Methane is the second largest driver of human-caused climate warming. Because of this, some researchers view its removal as crucial to mitigating the environmental impact of greenhouse gases.
Traditional strategies to limit atmospheric methane focus on finding ways to emit less of it, but some researchers, companies, and governments are funneling funds and resources into new alternatives that seek to actively remove methane from the atmosphere.
While these methane removal techniques show promise for their ability to swiftly decrease its concentration, a new study from Civil and Environmental Engineering Assistant Professor Hannah Horowitz reveals that they also produce a series of complex trade-offs and therefore require further research before they can be efficiently used in practice.
In her research, Horowitz focused on analyzing atmospheric oxidation enhancement (AOE), one such method that works by speeding up chemical reactions in the atmosphere that naturally break down methane. Using an open-source global 3D atmospheric chemistry model, she simulated over a dozen proposed AOE techniques and evaluated their impact on not only methane, but other greenhouse gases, surface air quality, and stratospheric ozone depleting substances.
Each AOE method showed differing degrees of success reducing methane, but they all shared one alarming consequence in common: every method increased surface particulate matter, which is the number one environmental factor that contributes to premature mortality worldwide.
Horowitz found in particular that hydrogen-peroxide-based methods of AOE increase surface ozone pollution in highly populated areas, while chlorine-based methods threaten the ozone layer by increasing the concentration of ozone depleting substances.
The study additionally examined the effectiveness of iron salt aerosol, a type of AOE gaining particular traction with private agencies across the US and Europe. The results showed that it requires much more iron emissions than suggested in previous research to reduce methane by even a small amount, and that trace bromine contamination can actually increase methane.
In each case, these side-effects have the potential to neutralize any intended climate benefit that comes from lower methane levels.
Overall, Horowitz’s research shows that deliberately altering global atmospheric chemistry to remove methane leads to unintended consequences. Though AOE continues to gain traction and funding, her work suggests that far more research is needed to understand the foundations, trade-offs, and scalability of AOE before real-world testing or application should proceed.
The paper, Intended and unintended consequences of atmospheric methane oxidation enhancement, was published in Atmospheric Chemistry & Physics on July 7, 2026, and can be read here.
Hannah Horowitz is an assistant professor of civil and environmental engineering in The Grainger College of Engineering, University of Illinois Urbana-Champaign and an affiliate assistant professor in Climate, Meteorology, & Atmospheric Sciences at the University of Illinois. This work builds upon Horowitz’s previous contributions to the National Academies of Science, Engineering, and Medicine’s 2024 consensus study, A Research Agenda Toward Atmospheric Methane Removal, which similarly advocated for further research on the risks of methane removal.