24th Pacific Science Congress (PSC-24)

The global food system accounts for 25%–30% of greenhouse gas emissions from human activities. As the largest country in population and food consumption, China’s food system is central to achieving its dual carbon objectives. Cities, as significant sources of emissions, offer potential for carbon mitigation through cross-boundary transportation networks. However, existing studies lack a comprehensive method for assessing the life cycle carbon footprint of urban food consumption, particularly based on food flows.

This study integrates the four-stage transport model with life cycle assessment methods to create a framework for calculating the carbon footprint of food consumed by urban residents, based on intercity food flows in China. It assesses CO₂, CH₄, and N₂O emissions across five stages: production, transportation, storage, cooking, and end-of-life treatment, providing a systematic evaluation of greenhouse gas emissions at the city level.

The results show that the total intercity transportation distance for food consumed by urban residents, including feed for animal-based products, was 259.532 billion ton-kilometers in 2020. Rice transportation accounted for 11%, emitting 3.717 million tons of CO₂e. During the storage and cooking stages, annual per capita carbon emissions ranged from 40 to 280 kg CO₂e, showing a sevenfold variation, attributed to differences in food consumption patterns and cooking energy structure. Regionally, in cities like Beijing and Shanghai, which rely heavily on external food supply, embedded carbon emissions make up more than 80% of the total emissions from food consumption. In contrast, cities in the Northwest show an annual per capita full life cycle carbon footprint ranging from 1.12 to 2.33 tons CO₂e, with embedded carbon emissions contributing less than 10%, indicative of a higher level of food self-sufficiency.

This study provides tools and data to identify key points for emission reduction, contributing to the improvement of low-carbon strategies in urban food supply chains.

Urban Food System, Cross-boundary Food Transportation, Four-Stage Model, Life Cycle Analysis, Carbon Footprint