Although the use of electric scooters on public roads falls into a legal grey area here in Ireland, it is possible to purchase or rent one. Aside from being handy for short urban commutes, the selling point is how climate-friendly they are. Dublin-based e-scooter rental firm Lifty, for example, declares: "We aim to leave future generations with a cleaner, healthier planet." San Francisco-based Lime issues receipts to scooter renters stating: "Your ride was carbon free."

Not so fast. Researchers at the University of North Carolina in the US carried out a "life-cycle assessment" of these vehicles to determine their carbon emissions when taking into account how they're manufactured, how long they last, and even how the rental company collects them. They found that in 65 per cent of cases, the carbon emissions for e-scooter use was higher than the mode of transport it replaced. Daily collection for transport back to charging stations, for example, accounted for 43 per cent of overall carbon footprint.

A survey of e-scooter users in North Carolina found that most of the time people were not renting them in place of driving or grabbing an Uber: 49 per cent admitted they would have walked or biked (zero carbon footprint) while 11 percent would have used public transport. iopscience.iop.org