Food grown in urban settings has much larger carbon footprint – study

A team of researchers at the University of Michigan have published a study investigating the carbon emissions associated with urban agriculture, and exploring whether the practice — which is becoming increasingly popular around the world — has a role to play in supplying us with sustainably grown food.

Urban agriculture, which encompasses backyard gardens, community plots, and city farms, typically reduces the ‘food mile’ — the distance that food travels from producer to consumer — and thus cuts transportation-related emissions. As a result, proponents have touted it as a straightforward solution to the ecological crisis.

However, the findings of the new study challenge this inference. Analysing 73 urban agriculture sites across five countries, researchers discovered that, on average, urban farming was six times more carbon-intensive per serving of produce than conventional agriculture. This revelation underscores the complexity of assessing urban agriculture’s true environmental footprint.

Nonetheless, the study did identify several practices that can significantly reduce the carbon footprint of urban agriculture. For example, using upcycled materials for farm infrastructure can halve a site’s emissions. Composting food waste, replacing up to 95% of synthetic fertilizers, can cut greenhouse gas emissions by nearly 40%. Additionally, capturing rainwater or reusing greywater can further reduce the environmental impact.

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The research emphasizes the importance of low-tech approaches over high-tech urban farming methods, which often have high energy demands due to electricity consumption. By focusing on sustainable practices like composting and upcycling, urban gardeners can mitigate some of the carbon footprint associated with urban agriculture.

The study also highlights the potential of certain crops, like tomatoes and asparagus, which have a higher carbon footprint when grown commercially due to energy-intensive methods or the need for air transport. Urban cultivation of these crops can thus offer significant reductions in net carbon impact.

Beyond its climate implications, urban agriculture provides essential ecosystem services and social benefits. These include offering fresh produce, fostering community engagement, supporting urban wildlife, and mitigating the urban heat island effect. With thoughtful site design and land use policies, urban agriculture can enhance its contributions to environmental justice and climate adaptation.

As cities evolve and the practice of urban farming expands, this research underscores the need for a nuanced understanding of its benefits and limitations. By adopting and promoting best practices identified in the study, urban farmers and gardeners can maximize their positive impact on both the community and the planet.