Open call for evidence

SAF Mandate: SAF supply and industry certainty in an evolving market

Published 16 June 2026

Introduction

The Sustainable Aviation Fuel (SAF) Mandate, which came into force on 1 January 2025, is the UK’s key policy mechanism to secure demand for SAF.

It delivers greenhouse gas (GHG) emission savings by encouraging the supply of SAF. The SAF Mandate sets a legal obligation on fuel suppliers in the UK to supply an increasing proportion of SAF over time. Suppliers receive certificates for the SAF they supply in proportion to the level of GHG emission reductions their fuel delivers.

Government has received positive feedback from industry on the SAF Mandate’s structure and support for diversifying SAF technologies. We want to ensure the SAF Mandate continues to incentivise a vast range of SAF technologies and support aviation decarbonisation for years to come.

The SAF Mandate has 2 obligations:

• the ‘main obligation’ from 2025
• a ‘power-to liquid (PtL) obligation’ from 2028

From 2027, the SAF Mandate also has a ‘hydroprocessed esters and fatty acids (HEFA) cap’. The HEFA cap is designed to encourage the development of more advanced fuels (both PtL and non-PtL).

From 2027 to 2040, HEFA SAF decreases as a proportion of total SAF supply eligible under the mandate. As the HEFA cap is set as a percentage of the main SAF obligation, the absolute amount of HEFA that can count towards compliance is likely to increase as the SAF Mandate rises.

This is even as HEFA’s share of the total obligation is reduced, due to the SAF Mandate’s increasing targets. This assumes jet fuel demand continues to increase, and the carbon intensity of HEFA remains stable as changes to the lifecycle GHG savings will impact the volumes supplied.

The SAF Mandate compliance guidance provides further detail on eligible SAF types and the obligations. 

It is crucial to diversify viable SAF pathways and scale up advanced technologies to avoid reliance on HEFA SAF. Future HEFA supply is predicted to be limited and demand is expected to significantly increase as more countries introduce SAF policies. This is in addition to competition from other sectors who rely on HEFA feedstocks. As SAF Mandate targets rise, a successful scale up of advanced SAF is required in order for the UK to meet its long-term aviation decarbonisation objectives.

Suppliers comply with the main obligation by redeeming certificates, which can be gained either by supplying SAF or purchased from others that have supplied fuel. Where an insufficient number of certificates have been redeemed, suppliers can buy out of their obligation. By creating guaranteed demand for SAF, the SAF Mandate is designed to accelerate the development of domestic and global supply, reduce aviation’s lifecycle carbon emissions, and support the UK’s wider net zero commitments.

Availability of future SAF supply 

The SAF mandate is intended to be ambitious but deliverable, setting a clear trajectory of increasing SAF uptake to drive up greenhouse gas (GHG) savings and speed up aviation decarbonisation.

Government recognises the interdependencies between demand and supply and remains steadfastly committed to encouraging the development of a domestic SAF industry alongside the SAF Mandate.

There are promising signs about global HEFA supply to the UK in the near term, however, it is essential to ensure that a future diverse supply of SAF continues to be available so that the SAF mandate remains effective at decarbonising aviation. Government is supporting industry to develop advanced SAF production in the UK though the revenue certainty mechanism, the Advanced Fuels Fund and successor schemes. 

The SAF Mandate allows compliance in 2 ways:

• by redeeming certificates (from supply or purchasing from other account holders)
• by paying the buyout price

We recognise that, if there is insufficient global supply available, this would reduce the options that fuel suppliers have to comply with the obligation to only buyout.

Buyout is an important mechanism for delivering aviation decarbonisation at a reasonable cost. It provides fuel suppliers with an option in circumstances where supply is unreasonably expensive, effectively capping the cost of the scheme. Some level of buyout can also be useful as an investment signal to the market that there is unmet demand available to be met. However, buyout does not deliver the carbon savings that the SAF Mandate is designed to deliver.

The nascency of the SAF industry makes it essential to provide a clear and stable demand signal to support investor confidence in advanced SAF technologies. The SAF Mandate provides certainty to industry by setting a legal framework that establishes the demand for SAF in the UK. This certainty facilitates an environment in which commercial decisions can be made confidently, supply chains are developed, and investment is attracted into the sector.

Therefore, while it is important that we monitor technical and commercial developments to ensure sufficient SAF availability over the long-term, government is committed to maintaining certainty and confidence in support of diversifying SAF feedstocks and technologies, which the SAF Mandate is designed to encourage.

