It’s a staple of the British diet and a popular choice for a quick and easy lunch. But new research reveals the carbon footprint of the humble sandwich could be fuelling harmful greenhouse emissions.

The worst offender is revealed as the ready-made “all-day breakfast” sandwich, crammed with egg, bacon and sausage.

Researchers at the University of Manchester carried out the first ever study of the carbon footprint of sandwiches – both home-made and ready-made. They considered the entire life cycle of sandwiches, including the production of ingredients, packaging, refrigeration and food waste.

The team scrutinised 40 different sandwich types, recipes and combinations and found the highest carbon footprints for the sandwiches containing pork meat (bacon, ham or sausages) and also those filled with cheese or prawns.

The researchers estimate that a ready-made (and highly calorific) all-day breakfast sandwich generates 1441g of carbon dioxide equivalent – equal to the emissions created by driving a car for 12 miles (19km).

The study found a home-made ham and cheese sandwich could have the lowest carbon footprint, depending on the recipe. The study also found that making your own sandwiches could reduce carbon emissions by half compared to shop-bought versions.

Keeping sandwiches chilled in supermarkets and shops also adds to their carbon footprint, accounting for up to a quarter of their greenhouse gas emission equivalent. Packaging comes in at up to 8.5% and, finally, transporting materials and refrigerating sandwiches adds a further 4%.

According to the British Sandwich Association, more than 11.5bn sandwiches are consumed each year in the UK alone. About half of those are made at home and the other half are bought over the counter in shops, supermarkets and service stations around the country. The UK spends nearly £8bn a year on sandwiches, at an average cost of £2.

“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,” said Professor Adisa Azapagic, one of the authors of the paper. “For example, consuming 11.5bn sandwiches annually in the UK generates, on average, 9.5m tonnes of CO2, equivalent to the annual use of 8.6m cars.”

The study also recommends reducing or omitting certain ingredients that have a higher carbon footprint, like lettuce, tomato, cheese and meat. Reducing ingredients such as cheese and meat would also reduce the amount of calories eaten, contributing towards healthier lifestyles.

The ready-made worst offenders

Total carbon footprint (grams of CO2 equivalent per sandwich)

All-day breakfast 1,441

Ham and cheese 1,350

Prawn and mayonnaise 1,255

Egg and bacon 1,182

Ham salad 1,119

Cheese ploughman’s 1,112

Sausage and brown sauce 1,087

Double cheese and onion 1,078

Cheese and tomato 1,067

Roast chicken and bacon 1,030