Replacing the carbon-heavy beef on your plate with carbon-light chicken will cut your dietary carbon footprint a shocking amount: in half. That’s according to a first-ever national study of U.S. eating habits and their carbon footprints.
To find out what Americans are actually eating, the National Health and Nutrition Examination Survey asked more than 16,000 participants to recall all the foods they had consumed in the previous 24 hours.
The study then calculated the carbon emissions of what people said they ate. If a meal involved beef, such as broiled beef steak, researchers estimated what the carbon footprint would be had they chosen to eat broiled chicken instead.
“We knew eating chicken instead of beef would lower carbon emissions related to diet but it was much lower than expected,” says Diego Rose, a researcher at Tulane University’s School of Public Health and Tropical Medicine and lead author of the study.
The study shows that one simple substitution can result in a big reduction in a person’s dietary carbon footprint—the amount of carbon dioxide emissions that result from energy, fertilizer, and land use involved in growing food, Rose said. It also shows you don't have to give up animal products to improve your carbon footprint. Food production accounts for about a quarter of total carbon emissions globally.
“Climate change is such a dramatic problem that all sectors of society need to be involved,” says Rose, who will present his research at the American Society for Nutrition annual meeting on Monday in Baltimore.
Without limiting the global rise in meat consumption, particularly beef, goat and lamb, keeping the increase in global warming to 1.5 degrees Celsius will be impossible, the World Resources Institute said in a report. It would also result in so many CO2 emissions that even keeping a global warming temperature increase below 2 C would be difficult.
Why is beef so carbon-heavy?
Animal-based foods have a bigger carbon footprint than plant-based foods. Producing beef, for example, uses 20 times the land and emits 20 times the emissions as growing beans, per gram of protein, and requires more than 10 times more resources than producing chicken. In the Tulane study the 10 foods with the highest impacts on the environment were all cuts of beef. Lamb and goat meat also have heavy footprints because, like cows, those animals release methane, a greenhouse gas many times more potent than carbon.
Calculating carbon footprints isn’t simple, given the vast diversity of agricultural production methods, says Kumar Venkat of CleanMetrics Corp., a Portland, Oregon-based environmental firm. That involves estimating the amount of CO2 emitted from the energy, fertilizer, and land use as well as in processing, packaging, and transportation. It took over two years for CleanMetrics to research the carbon footprints of hundreds of different agricultural commodities.
“No question chicken is a fraction of beef’s carbon emissions and it likely has the lowest carbon footprint of any animal protein,” says Venkat, who was not involved in the Tulane study. Chickens are far more efficient in converting feed into meat protein, and that reduces the amount of land, fertilizer, and energy involved, resulting in a light carbon footprint.
Earlier this year Rose and colleagues used the same diet survey data to determine that Americans with the lowest dietary carbon footprints ate a healthier diet, as measured by the U.S. Healthy Eating Index, a federal measure of diet quality. The paper was published online Jan. 29 in the American Journal of Clinical Nutrition.
The evidence is clear regarding the need to shift diets to less meat and more plant-based proteins for both health and environmental reasons, says study co-author Martin Heller of the University of Michigan Center for Sustainable Systems at the School for Environment and Sustainability.
The landmark EAT-Lancet Commission report released last fall involving 37 scientists from 16 countries concluded that a radical transformation of the global food system was needed because it threatens climate stability and is the single largest driver of environmental degradation. In addition, unhealthy diets posed a greater long-term health risk than unsafe sex, alcohol, drug, and tobacco use combined, the report said.
“A diet rich in plant-based foods and with fewer animal source foods confers both improved health and environmental benefits,” says Walter Willett, of the EAT-Lancet Commission and professor at the Harvard T.H. Chan School of Public Health.