Shared “stand-up” electric scooters are now being offered in many large cities as an option for short-term rental, and marketed for short-distance travel. Companies that distribute shared e-scooters tout the “environmental benefits of getting people out of cars” and “onto something that is battery-powered and emissions-free.” To determine whether the scooters are in fact a “green” form of transport, researchers at North Carolina State University disassembled a scooter in their lab and calculated what it took to produce it. Aluminum (in the scooter frame) and lithium (in the necessarily large battery) must be mined, and all the vehicle’s components must be manufactured. All this accounts for about half the greenhouse gases an e-scooter is advertised “to save,” over its lifetime. Adding up the environmental costs of collecting discarded scooters, transporting them to charging stations, maintenance of the e-scooters to keep them in service — and disposal, when old or damaged beyond repair — amounts to far more than the other half of greenhouse gases that e-scooters are supposed “to save.”
Using life cycle assessment, authors [see attached article] quantified the total environmental impacts of this mobility option associated with hypothetical “global warming,” “ocean acidification,” “eutrophication” (excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life due to lack of oxygen), and “respiratory impacts.” Authors found that environmental burdens — associated with charging the e-scooter — are small, relative to materials and manufacturing burdens of the e-scooters and the impacts associated with transporting the scooters to overnight charging stations (which of course use electricity). Results of a Monte Carlo analysis show an average value of life cycle global warming impacts of 202 grams of CO2-equivalents/passenger-mile, driven by materials and manufacturing (50%), followed by daily collection for charging (43% of impact).
Authors illustrated the potential to reduce life-cycle global warming impacts through improved scooter collection and charging approaches — including the use of fuel-efficient vehicles for collection (yielding 177 grams of CO2-equivalents/passenger-mile), limiting scooter collection to those with a low battery state of charge (164 grams of CO2-equivalents/passenger-mile), and reducing the driving distance per scooter for e-scooter collection and distribution (147 grams of CO2-equivalents/passenger-mile). The results prove to be highly sensitive to e-scooter lifetime; ensuring that the shared e-scooters are used for 2 years — decreases the average life cycle emissions to 141 grams of CO2-equivalents/passenger-mile. Under their Base Case assumptions, authors found that the life-cycle greenhouse gas emissions associated with e-scooter use is higher, by 65%, of their Monte Carlo simulations — than the suite of modes of transportation that are displaced. This likelihood drops to 35%–50%, under their proposed improved and efficient e-scooter collection processes, and drops to only 4% when one can assume 2-year e-scooter lifetimes.
When e-scooter usage replaces average personal automobile travel, authors nearly realize a net reduction in environmental impacts. However, using an e-scooter is more carbon-intensive than walking or biking. The scooters are environmentally friendly — only when people use them for trips they would otherwise take in cars. So — with e-scooters, it’s the same story as with solar panels, wind turbines, and electric cars: everyone feels “warm and fuzzy” about using “green energy” and keeping carbon out of the atmosphere, but the undesirable effects (of these sources of energy) on our environment actually far outweigh those using fossil fuels instead. And the benefit-to-risk ratio for atomic power energy is far better than that for fossil fuel energy. 😊
DwN
Environ Res Sci 2019; 14: 084031