It’s no easy task getting food from farm to plate. Consider the path of animal protein: It requires not just fattening and slaughtering, but the front-end growing, watering, and transporting of animal feed, and the back-end shipping of steaks, bacon, and chicken breasts to grocery stores.
That complexity is why it’s so difficult to uniformly quantify the climate impact of food production. One common way to present the data is by weight: For every kilogram of beef or chicken or cheese or lettuce, how much greenhouse gas is emitted?
Through that lens, animal products sit at the top of the list of emitters. For instance: Producing a kilogram of lamb means emitting 39 kilograms of carbon dioxide, 13 times as much as producing a kilogram of potatoes.
But there is no one correct way to measure emissions. Consider this: When you quantify emissions released on a per-calorie basis, broccoli emits more greenhouse gas than pork or chicken, according to data presented by The Washington Post.
Viewed through this lens, animal agriculture is still the biggest contributor to greenhouse gas emissions. But some types of meat actually started to look like less serious climate offenders. When factoring emissions by calorie of food produced rather than weight, emissions from eggs, cheese, and farmed salmon fall relative to other foods. Meanwhile, emissions from tofu, broccoli, tomatoes, and 2% milk production all climb relative to their by-weight emissions.
That makes a fun argument for someone who doesn’t like eating broccoli or tomatoes.
Simplifying food production in this way—whether by calories or weight—is clearly flawed. As the Post points out, if you gave up a kilogram of beef (2,280 calories), you’d need to replace it with 6.7 kilograms of broccoli to meet the same calorie count, but good nutrition is an issue of quality, not quantity. The calories you get from beef aren’t at all akin to the ones you get from a vegetable.
But to marry the goals of global health and environmental sustainability, we have to start somewhere. In early 2019, a team of scientists from around the world took a stab at the problem, publishing the EAT-Lancet report. It showed that, across the globe, people are generally over-consuming animal-based products, while not getting enough whole grains, legumes, fruit, and vegetables.
The suggestions that came out of that report weren’t without flaws. Its suggested sustainable diet wouldn’t be possible for some 1.6 billion people in the world due to cost. Still, it was a bold effort to investigate the balance between what we should eat to stay healthy and what we should eat to keep the planet healthy—broccoli or not.
