The global food system faces immense pressure from the COVID-19 pandemic, conflicts, resource depletion, biodiversity loss, and climate change, all while the global population continues to grow. This creates a paradox: our food production methods threaten our ability to produce food sustainably. This research addresses the challenge of supplying healthy diets to everyone while safeguarding planetary health. This is complex, requiring a food system transformation encompassing production, processing, distribution, retail, and consumption to respect both human and planetary well-being. One promising approach gaining traction is the circular food system, a key strategy of the European Union. Circular food systems minimize waste—food waste, human excreta, nutrient overconsumption—and utilize unavoidable waste sustainably. For instance, processing by-products can be used as fertilizer, reducing reliance on artificial fertilizers, or as animal feed, transforming inedible biomass into valuable food and ecosystem services. While studies have highlighted the environmental benefits of animals as recyclers, a holistic assessment of a circular food system is lacking. This is crucial due to the interconnectedness of the food system; for example, a shift towards whole grains impacts the role of animals as recyclers by altering by-product availability. This study assesses the potential of redesigning the European (EU27 + UK) food system based on circularity principles to ensure food security while minimizing environmental impact.

Several studies have explored the potential of circular food systems and the role of animals in recycling waste streams. These studies demonstrated significant environmental benefits associated with animal-based recycling (refs. 7–10). However, a comprehensive, holistic assessment incorporating the interdependencies within the entire food system has been absent. Existing models often rely on current linear food systems, offering only incremental improvements. The EAT-Lancet Commission's work on healthy diets from sustainable food systems (ref. 14) provides important dietary guidelines, but integrating these recommendations into a circular food system model requires further analysis. Studies have shown the potential for reducing emissions and land use through dietary changes (refs. 3, 32), but the added benefits of incorporating circularity principles remain to be explored in detail. This study aims to bridge this gap by employing a holistic approach and explicitly incorporating circularity principles into the modeling framework.

This study used the Circular Food System (CiFoS) model, a biophysical, data-driven optimization model building upon previous work (refs. 8, 12, 13). CiFoS optimizes food system redesigns by minimizing agricultural land use and GHG emissions while meeting dietary requirements. Four scenarios were compared: AgriBase (baseline representing current production), CirAgri (supply-side circularity), CirHealth (supply and consumption-side circularity with a healthy diet), and CirPop+ (supply and consumption-side circularity maximizing the population fed). The model integrates various modules: human systems (dietary constraints based on FAOSTAT, EFSA recommendations, and EAT-Lancet guidelines), cropping systems (land use, crop rotations, fertilization—artificial and organic—based on FAOSTAT, EuroStat, and other datasets), livestock systems (animal production, feed, and manure management), fisheries (capture and aquaculture, considering MSY), residual streams (crop residues, by-products, food loss and waste, manure, human excreta), transportation (inter-country transport of goods), and GHG emissions (using IPCC methodologies). The model operates at various scales, from the EU27+UK level down to agro-ecological zones, considering 42 nutritional values (Table 1) and food group requirements (Table 2) in the dietary constraints. Data sources include FAOSTAT, EUROSTAT, USDA National Nutrient Database, SPAM, EARTHSTAT, Eco-invent, and others. The model selects a combination of food items to meet dietary needs and minimize the chosen objective function (land use or GHG emissions).

The AgriBase scenario showed annual GHG emissions of 644 MtCO2e (1.17 tons CO2e per person per year) and 172 Mha of agricultural land. CirAgri, focusing on supply-side circularity, reduced GHG emissions by 22% and land use by 71%, while meeting current protein supply. CirHealth, integrating consumption changes towards a healthier diet, achieved a 29% reduction in GHG emissions and a 71% reduction in land use. The CirPop+ scenario, aiming to maximize the population fed, could nourish an additional 767 million people with a healthy circular diet, reducing per capita GHG emissions by 38% but increasing total emissions by 55%. Land use in CirPop+ differed by only 3% from the baseline. Analyzing land use changes, cropland was reduced by 53% in CirAgri and CirHealth, while grassland was reduced by almost 100%. CirPop+ showed a slight decrease in grassland. Crop patterns shifted towards more diverse production in CirHealth, with less cereals and fodder crops, and increased pulses, sorghum, and vegetables. Fertilizer use decreased in CirAgri and CirHealth due to increased organic fertilizer use, while CirPop+ showed increased artificial fertilizer use due to insufficient organic fertilizer. Livestock numbers decreased significantly in CirHealth and CirPop+ to align with the reduced animal product consumption. Feed-food competition decreased in all circular scenarios, yet fodder crops remained vital in feed due to limited availability of other feedstuffs. Consumption patterns shifted towards healthier diets in CirHealth and CirPop+, with a significant reduction in animal-based proteins and increased plant-based proteins, while still meeting all nutritional requirements. Total energy intake, EPA, iodine, vitamin B12, and calcium remained limiting in CirHealth and/or CirPop+.

This study demonstrates the significant potential of circularity principles in reshaping the European food system for enhanced sustainability and global food security. The substantial reductions in land use and GHG emissions, while maintaining sufficient and healthy food supply, highlight the transformative power of this approach. While GHG emissions remained above the recommended planetary boundary (ref. 14), the results still represent a substantial improvement compared to the current system. The ability of the EU to feed a substantially larger population while reducing per capita emissions showcases the global implications of such a transformation. The findings underscore the importance of crop diversification, reduced reliance on artificial fertilizers, and significant shifts in livestock production and consumption patterns. Current crop rotations, however, limit the circularity potential. The role of animals in circular food systems is pivotal but requires a drastic reduction in numbers. The availability of organic fertilizers, especially from human excreta, is critical for successful implementation. Reductions in grassland areas offer opportunities for biodiversity enhancement, although maintaining some grasslands for ecosystem services should be considered. Consumption must move toward healthier diets, emphasizing plant-based foods. Importantly, future work should consider indirect land use change emissions and the broader feed-food-fibre-fuel competition.

Redesigning the EU27+UK food system based on circularity principles drastically reduces agricultural land use and GHG emissions while ensuring sufficient healthy food. This transition also offers global food security benefits. Successful implementation requires systemic changes across all food system components, including crop diversification, reduced animal numbers, enhanced organic fertilizer utilization, and consumption shifts toward healthier diets. This research provides valuable insights for policy discussions and paves the way for long-term, sustainable food systems planning.

This study focused solely on interventions related to circularity principles within the European food system, neglecting other potential sustainability improvements (e.g., precision management). Data uncertainties, due to limited availability and inconsistencies across sources (e.g., food loss and waste data, fertilizer use statistics, land area maps), affected the model's precision. Furthermore, indirect land use change emissions outside the EU were not considered due to data and methodological limitations. The model's static approach to crop rotations simplifies the complex dynamics of real-world agricultural practices. Finally, the study did not explicitly incorporate social and economic factors that influence the feasibility of the proposed transitions.