The Prequel: Future possibilities of flying in green skies . . . .

There is indeed no debate that the sky is obviously ‘blue’, which is a result of the scattering of the blue rays or spectrum of the sunlight when in contact with tiny molecules and particles due to its shorter wavelength. However, motivated by the cumulative greenhouse gas (GHG) emissions from the aviation sector, and the creeping efforts towards electrification, biofuel researchers are willing to change that narrative to a ‘green’ sky (not literally). This impulse has triggered foreseeable goals, roadmaps, and policies such as ‘achieving net zero carbon in 2050 ’ and the ‘Biden administration advances ’ on sustainable aviation fuel (SAF) by achieving 3 billion gallons of SAF to reduce GHG emission by 20% in 2030, etc. discussed in conferences, symposia, and forums, with a common goal to decarbonize the aviation sector. In contrast with conventional jet fuels – sourced from petroleum, SAF is a ‘drop-in’ fuel generated from non-petroleum renewable feedstocks. The fungibility of SAF makes it suitable and highly amenable (as either standalone or blendstock) with jet engines that have a long shelf life lasting for several decades. Typically, a Boeing 787 Dreamliner is expected to travel 44000 flight cycles and the Iconic Boeing 747 a 135,000 to 165,000 flight cycles - that is quite a lot of flight cycles. With the awareness of this plethora of possibilities, are we still close to achieving net zero? Progressive steps are already in place: on the 1st of December 2021, General Electric achieved a milestone of the first experimental flight with 100% SAF from Chicago to Washington D.C. More so, Neste has made progressive efforts with Air Canada for 9.5 million liters of SAF blendstocks, and the Virgin Atlantic flight is ready to take off the first transatlantic flight which would be run on SAF blendstocks by November 2023, and many more. – Yes, there is progress, however, tiptoed.

How then and what efforts can we make to fast-track the flight in green skies?

The superabundance of unconventional feedstock available for SAF can be efficiently utilized to obtain a maximum output, depending on the process and the class of products desired. For hydrogenated vegetable oil or hydroprocessed esters and fatty acids (HEFA), which is the most developed and currently employed technology, co-processing of two or more different feedstocks that may be chemically distinguishable can be adopted to achieve optimum results. Although the utilization of biomass for biofuel purposes could result in concerns such as deforestation and biodiversity loss, but the use of co-products and the use of degraded abandoned farmland where non-edible, low fertilizer, and water crops like Jatropha and Camelina are grown could be an effective alternative.

In addition, the technology required to enhance biofuel processing should be centered on the nature, chemistry involved, the feedstock combination, and the kind of fuel targeted. Government policies that ensure feedstock and energy security and also attract incentives should be encouraged. This is important, as it may help cut the cost of feedstock and probably result in a decline in the production cost of SAF – since it has been reported that HEFA SAF from waste oils costs 50% more compared to conventional jet fuel.

Additionally, other associated challenges include the complexity of the SAF certification process, which may be resolved by curtailing the bureaucracy, time, and resources required in the American Society for Testing and Materials (ASTMD7566 – ‘Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons’) certification process in partner with the Federal Aviation Administration (FAA) and focusing more on the required ASTM fuel standard and properties of the proposed fuel. A much better way to hasten this process is an early step-by-step scrutiny and follow-up by ASTM and other regulating bodies and airworthiness certification services like FAA with registered companies and biofuel researchers willing to commercialize their technology and have made initial progressive steps through publication, I.P protection, license, and patents, etc. This follow-up is expected to come along with governmental and technological expertise, advice, and consultancy at that early research stage rather than till the end of the entire process when the SAF blendstock is ready to undergo the rigorous and laborious certification. This way, bureaucratic bottlenecks are constrained and truncated to the barest minimum, and this would in return create employment for experts in the aviation sector. Another important issue relating to supply and demand poses a greater challenge, and to balance the demand for SAF, there needs to be a huge supply, which is, in today’s reality, far-fetched. Projections made by S&P Global , taking into account feedstock limitations, estimate only a supply of 8.7 billion gallons of SAF by 2050. – This is still a challenge! A deeper look into more emerging SAF technologies : SAF from wet wastes and other carbon-rich wastes etc., are required to complement and scale up the S&P Global estimated 17.5 billion gallons SAF to be produced to meet the 2050 SAF blending target.

Ultimately, the sustainable roadmap towards net zero is a joint effort from not just researchers and technologists, but the government, economists, citizens, and agricultural communities, you, and I, are key players in this sustainable future.

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