NACO Northern Swedish Strategy for Sewage Sludge in the Transition to a Circular Economy
NACO is a feasibility study aimed at examining the current situation regarding the management of digested and undigested sewage sludge in the municipalities of Norrbotten.
The project was completed in July 2025.
The overall objective of the feasibility study was to promote a circular economy through sustainable management practices for municipal sewage sludge. Sewage sludge is generated after municipal wastewater has been treated in wastewater treatment plants. In some cases, the sludge is digested to produce biogas. Whether digested or not, the resulting sludge contains valuable resources such as nitrogen, phosphorus, potassium, and organic carbon, while also containing potentially harmful substances.
Today, there is considerable uncertainty regarding the future management of sewage sludge, as traditional applications such as landfill disposal, landfill cover material, and landscaping soils are gradually being phased out and/or questioned from an environmental perspective.
The following organizations contributed their own resources to the feasibility study: Tekniska Verken i Kiruna AB, Piteå Renhållning (PIREVA), Restproduktbearbetning i Boden AB (REBAB), Bodens Energi AB (BEAB), Boden Business Park, Bodens Municipality, and Luleå MiljöResurs AB (Lumire). Future Eco served as project manager and research provider. The feasibility study was carried out between August 2024 and July 2025.
The work also included collecting and evaluating analytical data on digested and undigested sewage sludge from the participating municipalities. In addition, various treatment technologies and potential markets for sludge utilization were investigated.
Potential Markets
- Production of landscaping soil, topsoil, and landfill cover material
- Application of sludge on agricultural land
- Application of sludge on forest land
Technologies Evaluated
- Mono-incineration
- Co-incineration
- Pyrolysis for the production of sewage sludge biochar
The conclusions of the feasibility study show that the long-term disposal and utilization options for sewage sludge vary considerably among the municipalities of Norrbotten. Some municipalities have an urgent need to establish new or improved utilization pathways, while others currently have more favorable conditions and therefore face less immediate pressure to develop alternative solutions.
The study highlighted the need for further research into how different substances—including both nutrients and environmentally harmful compounds—behave and are distributed among different phases during thermal treatment processes. Furthermore, the plant availability of nutrients following such treatments requires continued investigation.
One important conclusion and lesson learned from the study is the value of establishing a dedicated forum for municipalities and municipal companies to meet and exchange information. Wastewater treatment plants and sludge management are often handled by relatively small organizations with limited resources. A collaborative forum should therefore be organized in a way that makes participation straightforward and enables organizations to contribute effectively while benefiting from shared knowledge and experience.
