This is a key issue in more than one way, but all are related to the environment.
GAAC is involved in an initiative with associations such as the LAA and AOPA to look at the use of TEL (“lead”) additive in Avgas. Further information is expected to be published shortly after a funding proposal was provided to DfT.
Meanwhile Sustainable Aviation Fuel (SAF) is a growing area and production of drop-in biofuels for turbine aircraft, to replace JET A kerosene, is increasing gradually.
Thirdly, developments in battery and other technology are making electric aircraft increasingly viable. Already some manufacturers, such as Pipistrel, have certified electric aircraft but many more are coming.
Finally, tax on Avgas is a major issue. For light piston-powered aircraft used for training, in particular, this is an added expense in what is already a very expensive training environment.