Phosphorus is a finite resource; efficient usage and recycling are essential. Recycling human sewage can help close the phosphorus cycle, but only partially meets circular economy goals. Phosphorus recycling efforts must not neglect manure.
All life depends on phosphorus. But it is a finite resource for which there is no substitute. The inefficient and wasteful use of phosphorus in the agri-food system has implications for sustainability and also contributes to eutrophication of lakes, streams, and coastal areas. The responsible and sustainable use of phosphorus requires better use and re-use in all sectors of society, especially in agriculture.
The EU Circular Economy Action Plan has generated interest in recycling phosphorus contained in human sewage in agriculture. This effort is an important step in closing the phosphorus cycle. However, there is greater potential to improve the efficiency of manure used as crop fertiliser. In the Baltic Sea catchment, the amount of phosphorus in manure is more than 3 times greater than in human sewage. By using manure more efficiently, mineral fertiliser imports could be reduced by 0,11 - 0,17 million tons, compared to about 0,036 million tons by using sewage sludge. This would reduce phosphorus surpluses and the risk of leakage to inland waters and the Baltic Sea.
Challenge to meet Baltic Sea Action Plan reduction targets
Progress has been made in reducing nutrient inputs to the Baltic Sea. Since 1995, nitrogen inputs have decreased by 22% (250 000 tons) and phosphorus by 33% (15 000 tons).
To achieve the goals of the Baltic Sea Action Plan, further nutrient reductions are needed. Compared to average inputs for the 2012- 2014 period, nitrogen inputs must decrease by 12% (122 000 tons) and phosphorus by 55% (14 000 tons) to reach maximum allowable inputs.
Nutrients that cycle in the agri-food system contribute to eutrophication by, for example, leakage of fertiliser and manure, which have been applied to crop land, and discharge of sewage effluent to water bodies.