We will not propose changes unless:

• there is a strong rationale
• such changes are consistent with wider government objectives and maintain policy stability and investor confidence in the UK SAF industry

Government remains supportive of the diversification of SAF technologies, which are crucial for the long-term future of SAF.

We are seeking industry views

Since the SAF Mandate launched, we have received feedback from industry that once the HEFA cap and PtL obligation come into force, availability of advanced non-HEFA and PtL SAF risks being lower than previously anticipated.

Government recognises that the SAF Mandate interacts with the whole supply chain, not just the fuel suppliers who are obligated by it. This is why we are keen that this call for evidence is far-reaching and we welcome responses from:

• fuel producers and suppliers
• feedstock suppliers
• airlines
• airports and the wider aviation industry
• investors
• industry bodies, NGOs and other interested parties

This call for evidence provides those stakeholders with an opportunity to engage with DfT on the extent and drivers of uncertainty around future non-HEFA SAF supply.

We will maintain overall SAF Mandate targets

The government is dedicated to delivering greener transport, kickstarting economic growth and to making Britain a clean energy superpower.

We are not proposing any changes to the overall SAF Mandate targets nor are we seeking to reduce the SAF Mandate’s climate or environmental ambition. SAF is one of the key measures required to reach net zero emissions from aviation by 2050.

Rather, through this call for evidence we are seeking views on how government can best support industry in meeting the mandate to ensure delivery of this ambition. We want to ensure the SAF Mandate continues to support aviation decarbonisation for years to come.

We are seeking industry views on:

• the availability of advanced non-HEFA and PtL SAF
• the types of potential changes to the HEFA cap and PtL obligation and flexibility measures that could be introduced if there were significant concerns about availability - including making no changes to the SAF Mandate as currently designed

We are seeking evidence in relation to emissions reductions, costs, supply and industry certainty. Through this call for evidence, we are also seeking updated views and evidence on the impact of tankering as a result of the SAF Mandate.

We will not propose any changes to the SAF Mandate unless there is sufficient evidence that maintaining the same policy design would cause significant harm for industry and consumers.

Any decisions will be considered carefully, balancing the needs of the whole supply chain, whilst aiming to protect investment in developing an advanced SAF industry in the UK.

Any changes to the SAF Mandate policy design would be subject to a formal consultation (beyond this call for evidence), as required by the SAF Mandate’s legislation.

Areas for consideration and evidence

Questions are included within this document so you can see what we are asking in context. See the How to respond section of this page to see how you can respond to these questions.

Availability of advanced SAF

Feedback from industry stakeholders indicates that advanced, non-HEFA SAF is not yet being produced in significant quantities, and there are concerns over meeting the SAF Mandate’s future supply targets. We are seeking evidence from industry to understand the expected trajectory of this supply, as targets rise to 2040.

Question 1. Do you expect there to be sufficient non-HEFA SAF (either PtL or non-PtL SAF), domestically and globally, to meet the SAF Mandate targets until 2040?

Please provide any supporting evidence including how you expect availability to change over time.

The case for maintaining the current SAF Mandate policy design

Maintaining the current design of the SAF Mandate would maintain investment confidence that is vital to the development of the SAF industry, in particular the more advanced fuels necessary for meeting the mandate in later years.

Fuel suppliers would continue to be able to meet the SAF Mandate obligations through the established existing routes - physical supply, trading certificates, or paying the buy-out price. Retaining these established compliance routes of the mandate design maintains certainty and confidence for suppliers and the wider supply chain, who will be now familiar with the policy.

In the event that suppliers do buy out the non-HEFA share of the main obligation, this would be a relatively small percentage in the context of overall mandate demand. In 2027, non-HEFA SAF accounts for 7.7% of the total mandated SAF volume, meaning the vast majority of the SAF Mandate’s obligation could still be met using HEFA. Use of buyout in this instance would also provide a clear investment signal to the market to help support the scale-up of alternative SAF pathways.

We are supporting investment in the advanced SAF industry, including through the revenue certainty mechanism and £219 million in grant funding to support UK SAF production.

Government has consistently iterated that there is a high bar for changes under the SAF Mandate - creating certainty for industry is key.

Question 2. In your view, what would be the likely consequences of maintaining the current approach (no policy change)?

Please provide any supporting evidence.

Advanced non-HEFA non-PtL SAF

The  HEFA cap, which is scheduled to come into effect in 2027, decreases the allowed contribution from HEFA as a  proportion of total SAF supply annually. A supplier can still supply more HEFA than the cap determines and receive certificates for this SAF, but these certificates will not be eligible for redeeming against the obligation.

