The numbers don't add up on manure and fertiliser: one-pager

Abstract

The EU wants to reduce its dependency on imported fertilisers to boost the resilience and strategic autonomy of its food system, with the European Parliament claiming that livestock manure can reduce the EU’s reliance on imported fertilisers and that herd reductions may compromise its use as fertiliser for crop production. But the numbers don’t add up: Across the EU, livestock systems consume substantially more nitrogen from mineral fertiliser than they return to the rest of agriculture through manure. The same holds in grass-based systems such as Ireland, where livestock production is a large net consumer of mineral fertiliser. This is because animals do not produce the nutrients in manure. The nutrients come from what they eat – everything in manure is derived from feed and forage. In the case of nitrogen, crops obtain it mainly from mineral fertilisers, recycled nutrients in manure, biological fixation, and atmospheric deposition. This means that, in essence, nitrogen enters livestock systems through crops and grass. Once the nitrogen is within the system, a part of it is merely recycled via manure, another part leaves the system via animal products, and a further part is lost to the environment through volatilisation, leaching and runoff. The key distinction is between field- and system-level analysis: Individual farmers can replace fertiliser without yield losses by using more land to keep livestock or to grow nitrogen-fixing crops, or by importing manure from other farms – but those farms must then obtain the nitrogen they need from fertiliser or more land, too. While overall nitrogen flows are complex, assessing whether manure can replace mineral fertiliser is more straightforward: If the livestock sector uses more nitrogen from mineral fertiliser than it provides to the rest of agriculture via manure, it is a net consumer of mineral fertiliser. A new analysis has shown just that: Animal production adds to the EU’s dependency on mineral fertilisers rather than reducing it (see Figure). Optimising manure management can still reduce fertiliser demand, but livestock remains a key driver of the net consumption of mineral fertiliser. If manure is not the answer, what then? As livestock production is a structural driver of fertiliser demand, addressing the scale of animal production itself can help manage nitrogen flows more sustainably and reduce fertiliser dependency within the food system.