Whether it’s beans or beef, there are a lot of ways to get your protein. But the environmental impact of protein sources vary greatly. I’ll cover several here, breaking down the protein count for each. Where possible, I’ll also skim the surface of the respective carbon impact for these food types and give pointers about what to look for and what to avoid. Whether you’re an eco-friendly diet advocate looking to learn more about sustainable protein, or simply curious what the hype’s all about, I hope this article will be of help to you.
Why Sustainable Protein?
To start off with, context is important. After all, why sustainable protein? To clarify, “sustainable” is here measured in terms of CO2 emissions per serving.
In comparison to other protein sources, meat-based proteins are relatively unsustainable. Starting a high-level, we see that vegetables, fruit, and grains collectively contribute to 11.5% of greenhouse gases based on average food consumption. Comparatively, meat is responsible for almost half (47.6%) of all food-related greenhouse gases, making it significantly less eco-friendly:
The factors that contribute to meat-based protein’s lacking sustainability vary. Furthermore, not all meat proteins equally contribute to emissions. For example, ruminant livestock (cattle, sheep, and goats) contributed to 167 million metric tons (mmt) in CO2 emissions in 2015, in part due to methane output as a biproduct of their digestion (in other words, don’t stand behind a cow). However, this doesn’t apply across the board. Other meat types, such as chicken, contribute significantly less to overall emissions.
The figure below illustrates how protein sources, such as beef, cheese, and pork, disproportionately contribute to more CO2 emissions:
It’s clear which foods are the biggest contributors to emission. Equally, however, it’s clear there are numerous sources of low-emission protein. Using the above figure, I’ll next dive into the food sources that tip towards the sustainable end of the spectrum.
Eco-friendly Protein Sources
Without further adieu, here are your eco-friendly protein sources illustrated graphically:
This graph shows us two things. One, it ranks the protein levels of food sources from highest to lowest. Second, it shows the respective emission output per serving of that particular food (measured by kg/CO2 emissions).
As you’d intuit, vegetables rank better in terms of low emissions compared to the meat options. Foods that offer an optimal balance of protein and low emissions include tempeh, tofu, black beans, milk, eggs, nuts, and wild rice. The analysis is imperfect, however, as more robust data is needed to estimate the kgCO2e of more specific food items, with emissions adjusted based on recommended serving sizes (wouldn’t it be nice to haveCO2 emissions per serving on food labels?). Also, the actual kgCO2e depends on other factors that transcend this short analysis. For example, the “food miles,” i.e. the distance travelled between where the food was sourced and where you purchased it, plays a big role in carbon footprint. As a safe bet, opt for local, seasonal food (like farmer’s markets!).
What does this mean?
To follow an eco-friendly diet, good rules of thumb are to limit your intake of beef, pork, and cheese and to buy locally and seasonally as often as possible. With the higher carbon output per serving, it’s recommended that chicken intake is limited in comparison to other excellent sources of protein, such as tempeh, tofu, black beans, eggs, and wild rice. Complement your meals with vegetables such as broccoli, potatoes, and brussel sprouts, which add to your total protein count and generally offer numerous health benefits.
To look at the numbers more granularly, check out the table below. As you can see, you’ve got a lot of options to keep your meals diverse, delicious, and eco-friendly:
| Food | Protein/serving (g) | kgCO2e/serving | Serving size |
| Chicken (breast) | 35 | 6.9 | 4oz |
| Chicken (thigh) | 30 | 6.9 | 4oz |
| Wild salmon (US sourced) | 21 | 3.9 | 100g |
| Organic edamame | 18 | 2 | 1 cup |
| Seitan | 18 | / | 3oz |
| Organic tempeh | 16 | 2 | 3oz |
| Spelt | 14.57 | 3.5oz | |
| Organic tofu | 8-15 | 2 | 3oz |
| Kamut | 9.8 | 1 cup (172g) | |
| Lentils | 9 | 0.9 | 1/2 cup |
| Milk: | |||
| Non-fat | 8.75 | 1.062 | 1 cup |
| 1-2% | 8.53 | 1.062 | 1 cup |
| Whole milk (3.25% milk fat) | 7.69 | 1.062 | 1 cup |
| Black beans | 7.6 | 2 | 1/2 cup |
| Lima beans | 7.3 | 2 | 1/2 cup |
| Peanuts/peanut butter | 7 | 2.5 | 1/4 cup/2tbsp of peanut butter |
| Wild rice | 6.5 | 2.7 | 1 cup |
| Teff | 6.4 | / | 1/4 cup |
| Egg (full) | 6.3 | 1.8 | 1 egg |
| Egg white | 3.6 | 1.8 | 1 large egg white |
| Egg yolk | 2.7 | 1.8 | 1 large egg yolk |
| Chickpeas | 6 | 2 | 1/2 cup |
| Quinoa | 6 | / | 1/4 cup |
| Almonds | 6 | 2.3 | 1/2 cup |
| Chia seeds | 6 | / | 2tbsp |
| Sorghum | 5.1 | / | 1/4 cup |
| Steel cut oatmeal | 5 | / | 1/4 cup dry |
| Cashews | 5 | 2.3 | 1/4 cup |
| Pumpkin seeds | 5 | / | 1/4 cup |
| Amaranth | 4.7 | / | 1/2 cup |
| Potatoes | 4 | 2.9 | 1 medium |
| Spinach | 3 | / | 1/2 cup |
| Organic corn | 2.5 | / | 1/2 cup |
| Avocado | 2 | / | 1/2 avocado |
| Broccoli | 2 | 2 | 1/2 cup (cooked) |
| Brussel sprouts | 2 | / | 1/2 cup |
So, how do you get your protein?
It turns out, in a lot of ways! Luckily, there is no shortage of delicious, eco-friendly sources, many of which are packed with essential vitamins and micronutrients. Now, the next time someone asks you about where you get your protein, you’ve got plenty of data to share.
Happy Trail Tales 