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UM research: Food grown on urban farms has six times the carbon footprint of food grown conventionally

MDARD says do not eat produce with a Kuntry Gardens label because the farm used human waste as fertilizer
Elaine Casap
New research estimates that on average, produce grown on an urban farm has a six times higher carbon footprint than conventionally grown produce.

A new University of Michigan-led study finds that fruits and vegetables grown in urban farms and gardens have a carbon footprint that is, on average, six times greater than conventionally grown produce. 

Study co-lead author Jason Hawes, a doctoral student at U of M's School for Environment and Sustainability, acknowledged the results may be surprising to many people involved in raising food in cities.

"Urban agriculture has a climate change problem, right? It's clear that it is not what maybe people would assume just because it's local," Hawes said.

Hawes said the short-term use of infrastructure is responsible for most of the higher carbon footprint of urban-grown produce.

Since such farms often are in operation for less than a decade, the greenhouse gases used to produce farm materials are used inefficiently — in other words, the emissions are not spread out over a long period of time, which would mitigate their impact.

Hawes said more recycling and reuse of farm and garden materials would help, as would maximizing the considerable social benefits of urban farming.

For example, people involved in collective or individual gardens in urban areas, or working on the urban farms, tend to eat less meat than other people. And meat has a far higher carbon footprint than fruits and vegetables.

"So if we can simultaneously improve the footprint of urban agriculture, and get people that participate to eat less meat, then that's a win-win," Hawes said.

Another way to shrink the carbon footprint of urban farms is to focus on crops that are otherwise typically grown in higher-carbon environments — tomatoes, for example, which use less resources when grown in open beds than in greenhouses, and asparagus, which is frequently flown by plane to markets.

The study was published in the January 22 issue of the journal Nature Cities.

It used data from 73 urban farms and gardens in five countries. Researchers said it's the largest published study to compare the carbon footprints of urban and conventional agriculture.

Tracy Samilton covers energy and transportation, including the auto industry and the business response to climate change for Michigan Public. She began her career at Michigan Public as an intern, where she was promptly “bitten by the radio bug,” and never recovered.
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