Bio-based fertilizer— Custom-made method for evaluation of its production; environment, climate, and overarching economic performance

The European Union's Farm-to-Fork strategy and the HELCOM Baltic Sea Regional Nutrient Recycling Strategy emphasize the need to increase nutrient recycling and reduce the environmental and economic burdens associated with mineral fertilizers. To support this transition, the Interreg Baltic Sea-funded CiNURGi project evaluated 11 bio-based fertilizer (BBF) value chains selected from 24 identified cases across agricultural, municipal, and industrial waste streams. A streamlined assessment method based on the Single Operation Unit Process (SOUP) concept was developed to compare BBF production with relevant baseline waste management practices using three indicators: nutrient recycling impact (NRI), direct emission impact (DEI), and guiding social cost (GSC), including the capitalized social costs of nutrient losses and greenhouse gas emissions. Performance varied widely across cases, with NRI ranging from −9% (digestate-based BBF) to 100% (municipal wastewater sludge), DEI from −13.2 (manure processing) to +28.4 t CO 2 -eq per functional unit (food industry side-streams), and GSC from €−3,550 (manure processing) to €1,487 (digestate-based BBF). Municipal and industrial waste streams generally achieved the highest nutrient recycling benefits due to nutrient inefficient baselines such as incineration or conventional wastewater treatment, whereas farming-based chains showed limited or negative net benefits because they typically replace already nutrient-efficient baseline practices. Overall, the results demonstrate that the sustainability of BBF production depends strongly on baseline inefficiencies, nutrient-retention performance, and processing energy demand. BBF systems offer the greatest societal value where current waste management results in substantial nutrient losses, and targeted policy measures that internalize environmental and climate externalities may be required to improve the market competitiveness of these technologies.