The UK SAF Mandate, explained.
A blend mandate and a price backstop · the UK pairs an RTFO-style volume obligation with a buy-out mechanism and a dedicated Revenue Certainty Mechanism for Power-to-Liquid plants. The result is the strongest bankability signal in the G7 for new SAF capacity.
UK SAF Mandate
Effective 2025-01-01
UK Sustainable Aviation Fuels mandate requiring fuel suppliers to blend increasing percentages of SAF. Targets start at 2% in 2025 and increase to 22% by 2040.
How the mandate works
The UK mandate sits under the existing Renewable Transport Fuel Obligations (RTFO) framework, amended in 2024 to add a dedicated aviation stream. UK-registered aviation fuel suppliers are required to deliver a rising minimum share of SAF in the jet fuel they supply · measured by volume, reported annually to the Department for Transport, enforced through tradable RTFO aviation certificates.
The key architectural difference from ReFuelEU Aviation: the UK mandate is paired with a buy-out price. Suppliers who fall short can pay a fixed price per litre instead of delivering physical SAF · and that buy-out price becomes the de-facto ceiling on what compliant SAF can profitably be sold for. In 2025 the buy-out is set at £4.70 per litre.
The blend trajectory
| Year | Target |
|---|---|
| 2025 | 2% |
| 2027 | 3% |
| 2028 | 4% |
| 2029 | 5% |
| 2030 | 10% |
| 2035 | 15% |
| 2040 | 22% |
The 2025-2030 ramp is steep · 2% to 10% over five years. From 2030 onward the slope flattens, targeting 22% by 2040. The UK has not published a 2050 target in primary legislation; the trajectory is expected to be extended in a later RTFO review.
Scope · who is on the hook
Unlike ReFuelEU, there is no separate anti-tankering obligation for aircraft operators in UK primary legislation · the blend obligation sits entirely with fuel suppliers. Airlines are affected only indirectly, through the pass-through of SAF premiums in supplier pricing.
The buy-out price and what it means
The buy-out price serves two purposes. First, it caps the cost of non-compliance · a supplier who can source SAF below the buy-out price will do so; one who cannot will pay the buy-out. Second, because buy-out receipts flow back into the RTFO scheme, they create a redistribution mechanism that transfers money from laggard suppliers to those delivering physical SAF.
Supplier choice per tonne of shortfall: procure SAF at market price OR pay the buy-out (£4.70 per litre, 2025).
At a 2026 SAF market price of roughly $2.40 per litre and the £4.70 buy-out (~$6.00/L), compliance via procurement is about $3.60 per litre cheaper than paying the buy-out. The buy-out is therefore a soft ceiling on SAF wholesale pricing in the UK market · if the market price approaches the buy-out, non-compliance becomes the economic choice.
The Revenue Certainty Mechanism (RCM)
Parallel to the blend mandate, the UK is rolling out a dedicated Revenue Certainty Mechanism for qualifying SAF producers · in practice targeted at Power-to-Liquid plants where the cost gap versus fossil jet is structurally large and long-dated. The RCM works like a Contract-for-Difference (CfD): a strike price is agreed per tonne of SAF delivered, and the scheme pays the difference between the strike and the prevailing market price (or claws back if the market exceeds the strike).
For a PtL project, the RCM transforms the business case. Without it, an operator faces merchant price risk over a 20-year asset life against a variable fossil jet-fuel index. With it, revenue becomes effectively fixed · bankable. The mechanism is the reason several of the first large-scale European PtL FIDs are being sited in the UK rather than in continental Europe.
How it compares to ReFuelEU
| UK SAF Mandate | ReFuelEU Aviation | |
|---|---|---|
| Obligated party | Fuel suppliers only | Fuel suppliers + aircraft operators (anti-tankering) |
| Enforcement | Buy-out price (£4.70/L) | 2× price-gap penalty |
| Unit | Volume (% of litres) | Energy (% of MJ) |
| E-SAF carve-out | No explicit sub-mandate · RCM supports PtL separately | Yes · 1.2% (2030) → 35% (2050) |
| Producer support | Revenue Certainty Mechanism (CfD-style) | Innovation Fund grants only |
| Horizon in primary law | To 2040 | To 2050 |
For producers, the RCM is the decisive UK advantage · it directly addresses the bankability problem that continental European PtL projects still struggle with. For fuel suppliers, the buy-out price creates a predictable non-compliance cost that ReFuelEU's 2× formula does not.
Primary source
UK Department for Transport · external reference →
Secondary references: DfT SAF Mandate consultation response · SAF Revenue Certainty Mechanism (DfT).