Benefits of electrifying 30% HDVs

Traffic related air pollution, specifically tail-pipe emissions, are made up of a complex mixture of health-harming air pollutants. Heavy-duty vehicles, which represent only a small portion of the total vehicle fleet, disproportionately contribute to greenhouse gas (GHG) emissions as well as other health harming air pollutant emissions including oxides of nitrogen (NO_x) and particulate matter (PM_2.5). Thus, incentives aimed at reducing HDV emissions are ideal climate mitigation strategies but also have the potential to reduce health harming air pollution (e.g. Jaramillo et al., 2022; Hoekstra, 2019). Exposure to traffic related air pollutants is not equally shared amongst population subgroups. In the U.S., interstate roadways and high-trafficked distribution centers are often developed in disinvested and marginalized communities that are predominantly comprised of people of color. As such people of color are disproportionately burdened by traffic related air pollution.

Using a regulatory grade air quality model we study the air quality, health and equity implications of transitioning 30% of HDVs from internal combustion engines to electric engines over a Chicago-centric domain, home to North America’s largest freight hub. We run simulations at fine geographic scales (~1.3 km) and use census tract level health data to best represent neighborhood scale exposures and associated health impacts. In this work we show that shifting 30% of HDVs to electric results in net emission reductions, reflecting large reductions in on-road emissions as compared to increases in emissions from power plants for vehicle charging; even when considering a fossil fueled electric grid. We find large air quality benefits especially for nitrogen dioxide (NO₂: -6%) throughout our study domain, with larger reductions occurring along major roadways and within urban areas. 

Additional co-benefits of transitioning to eHDVs are the associated air pollution attributable health benefits. We estimate that within our modeling domain, transitioning 30% of HDVs to electric will result in around 590 annual avoided premature deaths. Taking the city of Chicago as an example, we find that, at all levels of NO₂ reductions, people of color represent the majority of the racial/ethnic composition (>50%). However, this impact is amplified when looking at health benefits.

Our results show that the racial/ethnic composition of the census tracts experiencing the largest health benefits are 68% Black, despite moderate reductions in NO₂ concentrations in these neighborhoods. This demonstrates the important role played by socio-demographic factors in determining health impacts such that moderate reductions in air pollution can result in large health benefits for population subgroups with high underlying susceptibilities.

Here we assume that the additional electricity needed for charging the eHDVs would be met by the 2016 grid infrastructure where reliance on fossil fuels is still important. For this reason, the air quality and health impacts presented in this study should be considered conservative given the ongoing transition of the electric grid to cleaner electric options.

Trade-offs of electrifying 30% HDVs

While we estimate large benefits associate with a 30% shift of HDVs to electric, we note some important trade-offs. Firstly, our results show that within urban areas and along highways, shifting to eHDVs can increase ozone concentrations (O₃). Ozone is a secondary pollutant which is not directly emitted into the atmosphere but forms through complex atmospheric and chemical interactions of pollutants such as NOx and volatile organic compounds in the presence of sunlight. Within the troposphere, O₃ exposure is not beneficial to human health and is linked to various adverse health outcomes such as asthma but can also lead to premature mortality. We estimate that within our study domain, the health impacts associated with increases in O₃ concentrations add up to 50 additional premature deaths per year. This suggests the need for holistic incentives targeting co-related pollutants including volatile organic compounds especially for regions with a similar atmospheric composition.  

Secondly, despite simulating domain-wide reductions in PM_2.5, we note changes in the composition of this pollutant such that the sulfate aerosol (SO₄) increases while nitrates (NO₃) decrease. This result is linked to increases in sulfur dioxide (SO₂) emissions within our domain, a source attributable to coal power plants. Lastly, in this work we only represent the impacts associated with electrification of HDVs however, we note that this transition will not occur in isolation, but rather will occur in conjunction with other vehicle classes (e.g. light-duty vehicles; Visa et al., 2023), alternative fuel technologies (e.g. hydrogen; Jacobson et al., 2005) and changes in other forms of emitting infrastructure (e.g. heating/cooling, cooking stoves; Gould et al., 2023) amongst others.

Conclusion

 In this study we leverage neighbourhood-scale chemistry transport model air pollution concentrations and census tract level health data to estimate the benefits, trade-offs and equity implications of electrifying HDVs at scales proposed by recent environmental justice initiatives. We show that electrification of heavy-duty vehicles is not a silver bullet to address climate, air quality, health and equity issues but nonetheless offers a number of potential benefits including reductions in air pollution and health burdens, especially in marginalized communities.

Other contributing authors of this work include Anastasia Montgomery, Maxime A. Visa, Jordan L. Schnell, Zachariah E. Adelman, Mark Janssen, Emily A. Grubert & Susan C. Anenberg. Research reported in this publication was supported by US National Science Foundation, Environmental Defense Fund, McCormick Center for Engineering Sustainability and Resilience and Ubben Program for Carbon and Climate Science, Trienens Institute for Sustainability and Energy, Northwestern University . 

References

Jaramillo, P., Kahn Ribeiro, S., Newman, P., Dhar, S., Diemuodeke, O. E., Kajino, T., Lee, D. S., Nugroho, S. B., Ou, X., Hammer Strømman, A., & Whitehead, J. (2022). Transport. In IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK and New York, NY, USA. https://doi.org/10.1017/9781009157926.012

Hoekstra, A. (2019). The Underestimated Potential of Battery Electric Vehicles to Reduce Emissions. In Joule (Vol. 3, Issue 6, pp. 1412–1414). Cell Press. https://doi.org/10.1016/j.joule.2019.06.002

Visa, M. A., Camilleri, S. F., Montgomery, A., Schnell, J. L., Janssen, M., Adelman, Z. E., Anenberg, S. C., Grubert, E. A., & Horton, D. E. (2023). Neighborhood-scale air quality, public health, and equity implications of multi-modal vehicle electrification. Environ. Res.: Infrastruct. Sustain.. 3, 035007. https://doi.org/10.1088/2634-4505/acf60d