Assessing the Economic Feasibility of Nitrogen and Phosphorus Recovery Systems in European Waste Valorization Case Studies

Nitrogen (N) and Phosphorus (P) are essential macronutrients whose unsustainable extraction and use pose growing environmental and geopolitical challenges. In the European Union, tightening regulatory frameworks, including the Urban Waste Water Treatment Directive (EU 2024/3019) and the Farm to Fork Strategy, have positioned nutrient recovery as a fundamental pillar of the circular economy. Despite the availability of mature technologies, comprehensive techno-economic assessments applied comparatively across multiple industrial sectors remain scarce. This study addresses that gap by evaluating the economic feasibility of five nutrient recovery systems across European waste valorization case studies: ammonia stripping from digestate (Spain), sewage sludge composting (Latvia/Lithuania), whey valorization via ultrafiltration and reverse osmosis (Hungary), algae-based dairy wastewater treatment (Slovakia), and pyrolysis of sewage sludge (Denmark). A structured data collection methodology was applied to assess capital expenditures (CAPEX), operational expenditures (OPEX), mass and energy flows, and nutrient recovery yields. Results demonstrate that all five systems show technical operability and economically relevant cost structures, with unit treatment costs ranging from €0.005/kg to €1.60/kg of waste treated, supporting their further development and scale-up as viable nutrient recovery pathways. N recovery was prioritized in most configurations, while P was predominantly co-recovered in solid residues. The findings provide a cross-sectoral comparative framework to support decision-making in the transition towards sustainable nutrient management and circular economy models.