Food Miles Calculator

Freight emissions are conventionally expressed per tonne-kilometre because the fuel a vehicle burns scales with both the mass it carries and the distance it covers, so multiplying payload in tonnes by distance in kilometres gives a quantity to which a single mode-specific factor can be applied. The factors used here follow the pattern found in DEFRA and GLEC freight guidance: about 0.008 kg CO2 per tonne-km for ocean container shipping, 0.022 for rail, 0.062 for a heavy goods vehicle, 0.150 for a light delivery van, and roughly 0.602 for air freight. The spread of nearly two orders of magnitude between ship and plane comes from the physics of the modes, since a container vessel moves thousands of tonnes at low speed against water resistance while an aircraft must expend energy continuously to generate lift. Temperature-controlled transport adds roughly 15 to 25 percent, modelled here as a flat 20 percent uplift. The critical limitation is that food miles are a poor proxy for the climate impact of food. Transport accounts for only about 5 to 10 percent of the greenhouse gas footprint of the average diet, while agricultural production and land-use change dominate. A tomato grown in a heated northern greenhouse can carry a larger footprint than one trucked 2,000 km from a field in a warm climate, and beef produced next door will outweigh almost any plant food flown across the world. The calculation also ignores load factor, empty return runs, and the emissions of the warehousing and refrigeration that sit between legs. It is most informative when comparing modes for the same commodity, particularly when the choice is between air freight and sea freight.

The phrase food miles was popularised in the early 1990s by Tim Lang, then working with the SAFE Alliance in London and later professor of food policy at City University. The idea was crystallised in the 1994 SAFE report The Food Miles Report, written by Angela Paxton, which argued that the growing distance between farm and plate carried hidden environmental and social costs. The metric spread quickly because it was intuitive and easy to communicate, and it became a standard talking point for local-food campaigns through the late 1990s and 2000s, appearing in supermarket labelling schemes and government sustainability indicators. Academic scrutiny then complicated the picture. In 2005 the UK Department for Environment, Food and Rural Affairs commissioned a report on the validity of food miles as a sustainability indicator, which concluded that distance alone was an inadequate measure and recommended mode-weighted accounting. A 2008 study by Christopher Weber and H. Scott Matthews of Carnegie Mellon University, published in Environmental Science and Technology, used input-output analysis of the US food system and found that transport contributed roughly 11 percent of household food emissions with final delivery to retail near 4 percent, while red meat and dairy production dominated. Subsequent life-cycle work reinforced that conclusion, and freight accounting moved toward tonne-kilometre frameworks such as the Global Logistics Emissions Council methodology first published in 2016.