|
|
| Fig. 1: Different types of biofuel. (Source: Wikimedia Commons) |
In 2019, transportation accounted for 29% of total U.S. greenhouse gas (GHG) emissions, with aircraft from commercial, military, and general uses covering 10% within this sector. [1] As the aviation sector is projected to continue to be a prevalent mode of transportation, there has been increasingly more attention in developing alternative jet fuels in an effort to decrease emissions. These proposals range from biofuels and electrofuels to changing aircraft, flight routes, and policy altogether. [2] Out of these options, biofuels from various production sources, as seen in Fig. 1, remains to be one of the most researched alternatives for jet fuel.
The immediate benefit of biofuel is the decrease in emissions. A study which evaluated the sustainability of biofuels for the U.S. Department of Defense, one of the biggest consumers of aviation fuel, yields interesting results for the potential of biofuels in this way. Calculated from nine different production sources in the terrestrial, marine, and byproducts sectors and assessed on metrics of cost, energy, GHG, water, land, and fertilizer, this research shows that each of these pathways "represent over 50% reduction in lifecycle GHG emissions compared to petroleum jet fuel". [3] Considering that the U.S. alone consumed a total of 18.2 billion gallons of jet fuel in 2019, these results of biofuels in decreasing emissions for the U.S. Department of Defense has huge implications for the rest of the country and the world. [1]
However, the study goes on to conclude that although these biofuels decrease GHG emissions, not a single production source could produce jet fuel at a lower cost than conventional jet fuel, a limitation that needs to be considered when evaluating these alternatives. [3] Indeed, another analysis that examined the cost of the production of biofuels reached the same consensus that the current cost of production is too great, and that all of the pathways evaluated need policy intervention to be successful. [4] United Airlines' Chief Executive Officer Scott Kirby further corroborated this by stating that converting even 10% of the global aviation supply would require a staggering $250 billion, a number that puts into perspective just how costly the adaptation of alternative and sustainable jet fuels might be. [5]
Although costs of production and resources pose a considerable challenge in developing sustainable jet fuel alternatives, there is still great promise in biofuels in lowering GHG emissions. There needs to be a steady push, perhaps in the form of more policy initiatives, toward creating solutions that can balance the limitations and benefits of jet fuel alternatives.
© Joanna Jo. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Fast Facts: U.S. Transportation Sector Greenhouse Gas Emissions, 1990-2019," United States Environmental Protection Agency, EPA-420-F-21-049, June 2021.
[2] J. Timperley, "The Fastest Ways Aviation Could Cut Emissions," BBC, 25 May 21.
[3] C. M. Beal, A. D. Cuellar, and T. J. Wagner, "Sustainability Assessment of Alternative Jet Fuel for the U.S. Department of Defense," Biomass Bioenerg. 144, 105881 (2021).
[4] S. J. Bann et al., "The Costs of Production of Alternative Jet Fuel: A Harmonized Stochastic Assessment," Bioresour. Technol. 227, 179 (2017).
[5] J. Bachman, "United Air Plans D.C. Flight on Greener Fuel to Nudge Lawmakers," Bloomberg, 1 Dec 21.
