Mineral phosphorus fertilizers are usually made from rock phosphate, which is mined in opencast mines. There will still be enough phosphorus for 50 to 200 years agriculture. The scientist Andrea Emmy Ulrich estimated this in one of her papers in 2013. After that it will probably be tight.
In order to conserve phosphate reserves, the federal government changed the sewage sludge regulation in 2017. Sewage sludge contains high amounts of phosphorus, but can also contain pollutants such as heavy metals, drug residues and other toxic compounds. Up to now, sewage sludge has been allowed to be applied directly to fields as fertilizer. To do this, its ingredients must comply with the limit values of the sewage sludge regulations. This will end for most sewage treatment plants by 2032 at the latest.
From 2029, wastewater treatment plant operators will have to recover phosphorus from sewage sludge if the phosphorus content is at least 2 percent. Only sewage sludge from plants with less than 100,000 population equivalents (PE) may be used as fertilizer. From 2032 the limit will decrease. Then only sludge from systems with less than 50,000 p.e. may be fertilized. If the sewage sludge is used as fertilizer, the phosphorus does not have to be recovered from it.
