Protein Intensity: Ranking Foods by CO₂ per Gram of Protein
Protein Intensity: Ranking Foods by CO₂ per Gram of Protein
When it comes to diet, protein is essential — but so is understanding the carbon cost of getting it. Some foods pack a lot of protein but carry a heavy footprint. Others deliver protein efficiently, with much lower CO₂ emissions.
This guide ranks foods by “protein intensity”: grams of protein delivered per kilogram of CO₂ emitted.
Why This Matters
- Food systems account for ~25% of global greenhouse gas emissions.
- Animal protein is not all equal: beef and lamb are far worse than chicken or fish.
- Plant-based proteins often deliver more grams of protein per unit of carbon.
By comparing protein intensity, you can see which foods give the best climate return for your nutrition.
What Is Protein Intensity?
We define protein intensity as:
This shows how much protein you get per kilogram of CO₂e. The higher the number, the better.
The Rankings (Per Serving)
Approximate global averages:
| Food | CO₂ per serving (kg) | Protein per serving (g) | Protein per kg CO₂ |
|---|---|---|---|
| Beef (100g) | 6.0 | 26 | ~4 g/kg CO₂ |
| Lamb (100g) | 5.0 | 25 | ~5 g/kg CO₂ |
| Pork (100g) | 1.7 | 27 | ~16 g/kg CO₂ |
| Chicken (100g) | 1.1 | 27 | ~25 g/kg CO₂ |
| Dairy (1 cup milk) | 0.5 | 8 | ~16 g/kg CO₂ |
| Rice (150g) | 0.6 | 4 | ~7 g/kg CO₂ |
| Legumes (150g) | 0.2 | 11 | ~55 g/kg CO₂ |
| Vegetables (200g) | 0.15 | 4 | ~27 g/kg CO₂ |
Key Insights
- Beef and lamb: lowest protein intensity, highest emissions.
- Chicken and pork: much better balance of protein and carbon.
- Legumes: the winner, delivering over 50 g protein per kg CO₂.
- Vegetables: good for nutrition overall, but lower in protein density.
Action Plan: Eating for Protein and Carbon
- Swap beef/lamb for chicken or legumes at least 1–2 meals per week.
- Mix proteins: beans + grains provide a complete amino acid profile.
- Reduce waste: food waste compounds your footprint.
- Try dairy alternatives if you consume a lot of milk.
Practical Examples
- Replace one beef burger with a chicken breast = ~5x improvement in protein intensity.
- Replace with a lentil patty = ~10x improvement.
- Add beans to rice → boosts protein intensity of the meal.
Frequently Asked Questions
Q: Is fish better than beef?
A: Generally yes, though it varies by species and farming methods. Wild-caught small fish often score better than large farmed fish.
Q: Do I have to go vegan to cut food emissions?
A: No. Even small swaps (beef → chicken or legumes) have a major impact.
Q: What about protein powders?
A: Plant-based powders usually have far lower footprints than whey or casein.
Related Tools & Guides
- Food CO₂ Calculator — estimate your diet’s emissions
- Blog: Beef vs Chicken — direct comparison
- Home Energy Calculator — tackle your other big footprint
Conclusion
Protein is non-negotiable for health. But how you source it matters for the climate. By shifting even part of your protein intake to higher-intensity foods like legumes or chicken, you can cut diet-related emissions dramatically.
The bottom line: eat smart, not less. Protein intensity shows you the path.