As the HEFA cap is set as a percentage of the main SAF obligation, the absolute amount of HEFA that can count towards compliance increases as the SAF Mandate rises. This is even as HEFA’s share of the total obligation is reduced – due to the SAF Mandate’s increasing targets. This assumes jet fuel demand continues to increase, and the carbon intensity of HEFA remains stable as changes to the lifecycle GHG savings will impact the volumes supplied.

Even with the HEFA cap, the UK SAF Mandate’s obligation for HEFA is currently one of the most ambitious globally.

HEFA SAF is derived from feedstocks such as used cooking oil and waste animal fats (including tallow). In the long term, feedstock constraints are expected to be the main limitation on HEFA production.

While recognising the important role that HEFA will play in the early years of the mandate, the cap limits the extent to which mandate compliance can be met through HEFA in order to avoid reliance on a single, feedstock‑constrained pathway. To reach higher SAF targets, we will need a diverse range of innovative technologies drawing upon a wide range of feedstocks.

The HEFA cap supports this diversification by creating crucial space for innovation and helps to encourage investment in alternative pathways. Its primary purpose is to provide a clear and credible market signal to support investment in advanced non‑HEFA SAF technologies.

The HEFA cap still allows near‑term HEFA SAF volumes to increase and does not set a limit on HEFA production in the UK or globally. The government is committed to supporting the development of UK production of non-HEFA SAF.

This is why, alongside this call for evidence, we are also announcing the Low Carbon Fuels Fund and intend to publish the RCM allocation strategy later this year, which sets out the size and timing of the forthcoming allocation round.

Some stakeholders have raised concerns that advanced non-HEFA SAF is not yet available at scale, creating a risk that, in the immediate term, suppliers may not be able to acquire enough non-HEFA SAF to meet the portion of their obligation above the HEFA cap. As a result, some stakeholders have argued that changes are required to the HEFA cap.

The government is committed to the long-term ambition of growing an advanced UK SAF industry. We recognise that providing a clear policy direction is key for investment in these technologies, but also want to understand the supply concerns raised by stakeholders in more detail.

We are seeking evidence on the impact of the HEFA cap and potential options for amending the HEFA cap. When answering, we ask you to consider how amending the HEFA cap could affect:

• SAF supply availability
• investor confidence
• the pace of scale‑up for advanced SAF

We are also seeking views on the potential implications of amending the HEFA cap on environmental outcomes. Please consider the impact on lifecycle greenhouse gas emissions as well as any indirect impacts on the long‑term objectives of the SAF Mandate in supporting a diverse, resilient and sustainable SAF industry.

Question 3. If you believe a change to the HEFA cap is required in 2027 or subsequent years to address insufficient supply, what type of change do you think is required?

Please provide detail of the change and evidence to support it. If you do not believe a change is required to the HEFA cap, please state why. Please provide any supporting evidence as justification. Consider supply availability, and the impact on investment, industry and the environment in your answer.

Question 4. What would be the impact on investment in non-HEFA production domestically and globally by any change in the HEFA cap?

Please provide evidence including differential impacts of different approaches to changing the HEFA cap. How could a change be implemented that mitigated impacts on non-HEFA production most effectively?

Advanced PtL SAF

PtL SAF plays an important role in meeting the UK’s decarbonisation goals, given its potential for increased emissions savings and reduced reliance on constrained feedstocks.

The SAF Mandate’s PtL obligation, which comes into force in 2028, supports the development and scale‑up of these technologies, recognising their strategic importance to delivering a resilient and sustainable SAF supply mix for the future. We have also provided significant support to PtL projects through our grant funding programmes and are committed to supporting the development of a viable PtL industry in the UK.

PtL SAF is commercially less established than some other SAF pathways. First‑of‑a‑kind projects need to progress through development, financing, and construction. As a result, stakeholders have expressed concern about the availability of PtL SAF when the PtL obligation enters in 2028.

We recognise that policy stability from government is critical to maintaining investor confidence in these technologies, particularly during their early commercialisation phase. At the same time, it is important to ensure that SAF Mandate requirements remain deliverable in the context of emerging supply.

We are therefore seeking views on expected availability of PtL SAF, domestically and globally. To reach higher SAF targets, we will need a diverse range of innovative technologies drawing upon a wide range of feedstocks. We want to support investment in these technologies through clear and ambitious policies. In particular, we are asking you to consider how supply is likely to change over time, how this relates to demand under the SAF Mandate and whether any changes to the PtL obligation are required.

