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Technical proposals for the safe use of processed manure above the threshold established for Nitrate Vulnerable Zones by the Nitrates Directive (91/676/EEC)

Abstract: 

Potential exists to reconcile on-going technological and market developments for the recycling of nutrients in a circular economy with the objective of protecting water bodies against pollution originating from livestock manure. The objective of this report is to help define those harmonised criteria that could allow nitrogen (N) fertilisers, partially or entirely derived from manure through processing, to be used in areas subject to the ceiling of 170 kg N/ha/yr prescribed in Annex III of the Nitrates Directive following otherwise identical provisions applied to N containing chemical fertilisers in the Nitrates Directive (91/676/EEC), while ensuring the achievement the Directive’s objectives and adequate agronomic benefits. Such materials are referred to as REcovered Nitrogen from manURE (RENURE) in this report. This work combines biogeochemical modelling techniques, analytical measurements and quantitative (meta-analysis) and qualitative literature review techniques to assess use impacts of candidate RENURE materials on environmental pollution, including nitrate leaching. The results indicated that processed manure characterised by a ratio of total organic carbon to total N ≤ 3 or a mineral N to total N ratio ≥ 90% may have a similar N leaching potential and agronomic efficiency to Haber-Bosch derived and equivalent chemical N fertilisers. In particular, nitrogen-rich processed manure materials, such as scrubbing salts, mineral concentrates, and liquid digestates obtained through centrifugation and/or advanced solids removal might be able to meet these requirements. To comply with the objectives of environmental protection, it is, however, necessary to combine the use of RENURE with good management practices, including the use of living plant covers or equivalent measures, low NH3 emission application techniques and good RENURE storage conditions. Altogether, this report proposes a set of material and use requirements to enable the safe use of RENURE in areas with water pollution by nitrogen, in amounts above the threshold established by the Nitrates Directive (91/676/EEC). It is concluded that the possible implementation of RENURE as part of manure management systems enables a progression towards a more circular economy and an avenue for increased resource efficiency in the EU food production system.