Greening up air travel: new rules on Sustainable Aviation Fuel (SAF) now in force in the UK

Last week, on 1 January 2025, the UK government’s new rules (known as the SAF Mandate) on the use of Sustainable Aviation Fuel (SAF) came into force. This is a welcome development that will make the UK a cleaner and greener place, and will encourage innovation in the production of SAF as well as helping to develop the industry here.

SAF, as the name suggests, is a replacement fuel for aviation that acts to reduce greenhouse gas emissions compared to standard kerosene jet fuel.

So what has changed? The new rules dictate that flights departing from the UK will now need a minimum of 2% SAF from 2025, rising each year to 10% by 2030 and 22% by 2040. This is known as the “main obligation”, and is designed to reduce the level of greenhouse gas emissions from the aviation industry.

A second obligation, known as the “Power-to-Liquid obligation” or “PtL obligation”, will come into force in 2028, and will require that 0.2% of total jet fuel demand is via PtL, rising to 3.5% of total jet fuel demand in 2040. PtL fuel is a type of SAF which is typically made from renewable energy and is less reliant on scarce feedstocks than other types of SAF such as those made from oils or fats (e.g. used cooking oil). Thus, the government is looking to boost the development of PtL fuels in particular with this second obligation.

Who must comply? The obligations to comply with the new requirements will fall on fuel suppliers rather than the airlines who use the fuel.

The UK is one of the first countries to legislate minimum use requirements for SAF, and it is hoped that doing so will encourage the rapid growth of an SAF industry in the UK to meet the new demands, in addition to encouraging further innovation in the area. It is well known that SAF is, at present, considerably more expensive than ordinary jet fuel (around 4 times the price) but with the new rules it is hoped that a significant number of areas of research that were previously not financially viable will now come into play, and that further innovation will drive the costs of SAF down.

There are, of course, some downsides to these changes, and in the short term there will be increases in costs for air travel which are likely to be borne by consumers and businesses travelling by air, but on balance I think the changes are positive and the government has done the right thing in pushing users towards more sustainable air travel.