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20% of American diets have the highest carbon footprint

Marty Heller
A University of Michigan and Tulane University study showed that the 20% of U.S. diets with the highest carbon footprint accounted for 46 percent of total diet-related greenhouse gas emissions.

Just 20% of Americans are responsible for 46% of the food-related greenhouse gas emissions in the U.S. That’s one of the findings of a new studyin the journal Environmental Research Letters.

Marty Heller, a senior research specialist with the University of Michigan’s Center for Sustainable Systems, says these American diets tend to include more red meat.

“One thing we do know is that diets in that fifth of the population are eating more food in total, or total calories,” Heller says. “They’re also eating more meat and, primarily, that meat is made up of more beef than other meats like chicken, compared with the lower end of the distribution.”

At the other end of the spectrum, he says those people whose diets contribute the least to greenhouse gas emissions are eating less meat.

“There isn’t any real standout identification for those diets,” he says. “But certainly they’re eating less meats and those meats tend to be more poultry than red meats.”

Heller says meat production results in a lot of greenhouse gasses.

“Eating higher up the trophic level takes a lot of feed to feed those animals through their lifetimes,” Heller says. "But then the one big thing that happens with cattle are these additional enteric methane emissions, which is a very potent greenhouse gas.”

In other words: cows burp methane.

“The microorganisms in those animals’ stomachs that allow them to break down cellulosic materials that you and I can’t digest, happen to have a byproduct which is methane,” Heller says.

If those 20% of Americans responsible for nearly half of our food-related greenhouse gas emissions were to move to an average diet, Heller says the U.S. could make more progress on meeting the goals of the Paris climate agreement.

“If those high-impact diets moved even just to an average emission diet, so again nothing dramatic, not going vegetarian or completely eliminating meat from their diet, but just moving to an average,” Heller says. “We found that that shift would represent close to 10% of the emissions reductions that the U.S. requires in order to meet something like a Paris agreement goal."

Heller notes that they studied greenhouse gas emissions related to food production up to the farm level, not including steps like processing, transportation, cooking, and so on. He says they estimate that including processing and packaging would increase emissions by about 25%.

Rebecca Williams is senior editor in the newsroom, where she edits stories and helps guide news coverage.
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