The Kainuu Centre for Economic Development, Transport and the Environment ran tests and conducted research on composting as a part of the “Eloperäiset jätteet kiertoon” (Recycling organic waste) initiative. The composts were used in landscaping ski slopes and gangue sites for the mining industry, planting lawns, growing energy plants, fertilising forests and in agriculture. The use of composts in planting lawns and growing energy plants was also studied in separate research projects. These projects were carried out by MTT Agrifood Research Finland. The data gathered in these projects has been included in this publication.

The compost tests and research were conducted using composts of the municipalities and the Municipal Waste Authority of Kainuu. These composts were all produced with the windrow composting method. The composts used by the Municipal Waste Authority of Kainuu consist purely of organic waste. The other composts consist of sludge from their respective municipal sewage treatment plants. The compost used in Kajaani is also called “biosoil”, and it is produced by A. & E. Juntunen Oy.

According to the test and research results of this study, compost produced by windrow composting is well suited for these various uses, especially when the challenges discovered are addressed. For example, when using compost in agriculture, forest fertilization and gangue site landscaping, mineral soil should not be used as a compound material. Tests revealed that in gangue sites compost heaps did not remain stationary when sand was mixed in. When sand was used, rainfall swept compost material down from the compost heap. However, when the heap consisted of only compost material, it remained stationary in any weather. The use of mineral soil was also deemed unnecessary in agriculture and forest fertilization. In addition, using sand and rocks in the compost material runs the risk of damaging distribution equipment.

The nutrients in compost are released slowly for plants to use. Therefore the effects of chemical fertilizers typically emerge faster. However, compost is especially well suited for environments where additional fertilization is not required and environments where fertilization is difficult to carry out. These environments include gangue and tailings sites used in mining, and other hard to reach areas. Compost is also well suited for agriculture and fertilizing forests, but in these areas compost is clearly under-used considering the capacity of the composts used by the Municipal Waste Authority of Kainuu.

The construction of a new organic waste disposal plant is currently being planned in Kajaani, and Pöyry Finland Oy has already prepared techno-economic plans for it. According to these plans, windrow composting all the sludge produced by the Kainuu region would produce 13,000 tons of compost a year after support material is separated. The alternative biogas plants would produce significantly less end-product. For example, decomposing only sewage sludge from the Kainuu region would produce 6,600 tons of compost a year after post-composting.

In the region of Kainuu, compost is commonly used in landscaping urban areas. This use has the potential for further growth, especially if the quality of compost is improved. In the town of Kajaani, landscaping alone would be enough to consume all the compost produced in the region of Kainuu if the consumption of compost soil is assumed to be 0.5 tons a year per capita. This would amount to a total of 27,000 tons of compost a year in the Kainuu region. However, the production of compost will be nowhere near this average soil consumption in the future. The weak market for compost has most likely been caused by the poor quality of compost produced by most municipalities, rather than by market saturation. However, the situation is improving thanks to the new organic waste disposal plant now being planned. With the new plant, the quality of compost can be improved much further than with the use of several smaller compost fields.