Process & contact
NPHarvest
(a spinoff from Aalto University, Finland)
Updated 11/2025
Input materials
Biogas digestate liquids, reject water from sewage sludge
Output products
Based on previous pilot trials, the company expects the recovered ammonium sulphate solution to respect the criteria of the European Fertilising Products Regulation CMC15 and the calcium phosphate CMC12 and the phosphate fertiliser criteria (Annex III, part II, 4(b): 75% solubility in neutral ammonium citrate NAC).
Process description
The process separates ammonia and phosphate from biogas digestate liquor or sewage sludge reject water. Ammonia is separated by using hydrophobic membranes, and absorbed into sulphuric acid to give ammonium sulphate solution. Phosphorus is recovered as calcium phosphate by precipitation. See SCOPE Newsletter n°147.
Operating status
Pilot P and N recovery unit, Aslan biogas plant, Ankara, Turkey. The mobile unit has 6 m3 volume and can process approximately 800 l/h of input. The pilot aims to produce 100 t/y of ammonium sulphate solution (30%) and 70 t/y of calcium phosphate. The technology has been previously tested for three months in Helsinborg sewage works, Sweden and one month at Viikinmäki sewage works, Finland.