In the words of the activist and author Michael Pollan: “Eat food. Not too much, mostly plants.” He was talking about healthy living but the message is the same if we want to save the planet.

Working out which foods carry the smallest carbon footprint is the tricky bit. So much depends on the way in which food is grown or reared, and how it is transported and packaged. Then there is the question of “embedded emissions”, meaning those arising from food production by-products, such as fertilisers for crops or fodder for meat. That is why definitive figures from the Department for Environment, Food and Rural Affairs for greenhouse emissions related to rabbit, venison and fish are still being worked out. This year, the Committee on Climate Change (CCC) and the Carbon Trust, which helps food companies to calculate products’ carbon footprints, reported on emissions created by some popular foods:

Lamb and beef With the highest carbon footprint of all UK foods assessed by the CCC, lamb creates 17kg of CO2 for every kilo of product. This is closely followed by beef, at 16kg per kilo of product. Ruminants (cattle and sheep) can graze land that is unsuitable for arable farming. The drawback is their flatulence. Flatulent farm animals create 14 per cent of global emissions of methane.

Pig meat and chicken Poultry and pigs fart less but their diet often contains soya, which may have been grown on deforested areas in the developing world. Pigs are more energy- intensive than poultry, emitting more than 6kg of CO2 per kilo of product.

Bread In contrast to meat, one kilo of bread produces less than one kilo of CO2. When the Carbon Trust assessed two Kingsmill loaves of bread, one white, one wholemeal, they both shared a carbon footprint of 1.3kg of CO2 per 800g loaf.

Tomatoes Most of the UK’s tomatoes are grown in heated glasshouses, which turns them into carbon-intensive vegetables. One kilo produces more than 9kg of CO2.

Potatoes For every 1kg of produce, they release only 450g of CO2.

Cadbury’s chocolate Less energy-intensive than meat but considerably more so than most UK vegetables. The Carbon Trust reports that for every 1kg of Cadbury’s chocolate, 2kg of CO2 is emitted.

Coca-cola A standard 330ml can of Coke embodies the equivalent of 170g of carbon dioxide, according to the Carbon Trust, while Diet Coke or Coke Zero produces 150g. This is less than the footprint created by smoothies from the eco-pioneering company Innocent. A 250ml mango and passion fruit smoothie has a carbon footprint of 209g, says the Carbon Trust.

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