Phosphate rock is the primary raw material source for phosphate production, but unfortunately mineable phosphate rock is a limited non-renewable resource that may only last an additional 100 years. Large amounts of phosphorus end up in manures and in urban waste, mainly in sewage sludge and slaughterhouse waste.
Today are EU countries re-circulating phosphorus by distributing 48% of the sludge back to farmland. The positive aspect is that phosphorus is re-circulated, but it’s not problem free. Sewage sludge can still contain viruses, heavy metals, and other substances that could be harmful to human health. Currently 27% of the phosphorus is being transported to land fills or “other”, which are routes that rarely recover any phosphorus. 25% of the sludge is incinerated and the ash is mainly transported to land fills.
Ash from mono-incinerated sewage sludge contain a high concentration of phosphorus (7-10%), iron (10-15%), and aluminium (5-10%), but also contains unwanted heavy metals such as cadmium. The high content of metal has up until now created an obstacle for possible applications for the phosphate rich ash.
As long as society exists, sewage sludge will be created. Combined with the end of phosphate rock reserves in sight and the need for phosphorus in our society, phosphorous recycling will be an inevitable part of the future society.