Methodology

Food numbers are kilograms of CO₂-equivalent per kilogram of food, from Poore & Nemecek's 2018 study via Our World in Data. They're global averages across the whole chain: land, farm, feed, processing, transport, retail, packaging.

CO₂-equivalent rolls methane and nitrous oxide into one figure, so a kilo of beef and a kilo of apples sit on the same scale.

The “everyday choices” rounds turn those numbers into one serving or one trip — a 150 g burger, 10 km on a bus — using DEFRA's 2022 transport factors. Each item spells out the portion or distance it used.

None of this is exact. Footprints swing with farm, region and method, so read the values as the shape of things, not a verdict to three decimals. Full citations live on the sources page.