The Best & Worst Protein Sources for the Environment, Explained

Most people know beef is bad for the climate. But how does tofu compare to other plant proteins, like almonds or hemp?

Plant based protein sources including beans and tofu

Explainer Climate Food

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Protein is one of the fundamental building blocks of life, and an essential part of our diets as humans. We can’t survive without it, and yet many protein sources inflict serious harm on the environment, animals, or both. Luckily, there are plenty of options that are much more environmentally friendly, and many of the most sustainable protein sources are widely available for anybody looking to reduce their environmental footprint.

Let’s break down the best — and worst — protein sources for the environment.

What Protein Is, and Why We Need It

The Short Answer:

Proteins are nutrients made up of amino acids, and the body can’t survive without them. There are seven different categories of protein, all of which serve a different purpose. There are nine essential amino acids that humans can only get through food, and it’s important to eat protein sources that contain all of these amino acids.

The Longer Answer:

A protein is a type of nutrient that plays a vital role in keeping us alive. There are around 10,000 different kinds of proteins, each of which serves a different function in the body. Our immune system, digestive system, bone and muscle growth, metabolic regulation, blood clotting and many more essential human functions would not be possible without proteins.

Proteins are made up of amino acids. There are 20 different amino acids that the human body utilizes, and they combine in different ways to form different amino acids. Although many amino acids are produced internally by the body,  nine kinds  are not. These “essential amino acids,” as they’re called, can only be obtained through food.

Although there are thousands of different proteins, they’re generally grouped into seven main categories:

  • Antibodies
  • Enzymes
  • Hormones
  • Contractile proteins
  • Structural proteins
  • Transport proteins
  • Storage proteins

Plenty of foods contain protein in varying amounts, but some don’t contain all nine essential amino acids. We need those essential amino acids to survive, so while it’s important to consume enough protein, it’s also important to pay attention to where that protein comes from.

What’s the Difference Between Complete and Incomplete Proteins?

Foods that contain all essential amino acids are sometimes referred to as “complete proteins.” Quinoa, soybeans, buckwheat, hempseed and blue-green algae are complete proteins, as are animal products like meat and dairy. Foods without all of the essential amino acids are called “incomplete proteins,” and they include nuts, whole grains, rice and vegetables.

It’s worth noting that, because different incomplete proteins lack different amino acids, they can be combined in a meal to create the equivalent of a complete protein. For example, rice and beans, when eaten together, form a complete protein.

How Does Producing Protein Affect the Environment?

The Short Answer:

The production of protein requires significant amounts of land and water. Food production in general is responsible for one-quarter of all greenhouse gas emissions.

The Longer Answer:

Because protein comes from such a wide variety of sources, there are many different ways in which its production affects the environment. Raising cattle for beef, for instance, has a much different set of effects on the environment than growing a field of buckwheat.

That said, there are a few general ways in which protein production affects the environment:

Because these effects are so different, there’s no single metric for measuring a food product’s overall sustainability. If a food requires a lot of water to create but emits very few greenhouse gasses — as is the case with many nuts — how do we assess its “sustainability?”

There’s no perfect answer to this question, but most experts use greenhouse emissions as a metric for a food’s overall environmental footprint.

With this in mind, let’s take a look at the worst offenders — as well as some of the most sustainable proteins you can eat.

The Worst Protein for the Environment: Beef

Beef is the most environmentally damaging protein to produce. All proteins derived from animals leave a bigger carbon footprint than those derived from other sources.

Greenhouse gasses are often measured in carbon dioxide equivalents, or CO2-eq. When assessing proteins specifically, experts generally look at how many kilograms of CO2-eq are emitted for every 100 grams of protein that are produced.

Using that as our metric, the worst proteins for the environment are those that come from animal products. Beef is the worst offender; on average, beef from beef farms emits 49.89kg of CO2-eq for every 100 grams of protein. Beef that comes from dairy cows is relatively more sustainable, producing 16.87kg of CO2-eq per 100 grams.

Next is lamb and mutton, with 19.85kg per 100g, followed by farmed prawns, beef from dairy cows and cheese.

The Other Worst Protein Sources for the Environment

The majority of meat we consume comes from factory farms, and in general, factory farms are terrible for the environment and the animals who live on them. Although beef is the worst offender, there are plenty of other animal protein sources that wreak havoc on the planet.

Farmed Prawns

Other than beef and mutton, farmed prawns  — as opposed to prawns that are caught in the wild — have the worst carbon footprint of any meat. Producing 100g worth of prawn protein emits 18.19kg of CO2-eq. (Farmed shrimp, often confused with prawns, also contribute heavily to the destruction of mangrove ecosystems.)


Pork emits 7.61kg of CO2-eq for every 100g of protein, which is less than most other meats. This statistic doesn’t capture the ghastly and disturbing treatment that pigs endure on industrial farms, but still, pork’s carbon emissions are on the low side — for animal meat.

