How much food does it take to generate 2.2 pounds of greenhouse gas?

Tiny burger
CC BY 2.0 James Creegan/Flickr

Try 50 onions or 1.3 ounces of beef, according to a new study that ranks the carbon footprints of the things we eat.

How did food get so complicated? Eating should be simple, but alas, by some accounts the global food system is responsible for up to one-third of all human-caused greenhouse-gas emissions. Is that which should be nurturing us actually scripting our doom? We are a species mired in irony, to say the least.

At this point in time, most of us are aware that food has a carbon footprint – and that things like beef create more of an impact. Now researchers from RMIT University and Lancaster University have compiled the first comprehensive “carbon footprint league table for fresh food” so that “chefs, caterers and everyday foodies can cook meals without cooking the planet.”

The aim of the study was to develop a dataset to help consumers and professionals understand the global warming potential of their ingredients and menus.

"We wanted to help people make informed choices, to empower consumers and people working in the food industry who would like to reduce their environmental impact," says RMIT Associate Professor Karli Verghese. Adding, "With this full picture of the greenhouse gas impact of different foods, people can reliably work out more sustainable diets and menus for themselves and for their customers."

The paper reviewed 369 published studies that provided 1718 global warming potential values for 168 varieties of fresh produce including vegetables, fruit, dairy products, staples, meat, chicken and fish.

It’s probably little surprise that grains, fruit and vegetables were found to have the lowest impact, followed by nuts and pulses. Non-ruminant meat like chicken and pork had a medium impact; fish has a medium impact as well, though levels varied depending on species.

Meat from beef and lamb was found to have the highest impact.

To give an idea of different food’s impact, the authors created a basic list to show how much it takes to contribute a kilogram (2.2 pounds) of greenhouse gas emissions.

On average, 1 kilogram of greenhouse gas emissions equals:

  • 5.8 kilograms (12.7 pounds) of onions (about 50 medium onions)
  • 3.5 kilograms (7.7 pounds) of apples (about 20 medium apples)
  • 2.6 kilograms (5.7 pounds) oats
  • 1 kilograms (2.2 pounds) lentils
  • 1.2 kilograms (2.6 pounds) of peanuts
  • 800 milliliters (27 fluid ounces) of milk
  • 290 grams (10.2 ounces) of salmon
  • 290 grams of eggs (about 5 small eggs)
  • 270 grams (9.5 ounces) of chicken
  • 244 grams (8.6 ounces) of kangaroo
  • 212 grams (7.5 ounces) of rabbit
  • 174 grams (6.1 ounces) of pork (world average)
  • 40 grams (1.4 ounces) of lamb (world average)
  • 38 grams (1.3 ounces) of beef (world average)

And while kangaroo may not play into the food choices for all of us, suffice to say that comparing onions and beef is a bit like comparing apples and oranges. Dr. Stephen Clune, from Lancaster University, acknowledges that saying, "You would have a hard time arguing that you can replace beef with onions as they serve very different culinary and dietary requirements.

"However, it is possible to substitute red meat (beef and lamb) with other meats," he add, "or plant-based protein sources such as lentils and nuts that have a lower impact."

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