Dietary greenhouse gas emissions twice as high in meat-eaters as in vegans

A new study* published in the journal Climatic Change has shown that the dietary greenhouse gas (GHG) emissions of vegans living in the UK are only half the size of comparable meat-eaters. The study estimated the dietary GHG emissions of meat-eaters, fish-eaters (who ate fish but not meat), vegetarians (who ate dairy products and/or eggs but neither meat nor fish) and vegans (who ate no animal products) in the UK, participants in the EPIC-Oxford study of diet and health. The meat-eaters were further subdivided into ‘high’ (at least 100 grams of meat per day, typical of that consumed by most people in the UK), medium (50-99 g/d) and low (<50 g/d) meat categories. After correcting for differences in age and gender between the diet groups and standardising to a 2000 kcal diet, the mean (average) dietary GHG emissions across the 6 diet groups in kilograms of carbon dioxide equivalents (kgCO2e) per day were 7.19 in high meat-eaters, 5.63 in medium meat-eaters, 4.67 in low meat-eaters, 3.91 in fish-eaters, 3.81 in vegetarians and 2.89 in vegans. On average, dietary GHG emissions among the meat-eaters were approximately twice as high as among the vegans.

It has long been established that animal-based foods are generally associated with higher GHG emissions than plant-based foods. For example, the influential report Livestock's Long Shadow, published by the United Nations Food and Agriculture Organisation (FAO) in 2006, found that 18% of anthropogenic GHG emissions (the gases implicated in global warming and climate change that are produced by human activities) were attributable to global livestock rearing. Although an update to the report published in 2013 downgraded the estimate somewhat to 14.5%, the rearing of animals for meat and milk still accounts for at least one-seventh of anthropogenic GHG emissions. However, the new study is one of the first to report estimated dietary GHG emissions in real people consuming a wide range of diets.

Putting the results of the study into context, the authors point out that:

Reducing the amount of animal-based products in the diet represents an achievable way for an individual to reduce their carbon footprint. Assuming that the average daily energy intake in the UK is 2,000 kcal, then moving from a high meat diet to a low meat diet would reduce an individual’s carbon footprint by 920 kgCO2e every year, moving from a high meat diet to a vegetarian diet would reduce the carbon footprint by 1,230 kgCO2e/year, and moving from a high meat diet to a vegan diet would reduce the carbon footprint by 1,560 kgCO2e/year. For context, an individual travelling on an economy return flight from London to New York has an addition to their carbon footprint of 960 kgCO2e (www.carbonfootprint.com/calculator.aspx). A family running a 10 year old small family car for 6,000 miles has a carbon footprint of 2,440 kgCO2e (www.carbonfootprint.com/calculator.aspx), roughly equivalent to the annual carbon saving of two high meat eating adults moving to a vegetarian diet.

With the UK committed to an 80% reduction in GHG emissions compared with 1990 levels by the year 2050 under the Climate Change Act of 2008, including a 26% reduction by 2020, the widespread adoption of a low-carbon, plant-based diet cannot come a moment too soon.

Paul Appleby

* Scarborough et al. Dietary greenhouse gas emissions of meat-eaters, fish-eaters, vegetarians and vegans in the UK. Climatic Change 2014; DOI 10.1007/s10584-014-1169-1. (The open access article can be read and downloaded at http://link.springer.com/article/10.1007/s10584-014-1169-1)

For New Scientist magazine’s take on the story go to: http://www.newscientist.com/article/dn25795-going-vegetarian-halves-co2-emissions-from-your-food.html

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