Challenging the food waste hierarchy.

Food waste is a multi-faceted and complex problem for urban circular economies with far-reaching environmental impacts. Effectively addressing this problem requires a comprehensive understanding of the food waste impacts on food, energy, water, and climate (FEWC) systems. Despite complex dynamics in the FEWC nexus, the most popular guidance for food waste management is the food waste hierarchy framework - which fails to account for ensuing impacts on all nexus elements. Aiming to optimise the framework, we adopt a participatory approach to develop the first comprehensive and replicable system dynamics model of the FEWC footprints of urban food waste throughout the agri-food supply chain. The quantitative model compares different food waste management options, and relevant policies in Bristol, UK (2018-2030). Unlike the guidance of the traditional waste hierarchy framework, our findings show that the preferability of each option can vary for each sector within the supply chain and for each FEWC element. Our results show that increasing food surplus redistribution in the supply sectors and reducing food waste in consumer sectors are the most preferable approaches to reduce the environmental impacts of food. Feeding food leftover to pets at household level also has a promising impact. Other options involve trade-offs between energy and carbon footprints, while having minimal impact on water footprint. We conclude that the traditional food waste hierarchy is too simplified to provide reliable guidance for environmentally sustainable food waste management and policy. Instead, we present an improved food waste hierarchy framework that accounts for the scale of preferability of each option for different sectors and different FEWC nexus elements. This novel framework thus provides more nuanced and more robust understanding of food waste impacts on the FEWC nexus in urban circular economies, thereby enabling the development of policy and management options that are optimised for environmental sustainability.