Speaker
Description
Introduction
Principles around circular agriculture are based on re-using by-products, closing nutrient cycles, minimal feed-food competition, low energy use and low GHG emissions [1]. Moving from current linear to more circular systems is a wicked problem as key trade-offs need to be overcome [2]. The objective here is to provide quantitative insights into such trade-offs and discuss consequences.
Methods
We have quantified all N and P flows in the North of the Netherlands (NN) as a starting point to assess the options to improve circularity [3]. Agricultural flows were based on data at farm level and aggregated to municipality level. Flows from processing, consumption, waste and residues were derived from statistical data complemented by available detailed studies. In a next step, future options for integrated crop-livestock systems (ICLS) were evaluated in which feed import and environmental constraints were varied and gross margin was maximized using a linear optimization model [4]. Lastly, trade-offs between land requirements and N intensity in mixed faring systems were assessed for mainstream and organic systems.
Results
Within the NN region, farms but also municipalities were specialised. At food system level, losses for N ranged from 181-480 kg ha-1 while P losses were 7-31 kg ha-1. Losses were largest in agriculture while recycling of nutrients in the food system was limited. The nutrient use efficiency was 25% for N and 59% for P, reflecting an inefficient and strongly linear system. Moving towards circular agriculture is expected to reduce these nutrient losses. However, potential benefits are not self-evident ICLS without constraints on NH3 and GHG emissions increased gross margins due to more animals and a larger proportion of intensive crops, resulting in more feed and N imports and consequently more emissions. In scenarios with NH3 and GHG emission constraints livestock strongly reduced, whereas more cash crops were grown. This negatively affected the gross margin of animal production system, while crop production systems benefitted. Also reducing N intensity increased land requirements exponentially for mainstream systems, while or organic systems least land was required at an N intensity equivalent to 90% of maximum yields.
Discussion
Re-integration of specialised crop and livestock systems is a key component of a more circular agriculture. Yet, it comes with trade-offs: ICLS without environmental constraints increases intensity [5]. This work shows that ICLS without limits for NH3 and GHG increases gross margins, but does not result in desired environmental outcomes and increases feed-food competition. An increase in food-feed competition reduces the area that can be set aside for conserving biodiversity, further amplified when mineral N inputs are reduced or replaced by leguminous cut-and-carry crops. Apparent ecosystem services at farm level by decreasing feed and mineral N inputs may be disservices at the regional scale due to increased feed-food competition. Addressing such undesired feed-food competition and spare land for biodiversity in a circular system requires a shift in diets with a smaller proportion of animal products [6].
Van Selm et al. [6] found that reducing feed imports to the Netherlands strongly reduces NH3 emissions and GHG emissions. We found the same for ICLS: restricting feed imports or imposing NH3 and GHG emission limits strongly reduced the number of animals and feed requirements. This also implies that the gross margins of livestock sectors decreases. Furthermore, such constraints reduced feed-food competition and increases the available area for cash crops [4], with benefits for cropping sectors.
Current animal production systems in areas with access to cheap feed are very competitive on export markets. Including environmental costs in feed imports through Europe’s harbours and pricing GHG emissions are key components to reduce profits and address environmental problems. Resulting revenues can be used to compensate incomes via targeted ecoservice payments that are needed to maintain specific habitats that are only found on low intensity farmland. We conclude that policies to address environmental impacts without changing the economic incentives for farmers are rowing against the current.
References
1. Muscat et al. 2021. Nature Food, 2021: https://dor.org/10.1038/s43016-021-00340-7.
2. Termeer and Dewulf 2019. Policy Soc.: https://doi.org/10.1080/14494035.2018.1497933.
3. Tamsma et al. 2024. Nutr. Cycl. Agroecosyst.: https://doi.org/10.1007/s10705-024-10352-x.
4. Alderkamp et al. Under review, 2024.
5. Schut, et al. 2021. Front. Agr. Sci. Eng.: https://doi.org/10.15302/J-FASE-2020373.
6. van Selm et al., 2023. Sci. Tot. Env.: https://doi.org/10.1016/j.scitotenv.2023.165540
| Keywords | nutrient cycling, nutrient use efficiency, cycle count |
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