Four ways to look at aviation’s energy transition

The commercial aviation industry set a high bar when it committed to achieving net zero carbon emissions in operations by 2050.

Jim Hileman, vice president and chief engineer of Sustainability and Future Mobility at Boeing, put the scale of this challenge into context during his presentation at the International Council of the Aeronautical Sciences’ (ICAS) annual congress in Florence. The full video can be accessed here.

Hileman explained why aircraft are just part of the solution, gave a breakdown of the four types of sustainable aviation fuels (SAF), spelled out why airports will play a critical role in the energy transition, and described the energy challenges associated with using hydrogen.

Takeaways:

Decarbonizing aviation is a system of systems problem

Commercial aviation’s pathway to net zero will not rely solely on new aircraft. The industry also needs to address the challenges and opportunities in propulsion and the primary source of energy, including where this energy comes from and how it is transported. As the accompanying chart demonstrates, a “well-to-wake” analysis of a fuel’s efficiency and lifecycle emissions is necessary.

The various categories of SAF feedstocks

The carbon in SAF comes from a variety of renewable materials, or feedstocks, which undergo robust evaluation for their environmental and social sustainability. The four categories of feedstocks are fats, oils and greases; sugars and starches; lignocellulosic biomass; and eFuels using electricity. “The challenges that we have with these different feedstocks are how much lifecycle CO2 emissions do they produce, how much do they cost (at full-scale production), how much feedstock can we get, and who else is getting this feedstock before aviation?” said Hileman.

To further explore SAF by feedstock, the Boeing Cascade Climate Impact Model team is working on a new feature that will enable customizing and visualizing various feedstocks. For example, the below chart shows forecasted jet fuel consumption by feedstock category through 2050.

Airports will play a critical role in the energy transition

Massive amounts of energy flow through the world’s busiest airports every day, and widebody airplanes at the world’s top 20 airports are responsible for about 20% of global jet fuel use. When evaluating new fuels like hydrogen, it is essential to thoroughly consider these airports and their supporting infrastructure requirements.

The energy requirements of using hydrogen fuels are enormous

Hydrogen-powered aircraft will use liquefied hydrogen, and the energy requirements for its transportation, storage, and management—maintained at -423 degrees Fahrenheit (-253 degrees Celsius)—are significant.

If airports aren’t able to store and manage liquid hydrogen, there is also an option to truck or pipe hydrogen in gaseous form and then convert onsite into liquid form. However, doing so at a large airport would require the energy equivalent of multiple nuclear reactors to convert gaseous hydrogen into liquid hydrogen.