Researchers at Kyushu University have found that Japan's current policy of stopping the sale of gas vehicles by 2035 and transitioning only to hybrids and electric vehicles may be insufficient to reduce the country's CO₂ emissions and prevent it from reaching its decarbonization target goals. In fact, emissions may temporarily increase.

The team's analysis showed that along with the policy, the Japanese government must simultaneously work to increase the production of clean energy, decarbonize the manufacturing process, and extend vehicle lifetime.

In the effort to combat the climate crisis, most countries in the world have implemented policies that reduce their production of greenhouse gases, such as CO₂, and Japan is no different. One such policy is banning the new sale of fossil fuel-powered vehicles. The country is working to ban the sale of new gas vehicles by 2035 and move only to sell EVs, HVs, FCVs, electric vehicles, hybrid vehicles, and fuel cell vehicles, respectively.

While this is a move in the right direction, Professor Shigemi Kagawa from Kyushu University's Faculty of Economics reports in his new paper, published in the Journal of Cleaner Production, that banning new gas vehicles may not be enough to reach Japan's decarbonization goals.

"Our team focused on how much CO₂ is produced during a car's entire lifetime, from the first resource extracted from the earth to when it gets destroyed. Looking at the lifecycle CO₂, or LC-CO₂, of a car allows us to take a larger view on a car's emissions," explains Kagawa.

The team found a number of policy points that need to be addressed, including decarbonizing the supply chain, improving the country's energy mix, and extending vehicle lifetime.

"Just building a car is energy intensive. All the building materials need to be mined, processed, shipped, and constructed. Every part of that process produces CO₂," Kagawa continues. "Construction of an EV can produce 1.5 to 2 times more emissions compared to a gas car. If car manufacturers increase their production of EVs without decarbonizing the supply chain, then emissions reduction will stagnate."

Moving Japan's energy mix to more renewable sources is also a vital step in this process. A country's energy mix is the ratio of fuel sources it uses to make electricity. In 2020, Japan's energy mix was 76% fossil fuels and 20% renewables. So, even if everybody switched to EVs the energy required to charge such vehicles still results in fossil fuel emissions.

"Japan's planned 2030 energy mix is 50% fossil fuels and 28% renewable energy. That will not adequately reduce LC-CO₂. The EV policy starting in 2035 aims to contribute to a 10% reduction or 2.9 Mt (million tons) of CO₂ in vehicle emissions in 2050. This reduction level falls far short of achieving a carbon-neutral vehicle society," explains Kagawa.

More information: Minami Kito et al, Environmental consequences of Japan's ban on sale of new fossil fuel-powered passenger vehicles from 2035, Journal of Cleaner Production (2024). DOI: 10.1016/j.jclepro.2024.140658