Nutrient recovery from digestate for sustainable agriculture

Nutrient recovery from digestate is a critical component of sustainable biomass management in North West Europe. This report, part of the ARBOR project, evaluates technologies and strategies for recovering nitrogen, phosphorus, and potassium from digestate to address nutrient pollution and reduce reliance on mineral fertilisers. Focused on Flanders, where strict regulations limit raw digestate use, the study examines full-scale techniques like ammonia stripping, membrane filtration, and acid air washing. Field trials on energy maize and lettuce demonstrate that digestate-derived fertilisers perform comparably to synthetic alternatives in yield and nutrient uptake, with reduced environmental impact. Economic and environmental assessments show treatment can be cost-effective, especially when products are sold at 50% of their fertilising and humus value. Composting and drying show moderate benefits, while reverse osmosis and drying systems offer higher recovery but increased costs. The findings support policy alignment with the EU Fertilisers Regulation and highlight the need for market incentives and consistent product standards to scale up recovery across agricultural, industrial, and domestic applications.