Analysis reveals flaw in U.S. plan to cut vehicle emissions — and a possible fix

A new analysis by a group of university researchers finds that the United States will miss its recently set goal of reducing vehicle emissions by nearly 15 percent over the next decade because of unrealistic targets for increasing electric vehicle production. But adding hybrid vehicles to the mix could help.

The study, published in Nature CommunicationsThe U.S. will miss its 2032 electric vehicle sales target, a study has found, largely due to supply chain bottlenecks for critical minerals like graphite and cobalt. If these issues aren’t addressed, it would result in nearly 60 million tons of additional carbon dioxide emissions over the next eight years.

Megan Yeo ’25, a co-author of the paper and an economics researcher, said the team sought to break down the EPA’s tough new emissions targets and assess whether they were realistic.

“We first asked, ‘How many electric vehicles need to be sold to reach this goal?’ Then we looked at different scenarios,” said Yeo, who co-authored the study with Ashley Nunes, a senior research fellow at Harvard Law School, and first author Lucas Woodley ’23 and Chung Yi See ’22.

The researchers found that meeting the new standards would require replacing at least 10.21 million internal combustion engine vehicles with electric vehicles between 2027 and 2032. But they estimated that the United States and its allies could support the manufacturing of only about 5.09 million electric vehicles over that period, about half the target.

Manufacturing electric vehicles and their rechargeable batteries requires large quantities of minerals, including cobalt, graphite, lithium and nickel. The United States and its allies likely have vast reserves of raw materials.

The problem lies in production capacity, that is, the ability to properly extract and refine materials. The challenge is particularly acute for graphite, which has not been mined domestically since the mid-20th century.

The team looked for solutions, including rethinking emissions targets by producing more hybrid electric vehicles. Hybrid electric vehicles require fewer mineral resources but have lower tailpipe emissions, offering a way to close the emissions gap and expand government action beyond electric vehicles.

“We suggest exploring hybrid electric vehicles as an alternative path,” Yeo said.

Nunes said the study also shows that the United States could produce enough electric cars if it relied more on China for its mineral resources. But U.S. lawmakers are wary of that approach on national security grounds.

“Americans may need to ask themselves what matters more to them: fewer emissions or energy security?” Nunes said.

Originally from Singapore, Yeo said she aspired to be a public sector economist in her home country and that joining Nunes’ research group to work on electric vehicle analysis opened her eyes to the rigors and constraints of evaluating public policy.

“Setting lower and upper bounds for different scenarios, and walking through alternative possibilities, robustness checks and assumptions, were all very valuable skills to learn,” Yeo said.

Working at the Nunes Group, “there’s never a dull moment,” she continued, with multiple projects related to electric vehicles and other transportation sector climate goals underway.

Other co-authors of the study were Peter Cook and Seaver Wang of the Breakthrough Institute, Laurena Huh of MIT, and Daniel Palmer, a Groton School senior who participated in Harvard’s pre-college and high school programs.

Provided by Harvard Gazette

This article is reprinted courtesy of the Harvard Gazette, the official newspaper of Harvard University. For more information about the university, visit Harvard.edu.