Organizations aiming to reduce their carbon footprint are discovering that not all “green” actions yield the same benefits for air quality. A new study conducted by researchers at the Massachusetts Institute of Technology (MIT) reveals that while initiatives such as purchasing renewable electricity and cutting air travel can each decrease carbon dioxide emissions, their effects on air quality differ significantly.
By employing a comprehensive modeling approach, the researchers quantified these air quality impacts, drawing data from three different organizations. Their findings indicate that air travel contributes to approximately three times more damage to air quality compared to equivalent electricity purchases. This is particularly concerning given that exposure to major air pollutants, such as ground-level ozone and fine particulate matter, is linked to serious health issues, including cardiovascular and respiratory diseases, as well as premature death.
The study highlights that the air quality impacts of decarbonization efforts can vary widely across different regions. For instance, in the northeastern United States, the consequences of energy use predominantly affect local air quality, whereas the impacts of air travel are felt on a global scale due to emissions occurring at higher altitudes.
Quantifying Air Quality Impacts
Researchers hope to emphasize how organizations can prioritize their climate actions to maximize immediate health benefits. According to Noelle Selin, a professor in the MIT Institute for Data, Systems, and Society and the Department of Earth, Atmospheric and Planetary Sciences, “If we are trying to get to net zero emissions, that trajectory could have very different implications for a lot of other things we care about, like air quality and health impacts.”
The study, published in Environmental Research Letters, also tackles the complexities of quantifying the air quality benefits of individual organizational efforts. Traditional climate science often focuses on national or regional policies, where the aggregate impacts are easier to model. In contrast, the effects of an organization going green exist within larger societal systems influenced by these very policies.
To address this, the MIT team utilized data from two universities and one company in the greater Boston area. They investigated whether organizational actions that reduce the same amount of carbon dioxide would have equivalent benefits for air quality. Yuang (Albert) Chen, the lead author and an MIT graduate student, noted that “From a climate standpoint, CO2 has a global impact because it mixes through the atmosphere, no matter where it is emitted. But air quality impacts are driven by co-pollutants that act locally, so where those emissions occur really matters.”
Insights on Emissions and Health
The research underscores that burning fossil fuels releases nitrogen oxides and sulfur dioxide, alongside CO2. These co-pollutants can react to form fine particulate matter and ground-level ozone, both of which contribute to smog. The nature of these pollutants, combined with local factors such as weather and existing emissions, complicates the air quality landscape.
To navigate this complexity, the researchers connected multiple models to analyze local and regional air quality impacts. By incorporating various factors, including power plant emissions data and aviation emissions linked to specific flight routes, they calculated the air quality and climate impacts for each activity.
In a notable finding, the researchers monetized the air quality impacts to enable comparison with climate impacts. They determined that the monetized damages associated with electricity purchases amounted to an additional $88 per ton of CO2, while air travel damages reached $265 per ton. This stark difference illustrates that the air quality impacts of CO2 emissions are heavily influenced by their source and method of production.
The team also discovered that emissions from aviation significantly affect regions far from their source, with atmospheric winds carrying pollutants across continents. Countries like India and China experience heightened air quality impacts due to existing ground-level emissions exacerbating the formation of fine particulate matter.
The research also delves into the specific impacts of short-haul flights, indicating that regional flights may have a more substantial effect on local air quality than longer domestic flights. “If an organization is thinking about how to benefit the neighborhoods in their backyard, then reducing short-haul flights could be a strategy with real benefits,” Selin added.
Looking ahead, the researchers plan to evaluate the air quality and climate impacts of alternatives like train travel, assessing whether replacing short-haul flights with train journeys could yield positive outcomes. They also intend to broaden their analysis to include other energy sources, such as data centers.
This research received support from Biogen, Inc., the Italian Ministry for Environment, Land, and Sea, and the MIT Center for Sustainability Science and Strategy, reflecting a collaborative effort to enhance our understanding of how organizational choices can contribute to a healthier planet.