A new study out of the University of Michigan has found that many fruits and vegetables grown in urban farms and gardens have a carbon footprint about six times greater than that of conventional farms.
Urban farms and gardens have become a popular way for urban areas to access locally-grown produce and to build community, so researchers aimed to explore a less-studied aspect of this growing trend — overall carbon impact. The study used data from 73 low-tech urban agricultural sites across five countries and considered the emissions associated with materials used on the farm and activities that took place over the farm’s lifetime. Included in the analyzed sites were professionally run urban farms, individual gardens, and collective gardens managed by multiple individuals.
On average, food produced through urban agriculture was found to emit 0.42 kilogram of carbon equivalents per serving, while conventionally-grown produce amounted to about 0.07 kilograms per serving.
Despite Emissions Difference, Urban Ag has Many Benefits
According to researchers, the main carbon impact of urban farms stems from materials used in construction and the fact that many such farms and gardens only operate for a few years to a decade. Conventional farms tend to use infrastructure for decades and produce a single crop, so they are able to reap larger harvests and achieve comparatively more efficient operations, reportedly amounting to a lower carbon footprint.
The study also showed that urban agriculture farmers and gardeners overwhelmingly cited improved mental health, diet, and social networks from farming activities, and the researchers added that “growing spaces which maximize social benefits can outcompete conventional agriculture when urban agriculture benefits are considered holistically.”
Additional studies on urban farming, including a recent study on scaling up urban agriculture from the University of Florida, have identified a range of environmental benefits from urban farming. The study claims that urban agriculture has immense potential as a global sustainability strategy if operationalized effectively.
How Urban Agriculture May Reduce Emissions Impact Going Forward
Recognizing the social and environmental benefits that may still be achieved through urban gardens, the study suggests that urban agriculture operations may commit to certain practices to reduce emissions impact going forward.
The study first recommends that urban farmers cultivate crops that are conventionally grown in greenhouses or are typically air freighted. For instance, tomatoes grown in open-air urban plots were found to have lower carbon intensity than tomatoes grown in conventional farm greenhouses.
It also suggests engaging in “urban symbiosis,” or using second-hand resources and creating a circular system for materials used. The study provides composting as an effective example of this kind of system and recommends using construction debris or demolition waste when building new urban gardens or farms.
The study claims that if such changes are adopted by urban farms and gardens, they would reportedly be carbon-competitive with conventional agriculture.