a burger and fries

Tracking Meat’s Environmental Hoofprint

By Matt Davenport | 

Although people may prefer not to know how the sausage is made, new research from the University of Michigan School for Environment and Sustainability (SEAS) highlights the importance of understanding where America’s meat comes from.

In two separate but related studies, SEAS research led by Benjamin Goldstein and Joshua Newell underscore how meat connects rural areas where it’s produced to urban areas responsible for most of its consumption. In doing so, the team also revealed how the environmental impacts of meat vary widely across the country while providing useful insights to address these burdens and inequalities.

“The meat you eat comes from somewhere. It takes up a lot of space and produces a lot of pollution,” says Goldstein, an assistant professor at SEAS. “And somebody else and [some other] place has to bear that pollution.”

The first study, published last summer in the journal Communications Earth & Environment, identified locations for thousands of the nation’s hog and cattle animal feeding operations, or AFOs. The researchers also started addressing questions about what these AFOs meant for their neighboring communities.

The second study, published this fall in Nature Climate Change, revealed the “carbon hoofprints” of more than 3,500 U.S. cities—the greenhouse gas emissions associated with supplying their beef, pork and chicken.

“For the first time, this detailed spatial mapping from city to farm enables us to investigate the environmental, social and economic impacts and connections between what have previously been disconnected places,” says Newell, a professor at SEAS. “It is our hope that this study provides an example of how we can foster better understanding between two different places: One largely urban and one distinctly rural where our food is produced.”

Finding Animal Feeding Operations (AFOs)

Despite hog and cattle AFOs supplying most of the nation’s pork and beef, data about where they are found was lacking in both scope and accuracy. Newell and Goldstein were interested in quantifying the impacts of meat supply chains and knowing the locations of AFOs was a missing link. Sanaz Chamanara (PhD ’22) took up the task of finding them as part of her dissertation work, with help from Dimitrios Gounaridis, a SEAS assistant research scientist and a coauthor of both studies.

The meat you eat comes from somewhere. It takes up a lot of space and produces a lot of pollution.”

Chamanara combed through satellite imagery of every county in the contiguous U.S. to confirm the location of more than 15,000 AFOs. About a quarter of these were found in just 30 counties. Knowing where the AFOs were, the researchers could then integrate other available data from those locations to draw further conclusions.

For example, they found that levels of air pollution made up of particulate matter less than 2.5 microns in size—also called PM2.5—were higher near AFOs. They also found that AFOs were often located closer to communities with lower levels of education and health insurance coverage.

“One of the things this study reveals is that we could focus on a limited number of counties to really address health impacts in these communities,” says Newell. “If you’re a policymaker, a government, or a community group or association concerned with these issues, this allows you to develop very targeted policies or measures. That’s one of the reasons why mapping this out spatially is so important.”

Carbon Hoofprints

Determining and mapping the carbon hoofprints of cities across the country also revealed some eye-popping stats, as well as opportunities to chart a path to a more sustainable future.

For example, the carbon footprint of U.S. cities is larger than all carbon emissions from the United Kingdom. But Americans can make relatively straightforward changes to help minimize their impact, such as substituting chicken for beef, reducing food waste and participating in Meatless Mondays.

To quantify these impacts and opportunities, the U-M team collaborated with University of Minnesota researchers led by Rylie Pelton and Jennifer Schmitt, who are on the team that developed a model called Food System Supply-Chain Sustainability, or FoodS3, to dig into meat’s supply chains in the U.S. This provided a more comprehensive accounting of greenhouse gas emissions from what it takes to produce beef, chicken and pork—from growing the feed for animals, to managing the manure at ranches and AFOs to shipping the processed meat to cities.

“This is something that has been largely missing,” says Goldstein. “We know that cities use these supply chains that span thousands of miles to get their resources and support their daily consumption. But we have lacked an analytical architecture to actually capture that consumption and link it to environmental changes at different locations until now.”

And the carbon hoofprint was just the first step. The team said the model can now be easily adapted for other commodities, both agricultural and otherwise, that cities depend on.

This work was funded, in part, by the U.S. National Science Foundation.

What's the carbon hoofprint of your city?

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