We are also interested to understand how any changes to the PtL obligation could affect future supply from projects and emissions reductions.

Question 5. If you believe a change to the power-to-liquid (PtL) obligation is required in 2028 or subsequent years to address insufficient supply, what type of change do you think is required?

Please provide detail of the change and evidence to support it. If you do not believe a change is required to the PtL obligation, please state why. Please provide any supporting evidence as justification. Consider supply availability, and the impact on investment, industry and the environment in your answer.

Question 6. What would be the impact on investment in non-HEFA production domestically and globally by any change to the PtL obligation?

Please provide evidence including differential impacts of different approaches to changing the PtL obligation. How could a change be implemented that mitigated impacts on non-HEFA production most effectively?

Wider flexibility options

The SAF Mandate design was based on the existing Renewable Transport Fuel Obligation (RTFO), with buyout as the primary flexibility method for compliance. However, we recognise that there are inherent differences between the markets affected by the schemes, particularly the maturity of supply chains.

Buyout effectively caps the cost of the scheme in circumstances where there are unreasonable costs to SAF, and it therefore remains a crucial flexibility measure of the mandate. We do, however, recognise that in the event of limited available supply, there could be significant buyout costs for suppliers.

We are interested to understand if there are any additional flexibilities that could be introduced to help support cost-effective compliance by reducing the risk of buyout.

Examples of such flexibilities could include:

• increasing the proportion of the obligation that can be met with the previous year’s certificates (from 25%)
• extending the regulation that a proportion of the obligation can be met with the previous year’s certificates to a greater number of years
• allowing a proportion of an obligation to be carried over between years, similar to the design of the zero emission vehicle (ZEV) mandate
• rewarding certain fuels (for example, advanced types of SAF) with additional certificates to incentivise their production and support achievement of targets (similar to how waste-based or development fuels are rewarded in the RTFO)

The above options are not an exhaustive list, and we invite views on the types of flexibilities that could be implemented to address any fluctuations in supply, without diminishing the SAF Mandate’s environmental ambition or investment signals to investors.

Question 7. Do you think there are additional options for flexibility within the SAF Mandate that should be considered to help support delivery of the mandate while not undermining investment in SAF production?

If so, what are these options and what would be their pros/cons. Please provide evidence. Consider supply availability, and the impact on investment, industry and the environment in your answer.

Wider system considerations

This government is also seeking evidence about the impacts of tankering.

Tankering is the practice whereby airlines opt to take on additional fuel for inbound journeys  to cover the outbound return, mainly for economic optimisation. Full tankering occurs when sufficient fuel is uplifted to cover the entire return flight, while partial tankering covers only part of the return journey.

We recognise that some tankering occurred as a practice before the introduction of the SAF Mandate. We understand that some industry members are reporting a risk that the SAF Mandate may exacerbate this practice and so undermine the carbon savings delivered by the SAF Mandate.

During the design of SAF Mandate policy, many industry respondents fed back to government that anti-tankering measures should only be considered once the SAF Mandate was operational, and there was sufficient evidence to show the practice was impacting emissions reductions.

The government wants to ensure that greenhouse gas (GHG) emissions reductions are maximised under the SAF mandate. When tankering occurs, the additional fuel carried increases aircraft weight, resulting in higher fuel burn and greater carbon emissions. Whilst emissions may be displaced from the UK to other countries, this may still cause an increase in total global carbon emissions (carbon leakage). We are seeking updated views on current and future concerns and asking stakeholders to submit any available evidence they can provide.

Question 8. In your view, what impact is the SAF Mandate expected to have on future tankering compared to current practices? 

Please provide any supporting evidence to highlight the environmental and economic impact.

Additional or alternative approaches 

Question 9. In your view, are there any alternative options which have not been considered in this call for evidence which would help delivery of carbon savings from the SAF Mandate and help maintain investment and supply certainty for industry?

Full list of questions

These questions are included here so you can see an overview of what we are asking.

See the How to respond section of this page to see how you can respond.

Q1. Do you expect there to be sufficient non-HEFA SAF (either PtL or non-PtL SAF), domestically and globally, to meet the SAF Mandate targets until 2040? Please provide any supporting evidence including how you expect availability to change over time.

Q2. In your view, what would be the likely consequences of maintaining the current approach (no policy change)? Please provide any supporting evidence.

