Is it better for the environment to drive an electric or hybrid vehicle? The answer might surprise you

For Hao Chen, a critical question about modern transportation can be summed up by paraphrasing a literary classic to sharpen the focus on the three-letter acronym for "battery electric vehicle."

"Are BEVs truly the environmental heroes they are made out to be?" the Clemson University Ph.D. candidate asked in a blog post. "Or, to borrow from Hamlet- 'to BEV or not to BEV'-do BEVs really rid us of 'a foul and pestilent congregation of vapours,' or is the reality far more complicated?"

Vehicles that run solely on batteries are often regarded as the gold standard in clean-energy transportation, but the answer to the Shakspearean question is far from simple, according to a research group that included Chen and was led by Mik Carbajales-Dale, an associate professor of environmental engineering and Earth sciences at Clemson.

"Despite their zero-tailpipe emissions, EV technologies alone are not inherently 'clean' or complete solutions for reducing transportation emissions," researchers wrote in a recent paper for Nature Communications Earth & Environment.

"The environmental benefits of EV use are closely tied to the cleanliness of the electricity grid they utilize for energy. While EVs offer considerable decarbonization potential as the grid mix becomes cleaner, their contribution does not ensure a win-win solution to mitigate other environmental impacts, such as increased respiratory effects."

In digging into Chen's question, the group sought to help figure out what makes for a sustainable vehicle. They looked at four types of light-duty vehicles: battery-powered vehicles, internal combustion engine vehicles that most commonly run on gasoline, and hybrid and plug-in hybrid vehicles that combine both battery power and gasoline.

Researchers focused primarily on how each type has an impact on global warming potential and respiratory effects, including illness linked to airborne particulate matter. Their analysis went beyond tailpipe emissions to encompass multiple factors, including:

* How various electrical grids get their power, and how that could change as renewable energy is adopted more widely

* The average lifetime driving distance of the four types of vehicles

* A lifecycle analysis that considered what it takes to manufacture, maintain and dispose of vehicles

* The environmental footprint that comes with extracting and processing materials for batteries, as well as manufacturing them

* The gasoline supply chain, including crude oil extraction, refining, storage and transportation

One of the study's key findings is that electric vehicles may inadvertently exacerbate environmental injustice in some cases.

Urban areas benefit more from electric vehicles' zero tailpipe emissions, while rural or poor communities experience more environmental burdens because they are often closer to power plants where the electricity is produced, researchers found.

So what is an environmentally conscious consumer to do? According to researchers, consumers ought to consider factors such as the expected lifetime driving distance of vehicles, daily commuting distance and individual driving and charging patterns, along with regional differences in charging station availability and how the local electrical grid gets its power.

Policymakers can focus on improving charging infrastructure, incentivizing early retirement of high-emission vehicles and extending battery life cycles for EVs, researchers found. Additionally, policies should address local emissions from fossil fuel-based power plants to avoid increasing pollution in vulnerable communities, they found.

The research was unique not only for its multifaceted look at the environmental impact of light-duty vehicles but also its origins.

The two-year project started as an assignment in a senior-level course taught by Carbajales-Dale and expanded to include not only undergraduates but also graduate students, a postdoctoral researcher and an Earth scientist at a national lab.

Researchers published their findings in a paper titled "Electric light-duty vehicles have decarbonization potential but may not reduce other environmental problems."

They drew their information from 48 different sources, including academic papers and reports by organizations such as the International Energy Agency, the U.S. Department of Energy and the U.S. Environmental Protection Agency.

Co-authors were: Chen, Serife Elif Can Sener, Miles Jones, Muzan Williams Ijeoma and Carbajales-Dale, all of the Department of Environmental Engineering and Earth Sciences; Cole Van Emburg of the Department of Mechanical Engineering; Taylor Bogucki of the Department of Industrial Engineering; Nicolas Bonilla of the Department of Parks, Recreation and Tourism Management; and Heng Wan of Earth Systems Predictability & Resiliency Group, Pacific Northwest National Laboratory. Carbajales-Dale is also prinicipal investigator of the Clemson Energy-Economy-Environment (E3) Systems Analysis Group.