Vegan vs Omnivore Carbon Footprint

Food production accounts for roughly 26% of global greenhouse gas emissions. The carbon footprint of different foods varies enormously. Beef is roughly 60 kg CO2e per kg of food, while lentils are about 0.9 kg CO2e per kg.

Emission factors used (kg CO2e per kg of food, based on Poore and Nemecek 2018 meta-analysis, the most comprehensive food LCA study to date):

• Beef: 60 kg CO2e/kg (avg. across production methods)
• Lamb: 24 kg CO2e/kg
• Pork: 7.6 kg CO2e/kg
• Chicken: 6.9 kg CO2e/kg
• Fish (farmed): 5.1 kg CO2e/kg
• Dairy (milk): 3.2 kg CO2e/kg
• Eggs: 4.5 kg CO2e/kg
• Rice: 4.0 kg CO2e/kg (methane from flooded paddies)
• Legumes (lentils, beans): 0.9 kg CO2e/kg
• Vegetables: 0.4 kg CO2e/kg (avg.)
• Fruits: 0.4 kg CO2e/kg

The gap between beef and vegetables is a factor of 150. To put that in something you can picture: swapping one weekly 150 g serving of beef for lentils saves about 460 kg CO2e a year, which is roughly a one-way economy seat from London to New York. Not a return trip, and not the two or three tonnes a full transatlantic return actually costs. That distinction matters, because the claim that giving up one steak a week beats a transatlantic flight gets repeated a lot and it is not true. Rice deserves a mention too: at 4.0 kg CO2e/kg it has a higher footprint than most vegetables, because flooded paddies go anaerobic and produce methane.

How the input categories map to those numbers

The boxes below group foods that have similar but not identical factors, so a few notes on what is actually being used. Pork and lamb share a box and are calculated at 8.5, close to pork’s 7.6, because most people eating from that box eat far more pork than lamb. If you eat lamb regularly your real figure is higher, potentially much higher, since lamb is 24. Chicken and fish share a box at chicken’s 6.9, which slightly overstates a fish-heavy diet. Plant foods use 0.5, a blend that sits between vegetables at 0.4 and legumes at 0.9.

A serving is taken as 150 g of meat or plant food, 200 ml for dairy, and one egg at 60 g.

Where the emissions actually sit

Transport is the thing people fixate on and it is close to irrelevant: for most foods it accounts for under 10% of the total, and for beef it is around 1%. Land use change and enteric fermentation, meaning the methane cattle belch, dominate. This is why buying local beef does essentially nothing to the number, while eating beef less often changes it enormously. If you only take one thing from this page, take that one.

The UK average diet produces about 2.5 tonnes CO2e per year just from food. A fully plant-based diet is typically 1.1 to 1.5 tonnes, and the reason it is not near zero is that growing, processing and shipping plants still costs something.