Q3. If you believe a change to the HEFA cap is required in 2027 or subsequent years to address insufficient supply, what type of change do you think is required? Please provide detail of the change and evidence to support it. If you do not believe a change is required to the HEFA cap, please state why. Please provide any supporting evidence as justification. Consider supply availability, and the impact on investment, industry and the environment in your answer.

Q4. What would be the impact on investment in non-HEFA production domestically and globally by any change in the HEFA cap? Please provide evidence including differential impacts of different approaches to changing the HEFA cap. How could a change be implemented that mitigated impacts on non-HEFA production most effectively?

Q5. If you believe a change to the Power-to-Liquid (PtL) obligation is required in 2028 or subsequent years to address insufficient supply, what type of change do you think is required? Please provide detail of the change and evidence to support it. If you do not believe a change is required to the PtL obligation, please state why. Please provide any supporting evidence as justification. Consider supply availability, and the impact on investment, industry and the environment in your answer.

Q6. What would be the impact on investment in non-HEFA production domestically and globally by any change to the PtL obligation? Please provide evidence including differential impacts of different approaches to changing the PtL obligation. How could a change be implemented that mitigated impacts on non-HEFA production most effectively?

Q7. Do you think there are additional options for flexibility within the SAF Mandate that should be considered to help support delivery of the mandate while not undermining investment in SAF production? If so, what are these options and what would be their pros/cons. Please provide evidence. Consider supply availability, and the impact on investment, industry and the environment in your answer.

Q8. In your view, what impact is the SAF Mandate expected to have on future tankering compared to current practices?  Please provide any supporting evidence to highlight the environmental and economic impact.

Q9. In your view, are there any alternative options which have not been considered in this call for evidence which would help delivery of carbon savings from the SAF Mandate and help maintain investment and supply certainty for industry?

How to respond

Email or post your response to us.

Email to lowcarbonfuel.consultation@dft.gov.uk.

Write to: 

Low Carbon Fuels
Department for Transport 
Great Minster House
33 Horseferry Road
London
SW1P 4DR

If you send your response by email or post: 

• answer the questions asked in the call for evidence and, if required, provide further comments and evidence 

• tell us if you are responding as an individual or on behalf of an organisation 

If responding on behalf of an organisation, you need to: 

• tell us the name of the organisation

• tell us your position within the organisation

• make it clear who the organisation represents 

• outline how the views of members were assembled (where applicable) 

You will receive an acknowledgement of receipt if you submit your response by email. Check your junk/spam folder if you do not receive this within 15 minutes of sending your email.

If you do not find a receipt, email lowcarbonfuel.consultation@dft.gov.uk with ‘missing receipt’ in the subject line.

We will only accept responses received before the closing date: 11:59pm on 28 July 2026. 

What will happen next

Following the closure of the call for evidence, government will review responses and publish a summary of responses, including next steps. Our intention is to publish this summary of responses in autumn 2026, subject to the usual approval processes. Paper copies will be available on request.

Any proposed changes to the scheme would need to undergo a focused consultation and be supported by analysis of the costs and benefits.

Freedom of information

Information provided in response to this call for evidence, including personal information, may be subject to publication or disclosure in accordance with the Freedom of Information Act 2000 (FOIA) or the Environmental Information Regulations 2004.

If you want information that you provide to be treated as confidential, please be aware that, under the FOIA, there is a statutory code of practice with which public authorities must comply and which deals, amongst other things, with obligations of confidence.

In view of this it would be helpful if you could explain to us why you regard the information you have provided as confidential. If we receive a request for disclosure of the information, we will take full account of your explanation, but we cannot give an assurance that confidentiality can be maintained in all circumstances. An automatic confidentiality disclaimer generated by your IT system will not, of itself, be regarded as binding on the department.

Data protection

This call for evidence is seeking your views on investment certainty and the evolving SAF market. 

View our DfT online form and survey privacy notice for more information on how your personal data is processed in relation to this survey.

In addition to the information given we are asking all organisations their area of work, to ascertain their relationship with the topic.

DfT’s privacy policy has more information about your rights in relation to your personal data, how to complain and how to contact the Data Protection Officer. 

To receive this information by telephone or post, contact us on 0300 330 3000 or write to:

Data Protection Officer
Department for Transport
3rd Floor
One Priory Square
Hastings 
East Sussex TN34 1EA

Your information will be kept securely on secure IT systems within DfT and will be destroyed within 24 months after the consultation has been completed.

Artificial intelligence  

Artificial intelligence (AI) may be used to analyse responses to this call for evidence. Where the call for evidence asks for directly identifiable information, such as your name or contact details, these will be removed before processing with AI tools.