Emissions from Diet Could Eat Up the Entire 1.5 Degree Carbon Budget

We are eating and wasting too much of the wrong kinds of food.

Cattle Grazing in Brazil
Cattle Grazing in Brazil.

Helder Faria/ Getty Images

In the 2018 Special Report on Global Warming, the Intergovernmental Panel on Climate Change (IPCC) concluded that to keep global warming under 1.5 degrees Celcius (3.6 Fahrenheit), "global net human-caused emissions of carbon dioxide (CO2) would need to fall by about 45 percent from 2010 levels by 2030, reaching 'net zero' around 2050." As I found in writing "Living the 1.5 Degree Lifestyle," that meant big changes in how we live, how we eat, and how we move.

Now new research from the Our World In Data (OWID) team at Oxford University concludes emissions from food production alone are enough to blow the entire 1.5 degree carbon budget and threaten the 2 degree budget.

Hannah Ritchie, senior researcher and head of research at OWID, writes that "one-quarter to one-third of global greenhouse gas emissions come from our food systems." These come from deforestation; methane from cattle and rice production; and fossil fuel use on the farm, in the supply chain, for refrigeration, transport, and storage.

Cumulative carbon
CC Our World in Data

The carbon budget is a fixed number and all the carbon dioxide equivalents (CO2e, which includes CO2, methane, fertilizer emissions, nitrous oxides, and refrigerants) that we add to it are cumulative, so Ritchie adds up all the emissions projected from now to 2100. She uses 500 gigatonnes as the budget; I actually thought it was 420 gigatonnes but that only makes it worse. Given we are supposed to be at net-zero emissions by 2050, it is pretty obvious we can't keep generating the CO2e that we are now. There is a little more room for a 2 degrees Celcius (3.6 degrees Fahrenheit) scenario, but not much.

And, as Ritchie writes:

"Ignoring food emissions is simply not an option if we want to get close to our international climate targets. Even if we stopped burning fossil fuels tomorrow – an impossibility – we would still go well beyond our 1.5°C target, and nearly miss our 2°C one."

What Can We Do?

how can we reduce greenhouse emissions
Our World in Data

I wish Ritchie had published this last year because this is a chapter in the "Living the 1.5 Degree Lifestyle" book and it has some suggestions that I had missed. Ritchie suggests 5 major changes:

Eat a Climatarian Diet

greenhouse gas emissions by calories
Our World in Data

This is a diet that focuses on carbon emissions. It is not vegan; as this earlier chart from OWID shows, hothouse tomatoes are twice as bad as pork or chicken. It's not vegetarian; cheese is worse than pork. Just cutting out red meat (and for some reason, shrimp) gets you halfway there.

Staying out of the hothouse and the transport truck is why a "climatarian" diet should be local and seasonal as well. Although Ritchie suggests transportation (other than air freight) doesn't have a big footprint, my research suggests OWID grossly underestimated the impact of the cold chain, the refrigeration from the farm to the grocery store.

In summary: eat local, seasonal, mostly plants, and no red meat. An occasional burger made from dairy cow meat won't break the carbon bank.

Reduce Food Waste

Man looks for food in dumpster
A man looks for food in a dumpster in Bogotá, Colombia, in April 2020. VIEW press / Getty Images 

Ritchie puts it nicely: "What we don’t eat can be just as important as what we do eat. One-quarter of food-related emissions come from food waste by consumers, or losses in supply chains due to spoilage, lack of refrigeration, etc." 

But there is a lot of post-consumer waste. I quoted a McKinsey study that found “household food losses are responsible for eight times the energy waste of farm-level food losses due to the energy used along the food supply chain and in preparation.”

Reduce the Amount of Food We Actually Eat

Portion size
Robert Couse-Baker on Flickr

Ritchie calls this section "healthy calories" noting many people eat more than is needed to maintain a healthy weight. This is an understatement. Kelly Rossiter used to write about how a piece of meat on your plate should be no bigger than a deck of cards. I wrote in my book about portion distortion— how portions have grown so much:

Everything has been supersized. Even healthy foods like bagels are 24% larger than they were 30 years ago. And as Marion Nestle wrote in her book What to Eat, “It is human nature to eat when presented with food, and to eat more when presented with more food.” This leads to a vicious circle of carbon emissions; having higher body mass means one consistently needs more calories just for maintenance. Heavier people mean greater fuel consumption when traveling.
One study concluded: "Compared with an individual with normal weight, researchers found an individual with obesity produces an extra 81 kg/y of carbon dioxide emissions from higher metabolism, an extra 593 kg/y of carbon dioxide emissions from greater food and drink consumption and an extra 476 kg/y of carbon dioxide emissions from car and air transportation. Overall, obesity is associated with approximately 20 percent greater greenhouse gas emissions when compared to people with normal weight."

When you add it all up, eating food we don't need has a bigger carbon footprint than the food we waste. I recommended people go to antique shops to buy dishes and glasses from a hundred years ago when dishes were all a lot smaller.

Don't Order In

Swiss Chalet Delivery
Swiss Chalet

One source of carbon Ritchie doesn't include but I think should be is the footprint of food delivery. Treehugger editorial director Melissa Breyer wrote that "on any given day, 37% of American adults eat fast food. For those between 20 and 39 years old, the number goes up to 45%—meaning that almost half of younger adults are eating fast food daily." That has a big footprint.

We do include the emissions from transportation of food before it is cooked, and it makes sense to include transportation after. I did an analysis of an order of our family's favorite chicken dinner, measuring the footprint of raising the chickens, cooking them, packaging them in far too much plastic, and delivery and that 5-mile drive in a Toyota Corolla came out to 56% of the total carbon footprint. So if you must order in, choose sources that use bike couriers or pick it up yourself.

High Yields and Farm Practices

These two categories are beyond individual control; higher yields come from improved crop genetics and management practices. To get serious improvements will involve "significant progress in bioengineering and crop genetics," which will be controversial. Farm practices involve how food is produced. "This scenario is one in which the average emissions intensity (emissions per unit of food) falls by 40% through improved practices (e.g. fertilizer management) and technology improvements (e.g. targeted fertilizers or additives to cattle feed)."

Going halfway in all these measures would reduce the CO2e emissions enough to stay under the 1.5 degree budget. if everyone got on board and gave up their cheeseburgers, the food system could actually be carbon positive.

Change of diet works in two ways
CC Our World in Data

That's because raising beef and lamb takes up a huge amount of land, much of which could be restored as forests and grasslands, which absorb a lot of CO2 as they grow, giving you more than twice the bang for your buck when you give up red meat.

I feel it necessary to conclude by noting that lowering one's carbon footprint isn't the only reason to change one's diet; there are also solid ethical reasons for becoming vegan, Eating less meat is said by many to be healthier, and eating less definitely is.

But if more of us changed what we eat, how much we eat, and where we get it, we would end up with healthier people living on a healthier planet.

View Article Sources
  1. Ritchie, Hannah. "Emissions from food alone could use up all of our budget for 1.5°C or 2°C – but we have a range of opportunities to avoid this." Our World in Data, 2021.

  2. Magkos, Faidon, et al. "The Environmental Foodprint of Obesity." Obesity, vol. 28, no. 1, 2019, pp. 73-79., doi:10.1002/oby.22657