E N V I R O N M E N TA L Fuelling the future Hydrogen could be the key as we strive to decarbonise the aviation industry but it comes with its challenges too By Debbie Thomas, Senior First Officer at easyJet and aerospace engineer T he global climate crisis remains at the forefront of international policy. Aviation contributes around 3% to global warming, but with the expected rise in aviation demand by 2050, and the reduction in carbon emissions in other industries by 2050, aviation could reach 22% if nothing changes. Decarbonising the aviation industry is a significant challenge because of its reliance on high-energydensity fuels, global operations, and long asset lifecycles. However, a range of opportunities is available to help meet emissions-reduction targets, including: sustainable aviation fuel; improving aircraft efficiency; more efficient air traffic management; carbon-capture technology; and zero-carbonemission aircraft. For zero-carbon-emission aircraft, there is growing global momentum in the industry towards hydrogen (H2), which is seen as a potential solution to operating with zero or low CO2 emissions by 2035-50 in the Decarbonising the aviation industry is essential but will be challenging regional to short-haul and, potentially, mediumrange operations. Hydrogen is gaining increasing attention in aviation because of its potential to revolutionise the industry with environmental and operational advantages. The key benefits and considerations are: 1. High energy density I t offers an energy density of 120 MJ/kg, significantly surpassing Jet A1s 43 MJ/kg. This means hydrogen is three times lighter for the same energy output, a critical factor in aviation. 2. Versatile usage I t can power aircraft via combustion engines or fuel cells, providing flexibility in design and application. 3. Environmental benefits T here are no carbon emissions during operation. G reen hydrogen, produced via renewable energy and water electrolysis, can achieve zero life-cycle emissions, eliminating dependence on fossil fuels. 4. Energy independence G reen hydrogen production enables a shift away from fossil fuel reliance. 5. Cost-efficiency potential C ompared with sustainable aviation fuel (SAF) produced via power-to-liquid methods, hydrogen could use 36% less energy in its production process. This efficiency could translate to lower costs over time. There are, however, challenges to be faced and considerations to be made when looking at hydrogen as an alternative: 1. Green hydrogen availability The environmental benefits of hydrogen rely on the use of green hydrogen. Producing it at scale requires significant investment in renewable energy infrastructure and production facilities. 2. Non-CO2 emissions C ontrail impact and water emissions: Hydrogen combustion emits water vapour, potentially affecting contrail formation, especially in icesupersaturated regions. Ongoing research aims to mitigate this via predictive modelling and air traffic management. Unlike Jet A1, however, hydrogen combustion does not produce soot, which may result in fewer contrails further studies are needed to confirm this benefit and understand the net environmental impact. N itrogen oxides (NOx): Hydrogen combustion could reduce NOx emissions by 5070% in optimised systems compared with Jet A1, and eliminate NOx entirely when using fuel cells. Impact on aircraft The chemical properties of hydrogen will necessitate 36 THE LOG Spring 25 pp36-37 Sustainability.indd 36 17/03/2025 14:22