Feb 17 2021
Poor air quality accounts for premature death in around 1.2 million Chinese citizens every year. And public health outcomes are especially ominous during adverse air quality events, like the infamous episodes of the 'Airpocalypse' winter haze.
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Now, a research team from Northwestern University speculated whether the extensive implementation of electric vehicles (EVs) could assist China to prevent these fatal events. The solution depends on several factors.
The investigators concluded in a recent study that air quality and the benefits of EVs toward public health—as well the potential of these EVs to decrease carbon emissions—in China depend on the composition of the electric grid and the type of transport electrified.
The new study was recently published in the February 2021 issue of the Earth’s Future journal, on February 16th, 2021.
A significant fraction of China’s electricity is currently sourced from the burning of coal, which is a very carbon-intensive power source. When the coal-heavy power is used to charge light-duty vehicles, carbon emissions are reduced because of the efficiency of light-duty EVs. Heavy-duty electric vehicles require significantly more energy, so we see a net increase in carbon dioxide emissions.
Jordan Schnell, Study Lead Author, Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder
Schnell continued, “However, even when heavy-duty vehicle power is sourced entirely by coal-fired electricity, we still see air quality improvements because the on-road emission reductions outweigh what the power plants add. Fine particulate matter emissions, which are a main ingredient in haze, are reduced.”
We find that to achieve net co-benefits from heavy-duty EV adoption, the real sticking point in China’s infrastructure lies in its power-generation sector. Greater adoption of emission-free renewable power generation is needed. For light-duty vehicles the co-benefits are already there under the current infrastructure.
Daniel Horton, Study Senior Author, Northwestern University
Horton is also an assistant professor of Earth and planetary sciences in the Weinberg College of Arts and Sciences at Northwestern University. During the study, Schnell was working as a postdoctoral fellow in Horton’s laboratory.
He is currently a research scientist at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder.
Pollutants emerge from many different sources, both human-caused and natural, and they include emissions discharged by power generation facilities and during transportation.
While the adoption of EVs decreases the discharge of greenhouse gases and air pollutants from the tailpipes of vehicles, the overall emissions budget should factor in the shifting of emissions to the power facilities used for charging EV batteries.
Energy consumption and vehicle distribution across the countries also contribute to the overall emissions profiles. For instance, light duty versus heavy duty vehicles vary considerably, which further complicates the net results.
Hence, to resolve these complex factors, the investigators integrated chemistry-climate modeling with the weather, emissions and public health data. They analyzed climate benefits, air quality, and also the tradeoffs of light duty against heavy duty vehicle adoption by utilizing meteorological conditions from an infamous Airpocalypse event that occurred back in January 2013.
But unlike prior EV-air quality research works that targeted chronic exposure, the team focused on the severe public health effects of exposure to this brief yet highly dangerous, haze event.
The investigators found that the adoption of EVs may probably play a modest role in decreasing the public health consequences of separate Airpocalypse events, with the extent based on the kind of vehicle electrified. The team also observed that the realization of the co-benefits of climate and public health relied on the inclusion of emission-free renewable energy to the electric grid.
Earlier in January 2013, most of the Chinese area, including the main population hubs of Hebei Beijing, and Tianjin, had experienced extreme pollution episodes of toxic haze.
Extreme exposure to the record high concentrations of nitrogen dioxide and fine particulate matter also increased stroke, heart disease, and pollution-related respiratory diseases, which according to the researchers, caused around $14.7 billion in terms of health care costs and led to about 32,000 premature deaths.
To evaluate the outcomes of EV adoption, the researchers used a specific model simulation scenario in which they substituted about 40% of China’s heavy duty vehicles (like buses, construction equipment, and long haul truck) with electrified models. Another scenario replicated the substitution of about 40% of China’s light duty vehicles with electric options.
In both scenarios, the energy required to charge the EV batteries was found to be equal and this energy was sourced from power-generation plants on the grid. Discharge of air pollutants and greenhouse gases are established based on the power plant profile and the battery-charging load.
The team observed that electrifying about 40% of heavy duty vehicles reliably enhanced air quality and prevented up to 562 premature deaths. However, it did not decrease the emissions of greenhouse gas. On the other hand, the adoption of Light duty EVs decreased the emissions of carbon dioxide by 2 megatons but provided more modest benefits in terms of air quality.
To reiterate this point further, the team provided another scenario comparison. When all traffic emissions are eliminated from the 2013 event, improvements in air quality decreased acute premature mortality by as much as 6%. But when all power-sector emissions are eliminated, there was a 24% drop in acute premature mortality.
Overall, we found that EV-induced pollution changes and avoided premature deaths were modest for the extreme event. But air quality will improve more drastically as the power-generation sector moves away from fossil fuel-fired electricity.
Jordan Schnell, Study Lead Author, Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder
The study titled, “Potential for electric vehicle adoption to mitigate extreme air quality events in China,” was funded by the Ubben Program for Carbon and Climate Science and the U.S. National Science Foundation under grant number CBET-1848683.
The team included researchers from Northwestern University, the Environmental Defense Fund, the U.S. EPA, UC Irvine, Tsinghua University, Boston University, and Fudan University.
Journal Reference:
Schnell, J. L., et al. (2020) Potential for electric vehicle adoption to mitigate extreme air quality events in China. Earth's Future. doi.org/10.1029/2020EF001788.