The climate impact of animal meat versus plant-based meat, explained

Americans eat well over 200 pounds of meat each per year, and it’s accelerating us along a collision course with climate catastrophe. While many other countries eat far less meat, global appetites are catching up quickly, spurred especially by the growing affluence of the rising middle class in Asia and Latin America.

Fossil fuels do make up a far greater proportion of emissions in the US and globally, but even if we reduced energy emissions down to zero, demand for meat and dairy alone could make us exceed critical levels of global warming. That makes shifting diets away from meat a critical tool in preventing global temperatures from rising above 1.5°C or 2°C by 2100.

There are a number of reasons for meat’s outsized ecological footprint. The first is that cows belch out methane created from fermenting grassy food in their multi-chambered stomachs. With a billion and a half cows on the planet — raised for both beef and dairy — that adds up to about 9 percent of all global greenhouse gas emissions alone.

Although pigs and chickens, the two most farmed species on the planet, don’t belch methane, they still produce lots of manure — and that generates nitrous oxide, another potent greenhouse gas. They also need to eat fertilized crops, like corn and soy, which generate more emissions. And while all cattle graze on grass, most in the United States are eventually fattened for slaughter on feedlots where they too eat corn and soy.

Feeding all of these crops to animals is far less efficient than feeding them more directly to humans. For example, every 12 calories from corn and soy fed to a pig provides just one calorie of meat back. The proposition of plant-based meats is that they cut out the animal, allowing more efficient use of land and resources.

Different animal products have vastly different emissions. For instance, pigs and chickens emit far less than cows and sheep. But according to recent peer-reviewed research from the University of Oxford and Johns Hopkins University, which compiled several estimates, all of these animal foods (except some chicken) generate more emissions than plant-based meats. (Editor’s note: Jan Dutkiewicz, one of the authors of this article, was a co-author on the Johns Hopkins paper.)

This research consisted of meta-analyses of multiple life-cycle assessments, or LCAs, which measure the total environmental impact of a product. While some of the plant-based meat estimates were commissioned by the faux meat companies themselves, including Beyond and Impossible, others were not, and all used internationally agreed-upon LCA standards for accounting of every emission source throughout processing.

Even the lowest-emitting beef from dedicated beef herds (34 kg carbon dioxide equivalent, or CO2e) and lower-emitting beef from dairy cow herds (15 kg CO2e) came in far above the highest-emitting tofu (4 kg CO2e) and plant-based meat (7 kg).

Chicken and pork production emit far less CO2 equivalent than beef. And while there is some overlap (the lowest-emitting chicken [3.2 kg CO2e] and pork [6 kg CO2e] rival the emissions of the highest-emitting plant-based meat), the average emissions of tofu and plant-based meats are still lower than the average emissions of both chicken and pork.

Of course, climate emissions aren’t the only environmental impacts from food. Producing animal-based food also requires large quantities of fresh water. For instance, one kilogram of pork requires 442 liters of water, versus 84 liters for one kilogram of plant-based meat. Similarly, producing beef, pork, and chicken requires far more land and causes much more pollution to waterways than plant-based alternatives.

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