Ah the sandwich, a solid lunch staple of many Brits. But it turns out the 11.5 billion sandwiches that are consumed each year in the UK have quite the environmental impact.
Researchers at the University of Manchester have carried out the first-ever study looking at the carbon footprint of sandwiches – both home-made and pre-packaged – tucking into 40 different types, recipes and combinations.
The whole life cycle of sandwiches was examined, including the production of ingredients, sandwiches and their packaging, as well as food waste discarded at home and elsewhere in the supply chain.
So which sandwich fillings were the worst offenders? And with the UK spending nearly £8bn a year on these popular eats, what can supermarkets and retailers do to cut down on carbon?
Step forward sandwiches with pork meat (bacon, ham or sausages) and those containing cheese or prawns – these have the highest carbon footprints.
But when it comes to recipes, the most carbon-intensive variety is a ready-made ‘all-day breakfast’ sandwich, which includes egg, bacon and sausage. It is estimated to generate CO2 emissions that are equal to driving a car for 12 miles.
The sandwich with the lowest carbon dioxide equivalent was the humble ham and cheese.
“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, from the university’s School of Chemical Engineering and Analytical Sciences.
“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.”
Science 101: what does C02 eq. mean?
- The C02 eq., or carbon dioxide equivalent, is a term used to refer to greenhouse gases as a whole
- Though people tend to think of greenhouse gases as simply carbon dioxide, there are a number of other chemical compounds that contribute, and each has a different magnitude of effect per tonne
- To make things nice and neat, the C02 eq. indicates the global warming impact of all those greenhouse gases in terms of carbon dioxide. Have a Trivial Pursuit wedge on us
So what is causing this carbon overload?
Agricultural production and processing of ingredients are the biggest culprits, and depending on the type of food, can account for around 37% to 67% of CO2 eq. for ready-made sandwiches.
Keeping sandwiches chilled in supermarkets and shops also contributes and are responsible for a quarter of their greenhouse gas emission equivalent.
Then there is the packaging material, which comes in at up to 8.5 %. Finally, transporting materials and refrigerating sandwiches themselves add a further 4%.
How can retailers and manufacturers alter sandwiches to cut the carbon?
A combination of things, like changes to recipe, packaging and waste disposal, could reduce the carbon footprint by as much as 50%, according to the study.
Specifically, it recommends reducing or omitting certain ingredients that have a higher carbon footprint, like lettuce, tomato, cheese and meat. Bye bye BLT…
But more realistically, extending the sell-by and use-by dates to reduce waste could be an easy way to reduce the carbon footprint, the study says.
“We need to change the labelling 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,” Professor Azapagic said.
The British Sandwich Association agrees. It estimates that extending the shelf life of sandwiches would help save at least 2,000 tonnes of sandwich waste annually.
Well, that’s something to get your bread around…
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