Growing green: Reducing urban agriculture’s carbon footprint

Nestled between the brick and concrete buildings of Boston, a flash of green stands out. Joyous voices carry through the urban bustle as a group gathers in a verdant garden, eager to try the first tomatoes of the season. After several months of careful tending, the fruits have finally ripened on their sprawling vines, gleaming in rich red hues. Faces alight as the gardeners taste their deliciously rewarding harvest, warmed by the summer sun. 

With nearly 200 community gardens scattered throughout Boston, such scenes enliven neighborhoods around the city. These lush oases are one type of urban agriculture, which is the practice of cultivating food or livestock in an urban area. From backyard gardens to communal plots to larger farms, urban agriculture initiatives have immense social and environmental benefits. However, though a seemingly sustainable way to acquire fresh, local food, not all urban farming practices are climate-friendly. The carbon footprint of urban-grown food is up to six times larger than its conventionally-grown counterpart, a new study reports.

“The carbon footprint of urban-grown food is up to 6 times larger than its conventionally-grown counterpart, a new study reports.”

Researchers from the University of Michigan examined 73 urban agriculture sites in cities throughout Europe and the United States. The selected sites all employed low-tech growing practices, which consist of open-air, soil-based plots as opposed to more energy-intensive operations such as vertical farms. The study followed the lifecycle emissions of food grown in individual plots, community gardens, and urban farms. To estimate the carbon footprint of urban produce, the researchers accounted for the impacts of farming activities, processing, and transportation. The results indicated that urban agriculture emits more greenhouse gases per serving for many fruit and vegetable varieties. Compared to conventional farms maximized for production, the lower yields of urban gardens are more resource-intensive, requiring proportionally greater amounts of water, fertilizer, and other materials.

Despite urban agriculture’s higher carbon footprint, 17 of the study sites outperformed conventional farms. By analyzing factors contributing to the lower emissions of these sites, the researchers identified multiple practices crucial to reducing the climate impacts of city-grown food. One proposed strategy is to preserve farm infrastructure as much as possible. Infrastructure is the largest contributor to urban agriculture’s carbon footprint, producing 63% of emissions. Raised beds, compost systems, and other structures such as sheds and greenhouses emit substantial amounts of carbon throughout their manufacturing and construction processes. Extending the life of existing materials significantly lowers these environmental impacts, and upcycling old building materials for new infrastructure can reduce emissions by over 50%. 

“By analyzing factors contributing to the lower emissions of these sites, the researchers identified multiple practices crucial to reducing the climate impacts of city-grown food.”

Additionally, efforts to reuse food waste and water are critical to growing urban food in a climate-friendly manner. Composting reduces reliance on synthetic fertilizers produced from fossil fuels and diverts food scraps from landfills, which are significant sources of methane. Proper compost management can decrease the amount of greenhouse gases released by almost 40%. Meanwhile, recycling rainwater and greywater lowers emissions associated with pumping, treating, and distributing water. 

Another strategy to lessen urban agriculture’s carbon impact is to prioritize crops that are carbon-intensive when farmed conventionally. Tomatoes are one example; many commercially produced tomatoes are grown in large greenhouses, which consume considerable amounts of energy and resources. Comparatively, tomatoes cultivated through low-tech urban agriculture have an equivalent or lower carbon footprint. Growing this produce locally in open-air plots is a viable way for urban growers to mitigate their carbon emissions.

“By adopting more climate-friendly practices, the benefits of urban agriculture can be reaped for years to come.”

By adopting more climate-friendly practices, the benefits of urban agriculture can be reaped for years to come. These green spaces enrich their surrounding communities, improving food access and security, boosting physical and mental health, and providing opportunities for economic development. As a powerful educational tool, urban farming enables people to build tangible skills while learning about food production and the natural world. Along with these social benefits, urban agricultural spaces support higher levels of biodiversity, enhance pollinator habitats, and alleviate the urban heat island effect. With a lower carbon footprint, urban agriculture’s numerous rewards can grow even greener.