Question to the Department for Transport:

To ask the Secretary of State for Transport, with reference to the Project Willow report, published on 19 March 2025, what assessment she has made of the potential merits of removing the Hydrotreated Esters and Fatty Acids cap in the Sustainable Aviation Fuel mandate.

We welcome the Project Willow Report and are pleased that nine potential business models have been identified to be taken forward at Grangemouth. To help make these models a reality, the Prime Minister recently announced a commitment of at least £200m through the National Wealth Fund for co-investment with the private sector once an investable proposition comes to the forefront. We will also consider Project Willow’s recommendations in due course.

We recognise that Hydrotreated Esters and Fatty Acids (HEFA) will play an important role in the global Sustainable Aviation Fuel (SAF) sector, particularly in the early years of the Mandate. We want to encourage UK production of HEFA in this global market and have not placed a cap on the amount of SAF produced in the UK.

However, certain feedstocks, such as used cooking oil, from which HEFA is made, are limited in volume and will not be able to provide the amounts of SAF we expect to need to in the long term. We therefore need to create space for a range of SAF technologies and feedstocks to develop.

The HEFA cap, which from 2027 will decrease the allowed contribution from HEFA as a proportion of total SAF supply annually, aims to create this space and encourage investment in alternative pathways. The cap would still allow around 1 million tonnes of HEFA SAF to be supplied in the UK each year from 2035 onwards.