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Startling evidence as to just how bad packaged food can be in terms of carbon emissions. Researchers from the University of Manchester have found that pre-packaged sarnies containing cheese, prawns or pork – such as bacon, ham or sausages – are bad news for the environment. And the worst is the ‘all-day breakfast’ sandwich featuring egg, bacon and sausage which generates 1,441 grams of carbon dioxide equivalent (CO₂ eq.) – roughly the same emissions as driving a car for 12 miles.

Sandwiches made in house are better for the planet, the researchers found, with the humble ham and cheese sarnie proving to be most environmentally-friendly of the nation’s favourites. Specifically a sandwich made from 58g of bread, 8g of ham, 20g of cheese and 13g of mayo.

The study considered the carbon footprint of 40 home-made and pre-packaged sandwiches, and looked at the whole life cycle of sandwiches: from the production of ingredients and packaging, to food waste. The most significant finding was that making your own sandwiches at home can reduce carbon emissions by a half. The difference primarily comes down to the transport miles.

Some of the largest contributors to a sandwich’s carbon footprint are: agricultural production, processing ingredients, keeping sandwiches chilled in supermarkets and shops, packaging material and transporting materials. In ready-made sandwiches in particular, researchers recommend avoiding ingredients that have a higher carbon footprint such as lettuce, tomato, cheese and meat.

The worst sandwiches in terms of carbon footprint

1. Ready-made all day breakfast: 1,441 CO₂eq.
2. Ready-made ham and cheese: 1,350 CO₂eq.
3. Ready-made prawn and mayo: 1,255 CO₂eq.
4. Ready-made egg and bacon: 1,182 CO₂eq.
5. Ready-made ham salad: 1,119 CO₂eq.

According to the British Sandwich Association (BSA) more than 11.5 billion sandwiches are consumed each year in the UK alone. Around half of those are made at home with the rest bought in shops, supermarkets and service stations.

That means the UK spends nearly £8 billion a year on them, at an average cost of £2 per snack.

Professor Adisa Azapagic, from University of Manchester’s School of Chemical Engineering and Analytical Sciences, said: “Given that sandwiches are a staple of the British diet as well as their significant market share in the food sector, it is important to understand the contribution from this sector to the emissions of greenhouse gases.”

She said consuming 11.5 billion sandwiches annually in the UK generates, on average, 9.5 million tonnes of CO₂ eq. This is equivalent to the annual