Understanding food's carbon footprint

DURHAM, N.C. — Most people don’t realize how much food production contributes to climate change – especially meat.

“Beef is the SUV of food,” said Rick Larrick, a professor of management and organizations at Duke’s Fuqua School of Business.

The massive carbon footprint of red meat means that even consuming slightly less of it – substituting something else for beef once a week, for instance – can make a huge difference to the environment.

“It’s more about slight changes, rather than all or nothing,” said Larrick, who found the same thing in his study of vehicles. Switching from a gas-guzzling SUV to a more efficient SUV saves more fuel than going from a compact car to a hybrid that gets 50 miles per gallon.

Larrick has a history of helping people understand how much energy they use. With Fuqua colleague Jack Soll, Larrick proposed a gallons-per-mile standard that the federal government added to new car stickers in 2013. More recently, he devised a blueprint to better explain household energy consumption.

“Food is one of those areas where we can also make a difference, it’s just not as obvious to people,” Larrick said. “We can change our diet much more easily than we can change what car we drive.”

The food system uses large amounts of energy, and generates about the same proportion of global greenhouse gas emissions as other major activities, such as transportation. But Larrick found people don’t give the same thought to food’s environmental impact.

“When we see a car on the road, or a light on in our room, we see the energy that’s being used,” Larrick said. “But we just don’t recognize it with the food we eat, because we’ve never had to articulate all the steps and costs of putting it on our tables.”

Larrick worked with Adrian Camilleri of the University of Technology, Sydney, Dalia Patino-Echeverri of the Nicholas School of the Environment at Duke, and Shajuti Hossain of Duke’s Law School on his new research. Their findings, “Consumers Underestimate the Emissions Associated with Food but can be Helped by Labels,” appear online in the journal Nature Climate Change.

The researchers asked more than 1,000 participants in a nationally-representative sample to rate the energy used – and the greenhouse gas emitted – by the production of one serving of 19 different kinds of food, and by using one of 18 different appliances for one hour. The measurement scale was based on the energy used and gas emissions generated by a 100-watt incandescent lightbulb.

Participants underestimated the environmental impacts of appliances and food production, but they underestimated the impacts of food significantly more than those of appliances. One serving of beef emits as much GHG emissions as running a microwave oven for two hours. But people equate the impact of one serving of beef with turning on a 25 watt CFL bulb for an hour.

The same results held when other measurement scales were used, such as the amount of energy and greenhouse gas emissions required to produce a tomato.

The first significant result is the sheer underestimation that happens, said Camilleri, who started the research while a postdoctoral research scientist at Duke. The other is that people don’t understand the huge differences in the environmental impacts of different types of food, just as we don’t with appliances, he said.

“We know a central air conditioner uses more energy than a lightbulb, but we don’t easily recognize how many times more energy they use,” Camilleri said.

“People think that running a central AC unit for an hour uses about 5 times more electricity than lighting a 25-watt CFL for an hour. The AC unit actually uses 100 times more electricity.”

The same thing holds for food, he said.

“For example, people know the production of beef releases more greenhouse gases than other foods, and they know to tick up their estimate slightly,” Camilleri said. “But overall they underestimate meat the most, because they don’t realize just how much higher an impact it has compared to, say, a serving of corn. To produce and distribute a serving of beef releases about 50 times more greenhouse gas than putting corn on your table; people think beef production emits only twice as much as the corn.”

The researchers also found that providing information to consumers about the carbon footprint of their foods can affect the choices they make.

For that study, 120 participants were shown images of six cans of different soups – three beef and three vegetable – and were asked to buy three cans using some of the money they received for taking part in the research. One group was also shown information expressing the relative carbon footprint of each soup, using a red-yellow-green scale and equivalent light bulb minutes.

The participants who were shown the environmental impacts of producing each type of soup chose less beef soup than those who weren’t – an average of about one can each, versus about one-and-a-half each.

Creating a carbon food label would not be a simple process, but Larrick said that is just one way to increase awareness.

“We need creative ways to get people this information,” Larrick said. “In the absence of information, people just aren’t thinking about this and aren’t aware of their impact of their choice.”

###

CITATION: “Consumers Underestimate The Emissions Associated With Food But Are Aided By Labels,” Adrian R. Camilleri, Richard P. Larrick, Shajuti Hossain & Dalia Patino-Echeverri. Nature Climate Change, Dec. 17, 2018. DOI: 10.1038/s41558-018-0354-z