However, waste from pig farms is notorious for polluting rural communities and environments.

Farmed Fish

The ocean absorbs carbon, which is one reason why farmed fish have a comparatively low carbon footprint: 5.98kg per 100g of protein. That said, fish farming has other harmful environmental impacts, and leads to pollution, sea lice and a lack of biodiversity. Fish farming is also harmful from an animal welfare standpoint.

Meanwhile, the environmental impact of commercial fishing in general is catastrophic and has led to the death of ecosystems, coral reef destruction and other harmful effects on the environment.


Poultry has the lowest carbon footprint of all the major meats, as it produces 5.7kg of CO2-eq per 100g of protein. However, this shouldn’t obscure the fact that like pigs, chickens suffer immensely on factory farms, their relatively low carbon emissions notwithstanding.

Once again, a protein source that has to be fed first, as chicken must, is still going to have a higher carbon footprint than a plant-based protein skipping that step. Chicken farms are also harmful to the environment for other reasons: runoff from farms (read: waste) ends up polluting waterways with high levels of nutrients that can lead to toxic algal blooms, mass fish die-offs and “dead zones” in water sources.


Chicken eggs have a slightly lower carbon footprint than chicken meat, emitting around 4.21kg of CO2-eq for every gram of protein produced. That’s less than every meat — but still more than every plant.

And, as we just went over above, chicken farms cause environmental damage through runoff and require the additional production of chicken feed.

The Most Sustainable Protein Sources

Using CO2-eq emissions per 100g of protein as our main metric, here are some of the most sustainable protein sources, in no particular order.


For the environmentalist seeking good sources of protein, it doesn’t get much better than lentils. They produce only .84kg of CO2-eq per 100g of protein.

Like nuts, lentils are carbon-negative when farmed sustainably, because lentil plants sequester carbon dioxide; unlike nuts, they don’t require an exorbitant amount of water to farm. As an added bonus, lentils also sequester nitrogen, which allows them to grow without fertilizer.


Another rich source of protein with a small environmental footprint is peas, which emit only .4kg of CO2-eq. For context, that’s almost 100 times less than beef. They also have a much smaller water footprint than nuts.

Tofu (Soy)

Soy, which is used to make tofu, only produces 1.98kg of CO2-eq for every 100g of protein.

Some have pointed out that demand for soy has contributed to deforestation in Latin America, as much of the land that’s been cleared is used to grow soy. While this is true, it’s also worth noting that only seven percent of all soy produced is made for human food products. The overwhelming majority of soy — between 77 and 96 percent worldwide — is used to feed livestock on factory farms.


Beans are also among the most environmentally friendly sources of protein, as producing 100g of bean protein emits around .37kg of CO2-eq.


Nuts are one of the most environmentally friendly sources of protein on the planet. Farming them produces just .26kg of CO2-eq for every 100g of protein — less than any other protein source. When nut trees are planted on previously-abandoned grasslands or pastures, they can even be carbon-negative, meaning they cause a net reduction in carbon emissions.

However, certain nuts require a lot of water to produce. Almonds, for instance, require slightly more water to make than beef. But that’s more than made up for by the massive difference in greenhouse emissions between the two foods. Some nuts and legumes, like peanuts, require far less water to make than any meat.

Lab-Grown Meat

Also known as cultivated meat, lab-grown meat is a fairly new innovation that allows scientists to create real, actual meat in a lab, without any need for slaughtering animals. Although the technology is still in its infancy, it’s already more carbon-efficient than meat: Producing 100g of lab-grown meat protein emits only 5.6kg of CO2-eq. That number will almost certainly decrease as the technology behind lab-grown meat continues to advance.


Another very environmentally-friendly protein source  that often gets overlooked, Quinoa produces around .63kg of CO2-eq for every 100g of protein.


Spirulina is believed to be one of the oldest life forms on Earth — and that’s not even the most impressive thing about it. It’s also packed with nutrients, has no sodium or cholesterol, can lower your cholesterol and blood pressure, and has even been known to reduce allergies.

But what’s most amazing about spirulina is that when it’s farmed using the right technology, it’s completely carbon neutral, emitting no CO2-eq at all.


Potatoes are a better source of protein than they often get credit for; they’re also a relatively sustainable one, with an output of 2.71kg of CO2-eq for every 100g of protein they provide.

The Bottom Line

Although many people associate protein with meat and dairy, getting your protein from animal sources is bad for the environment.

Luckily, there are a multitude of other ways to get protein that are cheaper, more sustainable, and if prepared correctly, just as delicious. Lentils, tofu, seeds and nuts are some of the highest-plant-based-protein sources — and are much more environmentally friendly.

Also worth remembering: many people overestimate the amount of protein they need while forgetting about other crucial nutritional components, such as fiber. A well-balanced, whole foods plant-based diet is the most environmentally friendly way to ensure you are getting everything your body needs — not just protein.

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