Science communication


A new sewage sludge directive should focus more on the marine environment

The debate on new rules for how sewage sludge should be used should take greater account of how the sea and fresh water are affected, the Baltic Sea Centre writes in its response to the European Commission's consultation on a roadmap for a possible revision of the sludge directive.

Text: Gun Rudquist

The debate on the reuse of sewage sludge has been going on for decades and has mainly been focused on the benefits and risks of spreading the sludge on arable land. When the EU now reopens for the revision of the old and outdated sludge directive from 1986, agriculture and food production are once again in sole focus.

In the European Commission's recently concluded consultation on a roadmap for a new sludge directive, the Baltic Sea Centre emphasized the importance of revising the directive as today's directive is irrelevant to environmental protection and the circular economy. At the same time, the focus on agriculture alone was questioned. A new directive must focus not only on preventing negative effects on land, vegetation animals and humans, but also on drinking water, fresh water and the marine environment.

Furthermore, the Baltic Sea Centre considers that the new directive should not assume that sludge spreading on, for example, arable land is the only way to make use of the sewage sludge. New technologies should also be enabled to extract, for example phosphorus from the sludge, and at the same time prevent the spread of hazardous substances such as heavy metals, drug residues and microplastics.

A revised sludge directive can certainly contribute to the circular economy through improving the use of the finite resource that phosphorus is. But research from, among others, the Baltic Sea Centre shows that in the Baltic Sea catchment area, the amount of phosphorus in manure is more than three times as large as in the sludge from society's treatment plants. In other words, the phosphorus work must primarily be focused on taking care of and using the manure more efficiently. If the manure was used more efficiently, purchases of mineral fertilizers could be reduced by 0.11 - 0.17 million tonnes, compared with around 0.036 million tonnes through the use of sewage sludge. Reducing the import of mineral fertilizers is an important part of reducing the amount of phosphorus imported into the agricultural systems. This would reduce the excess phosphorus and the risk of leakage to lakes, watercourses and the Baltic Sea. However, this aspect of the sludge issue is seldom addressed in discussions. When designing a roadmap for a new sludge directive, time has come to change that.

Read the Baltic Sea Centre's reply to the consultation here.