‘How bad is your sandwich?’ ask scientists probing its carbon footprint
Image credit: All day breakfast sandwich
Professor who led investigation reveals she is “not a fan” of sandwiches – but says her study is intended to raise awareness of the issue of their CO2 impact.
Is your lunch killing the planet? Yes, if it consists of an all-day breakfast squashed between two slices of bread - but rather less so if it is a plain old ham and cheese sandwich that you put together at home.
That is one of the findings of the first ever comprehensive study of the carbon footprint of sandwiches.
University of Manchester researchers scrutinised the “life cycle” of 40 different sandwiches – both homemade and pre-packaged.
They considered all factors, including the production of ingredients, as well as packaging and food waste, and found that the most carbon-intensive variety was one containing a version of the ‘English breakfast’.
The researchers estimate that this type of sandwich generates on average 1,441 grammes of carbon dioxide equivalent (CO2 eq.), which apparently amounts to the same impact as driving a car for 12 miles.
Of the dozens of varieties studied, the sandwich with the lowest carbon footprint was found to be ham and cheese.
Professor Adisa Azapagic, who works in the university’s School of Chemical Engineering and Analytical Sciences and was co-author of the study, told E&T that she is “not a fan of sandwiches” – but she denied having any personal vendetta against them.
She said: “I don’t eat them regularly. I eat them if I can’t help it. I prefer salads and so on, but it’s just a preference.”
Sandwiches are one of the most ubiquitous food items globally and are particularly prevalent in Britain. Around 11.5 billion are consumed each year in the UK alone. However, their impact on the environment has hitherto been little understood.
Azapagic said cucumber sandwiches, a traditional English favourite, would probably have relatively little adverse environmental impact, particularly if the butter was left out.
Marmalade sandwiches, made famous by Paddington Bear, are also thought to be reasonably environmentally friendly.
The carbon impact of homemade sandwiches is typically two times lower than for shop-bought ones.
Excluding tomato and lettuce lowers the carbon footprint by 3.3 to 8.9 per cent and not using mayonnaise yields a further reduction of 1.7 to 8.4 per cent.
The study concluded there is no clear relationship between the nutritional value of sandwiches and their carbon footprint.
Substituting white with wholemeal bread leads to only a very marginal reduction in the carbon footprint.
Keeping sandwiches chilled in supermarkets and shops contributes to their carbon footprint and can account for up to a quarter of their greenhouse gas emission equivalent.
In her paper, entitled ‘Understanding the impact on climate change of convenience food: Carbon footprint of sandwiches’, Azapagic wrote that comparisons of two parallel “sandwich systems” – namely, homemade and shop-bought – can be made relatively easily.
The work was funded by the UK Research Councils.
Azapagic told E&T: “What we are saying is, these are the facts. What can you do about it if you are so inclined? Well, first of all you could start making your own sandwiches, because immediately you will halve the impact compared with the commercial sandwich.
“You could be making those sandwiches using leftovers, which also means you would be reducing household food waste, which is a big issue.
“This is all about awareness raising. It isn’t dogmatic.”
A change to the labelling of food to increase use-by dates could help make sandwiches more environmentally sustainable, Azapagic added.
The earliest formal mention of the sandwich dates back to 1762, when the English historian Edward Gibbon called bits of cold meat “sandwiches”, after John Montagu, the 4th Earl of Sandwich who preferred to eat his food in this form so that he could continue playing without leaving the gaming-table.
Earlier this month it was suggested microwaves could be as bad for the environment as cars – something that will come as bad news for people who microwave their sandwiches, as is a custom in certain parts of Holland.