The US Air Force has been nosing around the area of fossil-free jet fuel for years, and the latest candidate takes the concept into the rarified territory of electrolysis. If all goes according to plan, the jet fighter of the future will grab renewable fuel on-the-go from modular systems that tease hydrogen and carbon from water and air.
Beyond Plain Old Renewable Fuel
The electrolysis approach is a sharp departure from previous efforts to shake the US military free of fossil fuels for air and marine craft. Just a few years ago, everyone was all excited about producing jet fuel from renewable resources like algae oil, used cooking oil, and other bio-based resources, including a sort of fermented biofuel cocktail. At one point it seemed like the whole Department of Defense was pursuing bio-based, fossil-free fuel alternatives for aircraft and watercraft, too.
Algae has been a particular area of focus, partly due to its potential for scaling up production with rapid harvesting cycles, and partly for opportunities to grow algae without bumping into land use and nature conservation walls.
The Problem With Renewable Fuel, Air Force Edition
Well, dream on, Klingon. For reasons best known only to itself, ExxonMobil been doggedly pursuing the algae biofuel unicorn with varying degrees of effort. One day in the sparkling green future that may pan out, but not in the area of national defense.
The problem is that practically every kind of renewable fuel on the market today is subject to the same key problem that makes fossil fuels a less than ideal way to power a modern military operation: you have to produce them at point A, and transport them to point B, which could require long distance ferrying by truck, ship, aircraft, or a combination of all three.
Here, let’s have the US Air Force explain the problem with fuel transportation:
“Recent joint wargaming and operational exercises have underlined the significant risk that transporting, storing, and delivering fuel poses to troops – both at home and abroad. At the height of the war in Afghanistan, attacks on fuel and water convoys accounted for more than 30% of casualties.
“Yet, fuel demand is only expected to increase as advanced weapon systems and operations require increasing levels of power. ”
Don’t look now, but recent moves by Russia and China already have US military planners pivoting from a focus on urban guerilla warfare to anticipating more conventional modes of battle, which will both increase the need for fuel and increase the risk of transporting it, too.
“History has taught us that our logistics supply chains are one of the first things the enemy attacks. As peer-adversaries pose more and more of a threat, what we do to reduce our fuel and logistics demand will be critical to avoid risk and win any potential war,” emphasizes Roberto Guerrero, deputy assistant secretary of the Air Force for operational energy.
The Rise Of Electric Fuel
If you’ve been tracking the green hydrogen trend, you can see where this is going. Hydrogen is a zero emission fuel but it is not a renewable fuel — yet. The global supply of hydrogen comes primarily from natural gas. However, it appears that the hydrogen supply chain is set to undergo a sea change.
Hydrogen is beginning to claim new status as a renewable fuel, thanks largely to the steep and still-falling cost of wind and solar power. That has made it commercially feasible to extract hydrogen from water through electrolysis, which involves applying an electrical current. Electrolysis systems tend to be scalable, which means you could produce hydrogen practically anywhere a supply of water and electricity from renewable resources are available. Local supplies of biogas, wastewater, and other bio-based resources could also be used as hydrogen feedstock.
What Is Missing From The E-Fuel Equation?
The green hydrogen angle is all well and good, but if the idea is to produce renewable fuel for jet engines, carbon is going to have to come into the picture somehow.
That’s where the next-generation energy company Twelve comes in. Last year the Air Force tapped Twelve to deliver jet fuel produced from green hydrogen plus carbon dioxide from the air, in partnership with the company Emerging Fuels Technology.
It seems that all has gone according to plan, so far. Last August Twelve established the feasibility of its process for producing liquid renewable fuel from airborne carbon dioxide, water, and renewable power.
Last month, Twelve delivered its first batch of its new fossil-free jet fuel, under the proprietary name E-Jet®.
“Initial testing shows that the system is highly deployable and scalable, enabling the warfighter to access synthetic fuel from anywhere in the world,” enthused the Air Force, noting that Twelve’s system would not require highly specialized fuel-producing skills to operate.
The Long Road To Renewable Fuel For Aircraft
The Air Force calls its fresh batch of E-Jet fuel “a positive first step in a truly innovative program,” which is a hint that you shouldn’t hold your breath for the first 100% E-Jet flight. For now, the maximum blend permitted is 50% for the fuel, otherwise known as FT-Synthetic Parffinic Kerosene.
However, the Air Force does hint that it is eager to pursue the e-fuel pathway. “If brought to scale, the platform would enable more agile operations and decrease dependence on foreign oil, while having the added benefit of mitigating carbon emissions,” it explains.
As further evidence of good intentions, the Air Force is also supporting the startup aerospace company Exosonic, and last week Exosonic announced that it has hooked up with Twelve to produce a new supersonic jet engine compatible with E-Jet fuel.
“Exosonic and Twelve are working with the USAF through independent small business innovation research (SBIR) contracts sponsored by the Air Force Research Laboratory,” Exosonic explained in a blog post, noting that its end of the deal involves modifying a commercial supersonic aircraft “to serve as an executive transport vehicle.”
Interesting! Could this be the Air Force One of the future?
Time will tell. The idea of using supersonic technology for military operations is hobbled by the noise that supersonic aircraft tend to make, but Exosonic has staked its claim to producing the “world’s first low boom, quiet supersonic passenger airliner using shaped sonic boom technology.”
“By muting the sonic boom, Exosonic will be able to fly supersonic everywhere — overland and overwater to take passengers to their destinations twice as fast as commercial flights available today,” the company explains.
Well, that certainly sounds a bit more military. In the meantime, there is still a place in the sustainability pie for renewable fuel made from things of a solid nature. Aside from biofuel from plants, the idea of reclaiming plastic waste to make fuels and other products is also beginning to take off. So to speak.
Follow me on Twitter @TinaMCasey.
Image (screenshot): Supersonic jet by Exosonic could run on E-Jet renewable fuel produced by the next-generation energy company Twelve (credit: Exosonic).