The vast majority of the world’s population consumes some source of carbohydrates in every meal. Although emissions for carbohydrate sources are typically not as high as common sources of protein (meat, fish, dairy), its frequent consumption still presents an opportunity to systematically lower one’s carbon footprint.

In the table below, we compare emissions of the most common carbohydrate sources consumed in Europe: bread, potatoes, pasta and rice. Although each source has a unique combination of nutrients, for simplicity, we define a serving as 200 grams of ready-to-eat product. Most emission factors in our database concern the raw, uncooked product. We, therefore, calculate a conversion factor between raw and cooked product based on the ratio of calories between the two as given by the US Department of Agriculture¹.

Looking purely at emissions, potatoes are the clear winners with 80 g CO2e / serving, about 3 times less than bread. However, as potatoes are comparatively low in calories, both pasta and bread are also good choices when looking at energy content. Rice appears to be the worst when considering emissions per calorie, though it has to be noted that there is more uncertainty in its emission factor. Half the studies report an emission factor <=2 kg CO2e / kg instead of the average across all studies of 2.5 kg CO2e / kg used here, which would bring it in the same ballpark per calorie as the other 3 carbohydrates.

Of course, there are plenty of other carbohydrate sources, some of which are staple foods in certain regions of the world. These are, however, not as well-studied as the four products above, but the results can give us a general idea about their sustainability nonetheless. Both bulgur and couscous (both made from durum wheat, as is dried pasta), appear to be very climate friendly while also being high in energy content. Noodles also perform well, however slightly worse than bulgur and couscous. The other carbohydrate sources (quinoa, rice noodles, tortilla and sweet potatoes) are comparable to bread and pasta.

So, can we make a big impact by switching carbohydrate sources? Switching from the source with the highest (bread) to the lowest (potatoes) emissions would save 0.14 kg CO2e per serving. Counting 3 servings of carbohydrates a day, you could theoretically save about 150 kg CO2e per year. This is ~8% of a person’s yearly food emissions (~2000 kg CO2e per year) and about 15% of the personal CO2e food budget we work with (~1000 kg CO2e per year). However, similar gains are more easily obtained by switching or cutting down on sources of protein. For example, the 0.14 kg CO2e saved per serving is also equivalent to cutting a serving of beef from 100 to 95 grams. In summary, you can make some impact by rethinking your carbohydrate sources, but do not expect miracles. If the variety in carbohydrates makes you less likely to consume products with high emission factors, that is likely the far more sustainable way to go.