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)
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.