What is the best way to reduce the carbon footprint of our diet?
I have shown previously that what we choose to eat has the largest impact, making a bigger difference than how far our food has traveled, or how much packaging it’s wrapped in. This is because only a small fraction comes from transport and packaging and most of our food emissions come from processes on the farm, or from land use change.
Regardless of whether you compare the footprint of foods in terms of their weight (e.g. one kilogram of cheese versus one kilogram of peas); protein content ; or calories, the overall conclusion is the same: plant-based foods tend to have a lower carbon footprint than meat and dairy. In many cases a much smaller footprint.
As an example: producing 100 grams of protein from peas emits just 0.4 kilograms of carbon dioxide equivalents (CO2eq). To get the same amount of protein from beef, emissions would be nearly 90 times higher, at 35 kgCO2eq.1
But it comes with the caveat that comparisons are made based on global averages.
Many argue that this overlooks the large variation in the footprints of foods across the world. Using global averages might give us a misleading picture for some parts of the world or some producers. If I source my beef or lamb from low-impact producers, could they have a lower footprint than plant-based alternatives?
The evidence suggests, no: plant-based foods emit fewer greenhouse gases than meat and dairy, regardless of how they are produced.
Let’s take a look at the full range of footprints for protein-rich foods.
Protein-rich foods account for the bulk of our dietary emissions. In European diets, meat, dairy and eggs account for 83%. That’s why I focus on them here.
In the visualization we see the range of carbon footprints for these foods. This data is from the largest meta-analysis of global food systems to date, published in Science by Joseph Poore and Thomas Nemecek (2018).2 In this study, the authors looked at data across more than 38,000 commercial farms in 119 countries.
All greenhouse gas (GHG) emissions are measured in kilograms of carbon dioxide equivalents per 100 grams of protein; this metric takes account of not only carbon dioxide but also the range of other greenhouse gases – this is further explained in the footnote.3 To make reading less repetitive, I refer to it as ‘kgCO2eq’ below.
The visualization shows the median footprint – highlighted by a small white circle for each food product.
But since there are large differences between producers, this chart also shows the full spectrum of emissions – from the lowest to highest producers. The height at each point in the curve represents the amount of global production with that specific footprint.
The median footprint for beef is 25 kgCO2eq.4 But some producers have a much higher footprint: ten percent emit more than 105 kgCO2eq per 100 grams. At the other end, some are much lower. Ten percent emit less than 9 kgCO2eq. We see from the height of the curve that most beef production lies in the range between 17 to 27 kgCO2eq.
How do the distributions between plant-based and meat-based sources compare?
Plant-based protein sources – tofu, beans, peas and nuts – have the lowest carbon footprint. This is certainly true when you compare average emissions. But it’s still true when you compare the extremes: there’s not much overlap in emissions between the worst producers of plant proteins, and the best producers of meat and dairy.
Let’s compare the highest-impact producers (the top ten percent) of plant-based proteins with the lowest-impact producers (the bottom ten percent) of meat and dairy.
The pea producers with the highest footprint emit just 0.8 kgCO2eq per 100 grams of protein.5 For nuts it is 2.4 and for tofu, 3.5 kgCO2eq. All are several times less than the lowest impact lamb (12 kgCO2eq) and beef (9 kgCO2eq). Emissions are also lower than those from the best cheese and pork (4.5 kgCO2eq); and slightly lower or comparable to those from the lowest-footprint chicken (2.4 kgCO2eq).6
If you want a lower-carbon diet, eating less meat is nearly always better than eating the most sustainable meat.
This is also true for the differences between meat products. Chicken, eggs, and pork nearly always have a lower footprint than beef and lamb: there is some, but not much overlap between the worst poultry and pork producers, and the best beef and lamb producers. The world’s highest impact chicken and pork have a footprint of 12 and 14 kgCO2eq. This is similar to, or only slightly higher than, the world’s best beef and lamb.
Regardless of where you get your beef or lamb from, substituting with chicken and pork is likely to reduce your carbon footprint.
Eating less meat, or switching to lower impact meats such as chicken, eggs or pork is the most effective way for individuals to reduce their dietary footprint.
But if you want to eat meat, then the choice of meat also matters. Consumers can have an impact, but so can food producers.
The world is not going to abandon livestock farming completely – at least not any time soon. And there are a number of reasons we wouldn’t want it to: it is not only an important source of income for many, but can also be a key source of nutrition in local settings. Particularly in lower-income countries where diets lack diversity, small amounts of meat and dairy can be an essential source of protein and micronutrients.
Globally, greenhouse gas emissions are massively skewed towards high-impact producers. This can be seen at the bottom of our visualization. The red curve shows the sum of all protein products.
Most of the protein we produce is relatively low-impact: 75% of production has a footprint between -3 and 11 kgCO2eq per 100 grams of protein. This creates just 30% of protein’s emissions.
High-impact production – with a footprint greater than 11 kgCO2eq – produces just 25% of our protein, but 70% of its emissions. To put this ‘high-impact production’ in context: the top quarter of protein production emits more than five billion tonnes of CO2eq each year. This is more than the EU’s total annual greenhouse gas emissions from all sectors.7
Much of this skew, as we’ve already discussed, comes from the differences between plant-based sources and meats such as beef and lamb. But a lot comes from the large variations in footprint for specific products.
There is much more variation in the footprints of beef, lamb, dairy, and aquaculture production than for other foods. This is because there are large differences in the intensity and practices used in ruminant livestock, and fish farming across the world. This is different from poultry and pig farming: 61% of pork, 81% of chicken and 86% of eggs are produced intensively in industrial-farm settings.8 These systems are very similar wherever they are in the world.
One factor which explains a lot of the variation for beef is whether it’s sourced from a dairy herd (where the cattle also produce milk) or a herd dedicated to beef production. Just under half (44%) of the world’s beef comes from the dairy sector. And it produces 60% lower emissions because its footprint is shared with dairy co-products.
Geography also plays a role in the large variations we see for beef, lamb and aquaculture: farming approaches are often adopted in line with local conditions such as soil fertility, terrain and temperature.9 Opportunities for food producers to reduce emissions are therefore very specific to local conditions.
But there are some general recommendations that are clear from the research: improving degraded pasture; improving lifetime animal productivity; increasing oxygen flow in aquaculture ponds, particularly in warm climates; and avoiding the conversion of forests and peatlands for agriculture will all make a difference.10 Land use change can play a large role in the final emissions; this means beef from South America often has a high footprint due to deforestation. Good pasture quality is also important: climate has a strong impact on this, but effective management practices can also make a difference; New Zealand, France and the UK are some examples where footprints are often lower.
If we want to reduce the emissions from our food, there is massive scope for both consumers and producers. For producers, understanding and adopting best farm and land management practices can mitigate the highest impacts of production.
As consumers, the biggest difference we can make is to eat more plant-based sources of protein such as tofu, nuts, peas, and beans. This is the case regardless of where you are in the world.