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Expert group: Use nutrients in wastewater to safeguard food production during the fertiliser crisis

Food security and nutrient self-sufficiency can be improved by enhancing nutrient recycling. A group of leading experts in agriculture, food production and the environment proposes a set of measures to safeguard Finland’s food production both in times of crisis and in the longer term. The measures focus particularly on recycling nitrogen in wastewater.


A group of leading agricultural, food production and the environmental experts from five organisations, have proposed a set of measures for Finland to help safeguard its food production, both in times of crisis and in the longer term.

Concerns have emerged in Finland about the price and availability of fertilisers for agriculture, as energy and raw material prices have risen, especially since Russia launched a war of aggression against Ukraine. A significant proportion of the fertilisers or their raw materials used in Finland has previously been imported from Russia. Dependence on Russia has been the greatest for nitrogen fertilisers.

The Finnish Innovation Fund Sitra and the Central Union of Agricultural Producers and Forest Owners (MTK) convened an expert group to find solutions for replacing imported fertilisers with nutrient recycling. This would improve Finland’s security of supply, self-sufficiency and reduce dependence on mineral fertilisers produced with fossil fuels. Sitra and MTK invited experts from Natural Resources Institute Finland (Luke), the Finnish Environment Institute (SYKE) and the Finnish Water Utilities Association (FIWA).

Using nutrients from wastewater provides quick solutions

The main proposals of the working group relate to the use of municipal sewage sludge to improve the recovery of nitrogen, for agricultural use. The group also explored the recovery and recycling of phosphorus and potassium from wastewater.

Nitrogen is the most critical nutrient for crops. Plants need nitrogen for growth, especially for the formation of proteins. By improving nitrogen recycling we could reduce our dependence on mineral nitrogen produced by binding nitrogen from the atmosphere by fossil energy, although the total potential of recycled nitrogen and increased biological nitrogen fixation would not be enough to meet the nitrogen fertiliser needs of our food production.

Nutrients from food consumption of food end up in wastewater treatment plants, where only part of the nitrogen is recovered for subsequent use. According to the experts, the proportion of nitrogen recovered could be rapidly increased: the drying of digested sludge leaves a nitrogen-rich liquid that, at present, is often returned to the wastewater treatment process. If the nitrogen in this liquid were recovered in the form of ammonium sulphate or ammonium nitrate, for instance, this would provide a suitable fertiliser for crops. It would require investment in nitrogen recovery technology.

Safety of recycled fertilisers needs to be ensured

Sewage sludge contains not only nutrients but also contaminants originating from households and industry, such as organic chemicals and pharmaceuticals. Studies on the concentrations of contaminants have found that they pose minimal risk to people. However, the effects of contaminants on field ecosystems, for example, are not yet sufficiently understood.

Protecting soil biodiversity and microfauna is also essential for more efficient use of nutrients in arable farming, and therefore more research in this area is needed.  But the experts point out that in a crisis situation, the question of whether the use of nutrients in wastewater can be increased by allowing the use of the above-mentioned liquid fraction to increase nitrogen availability needs to be considered.

“Wastewater treatment plants do a good job of cleaning up wastewater and reducing the load on water bodies, but the process was not designed with nutrient recovery and recycling in mind, the need for which is now increased in the current crisis situation,” explain Director Mari Pantsar from Sitra and Head of Environmental Affairs Liisa Pietola from the Central Union of Agricultural Producers and Forest Owners, who convened the working group.

Complementing quick action with longer-term solutions to tackle the sustainability crisis

The solutions proposed by the working group could improve Finland’s nitrogen self-sufficiency relatively quickly if the crisis were to deteriorate. However, the working group stresses the importance of developing longer-term solutions for nutrient recycling to address issues such as the overconsumption of natural resources. The working group proposes the following measures to promote nutrient recycling in wastewater in the short term and further in the future:

  • Nitrogen: Utilising nitrogen from wastewater

Promoting the processing of nitrogenous liquid fraction (so called reject water) from sludge drying in biogas plants and wastewater treatment plants is dried, and enabling investment in this area.

In the longer term, identifying solutions to increase the recycling of nitrogen in the wastewater treatment process, and exploring the potential of the separate collection of different waste materials to improve the recycling of consumption-based emissions in the most energy and cost efficient and safe ways possible.

  • Phosphorus: Recycled fertiliser products

Using existing recycled fertiliser products in a manner that minimises the risk to soil organisms. Identifying solutions and facilitating investments in the longer term.

  • Potassium: Biomass assessment

Identifying recyclable biomasses and potential recovery or recycling opportunities.

  • Assessment and identification of potential obstacles

Assessing contaminants in fertiliser products and, in particular, their long-term environmental impact on soil. Compilation of existing data and identification of gaps. Ensuring legislation to promote the use of recycled fertiliser products.

The expert group’s working paper: (in Finnish)

Members of the working group:

Paula Lindell, Senior Adviser, Finnish Water Utilities Association (FIWA),, tel. +358 9 8689 0121
Sari Luostarinen, Principal Specialist, Natural Resources Institute Finland (Luke),, tel. +358 295 326 346
Mari Pantsar, Director, Sustainability solutions, Sitra,, tel. +358 294 618 210
Liisa Pietola, Head of Environmental Affairs, Central Union of Agricultural Producers and Forest Owners (MTK),, tel. +358 50 438 4014
Timo Seppälä, Senior Adviser (contaminants), Finnish Environment Institute,, tel. +358 295 251 630