Which protein source has the lowest carbon footprint?

Pulses — beans, lentils and peas — are the lowest at roughly 0.8 kg CO2-equivalent per 100 g of protein, followed by nuts and tofu.

Is chicken a good climate choice?

Chicken is far lower than beef or lamb, at about 5.7 kg CO2e per 100 g protein, but still several times higher than tofu or pulses, and it involves the most individual animals per kilogram.

Do plant proteins provide all essential amino acids?

Yes. A varied plant diet supplies all nine essential amino acids across the day; soy, quinoa and buckwheat each supply them in a single food.

Protein Swap Comparison

Protein is the argument people reach for most often, so it is worth comparing sources on a like-for-like basis: emissions per 100 grams of protein delivered, not per kilogram of raw product. The figures below come from the Poore & Nemecek (2018) global meta-analysis covering roughly 38,700 farms in 119 countries.

Short answer: Per 100 g of protein, beef averages about 50 kg CO2-equivalent while tofu averages about 2 kg and pulses about 0.8 kg — a difference of roughly 25 to 60 times.

Swap fromSwap toServings a week

2595kg CO₂e

Beef (beef herd), per year

42kg CO₂e

Peas, beans & lentils, per year

2553kg saved

62.4× lower

Greenhouse gas emissions per 100 g of protein by food
Source	kg CO₂e / 100 g protein	Relative
Beef (beef herd)	49.9
Lamb & mutton	19.9
Cheese	10.8
Pork	7.6
Farmed fish	6.0
Poultry	5.7
Eggs	4.2
Milk	3.2
Grains	2.7
Tofu	2.0
Peas, beans & lentils	0.8
Nuts	0.3

Global means · Poore & Nemecek 2018

How this is calculated

Emissions are global mean values per 100 g of protein, cradle to retail, from Poore & Nemecek (2018).
A serving is treated as 20 g of protein.
Means hide wide production spreads; the best and worst producers of the same food can differ by an order of magnitude.

Frequently asked

Which protein source has the lowest carbon footprint?: Pulses — beans, lentils and peas — are the lowest at roughly 0.8 kg CO2-equivalent per 100 g of protein, followed by nuts and tofu.
Is chicken a good climate choice?: Chicken is far lower than beef or lamb, at about 5.7 kg CO2e per 100 g protein, but still several times higher than tofu or pulses, and it involves the most individual animals per kilogram.
Do plant proteins provide all essential amino acids?: Yes. A varied plant diet supplies all nine essential amino acids across the day; soy, quinoa and buckwheat each supply them in a single food.

Sources

More tools

Diet Carbon Footprint Calculator

Estimate the annual greenhouse gas emissions of your diet and see what switching would save.

Animals Spared Calculator

Turn weekly servings into an estimate of how many animals a year your food choices involve.

Estimates, not personal measurements

Calculators use published averages and simplified assumptions. Results describe possible differences, not your precise footprint or an exact count of animals spared. Check each tool’s method, units and sources before comparing results.

Reference sources

Weighing pulses alongside vegetables for a meal.