Although countries hurry to make the switch to green vehicles and alternative fuels, such as electricity and hydrogen, a new study of car use in Japan shows that, even with gasoline vehicles, keeping and using cars with good fuel efficiency longer could reduce CO2 emissions significantly more than an accelerated transition to alternative fuel vehicles.
“The faster you replace a car, the more CO2 it emits. It’s no different with electric cars, because when the demand for new cars increases, it shoots up manufacturing emissions,” says Shigemi Kagawa, professor of Kyushu University’s Faculty of Economics and leader of the study.
In Japan, car replacement tends to be quick. The average life expectancy of a car, from factory to its end in a scrapyard, is around thirteen years. Moreover, the average length of ownership of a new car by its first owner is seven years.
Kagawa explains that we need to diligently look at the supply chain to maximize carbon reductions.
“The carbon footprint of a car goes far beyond just the fuel it uses. To produce alternative fuel cars intended to reduce emissions from driving, you need iron, nuts, and bolts for construction, factories for assembly, and mega-containerships for transport. All these points in the supply chain produce CO2.”
An approximate 9% of Japan’s total GHG emissions is attributed to cars; and of that fraction, about 40% is due to gasoline combustion from driving new cars and 24% due to their manufacturing.
Using economic statistics, Kagawa’s group conducted a case study of newly registered and used cars in Japan between 1990 and 2016. The group modeled how replacement behavior of car owners affects their carbon footprint. Their modeling shows that, if cars had been kept 10% longer before being scrapped, the cumulative carbon footprint from cars would have decreased by 30.7 million tonnes, or 1%, during this period. This is because the decrease in manufacturing emissions more than offsets additional emissions produced by existing cars.
“What this means is that we can reduce CO2 emissions just by keeping and driving cars longer,” concludes Kagawa. “Moreover, if the car we keep is relatively new and fuel-efficient, the effect is greater. So the next time you are thinking of getting a new car, perhaps consider if your current car has a few more kilometers left in it.”