In March, Joe Hollingsworth hopped on a Lime scooter and zipped across the campus of North Carolina State University. At the end of the ride, a message appeared on the screen: “Your ride was carbon free.”
The pronouncement embodied the climate-friendly marketing of e-scooter companies like Lime and Bird. But it puzzled Hollingsworth, then a graduate student in environmental engineering, and his advisor, Jeremiah Johnson.
Sure, scooters don’t have a tailpipe. “But you have to think about the other things that are required to have the scooter ready, charged and available for you to use,” Johnson said.
So he and his students decided to tally up the full environmental impact of electric scooters over their lifetimes. The results, published last week in the journal Environmental Research Letters, suggest that e-scooters aren’t quite as eco-friendly as they may seem.
While traveling a mile by scooter is better than driving the same distance by car, it’s worse than biking, walking or taking a bus — the modes of transportation that scooters most often replace. That’s primarily because of the energy-intensive materials that go into making the vehicles, and because of the driving required to collect, charge, and redistribute them.
“That actual trip somebody’s taking on the scooter — that’s pretty green,” said Juan Matute, the deputy director of the UCLA Institute of Transportation Studies who was not involved with the study. “What’s not green is everything you don’t see.”
Dockless e-scooters, which you can unlock with an app and leave wherever you please, have flooded cities over the last year and half.
So Johnson and his students purchased a Xiaomi M365 scooter, which was used for the first generation of Birds, and took it apart. They made precise measurements of each component’s weight and calculated the greenhouse gas emissions associated with making it. They also looked at the resulting air and water pollution.
Those impacts were significant, the researchers found, especially for the scooter’s 13-pound aluminum frame and its 2-pound lithium ion battery. Using their best estimates about scooter use and management in Raleigh, N.C., they found that materials and manufacturing accounted for roughly half of its global warming impact and an even greater proportion of its other pollution footprints.
Those results depend heavily on scooter longevity, which influences how many rides companies can get out of those parts. And urban life is hard on shared e-scooters.
The other big environmental cost associated with scooters comes from the laborious process of collecting, charging and redeploying them each night.
Based on their estimates for Raleigh, Johnson and his colleagues found that the nightly collection and redistribution of scooters accounted for 43% of their overall global warming impact. Electricity for charging the scooters represented just 5%, and shipping even less.
Scooters could come out on top in cities where a larger fraction of riders used them as a substitute for driving. And there are ways to reduce the environmental impacts.
When asked about the study, both Bird and Lime reiterated their commitment to sustainability.
A spokesperson for Lime said the company welcomed the new research, but added that the study is “largely based on assumptions and incomplete data that produces high variability in the results.”
Melinda Hanson, Bird’s head of sustainability, said the company is confident that its scooters can play a role in combating climate change. “We can only hope that other transportation providers similarly consider their own environmental impact and help do what is necessary to address this crisis,” she said.