Beyond Carbon: Understanding Aviation’s Full Climate Impact
When we talk about the environmental footprint of aviation, CO2 emissions often dominate the conversation. Yet, this focus overlooks a significant component of the industry’s climate impact—non-CO2 effects such as nitrogen oxides (NOx) and contrail-induced cirrus clouds. These short-lived climate pollutants are estimated to contribute nearly as much to aviation’s warming footprint as carbon dioxide, but remain harder to quantify and control.
The Promise of Low-Aromatic, Low-Sulfur Jet Fuels
Sustainable Aviation Fuel (SAF), especially those made through HEFA and similar pathways, not only reduces lifecycle CO2 emissions but also alters the chemical profile of engine exhaust. SAF contains lower levels of sulfur and aromatic hydrocarbons like naphthalenes. These changes reduce soot formation—a key precursor for contrail ice crystal nucleation. In short, SAF helps cut down the ingredients for contrails that trap heat in the atmosphere.
This might seem like a niche benefit, but in climate science, small tweaks often lead to outsized gains. Reducing soot can limit contrail formation and the associated short-term warming—an often underestimated climate win.
High-Impact Flights, High-Yield Solutions
A less obvious but powerful insight is the strategic targeting of SAF deployment. Research shows that a small percentage of flights create the majority of contrail-related climate warming. By prioritizing SAF use on routes and altitudes most likely to produce warming contrails—typically high-altitude, long-haul flights crossing moist, cold air layers—operators could amplify climate benefits without requiring full fleet-wide SAF substitution.
Such a targeted approach allows the industry to stretch limited SAF supplies more effectively while buying time for scaling up production capacity.
Cleaner Conventional Fuels: A Bridge Strategy
Even without a full shift to SAF, marginal gains are possible through the optimization of current jet fuels. Adjusting the refining process to reduce naphthalene and sulfur content in Conventional Aviation Fuel (CAF) can decrease particulate emissions. However, this comes with caveats. More extensive refining increases energy use and overall life cycle emissions, which could offset some benefits. Economic and infrastructural feasibility also becomes a key concern, especially when considering global fuel logistics and certification processes.
Still, where SAF is unavailable, cleaner CAF blends could serve as an interim tool in reducing short-term climate effects.
The Contrail Complexity: Why Particle Size Matters
Contrails form when aircraft exhaust meets cold, moist air. Soot particles help nucleate ice crystals, but newer engines or ultra-clean fuels may emit fewer large particles. Surprisingly, this doesn’t eliminate contrail formation—it changes it. Tiny sulfate or ambient particles may still seed contrails, albeit with different radiative properties. This adds complexity: in low-soot conditions, other emissions might take on a larger role.
Therefore, future mitigation must address both soot and non-soot particles to reduce total contrail impact. The evolving atmospheric background—shaped by climate change and emissions reductions in other sectors—will also influence outcomes.
Engineering Solutions in a Policy Vacuum
Altering jet fuel specs to limit non-CO2 emissions requires more than technical ingenuity. It demands industry-wide collaboration, updated safety and performance certifications, and robust regulatory incentives. Without clear policy direction, there’s little business case for producers to invest in cleaner but more expensive refining processes.
Furthermore, fuel changes cannot compromise safety, performance, or cost-effectiveness—especially when global aviation operates on tight economic margins and diverse geographies.
Future-Proofing Climate Strategies
As cleaner-burning engines like LEAP and GE9X become the new norm through fleet renewal, their lower soot emissions may reduce the need for chemical intervention. However, they won’t eliminate non-CO2 effects entirely. A layered strategy—combining SAF, optimized CAF, smarter routing, and advanced combustion technology—will offer the best path forward.
What’s often missed in the SAF conversation is this: even a limited deployment today can produce disproportionately large climate gains if strategically applied. That makes the co-benefits of SAF more than a footnote—they are an underleveraged climate opportunity.
Conclusion: Rethinking Fuel as a Climate Lever
The aviation sector’s path to decarbonization is complex, but SAF and fuel reformulation present not just carbon benefits, but non-CO2 advantages as well. These co-benefits—soot reduction, contrail mitigation, and improved air quality—deserve greater emphasis in climate strategies.
The real opportunity lies in using existing tools with surgical precision. By aligning SAF use with flight-specific impact patterns, and exploring feasible improvements in conventional fuels, the industry can make meaningful climate progress even before SAF becomes ubiquitous. This approach offers a practical way to reduce warming now, while building momentum for deeper, systemic transformation in the decades ahead.