Whether you make your sandwich or buy it from a shop could have a major impact on greenhouse gas emissions. Little was known about the environmental impacts of the humble sandwich until a comprehensive study of the carbon footprint of sandwiches was conducted.
The new research studied both home-made and pre-packaged, and took into consideration the whole life cycle of the sandwiches. This included the production of the ingredients, their packaging, and food waste discarded at home and elsewhere in the supply chain.
The study found those sandwiches with pork meat (bacon, ham, or sausages) and those containing cheese or prawns had the highest carbon footprints. A sandwich that included egg, bacon, and sausage (all-day breakfast) was the most carbon-intensive.
This type of sandwich generates 1441 grams of carbon dioxide equivalent (CO2 eq.). This is the same as the CO2 emissions of a car driving for 12 miles. The researchers looked at 40 different types of sandwiches, their recipes, and different combinations.
It’s not all bad; the simple home-made ham and cheese sandwich had the lowest carbon emission. In fact, if we all made sandwiches at home, we could reduce carbon emissions by a half when compared to the ready-made equivalents.
According to the British Sandwich Association (BSA) (yes there is an association for sandwiches), in the UK alone there are more than 11.5 billion sandwiches consumed each year. Half are homemade, the other half are pre-packaged from shops, supermarkets, and service stations.
This means the UK spends nearly £8 billion a year on sandwiches, at an average cost of £2 per snack. Professor Adisa Azapagic, from the School of Chemical Engineering and Analytical Sciences and the study author, said in a statement:
“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.
“For example, 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.”
The largest contributor to its carbon footprint is in the agricultural production and the processing of the ingredients. Depending on the type of production and processing, this could account for around 37%-67% of CO2 eq. for ready-made sandwiches.
Shops and supermarkets keep sandwiches chilled in refrigerators, which also contribute to their carbon footprint, increasing up to a quarter of their greenhouse gas emission. The packaging material adds a further 8.5 percent, and then there is the transportation of everything, adding another 4 percent.
Not all is lost; the carbon footprint could be reduced by as much as 50 percent if changes were made to the recipes, packaging, and waste disposal. It has also been suggested that extending sell-by and use-by dates could significantly reduce waste. Azapagic explained:
“We need to change the labeling of food to increase the use-by date, as these are usually quite conservative.
“Commercial sandwiches undergo rigorous shelf-life testing and are normally safe for consumption beyond the use-by date stated on the label.”
By extending the shelf life of sandwiches, the BSA estimates that it would help save at least 2,000 tons of sandwichs wasted every year. The study goes further, recommending reducing or even omitting certain ingredients, such as lettuce, tomato, cheese, and meat.
The study authors believe by reducing ingredients like cheese and meat, it would contribute to healthier lifestyles by reducing the number of calories eaten.