Biogas producers have faced challenges to find functioning and cost-efficient processing technologies. Solids and liquids can be separated from digestate, in which case the phosphorous-rich solids (dry content 20-30 %) can be cost-efficiently transported further. The nitrogen-rich liquids can be concentrated, but many of the tested technologies have not been successful due to the heterogenic liquids. This is the reason why digestate processing is not very common. Digestate processing is currently under an active development and successful demonstrations are needed.
It is essential to understand, what kind of recycled fertilizers should be produced and adjust the processing technologies accordingly.Well-adjusted processing technologies are not sufficient to guarantee market acceptance, as the products need to meet the needs of end users as well. Producers of fertilizers need to be aware about the end-users perceptions and needs, restrictions connected to spreading machinery and requirements of the cultivated plants.