Wetsus soil theme scientists have shown the formation of calcium phosphate granules during anaerobic treatment of pig manure – enabling efficient phosphorus recovery from one of the largest secondary phosphorus resources.
With the addition of calcium ions, the researchers were able to transform the – already present – phosphorus in struvite minerals into calcium phosphate granules. The granules contained 79% of the phosphorus and were larger than 0.4 mm, allowing simple separation. This way the recovery product granules has a sixfold increase in phosphorus concentration compared to raw pig manure.
The recovered granules could reduce the use of mineral phosphorus fertilizer and the transport of phosphorus from pig manure up to 85%, reducing emissions and providing economic relief to farmers around the world.
Schott, C., Cunha, J. R., van der Weijden, R. D., & Buisman, C. (2022). Phosphorus recovery from pig manure: Dissolution of struvite and formation of calcium phosphate granules during anaerobic digestion with calcium addition. Chemical Engineering Journal (Lausanne, Switzerland: 1996), 437(135406), 135406. doi:10.1016/j.cej.2022.135406