The Aviation Industry's Journey Might Conclude in Hydrogen-Powered Aircraft
Airplanes contribute around 2% to 2.5% of worldwide greenhouse gas emissions, which is minimal compared to the industrial sector. However, as aviation technology advances, this figure could rise. Aircraft are primarily fueled by kerosene, but the sector is researching alternatives like hydrogen, electricity, and sustainable aviation fuels.
Hydrogen and electric planes represent a significant leap in aviation, but they are unlikely to entirely replace kerosene-powered planes in the near future. Instead, they will complement existing technologies, gradually decreasing emissions.
By mid-century, we could observe a varied fleet of aircraft. Electricity or hydrogen might power short trips, while sustainable aviation fuels from biomass would power longer journeys. The future path is challenging, but the potential advantages for the environment and the aviation sector could make it a profitable undertaking.
Rob Miller, an aviation professor at the University of Cambridge, likens today's aviation sector to the car industry in the early 2000s. At that time, biofuels were thought to be the solution, and significant investments were made in them. Then came the 'Tesla moment,' when battery-electric cars emerged and changed everything.
Last week, Miller and I discussed at length during a virtual conference organized by ZeroAvia, a company that develops hydrogen-electric engines for aircraft. The Whittle Lab at the university, where Miller serves as director, is researching all potential solutions. The goal is to reach a tipping point at which the aviation sector can revolutionize and transform the world. Hydrogen might be the key to achieving this. If not, as Miller acknowledges, "we may need to double down on sustainable fuels."
The U.S. Energy Department reports that the biofuel industry has produced 17 billion gallons of fuel and prevented 544 million tons of CO2 from being released into the atmosphere. The main objective is to reduce petroleum reliance by using this biofuel. Renewable energy sources such as food waste, animal waste, and sewage sludge can make aviation fuels sustainable. According to the department, the carbon footprint of sustainable aviation fuels can be up to 165% smaller than traditional petroleum-based jet fuel.
Sustainable aviation fuels are expected to be the preferred option for international routes for the time being. This source can significantly reduce emissions while utilizing existing planes and infrastructure.
Sustainable Aviation Fuels or Electric Planes
Does producing biofuels result in more greenhouse gas emissions than directly burning fuel? The Journal of Environmental Science and Technology analyzed the lifecycle of algae compared to other biofuels, such as corn and switchgrass. It found that using conventional crops to create fuels leads to fewer greenhouse gas emissions and less water consumption than using algae to do the same.
However, Professor Miller states that this is not ideal. He points out that the global biomass supply is limited, and several industries are competing for it. Furthermore, green hydrogen or green electricity can produce more fuel, which is a more carbon-efficient solution, according to Miller.
Aircraft manufacturers have submitted several applications to the Energy Department. For instance, Air Canada aims to be net-zero by 2050: It has ordered 30 hybrid aircraft from Heart Aerospace—the ES-30. Not only has the airline invested $5 billion, but so has Bill Gates, the founder of Corp. United Airlines is also an investor in Heart and will purchase up to 100 electric aircraft. These planes have an all-electric range of 124 miles, which doubles if combined with jet fuel. They fly at an altitude of 20,000 feet and will serve regional airports with 30 passenger capacity.
Meanwhile, hydrogen can power aircraft through combustion or fuel cells. In fuel cells, hydrogen combines with oxygen to produce electricity, with water as the only byproduct. This makes hydrogen an excellent choice for reducing greenhouse gas emissions. It also offers high energy density, potentially supporting longer flights than batteries. American Airlines, KLM Royal Dutch Airlines, and ASL Aviation Holdings are collaborating with ZeroAvia.
Weight is a critical factor in aviation: According to Cambridge's Miller, jet fuel accounts for 45% of the weight on a long-haul flight. "We think there is an advantage of hydrogen over kerosene. Hydrogen is a third of the weight. So, you're at least 15% lower fuel burn than a kerosene aircraft for long-range flights."
The timeline? Miller expects hydrogen fuel cell aircraft to take off within a decade, traveling 1,000 to 1,500 kilometers. Their performance will improve exponentially; by 2035 or 2040, they will fly 4,000 kilometers.
It Won’t Come Easy
The aviation industry faces several challenges. Jet fuel is energy-dense, which allows airliners to achieve the necessary range and payload capacity for long-haul flights. In contrast, batteries are considerably heavier and provide lower energy density. While hydrogen is more energy-dense than batteries, it requires large, pressurized tanks, complicating aircraft design. Hydrogen production must also scale up, relying on green hydrogen from renewable energy sources, while airports must have hydrogen refueling stations or charging facilities.
Professor Miller and the Whittle Lab are tackling some of these issues. The aviation industry is making strides to improve fuel efficiency and reduce fuel burn, although it has much room for improvement. According to Miller, potential improvements could reduce fuel burn by 2050, potentially halving the figure. However, this may not be the winning solution three decades from now. A better bet could be hydrogen aircraft, provided that hydrogen fuel prices decrease. If that becomes economical, producing kerosene for aviation would not make sense. "These transformative innovations happen once in a generation," says Miller. "I'm not certain if hydrogen will win, but it's worth a chance."
Regardless of the circumstances, "Air travel is hands down the safest mode of transportation," is a fact that'll persist, according to him.
The aviation field has made significant strides, allowing individuals to traverse different continents. The future holds promising advancements, such as switching to hydrogen as the main fuel for long-haul trips and electric planes for shorter journeys by mid-21st century. These innovations will synchronize to decrease aviation's environmental impact.
In the future, electricity or hydrogen might power short trips in aviation, while sustainable aviation fuels from biomass are expected to power longer journeys. This shift towards more environmentally friendly alternatives could make aviation a profitable undertaking.
As the aviation sector explores various options to reduce its carbon footprint, hydrogen is being widely researched as a potential fuel source. If successful, hydrogen could revolutionize and transform the aviation industry.
