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. They considered the whole life cycle of sandwiches, including the production of ingredients, sandwiches and their packaging, as well as food waste discarded at home and elsewhere in the supply chain.
‘The carbon footprint of these sandwiches can be reduced by 50 percent, if some combination of changes were made to the recipes, packaging and waste disposal. Extending sell-by and use-by dates can also help reduce waste created by these sandwiches.’
Altogether the team looked at 40 different sandwich types, recipes and combinations. They found the highest carbon footprints for the sandwiches with pork meat (bacon, ham or sausages) and those containing cheese or prawns
Of the recipes considered, the most carbon-intensive variety is a ready-made 'all-day breakfast' sandwich which includes egg, bacon, and sausage. The researchers estimate that this type of sandwiches generates 1441 grams of carbon dioxide equivalent (CO2 eq.). This is equivalent to CO2 emissions from driving a car for 12 miles.The sandwich with the lowest carbon emission equivalent is a simple home-made favorite, ham, and cheese
The study also found that making your own sandwiches at home could reduce carbon emissions by a half compared to ready-made equivalents.
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 and the other half are bought over the counter in shops, supermarkets and service stations around the country. That means the UK spends nearly Ģ8 billion a year on the breaded snack, at an average cost of Ģ2 per snack.
Professor Adisa Azapagic, from the 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.
'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 results show the largest contributor to a sandwich's carbon footprint is the agricultural production and processing of their ingredients. Depending on the type, this can account for around 37%-67% of CO2 eq. for ready-made sandwiches.
Keeping sandwiches chilled in supermarkets and shops also contributes to their carbon footprint. This can account for up to a quarter of their greenhouse gas emission equivalent. Then there is the packaging material which comes in at up to 8.5 % and, finally, transporting materials and refrigerating sandwiches themselves adds a further 4%.
The study concludes that the carbon footprint of the snacks could be reduced by as much as 50 percent if a combination of changes were made to the recipes, packaging and waste disposal. The researchers also suggest extending sell-by and use-by dates to reduce waste.
Professor Azapagic, who also heads up the Sustainable Industrial Systems research group, added: '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.'
The BSA also estimate that extending the shelf life of sandwiches by relaxing such dates would help save at least 2000 tonnes of sandwich waste annually.
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 number of calories eaten, contributing towards healthier lifestyles.