A new report from Carbon Tracker, Fuel Disclosure, warns that alternative jet fuels (AJF), commonly referred to as sustainable aviation fuels (SAF), are unlikely to significantly reduce aviation emissions before 2030. Even if all current, under-development, and announced projects operate at full capacity, AJF production would cover only about 5% of global jet fuel demand and less than half of the projected growth in total consumption.
The analysis highlights that high costs, limited sustainable feedstocks, and weak bankability will constrain AJF’s impact in the coming decade.
Seven Barriers to Scaling AJF
Carbon Tracker identifies seven structural hurdles limiting the scale-up of AJF. The first four apply to all types of alternative jet fuels, while the last three specifically affect truly sustainable options:
- Costs and price premiums – AJF is more expensive than fossil jet fuel, reducing demand and slowing adoption.
- Regulatory uncertainty – Fragmented rules across jurisdictions hinder market growth.
- Lack of long-term offtake commitments – Limited long-term agreements reduce revenue visibility for producers.
- Weak bankability – Technology, feedstock, and policy risks make financing new AJF projects difficult.
- Feedstock availability – Sustainable wastes and residues are scarce and challenging to collect.
- Feedstock sustainability – Lifecycle emissions, land-use impacts, and biodiversity concerns restrict eligible supply.
- Opportunity costs – Scarce sustainable feedstocks might achieve greater emission reductions in other sectors where mitigation is faster or cheaper.
Saidrasul Ashrafkhanov, Carbon Tracker analyst and lead report author, said:
“Beyond high costs, hesitant offtakers, and financing barriers, many alternative jet fuels also carry environmental downsides. While AJF could play a larger role in decarbonising aviation in the future, the industry must demonstrate a pathway to fuels that are truly sustainable, abundant, and feasible.”
The Need for Policy Coherence
Despite numerous support schemes, investors and environmental outcomes are not seeing clear results. Rich Collett-White, Carbon Tracker energy analyst and co-author, explained:
“A confusing mix of policies aimed at scaling alternative jet fuels, with differing definitions and eligibility rules across regions, is creating uncertainty. Consistent regulations are essential to prioritise fuels with strong environmental integrity and avoid unintended consequences.”
Short-Haul Offers Faster Gains
Significant emission reductions may be achievable sooner on short-haul routes. Nearly half of all flights cover less than 270 nautical miles (500 km). Battery-electric and hybrid-electric aircraft carrying 5–100 passengers are nearing entry into service, offering a direct route to zero-emission operations on regional legs. Hydrogen-electric aircraft could extend medium-haul operations from the mid-2030s.
This presents a clearer near-term investment opportunity while preserving scarce sustainable AJF for long-haul flights. However, funding for new-propulsion aircraft remains low compared with AJF investments.
Right-Sizing AJF’s Role
AJF will remain important for long-haul decarbonisation, where batteries cannot match the range or payload of conventional aircraft, but its role is smaller than often assumed. Carbon Tracker recommends a pragmatic, portfolio-based approach:
- Manage AJF expectations – Focus on pathways with strong sustainability credentials and predictable costs, avoiding options with poor lifecycle performance or food-security risks.
- Support zero-emission short-haul – Invest in battery-electric, hydrogen-electric, and hybrid-electric aircraft for sub-500 km routes, where readiness is advancing fastest.
- Design smarter policy and finance – Strengthen sustainability criteria, implement revenue-certainty mechanisms, and reward genuine emissions reductions.
Bottom Line
AJF is part of the solution but not the silver bullet. Treating it as the main avenue for emission reductions risks misallocating capital and consuming finite feedstocks without significantly reducing fossil jet fuel use this decade. A balanced strategy—accelerating zero-emission aircraft on short-haul routes, conserving sustainable AJF for long-haul, and aligning policy with climate goals—offers a faster, more cost-effective, and credible path to decarbonising aviation.
