Compile / Wenlong
For a long time, electric vehicle manufacturers have been promoting energy conservation and emission reduction. However, some analysts have expressed concern about how green the ev industry actually is. They argue that indirect emissions from electricity and battery production are likely to increase, and that these emissions are not only large but often overlooked.
But a recent study by the Yale School of the Environment, published in Nature Communications, found that the total amount of indirect emissions from electric vehicles pales in comparison to the indirect emissions of fossil fuel vehicles. This is in addition to the direct emissions from burning fossil fuels, that is, whether from the exhaust pipe of the car or from the chimney of the power plant, the data shows that electric vehicles have a clear advantage over internal combustion engine vehicles in terms of emissions.
The indirect emissions of electric vehicles are lower than those of fuel vehicles
The research team combined energy modelling with life cycle assessment and found that carbon emissions are still reduced when indirect emissions from the EV supply chain are taken into account. According to the technology in 2020, the electricity required for each electric vehicle to travel 1 kilometer generates about 66-86g of CO2; the vehicle produces about 16-38g of CO2 per kilometer.
It was only recently recognized that emissions from gasoline production vary widely from less than 15 to about 320 g CO2/kWh compared to direct (exhaust) emissions per kilometer of about 250 g CO2. Overall, indirect emissions account for about 26% of the 1.5 Gt CO2 generated by U.S. light vehicles in 2020.
"Surprisingly, emissions from electric vehicles have dropped a lot," says Stephanie Weber, a postdoctoral assistant, "and the supply chain for internal combustion engine vehicles is so 'dirty' that electric vehicles cannot surpass them, even when indirect emissions are taken into account."
(Linking the LCA model to a simplified representation of the national energy modeling system NEMS)
The research team collected data using the National Energy Modeling System (NEMS) created by the U.S. Energy Information Administration, which modeled the entire U.S. energy system using details of the current U.S. domestic energy system and projections for the future of the power system.
Among them, PhD student Pual Wolfram completed a life cycle assessment that provided indirect emissions outputs and then inserted them into the NEMS model to understand how a carbon tax on these indirect emissions would change the behavior of consumers and manufacturers.
It is worth mentioning that the research team includes Ken Gillingham, a professor of economics at Yale University, and Edgar Hertwich, a professor of industrial ecology from the University of Maryland, and the carbon pricing, life cycle assessment, and energy system modeling used in the study come from concepts in energy economics and industrial ecology, respectively.
Carbon pricing is expected to boost the electric vehicle market
California has introduced low-carbon fuel standards to regulate all fuel and electricity production and combustion emissions, while indirect emissions are not included in the regulatory scope. So the team explored the actual average fuel economy of U.S. light vehicles when pricing all emissions and direct emissions only.
(Fully priced and direct emissions only, the actual average fuel economy of u.S. light vehicles.) ）
The results show that when full-life cycle emissions are priced, the accelerated popularity of battery electric vehicles makes the average fuel economy of full pricing higher than that of direct emissions pricing. However, side cases with a higher share of hydrogen fuel cell electric vehicles showed significantly lower average fuel economy.
(By 2050, full pricing will result in changes relative to direct emissions pricing.) Gray indicates growth, and green indicates decrease. ）
Gillingham explains: "One of the main concerns about electric vehicles is that supply chain emissions, including the extraction and processing of raw materials and the manufacture of batteries, are considered far from being 'clean'. As a result, many people think that if the carbon contained in these processes is priced, electric vehicles are expected to be very expensive. But that's not the case: If you also balance the playing field by pricing carbon in the supply chain of fossil fuel vehicles, EV sales will actually increase."
In addition, the study also considers future technological changes, such as the continued decarbonization of the electricity supply, which will strengthen the outcome of the dominance of electric vehicles when considering indirect emissions. Research shows that the United States and other countries with low-carbon grids should aim to deploy battery electric vehicles.