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Plant-Based is Best

Moving closer to a plant-based diet saves 643 kilograms CO2e per person per year.

Left, the average Australian Molloy family with one week of groceries = 1.4 tonnes CO2e per person per year. Image from 'Hungry Planet'. The Molloys eat a lot of fish, meat and dairy.
Right, my groceries during a vegan week = 450 kilograms CO2e per person per year.

The food we eat makes a big impact on our overall carbon footprints. Earlier in this project, I ran eight different experiments to cut carbon from my food. Here's what I found. All figures are for carbon dioxide and equivalent emissions (CO2e) per person per year.

  • Average Australian diet. Embedded emissions in the average Australian diet are around 1.4 tonnes CO2e plus another 500 kilograms CO2e for food waste.
  • Vegan. A vegan diet cut 973 kilograms CO2e from the average. This was by far the most effective carbon reduction that I trialled.
  • Vegetarian. A vegetarian diet with fish and dairy cut 451 kilograms CO2e from the average.
  • Food waste. Most people claim they never waste food but everyone does (even if you never put food in the bin). The average Australian can cut 100 kilograms CO2e by following simple steps to reduce food waste. Systemic change would save more.
  • Intermittent fasting. Intermittent 5:2 fasting cut 357 kilograms CO2e from the average, but only when fast days were plant-based with a little egg, fish or chicken. A fast day containing steak emitted more CO2e than a feast day.
  • Supermarket Swap. I made some smart swaps to the average diet and saved 643 kilograms CO2e. This revised diet still contained over 1 kilogram of dairy + 750 kilograms meat + 415 grams fish + 100 grams eggs per person per week. This shows that small, strategic steps towards a plant-based diet with some smart meat choices make big carbon savings.

What experiments failed to reduce CO2e?

I tried to cut CO2e by reducing plastic food packaging. This backfired. I could avoid plastics by shopping in specialty shops, but the extra short drive in my small car emitted more CO2e than I saved. Plastic packaging also reduces food waste by extending shelf life, so getting rid of it increases CO2e from food waste. Plastic packaging is light, contains little material and low embedded emissions. Most plastics are recyclable and the alternatives often aren't. For instance, cornstarch plastic is great if composted but generates methane in landfill if put in a bin, and ceramic food containers can't be recycled at all. Stripping the plastic from food does not save CO2e. It has caught the public eye and it's good for reducing marine litter, but it won't fight climate change.
 

'Eat local' is popular advice but I found it didn't stack up. Long-distance shipping and road freight to a supermarket are very efficient, but driving a passenger car to a farmer's market is inefficient. I analysed transport on a 20-kilogram load of food and found that shipping it from India to Sydney and then road-freighting it to Canberra emitted less CO2e than my car emitted on a 13.5-kilometre return trip. BUT we should all avoid air freight, which is very high in CO2e. Unfortunately, avoiding air freighted food is hard. I wrote to Coles, Aldi and Woolworths and none could advise which food travelled by plane.

Eat organic / eat grass-fed beef is also popular advice. I couldn't find data to back this up. Organic farming can decrease inputs like fertiliser, pesticide & concentrated feedstock. Organic soils may store more carbon. However, organic farming is usually lower yield per hectare which can increase CO2e. Some studies show a small benefit from organics (eg. 9% CO2e decrease) but a plant-based conventional diet will save more CO2e. Meat in general and beef in particular are very carbon-intense, regardless of how they are produced.

Animal-based foods generate more carbon than plant-based foods.

Should we all be vegan?

If the ACT went vegan, we'd save 412,000 tonnes CO2e per year. But we don't all have to be vegan to make big cuts. If we moved closer to a plant-based diet with some meat and dairy, like the Supermarket Swap above, we'd still save 264,000 tonnes CO2e per year.
 

Calculations, notes and references under 'Plant-Based is Best' at in the Notes section.

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