Which protein has the lowest carbon footprint? A per gram ranking
Beef, chicken, eggs, tofu, lentils and more, ranked by kg CO2e per 100 g of protein. See which foods give you the most protein for the least carbon.
Most carbon comparisons look at a kilo of food. That is a bit unfair. A kilo of lentils and a kilo of lettuce do very different jobs on your plate. If protein is what you are shopping for, the fair question is simple: how much carbon does each gram of protein cost?
That is the number Per Gram is built on, so here is the full ranking.
The ranking: kg CO2e per 100 g of protein
These are global averages from the largest study of food footprints so far, Poore and Nemecek (2018), which covered around 38,000 farms in 119 countries. The numbers count the whole life of the food: land use, farming, feed, processing, transport, packaging and retail.
| Food | kg CO2e per 100 g protein |
|---|---|
| Beef (beef herd) | 49.9 |
| Lamb and mutton | 19.9 |
| Prawns (farmed) | 18.2 |
| Beef (dairy herd) | 16.9 |
| Cheese | 10.8 |
| Milk | 9.5 |
| Pork | 7.6 |
| Fish (farmed) | 6.0 |
| Poultry | 5.7 |
| Eggs | 4.2 |
| Grains | 2.7 |
| Tofu | 2.0 |
| Peanuts | 1.2 |
| Other pulses (beans, lentils) | 0.8 |
| Peas | 0.4 |
| Nuts | 0.3 |
Source: Poore and Nemecek (2018), Science, via Our World in Data. Figures are global means.
What jumps out
Beef is in a league of its own. 100 g of protein from a beef herd costs about 50 kg of CO2e. The same protein from peas costs under half a kilo. That is more than 100 times less.
Chicken and eggs sit in the middle. If you eat meat, swapping beef for chicken cuts the carbon of that protein by close to 90%. Eggs do a little better again.
Tofu, beans and lentils are the quiet winners. They pack a lot of protein and need little land, so they land near the bottom of the chart. Protein from tofu has about a fifth of the footprint of the same protein from cheese.
Not all dairy is equal. Cheese is high because it takes about 10 litres of milk to make 1 kg.
Averages hide a big spread
The study found huge gaps between the best and worst farms for the same food. The highest impact beef producers emit many times more than the lowest. Still, even low impact beef usually comes out above high impact peas or tofu. The choice of food matters more than where it came from.
Transport is a smaller slice than most people think. For most foods it is under 10% of the total. What you eat matters far more than how far it travelled.
How Per Gram uses these numbers
Per Gram turns this table into something you can act on at the till.
- Buy your groceries as usual.
- Scan the barcode or snap your receipt in the app at pergramapp.com.
- We work out the protein in each item from the pack label and product data from Open Food Facts.
- Lower carbon protein earns more B3TR, the reward token of the VeBetterDAO ecosystem.
You do not have to give anything up. A few swaps a week, like lentils in the chilli or chicken instead of beef, moves you down the chart and earns you more.
Quick answers
What is the lowest carbon source of protein? Peas, nuts, beans, lentils and tofu all come in under about 2 kg CO2e per 100 g of protein.
Is chicken better than beef for the climate? Yes. Per gram of protein, chicken has roughly a ninth of the footprint of beef from a beef herd.
Are eggs a low carbon protein? Eggs are one of the lowest carbon animal proteins, at about 4.2 kg CO2e per 100 g of protein.
Does buying local fix the footprint of beef? Not really. Transport is a small share of the total for most foods. The farming itself is the big part.
Want to see how your own shop scores? Open Per Gram and scan your next receipt.