By Professor Dato Dr Ahmad Ibrahim
The future of flying is already here. Itโs called Sustainable Aviation Fuel (SAF). Itโs being hailed as the magic bullet that will allow us to keep our wanderlust without cooking the planet. A new comprehensive review by Klimczyk, Jasiลski, Niklas, and Siedlecki cuts through the hype with precision, revealing a simple, uncomfortable truth: SAF is indeed the only viable path to decarbonizing aviation in the near-term, but the journey to making it truly sustainable is far more complex and perilous than weโve been led to believe.
The authors clearly lay out the menu of production pathways. We have the established workhorses, like HEFA (Hydroprocessed Esters and Fatty Acids), which can turn used cooking oil into jet fuel today. Itโs the low-hanging fruit. Then we have the promising but pricey future: alcohol-to-jet, gasification of agricultural residues, and the holy grailโpower-to-liquid (PtL) or e-fuels, synthesized from captured carbon and green hydrogen. And herein lies the first critical insight: There is no single “best” SAF. The right choice is entirely contextual, a delicate and location-specific calculus of feedstock availability, energy input, and ultimate environmental payoff. This is where the studyโs focus on Lifecycle Assessment (LCA) becomes paramount, delivering its most potent dose of reality. The “sustainable” in SAF is not a given; it must be earned. The core promise of SAF is its potential for near-carbon-neutral flight, as the CO2 released when it burns is roughly equal to the CO2 absorbed by its biomass feedstocks during growth. But LCA forces us to look at the entire picture: the emissions from farming, fertilizing, harvesting, transporting, and processing. Itโs a full accounting, and the devil is in the details.
The review exposes the critical trade-offs. Do we use a waste feedstock like forestry residues, which has minimal land-use impact, or do we cultivate dedicated energy crops that might be more efficient but could compete with food production or drive deforestation? This “indirect land-use change” (ILUC) is the ghost in the many well-intentioned biofuels. A fuel that looks clean on paper can be responsible for a carbon bomb if it indirectly causes a rainforest to be cleared elsewhere.
This brings us to the crux of the argument: Our current obsession with a single numberโthe percentage blend of SAFโis dangerously myopic. The EUโs ReFuelEU mandate and the US Inflation Reduction Act tax credits are powerful drivers, but if they focus only on volume and not on quality, they risk creating a monster. We could hit our 10% SAF target by 2030, but if that fuel is primarily made from questionable feedstocks with high ILUC values, we may have solved a political problem while exacerbating an ecological one. We will have created a booming market for “green” fuel that isn’t truly green.
This is where the authorsโ discussion of certification frameworks becomes vital. Systems like CORSIA and the EUโs Renewable Energy Directive II are the arbiters of truth, the ones tasked with defining the rulebook for what counts as “sustainable.” The review suggests that while these frameworks are a necessary starting point, they are not yet sufficient. They must be strengthened to fully account for ILUC, water usage, and social impacts with unflinching rigor. A weak certification is a greenwashing enabler.
So, where does this leave us? The work of Klimczyk et al. is not a obituary for SAF, but crucial for its responsible deployment. We must prioritize the right pathways. While HEFA gets us started, we cannot be lulled into complacency. The real endgame must be the scaling of advanced biofuels from true residues, and a massive, global push to bring down the cost of power-to-liquid fuels. This requires a Manhattan Project-level investment in electrolyzer and direct air capture technology. Policy must reward carbon intensity, not just volume. A liter of SAF should be valued based on its actual, certified lifecycle emissions. This would create a market pull for the best fuels, not just the cheapest ones. We must be honest about limits. Even with an all-out effort, SAF production will be constrained for decades. It cannot be the only solution. It must be paired with radical efficiency gains in aircraft and operations, and a sober conversation about the necessity of some air travel.
SAF is not a get-out-of-jail-free card. It is a bridge to a future of truly clean aviation. The comprehensive review is the essential blueprint. It tells us the bridge is possible, but it also shows us where the foundations are weak and the design is flawed. Our job is to build it right, lest it collapses under the weight of our expectations.
The author is affiliated with the Tan Sri Omar Centre for STI Policy Studies at UCSI University and is an Adjunct Professor at the Ungku Aziz Centre for Development Studies, Universiti Malaya. He can be reached at ahmadibrahim@ucsiuniversity.edu.my.