Crystals and Manure for Food

This thesis examines how phosphorus (P), an essential nutrient for crop production and food security, can be managed more sustainably in organic farming across the European Union (EU). Phosphorus is indispensable to agriculture, yet its current management is characterised by a strong dependence on finite phosphate rock, geographically concentrated supply chains, and large losses to the environment. These pressures are particularly important in the EU context, where the Farm to Fork and Biodiversity strategies aim to expand organic farming to 25% of agricultural land by 2030 while simultaneously reducing nutrient pollution. Organic farming is often presented as a pathway towards more sustainable agriculture, but it also faces specific nutrient supply challenges because the range of permitted phosphorus inputs is limited. Against this background, the thesis investigates current P demand in organic farming, the potential contribution of recycled P products, and the socio-technical conditions that shape their adoption. The first empirical contribution of the thesis is a spatial quantification of phosphorus demand in EU organic farming. Using crop production data and phosphorus removal through harvest as a proxy for demand, the research provides the first EU-wide, spatially explicit estimate of P demand in organic crop systems. The findings show that total annual P demand in organic farming is substantial and unevenly distributed across Europe, with around half linked to food crops. Regions with larger areas of organic farming, particularly in southern Europe, also show the highest total P demand. The analysis further demonstrates that while organic farming uses relatively little mineral fertiliser P compared with conventional systems, the mineral inputs that are currently used are spatially concentrated in regions with high P demand. This suggests that, under current policies, expanding organic farmland is likely not only to increase total phosphorus demand but also to reinforce dependence on the small set of mineral fertilisers still permitted in organic systems. The second contribution of the thesis is an assessment of the extent to which recycled phosphorus sources could meet this demand. Particular attention is given to struvite recovery from municipal wastewater treatment plants and to livestock manure, two prominent recycled P sources discussed in European circular economy debates. Scenario analysis shows that struvite already has meaningful potential to contribute to organic farming and, under moderate recovery assumptions, could satisfy a substantial share of current P demand. Livestock manure contains enough phosphorus in aggregate to meet organic crop demand, but its use is constrained by spatial mismatch, variable nutrient content, and logistical difficulties. Both manure and struvite are often available in regions different from those where demand is highest. The thesis therefore highlights that the challenge is not only one of total availability but also of redistribution. It argues that regionally coordinated nutrient transfer systems, or “P corridors,” may be necessary to connect surplus and deficit areas efficiently. Another contribution of the thesis is its analysis of the barriers and enablers shaping adoption of recycled phosphorus products in organic farming. Drawing on stakeholder perspectives from across the phosphorus value chain, the thesis shows that adoption is influenced by a combination of regulatory, technological, financial, and social factors. Organic regulations, while intended to protect environmental and consumer values, currently restrict several waste-derived nutrient sources. Farmers and other actors also express concerns about product quality, agronomic reliability, and affordability. At the same time, the research identifies important opportunities: clear quality standards, harmonised rules, targeted financial support, and better cross-sector coordination could significantly improve the use of recycled phosphorus in both organic and conventional systems.