Abandoned shopping carts – pushed into hedges, dumped in rivers, or stranded on city streets – have become symbols of pollution and waste, and a new study shows just how bad for our planet they actually are.
The research was carried out in the UK, where these grocery carriers are known as trolleys, and around 520,000 of them are deserted annually. Recovering, repairing, or replacing derelict carts comes with a sizable environmental cost.
"Thousands of shopping trolleys are reported as abandoned in the UK every year," says materials engineer Neill Raath from the University of Warwick. "When you multiply the carbon impact of retrieving each one, it becomes both significant and concerning."
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Raath and his colleague, University of Warwick materials engineer Darren Hughes, calculated that the diesel required to retrieve all of these trolleys in vans adds up to 343 metric tons (378 US tons) of carbon dioxide – similar to the emissions involved in driving 80 petrol cars for a year.
If just 10 percent of those half a million trolleys also required refurbishing with a zinc coating, to prevent corrosion, those carbon emissions would almost double. And yet, recovery and refurbishment can massively reduce the cost to the planet of having to replace a shopping cart – by as much as 92–99 percent.
The researchers focused their attention on a suburban area in the city of Coventry, figuring out the environmental price of each trolley through its entire life cycle. Around 30 trolleys a week are recovered in the area, and roughly 100 a year need refurbishing.
As per the study's calculations, manufacturing one trolley has a global warming impact equivalent to 65.14 kg CO2, collecting and returning a trolley works out at 0.69 kg CO2, and transporting and refurbishing one equals 5.50 kg CO2.
"We found that one trolley would have to be collected 93 times by a diesel van to have the same environmental impact as manufacturing a new one," says Raath.
While recovering and repairing trolleys is clearly beneficial in terms of eco-friendliness, a much better option is to simply make sure they're returned in the first place – something to consider the next time you're shopping.
This is by no means a UK-only problem either, and the study cites other reports from Australia and South Africa about the impact of trolleys that aren't returned to their proper place after being used.
And these carbon dioxide calculations are just the start of the issue: abandoned carts represent safety risks to pedestrians and motorists, cause pollution and waste to build up in waterways, and turn public spaces into eyesores.
The researchers want to see more done to reduce the number of shopping trolleys abandoned – perhaps with increased use of CCTV or more physical barriers – as well as future research on materials and processes that are kinder to the environment.
"While it is unlikely that we can ever stop trolleys being abandoned, we hope that next time people see a trolley in an alley or park bush, they'll consider the environmental impact of letting it go unused," says Raath.
The research has been published in Sustainability.