Should the environmental impact of sandwiches be improved?

Researchers at the University of Manchester have for the first time highlighted the carbon impact that sandwiches have on the environment, including data on the production and transport of ingredients, as well as of packaging and food waste.

The British Sandwich Association (BSA) reports that more than 11.5 billion sandwiches are eaten in the UK every year, with around half being eaten at home, and half being purchased over the counter, or ready-to-eat in pre-packaged containers. Considering the size of the marketplace, even minor improvements to carbon efficiency of the industry could have a monumental impact on emission levels, potentially saving the environment from thousands of tonnes of carbon being spewed into the atmosphere.

Analysing the impact

“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 University of Manchester School of Chemical Engineering and Analytical Sciences professor Adisa Azapagic, “consuming 11.5 billion sandwiches annually in the UK generates, on average, 9.5 million tonnes of CO2 eq., equivalent to the annual use of 8.6 million cars.”

According to the researchers, the largest contributor is the agricultural production and processing of ingredients, which for ready-made sandwiches can amount to 37%-67% of CO2 equivalent. Other contributing factors include keeping supermarket sandwiches chilled, which can equal up to a quarter of their emission output, and the cardboard cartons housing the meal, adding around 8.5% CO2 eq.

The BSA has also commented on labelling and sell/use-by dates, pointing out that if the shelf life of sandwiches was improved and expiry dates relaxed at least 2,000 tonnes a year of waste would be saved. Displaying meals for longer would put less of a strain on the agricultural processing, as fewer ingredients would need to be produced. The researchers also recommend omitting some of the more carbon-intensive ingredients, such as lettuce, tomato, meat, and cheese.

The study concludes that for ready-made sandwiches a total reduction in carbon impact of up to 50% is possible if better practice is adhered to.

Is home-made the answer?

Different sandwiches can have wildly different carbon impacts, depending on their ingredients. Of all the varieties the researchers analysed, ready-made ‘all-day breakfast’ options had the highest impact, with the egg, bacon and sausage contents contributing to a CO2 equivalent of driving a car for 12 miles. The study reads that: “The carbon footprint of a ready-made sandwich ranges from 739g CO2 eq. for egg & cress to 1441g CO2 eq. for the breakfast option.”

It also appears as though simply making a sandwich at home rather than purchasing one in a shop can dramatically reduce carbon impact, with the study going on to read: “The carbon footprint of the most popular home-made sandwich (ham & cheese) varies from 399g to 843g CO2 eq. per serving. The average impact from the home-made option (609g CO2 eq.) is 2.2 times lower than the impact from the commercial equivalent with the same ingredients (ham, cheese and mayonnaise).”