The aviation industry, emboldened by global governments and environmental targets, has made ambitious pledges to achieve a net-zero industry by 2050. If this is to be achieved, drastic changes must be made now; the goal is currently slipping further out of reach as carbon emissions continue to rise.
Today, aviation accounts for 2.5 per cent of global CO2 emissions, a large proportion when you consider that only 10 per cent of the global population actually uses air travel; this number is only set to grow as flying is made more accessible.
Current pledges, plans and efforts are falling short. We are behind the curve if we are to make flying sustainable any time soon. Even the most recent report published by Cambridge University and Aviation Impact Accelerator, which sets out a 5-year plan to reach 2030 targets, is somewhat missing a trick when it comes to harnessing the power of hydrogen technology.
Tackling contrails
A principal environmental challenge posed by aviation is contrail formation, which occurs when hot, moist air from engine exhausts mixes with the colder atmosphere at high altitudes. This mixing creates ice crystals that can persist as clouds, contributing to warming effects.
Hydrogen-electric propulsion systems generate electricity through an electrochemical reaction between hydrogen and oxygen in the fuel cells, producing only water as a byproduct. This process emits approximately 90 per cent of its water in liquid form and the remaining 10 per cent as cooler water vapour. In contrast, traditional jet engines burn fuel at high temperatures, resulting in hot exhaust gases that produce water vapour conducive to contrail formation.
The report referenced above claims that reducing contrail formation through optimising flight routes could reduce the aviation industry’s impact on carbon contribution by 40 per cent. However, the aviation industry should go further. Rather than just reducing contrails, hydrogen-electric aircrafts can fully reduce harmful emissions such as CO2, and NOx and help mitigate the warming effects associated with these GHG emissions.
Thinking bigger
Green road maps rely heavily on increased use of sustainable aviation fuel (SAF) (with plans that it will account for 83 per cent of total fuel consumption by 2050); however, scaling up production is an energy-intensive and expensive process; using SAF exclusively might not be the most efficient path, after all.
Beyond this, operational improvements could make a difference. Enhancements in air traffic management and operational efficiencies can lead to significant reductions in emissions and technologies like automation and big data management are being integrated to optimise flight paths and reduce fuel consumption.
Hydrogen: a viable solution
The industry should look to harness the power of emerging technologies to find a solution. For example, hydrogen-electric propulsion systems represent a transformative approach to achieving zero-emission aviation. By coupling a fuel cell system, a liquid hydrogen storage system and an electric motor, this propulsion technology offers significant benefits.
No transition is seamless, and admittedly, a crossover to hydrogen-powered aviation presents challenges in technological advances and the development of infrastructure on a commercial scale. However, the long-term benefits far outweigh the initial effort and investment, driving a measurable, lasting transformation in reducing aviation industry emissions and improving the overall quality of life for future generations.
The sustainability of hydrogen hinges on how it is extracted, processed, and stored. The most environmentally friendly method for producing hydrogen is through electrolysis, where water is split into hydrogen and oxygen using electricity from renewable sources such as solar, wind, or hydroelectric power. This "green hydrogen" approach ensures that the hydrogen production process has a minimal carbon footprint.
In comparison, SAF production can be energy intensive, requiring significant swathes of farmland to produce enough biomass for the Fischer-Tropsch (FT) synthesis or renewable energy to produce e-fuels through the Power-to-Liquid (PtL) process. In contrast, the direct use of green hydrogen as a fuel offers a potentially more sustainable and less costly solution.
Ultimately, hydrogen must be viewed with a lens of longevity; early investment and adoption will provide a long-term solution to an ever-growing issue. Realising its potential now, the industry can move decisively towards greener skies.
Dr Josef Kallo, co-founder & CTO of H2FLY
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