- digestate from waste
- ammonium sulphate as a secondary raw material (REACH registered)
- biogas.
Digestate fertilisation (as opposed to traditional chemical fertilisation) produces an organic substance, thus contributing to the improvement and preservation of soil structure, fertility, water retention and biodiversity.
Phosphorus is a critical material in agriculture fertilisation, but global stocks are finite and depleting. In 2020, the use of around 120 000 tons of digestate allowed for the recovery of:
- 900 tons of phosphorus,
- 90 tons of potassium and
- 950 tons of nitrogen.
In 2020, around 4 000 tons of carbon were added to agricultural soils. The industrial-scale plant verified the economic sustainability of the initiative, which appears to be profitable.