Aviation contributes a non-trivial share of global greenhouse gas emissions, and because aircraft rely heavily on high energy-density fuels, finding viable sustainable alternatives has become a major research focus. Below, we lay out the current state of play: what kinds of sustainable aviation fuels (SAFs) are being developed, recent technological advances, and the obstacles to scaling them.
What Counts as a Sustainable Aviation Fuel
“SAF” is a broad term encompassing fuels that reduce lifecycle emissions compared to conventional jet fuel. Some of the main pathways include:
- Bio-based fuels, including hydroprocessed esters and fatty acids (HEFA), Fischer-Tropsch (FT) synthetic fuels, alcohol-to-jet (ATJ) fuel, and oils derived from algae
- Synthetic or e-fuels, made from captured CO₂ + hydrogen raised using renewable energy. These can in principle get you nearer to carbon neutrality
- Novel feedstocks, including non-edible and waste oils, plant residues, lignocellulose, algal biomass, and even human or sewage waste in some studies
Recent Research and Technological Advances
Here are several of the most promising recent developments.
Catalysis Improvements
A recent review focuses on advanced monometallic and bimetallic catalysts (e.g. nickel-cobalt supported on magnetite) for converting non-edible oils (like palm kernel oil) into drop-in SAFs, with better yield, selectivity, and stability. These catalysts help with deoxygenation and mimic hydrocarbon fuel profiles needed for jet engines.
Lifecycle Emissions Reductions
A study by the UK’s NCAS (with the University of Manchester) has shown that certain blended SAFs (mixing conventional jet fuel and SAF) can reduce greenhouse gas emissions by up to ~80%, particularly when looking at black carbon emissions at low thrust settings (important for take-off, climb, etc.).
Feedstock Innovation
- Work is underway to use plentiful and underutilized biomass, including lignin (a tough structural polymer in plants) to produce jet-compatible hydrocarbons. These methods aim to avoid competition with food crops.
- Converting waste streams (e.g. human sewage, “biosolids”) into SAF is being explored. For example, a UK startup is planning a refinery to turn biosolids into aviation fuel.
Policy, Economics, and Scaling
- Research shows that most SAF technologies are still significantly more expensive than traditional jet fuels — often 120-700% higher cost depending on feedstock, process, and scale.
- Emissions reductions vary depending on the pathway: from ~27% up to ~87% for certain types. The more processing, higher tech (e.g. FT, e-fuels), renewable electricity, and better feedstocks, the higher the reductions.
- Current production is far below what would be needed to meet aviation sector net-zero targets by 2050. Research often points out the gap between demand projections, policy mandates, and actual supply capacity.
What’s New and Emerging
Some of the “newer” stuff or what’s moving from the lab toward commercial reality:
- “Drop-in” fuels with full compatibility: Research is intensifying on SAFs that can be used as direct substitutes (or very high blends) in existing aircraft without needing engine modifications
- Electro-fuels (e-fuels): Using CO₂ capture plus hydrogen generated from renewables. The hope is these can be scaled if clean energy becomes abundant
- Regulation and mandates: Laws are being tightened in various jurisdictions (EU, UK, etc.), pushing for SAF blending mandates, subsidies, and incentives that make SAF production more economically viable
- Large scale facilities and hubs: Investment flows are increasing for SAF production facilities (e.g. Australia has recently planned large biofuel hubs) and there are new SAF fund initiatives backed by airlines and governments
Major Challenges and Bottlenecks
Despite the progress, several big hurdles remain.
Challenge | What's the Issue |
Cost / price competitiveness | SAF and synthetic fuels remain expensive vs fossil jet fuel. Economies of scale, feedstock cost, energy input (especially for synthetic fuels from CO₂ + H₂) push up cost. Subsidies or carbon pricing needed to close gaps. |
Feedstock availability and sustainability | Ensuring feedstocks don’t compete with food, don’t lead to deforestation, etc. Waste and non-edible oils help, but volumes are limited. Algae and lignocellulosic biomass offer promise but are more difficult/costly to grow or process. |
Technical compatibility | Jet engines, fuel storage, handling, blend limits, fuel stability, “drop-in” behavior, seal swelling, low temperature properties etc. Ensuring safety, reliability, certification. |
| Regulation, policy, and investment risk | Investment requires certainty: mandates for SAF blending, subsidies or incentives, carbon pricing. Without policy support, scale is delayed. Also, infrastructure must adapt (fuel production, logistics, airport fuel supply). |
| Energy / carbon inputs | For pathways like synthetic fuels (e-fuels), production can require a lot of clean electricity; CO₂ capture; hydrogen. If those upstream inputs aren’t clean, they compromise overall emissions reductions. |
Outlook: Where We Might Be Going
Here are some possible trajectories, based on the research:
- Short to medium term (next 5-10 years):
Expect growing adoption of HEFA-based and other bio-jet fuels, increased mandates for blending (e.g. 5-20%), more operational test flights, more SAF supply hubs, incremental improvements in catalytic processing and possible drop-in fuels at higher blends. Cost reductions from scaling, better supply chains, and improved catalysts - Longer term (2030-2050):
Greater penetration of synthetic fuels / e-kerosene, maybe hydrogen (for certain aircraft types/routes), more radical engine designs (e.g. open rotor engines, hybrid systems), and possibly full 100% SAF in some aircraft. Significant policy, infrastructure, and renewable electricity supply growth in parallel. The goal in many roadmaps is net-zero carbon, or close to it by mid-century
Conclusions
Sustainable aviation fuels are no longer science fiction; many technologies are already fairly mature, and emission reductions of between ~30-80% are observable in various tests. However, converting that into a large, affordable, reliable supply is the sticking point. Research is making headway on catalysts, novel feedstocks, synthetic fuel pathways, and lifecycle analyses but, to get to net zero, SAFs will need to be part of a portfolio solution combining cleaner fuels, more efficient aircraft/engine designs, operational improvements (e.g. better routing, traffic management), and policy support.
Sources: www.couriermail.com.au, www.sciencedirect.com
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