Calculating the environmental cost of a meal

Large institutions, caterers and home cooks will be able to confidently calculate the environmental impact of their menus thanks to a collaborative project between researchers in Australia and the UK.

The work by researchers from RMIT and Lancaster University has produced a carbon footprint ‘league table’ for fresh food, with a clear greenhouse gas emissions hierarchy emerging across food categories

Grains, fruit and vegetables were found to have the lowest impact, followed by nuts and pulses. Non-ruminant meat such as chicken and pork had a medium impact, as did fish when calculated as an average across all species, although results between species varied significantly. The highest environmental impact came from ruminant animals with multiple guts, such as beef and lamb.

The authors had worked with a residential aged care organisation to help reduce their greenhouse gas emissions. A key finding was that the food served to residents contributed to a large portion of the environmental impact, prompting the attempt to understand more clearly the global warming potential of differing foods.

The authors have produced a simple list to illustrate how much — or how little — it takes for different foods to contribute 1 kg of greenhouse gas emissions:

• 5.8 kg onions (about 50 medium onions)
• 3.5 kg apples (about 20 medium apples)
• 2.6 kg oats
• 1 kg lentils
• 1.2 kg peanuts
• 800 mL milk
• 290 g salmon
• 290 g eggs (about five small eggs)
• 270 g chicken
• 244 g kangaroo
• 212 g rabbit
• 131 g Australian pork
• 44 g Australian beef
• 57 g Australian lamb

Associate Professor Karli Verghese said the study was the largest and most comprehensive examination of its kind, providing the first global league table for fresh food.

“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,” said Professor Verghese.

Dr Stephen Clune, from Lancaster University, said that while it was impractical to replace beef with onions, the study showed that replacing it with other meats or plant-based protein sources would lower the environmental impact.

The paper, ‘Systematic review of greenhouse gas emissions for different fresh food categories’, has been published in the Journal of Cleaner Production.