Sustainable Aviation Fuels?

The chemicals we use today overwhelmingly come from refineries that also make fuels. This interplay, both in terms of economics and of science and engineering, is the foundation of the petrochemical technology that our civilisation relies on today.

This Prosperity Partnership is focussed on new routes to chemicals, both drop-in replacements and new chemical entities offering enhanced functionality over that of the incumbent fossil-derived products, driven by the change of supply chains mandated by Unilever’s Clean Future framework. We must thus be aware of likely developments in fuels manufacture and use as it is that interaction which will determine the rate at which fossil-based incumbent species need to be replaced. The economics of refineries will be dramatically disrupted by the global phase-out of petroleum-fuelled vehicles for transport by 2050 at the latest. While it can be argued that a fossil-derived chemical such as polypropylene that is landfilled at end of use has no carbon footprint, at the very least the shift in economics of refineries not to say the role of both societal opinion and thermodynamic outcomes make the overall consideration of non-fossil carbon use for chemicals pressing.

The sector of the fuels industry most visible in this discussion in society today is aviation. Everyone in society knows that flying with hydrocarbon fuels is a powerful contribution to global warming, with attention drawn by recent rulings on greenwashing in advertising to the reality of this. The energy density of kerosene is such that electrification is simply not an option, so what to replace it with? This is an example of the difficult challenges ahead – fossil products can be high-performing and thus hard to replace. Without the science in place to properly assess the alternatives, misunderstanding over the readiness and scope of current technologies can proliferate.

With this in mind, the Royal Society recently produced a report that sets out the science behind sustainable aviation fuels (SAF), without making recommendations for policy action, as part of its Low Carbon Energy Programme (  PP investigator Matt Rosseinsky contributed to the writing of the report. Its conclusions are stark – there is currently no viable alternative to kerosene that is deployable and sustainable. For example, considerations of land and water use and the competition with food make crop growth for fuels uncompetitive, certainly in the UK – in this context, the scale of the demand and the definition of waste need to be carefully considered in any proposals for alternative fuels. This outcome emphasises the need for research in physical science and engineering to minimise the climate impact of aviation. As the chemicals and fuels supply chains are so entwined today, the same net-zero driven disruption motivates the research into sustainable chemicals production that this project tackles.