The root cause of eutrophication in the Baltic Sea is addressed through nutrient maps and strategies

The Sustainable Biogas project, funded by the EU’s Interreg Central Baltic program, produces nutrient maps for southwestern Finland, Åland and the Zemgale region in Latvia. Maps can be used to identify nutrient-surplus areas from which nutrients should be transferred to nutrient-deficient areas.

The maps give an overview of the nutrients generated in the area

Nutrient maps enable a detailed examination of nitrogen and phosphorus production in the target area and give an overall picture of the nutrient-rich biomasses formed in the area. By comparing the nutrient production and their potential as field fertilizers, it is seen whether a surplus or deficit of nitrogen or phosphorus is formed in an area. In the event of a surplus, nutrients or biomass containing them should be transferred to nutrient-deficient areas.

The nutrient maps produced in the Sustainable Biogas project are available for everyone who are interested in the use of biomass and nutrients in these regions.

In the future, regional nutrient management plans will be created

Nutrient maps serve as tools when project experts make nutrient management plans in collaboration with various stakeholders in the southwestern Finland, Åland and Zemgale region in Latvia.

The information on biomass and nutrient status and nutrient demand of fields produced by regional nutrient maps can be used, for example, to plan the location and operation of a biogas plant: where and how much biomass suitable for biogas production is generated and where biogas plant nutrients are needed. Ideally, biomass processing plants would be wisely located, from technical and environmental perspective, to make the best use of organic nutrients and minimize emissions to water systems.

Nutrient balances in southwestern Finland have already been mapped

For southwestern Finland, the maps are already ready and cover the provinces of Varsinais-Suomi and Satakunta. The first step of the work was to map the origins, formation rates and nutrient concentrations of biomass. The biomasses to be considered were manure from farm animals, municipal sewage sludge and household biowaste, some organic waste from the food and other industries, and crop residues from agriculture. In the next step, the potential for nutrient use as field nutrients was examined. The result was a visual overview of how much biomass is produced in different parts of the target area, how much phosphorus and nitrogen they contain, and how much phosphorus could be utilized in the area for crop production. The maps also show composting and biogas plants that further process biomass.

“The most significant nutrient sources in the region are manure from more than 9 million farm animals and agricultural crop residues. The wastewater of nearly 700,000 inhabitants is also rich in nutrients. Together, these and other biomasses considered form an annual source of about 28,300 tons of nitrogen and 5,700 tons of phosphorus, which should be better utilized in crop production in the area”, says Sanna Tikander from the Centre for Economic Development, Transport and the Environment for Southwest Finland.

Phosphorus generated in the study area of southwestern Finland (tons / year) (Vahanen Environment Oy 2021)

Nitrogen generated in the study area of southwestern Finland (tons / year) (Vahanen Environment Oy 2021)

The phosphorus uptake potential of the fields in the study area, in the provinces of Southwest Finland and Satakunta, was examined based on the calculated phosphorus demand of the plants. There are a total of about 457,900 hectares of arable land in the area, of which more than 10% is uncultivated or for some other reason not fertilized. No phosphorus fertilizer was expected to be applied to these fields.

The calculation method based on the phosphorus demand of the plants indicated that a total of 2 991 tons of phosphorus is needed to be applied to the fields of the study area.  When the biomass produced in the area contains 5 658 tons of phosphorus, there is a surplus of about 2 539 tons. The result is only indicative, as in reality it is not possible to use all the nutrients generated in biomasses as crop nutrients. However, the review shows that the area could be self-sufficient in phosphorus and that the resulting nutrient surplus may pose local risks to nutrient leaching into water bodies.

In addition, the amount of nutrients was compared to the maximum amounts allowed under the current environmental compensation scheme. These will change with the start of the new rural development program in 2023.

“The nutrient surplus generated in southwestern Finland maintains the high phosphorus content of the fields and the high nutrient load on the Baltic Sea and inland water systems. Nutrient surpluses should be directed to those areas where nutrients can be used sustainably. Support for manure phosphorus recycling should be allocated, e.g., from the new EU Common Agricultural Policy (CAP),” says Marjukka Porvari from the John Nurminen Foundation.

There are large local variations in nutrient balances

The scale of the map survey carried out in south-western Finland (5 x 5 kilometer resolution) illustrates that nutrients are not generated or needed in the fields evenly throughout the area. Significant phosphorus surplus areas appear on the map as dark spots. Those spots contain, e.g., intensive animal production. Phosphorus deficit areas are indicated as light-yellow color on the map.

Phosphorus surplus and deficit areas in southwestern Finland calculated according to the need for cultivated crops. (Vahanen Environment Oy 2021)

Nutrient maps for Southwest Finland were produced by Vahanen Environment Oy. The maps and report can be downloaded Sustainable Biogas project website and the Centre for Economic Development, Transport and the Environment for Southwest Finland’s webpage.

Sustainable Biogas project reduces nutrient load risks from biogas production to the Baltic Sea and other water systems

Climate-friendly biogas can pose a risk of nutrient runoffs to water bodies if the treatment of biogas plant digests and wastewater is not carefully planned. The Sustainable Biogas project, funded by the EU’s Interreg Central Baltic program, aims to promote the sustainability of biogas from the water protection perspective. The project is implemented by the John Nurminen Foundation, the Centre for Economic Development, Transport and the Environment for Southwest Finland, the Finnish Biocycle and Biogas Association, the Latvian State Environmental Services and the Latvian Biogas Association.