Biofuels in Aviation

Background

Fig. 1: United Airlines has invested in their "Eco-skies" program, which uses sustainable biofuel to power their flights. (Source: Wikimedia Commons)

As the world becomes more and more reliant on technology and manufacturing, especially in the next few decades, one notion has catapulted itself to the top of the leaderboard: alternative energy. While countries have already took initiative to limit and stop the use of fossil fuels, an industry that could play a vital part in this motion is aviation (See Fig. 1). The aviation industry has allowed our lives to become massively more efficient, but much of this is provided by fossil-fueled energy. By creating fuel out of living matter to power our airplanes, we could prevent up to and possibly more than 650 million tons, and 800+ million tons by 2020, of CO₂ (See Fig. 2). [1]

Non-renewable energies, such as fossil fuels, pose major health and environmental concerns to humans all over the globe. Emissions from traditional jet fuel cause and alter different formations of natural clouds and contribute to global warming. [2] Specifically, the harmful air pollutants such as CO₂, NO_x, soot, and SO_x have caused significant health issues such as respiratory and cardiovascular disease; CO₂ and NO_x emissions have been increasing linearly for the past decade. [2] Fortunately, new technological advances in aircraft and operational improvement will ease this trend, but additional steps must still be taken in order to reduce the industry's carbon footprint for the future.

Efficiency

Jet fuel is consumed by billions of barrels every year. For it to be practical crops must be able to withstand the use of yearly jet fuel consumption. To calculate this energy, we can use the following equations:

• 1 barrel = 42 gallons

• Kerosene energy density is about 43 MJ/kg

• 1 gallon of jet fuel weighs 6.8 pounds = .4356 kg

While this may seem like a lot of energy output, even more land must be needed to make this feasible. Land area equivalents for algae, one of the best sources of biofuels, would be 68,000 sq. km to fuel the entire aviation industry. [1] Since it is unlikely for one country to give up that much land for just one crop, it is unlikely for commercial aviation to rely solely on biofuels.

Biofuel Opportunities

In order for biofuels to be acceptable in the aviation industry, it must be practical and efficient for airliners to use. Since biofuels can be derived from oil-based plants, municipal waste, or recyclable biomass, there is a very diverse supply all over the world. Crops may be grown all over the world while fossil fuels may only be found on certain parts of the planet. [1] Bioethanol, a form of biofuel, can be derived from corn or sugar and technological advances have already made it a cheaper option than conventional gasoline. Studies have estimated that costs range to as low as $2/gallon. [3] With rising fuel costs around the world, sourcing fuel locally not only is cheaper but it also decreases the carbon output even before the fuel is burned for flight.

Fig. 2: Biofuels can be produced from any biological carbon material making it an advanced fuel supply for the future. (Source: Wikimedia Commons)

The largest and most pressing concern about traditional petroleum jet fuel is the environmental impact. In a conventional process, fossil fuels are drilled, then followed by being transported to a refinery and processing plant(s). The gasoline is then finally brought to the airport for distribution to airliners. Every stage in this procedure creates toxic waste in the air. In a biofuel approach, instead the emissions from each stage aid the plants by producing CO₂ for them. [1] In this positive feedback loop, the cycle of production would be sustainable while eliminating the risks for NO_x, SO_x, and soot.

In terms of socio-economic benefits, sustainable biofuels creates potential in rural parts of the world. Creating the ingredients for biofuels, development and resources will be used to invest in those communities that desperately need the help. While much of this will be a long-term project, there is a potential that biofuels could fuel the entire commercial aviation sector. [3]

Conclusion

Biofuels is a candidate to change the global expectation of aviation. It is a clean, renewable resource that has potential benefits for many. With continued advancement in biofuel technologies as well as aircraft development, the commercial aviation industry has the capability to run solely on biofuels from organic matter. This change will be for the better future of our planet creating an environment suitable for all.

© Alex Liang. 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.

References

[1] "Biofuels for Aviation: Technology Brief," International Renewable Energy Agency, January 2017.

[2] "BP Statistical Review of World Energy," British Petroleum, June 2018.

[3] "Alternative Aviation Fuels," United States Department of Energy, March 2017.