As major players like Shell, British Petroleum (BP), Chevron, Exxon and Total Energies are all getting behind sustainable aviation fuel (SAF), we take a better look at how sustainable SAF really is.
Pre-pandemic levels of worldwide jet fuel consumption were about to break the 100 billion gallons per year mark, but have been rolled back to pre-2005 levels in 2020. Despite that, the demand is expected to significantly increase and SAF comprises a significant portion of the industry’s strategy for CO2 reductions given the limited near-term prospects of electrification. This leaves us with one question. Where will all this SAF come from?
There are multiple pathways of SAF production. All include agricultural waste, used cooking oils or animal fats. In the US, the primary method of fabrication relies on hydrotreating of esters and fatty acids (HEFA) using vegetable oils, fats and greases from waste. But how much waste can there be and how will these methods keep up with the ever-growing demand for air travel?
These feedstocks also serve the renewable diesel market which, in 2018, produced 300 million gallons of HEFA diesel compared to 2 million gallons of HEFA SAF. Global HEFA capacity was estimated to be 1.1 billion gallons per year back in 2017. That only represents 1 percent of the amount of jet fuel used worldwide in aviation in 2019. About 90 billion gallons per year short.
Growing new crops of sugarcane, soybean and palm exclusively for SAF production is never going to be a viable option due to the sheer size of demand that will have to be satisfied and the additional upstream emissions that will come as a result, which would go against the point of SAF. On top of the fact that SAF is struggling to justify its production methods, the alleged reductions in emissions are also eyebrow raising.
BP released an article describing the importance of SAF and claims that it will reduce emissions by 80%. Other sources argue that reductions of up to 165% will be seen as a result of replacing fossil fuel-based jet fuel with SAF but the calculations rely heavily on the assumed reduction in methane emissions that would otherwise be released into the atmosphere by rotting waste, which are a bit vague given that no one measures them. In fact, the same source claims that the in-flight emissions are actually greater than the ones produced by burning typical jet fuels, due to the higher carbon content of this waste produced fuel which has been chemically proven.
While we are left to digest the multitude of research papers and articles that glorify SAF, Lufthansa has signed a Memorandum of Understanding with Shell for an order of around half a billion gallons of SAF. The deal will facilitate the airline with SAF starting in 2024 for a period of 7 years. This is not only one of the more significant deals in the brief history of SAF but also the largest commitment to SAF seen from both these companies. Currently some civil aviation aircraft use SAF in small blend percentages of 5-10%, but that number will increase to about 50% in the next 25 years.
With an increased commitment to SAF not only from fossil fuel giants like Shell and BP, but also from aircraft systems manufacturers like Rolls Royce and Airbus, we can’t help but argue that SAF is only a smokescreen for what really is the industry’s inability to decarbonize.
Small planes can benefit from battery storage and short haul aviation will, at some point in the next 20 years, transition to hydrogen, but the crippling specific energy limitations (the available energy per unit mass) of batteries and fairly uncharted territory of large aircraft fitted with electric motors powered by fuel cells, are leaving the industry without an answer.
So, until hydrogen catches up in terms of infrastructure, reliability and technological advancements, SAF will continue to be held in the highest regard as the saviour of an industry that is crashing down at the reality that it just needed some new ways of making money while wearing the “I’m going green” hat.