With new major spending packages in the United States investing billions of dollars in electric vehicles, some analysts are raising concerns about how green the industry is, focusing specifically on indirect emissions caused by vehicle component supply chains and the fuels used to power the electricity that charges the vehicles.
However, according to a recent study published in Nature Communications by the Yale School of Environment, the total indirect emissions from electric vehicles pale in contrast to the indirect emissions from fossil fuel-powered vehicles.
This is in addition to direct emissions from the combustion of fossil fuels, which are emitted either at the tailpipe for conventional vehicles or at the power plant smokestack for electricity generation, demonstrating that electric vehicles have a clear emissions advantage over conventional vehicles.
“The surprising element was how much lower the emissions of electric vehicles were,” says postdoctoral associate Stephanie Weber. “The supply chain for combustion vehicles is just so dirty that electric vehicles can’t surpass them, even when you factor in indirect emissions.”
Weber was part of a team that included YSE economics professor Ken Gillingham and Edgar Hertwich, an industrial ecologist from the Norwegian University of Science and Technology and a former YSE faculty member, and was led by Paul Wolfram ’21 Ph.D., now a postdoc with the Joint Global Change Research Institute at the University of Maryland.
To see if carbon emissions were still reduced when indirect emissions from the electric vehicle supply chain were taken in, the research team blended concepts from energy economics and industrial ecology carbon pricing, life cycle assessment, and modeling energy systems.
The surprising element was how much lower the emissions of electric vehicles were. The supply chain for combustion vehicles is just so dirty that electric vehicles can’t surpass them, even when you factor in indirect emissions.
Stephanie Weber
“A major concern about electric vehicles is that the supply chain, including the mining and processing of raw materials and the manufacturing of batteries, is far from clean,” says Gillingham.
“So, if we priced the carbon embodied in these processes, the expectation is electric vehicles would be exorbitantly expensive. It turns out that’s not the case; if you level the playing field by also pricing the carbon in the fossil fuel vehicle supply chain, electric vehicle sales would actually increase.”
The study also took into account future technological progress, such as decarbonization of the electrical supply, and concluded that when indirect supply chain emissions are taken into account, electric vehicles come out on top.
The research team acquired data using the Energy Information Administration’s National Energy Modeling System (NEMS), which simulates the whole US energy system using precise data from the existing domestic energy system and a forecast of the electric system’s future.
Wolfram did a life cycle assessment, which resulted in indirect emission outputs that were then entered into the NEMS model to determine how a carbon price on these indirect emissions might affect consumer and manufacturing behavior. Weber aided with the modification of the NEMS code.
The study reveals that “the elephant in the room is the supply chain of fossil fuel-powered automobiles, not that of electric vehicles,” according to Wolfram. He points out that, at least in countries with a sufficiently decarbonized electrical supply, such as the United States, the faster we move to electric vehicles, the better.
This research, according to Gillingham, provides a clearer understanding of how to complete carbon pricing, which includes the entire supply chain, might shift consumers toward electric vehicles. Gillingham’s research has concentrated heavily on alternative energy adoption in transportation.
