Clearing the Clouds - The Promise and Pitfalls of Hydrogen in Aviation

Long powered by fossil fuels, aviation has historically accounted for approximately 2.5% of global Carbon Dioxide (CO₂)emissions – however, this figure doesn't fully capture aviation's total environmental impact. When accounting for non-CO₂ factors, such as contrails and Nitrogen Oxides (NOx), aviation's true climate impact is estimated to be as much as three times that of its CO₂ emissions alone.

The pursuit of sustainable alternatives to conventional jet fuel has introduced hydrogen as a frontrunner for reducing aviation’s carbon footprint. Hydrogen offers the tantalizing possibility of zero-emission flight, yet the complexities involved in developing a hydrogen-based aviation sector demand careful analysis and a multifaceted approach. From clean production to regulatory frameworks, infrastructure development, and public buy-in, hydrogen-powered flight requires reimagining the entire aviation ecosystem.

In this editorial, I hope to illustrate the significant challenges and opportunities of hydrogen aviation, examining the innovations and more importantly the essential collaborations necessary to get there.

1. Hydrogen Production: The misunderstood foundation for Aviation Decarbonization

The environmental promise of hydrogen-powered aviation hinges upon a sustainable hydrogen production process. Currently, most of the world’s hydrogen is produced through methods that emit significant amounts of CO₂, that arguably defeat the purpose of the process.

Known as ‘Grey’ hydrogen, this method involves natural gas reforming, which, while relatively inexpensive, negates the environmental benefits that hydrogen promises. Moving away from grey hydrogen to more sustainable alternatives is a basic imperative.

• Blue Hydrogen as an Interim Step: ‘Blue’ hydrogen is effectively a bridge solution, capturing CO₂ emissions produced by fossil fuels and storing them to reduce atmospheric release. While this mitigates some of the environmental impacts, the long-term viability of carbon capture and storage (CCS) remains contentious. Infrastructure for CCS is very costly and significantly complex, and any leaks could compromise the technology’s effectiveness, leaving blue hydrogen as an imperfect short-term answer. Yet, it remains essential, as blue hydrogen offers a temporary supply while ‘Green’ hydrogen production scales up. 
• Green Hydrogen and Electrolyser Technology: Green hydrogen, produced through electrolysis powered by renewable energy, is the only truly sustainable solution for aviation. Electrolysis splits water into hydrogen and oxygen, yielding pure hydrogen with zero CO₂ emissions if powered by renewable sources. Yet, green hydrogen constitutes less than 5% of the current global hydrogen supply due to high costs and the infrastructure required for production. Current estimates suggest that scaling green hydrogen production to meet future aviation demands would require up to $11 trillion USD in investment worldwide by 2050.

Key players, including the European Union (EU) and nations like Japan and South Korea, have begun implementing ambitious green hydrogen targets. The EU’s Green Deal aims to achieve 40 GW of electrolyser capacity by 2030. Achieving such targets will require substantial advancements in electrolyser technology, improving efficiency, lowering costs, and expanding renewable energy infrastructure. Industry partnerships, government subsidies, and private investments will be instrumental in accelerating this transition. Beyond Europe, estimations of global installed electrolysis capacity are in the range of 600 - 700 MW at the end of 2022. Latest available information suggests a global capacity reached the 2 GW mark at the end of 2023; this marks just how ambitious the EU green deal remains.

2. Technical Challenges: Adapting Aircraft Design for Hydrogen’s Unique Properties

Hydrogen presents unique technical challenges that must be addressed to make it a feasible aviation fuel. Unlike traditional jet fuel, hydrogen has a lower energy density per unit volume, meaning it takes significantly more space for the same amount of energy. Liquid hydrogen, stored at cryogenic temperatures (-253°C), has about four times the volume of jet fuel per unit of energy. This poses a major obstacle, as it impacts aircraft design, aerodynamics, and payload capacity. 

• Airframe Redesigns and Weight Distribution: Engineers are exploring novel airframe designs to accommodate large hydrogen tanks without compromising aircraft balance or aerodynamics. Airbus, for instance, has developed conceptual designs under its ZeroE project, which include three hydrogen-powered aircraft aimed at regional routes by 2035. These designs feature modified fuselages that enable larger fuel storage yet balancing the aircraft while maintaining passenger comfort and range remains a major challenge. 
• Hydrogen Fuel Cells vs. Combustion Engines: There are two main methods for using hydrogen in aviation: combustion engines and fuel cells. Combustion engines burn hydrogen directly, much like current jet engines burn kerosene. While this method allows relatively easy adaptation of existing engine technologies, it can still produce NOx emissions under high-temperature combustion, potentially requiring emission control systems. Fuel cells, on the other hand, convert hydrogen directly into electricity through an electrochemical process, emitting only water vapor. Fuel cells offer efficiency advantages but generate less power than traditional engines, making them more suitable for short-haul or hybrid aircraft. For long-haul flights, hybrid systems combining hydrogen combustion engines with electric power could provide a transition solution, balancing power, range, and emissions.
• Hybrid Solutions: Given the energy demands of long-haul flights, hydrogen-powered hybrids might offer a crucial intermediary step. Hybrid systems, which combine hydrogen fuel cells with traditional engines or electric motors, could provide an efficient balance of energy, helping to extend the range and payload capacity. Rolls-Royce and other engine manufacturers are exploring these solutions, as hybrids could serve medium-haul flights while fully hydrogen-powered designs evolve. 

3. Infrastructure and Distribution: Building a Hydrogen Ecosystem for Aviation

The existing aviation infrastructure is deeply entrenched in the use of kerosene-based jet fuel, which has a well-established global network of refineries, pipelines, and fuel trucks. Hydrogen introduces a fundamentally different set of requirements, necessitating an entirely new approach to fuel production, storage, and transportation at airports. 

• On-Site Production and Storage: Storing hydrogen requires specialized cryogenic facilities to keep the fuel at extremely low temperatures. Few airports are equipped to handle such infrastructure, and the cost of retrofitting thousands of airports globally would be astronomical. On-site hydrogen production via electrolysis could reduce transport costs, but this requires consistent access to renewable energy sources, further complicating the logistics of airport operations. Large-scale airport projects are underway to address these needs. Frankfurt Airport has begun trials with on-site electrolyser facilities, while California’s ZeroAvia project has secured grants for mobile hydrogen refuelling solutions. Initial investments in hydrogen infrastructure are heavily reliant on government subsidies, as the costs are currently prohibitive for airlines and airports alone. 
• Safety and Hazard Management: Hydrogen is highly flammable, and cryogenic storage introduces additional safety considerations. The storage tanks, pipelines, and refuelling equipment must meet stringent safety standards to prevent leaks or explosions, which requires robust regulatory oversight. Handling and storage protocols are robust, so airport staff will need specialized training and ensure adherence to international standards, potentially slowing hydrogen’s adoption due to rigorous certification processes. 

4. Regulatory Frameworks: Establishing Global Standards for Hydrogen Flight 

The development of hydrogen-powered aviation is dependent on a supportive regulatory environment, but creating these frameworks will involve navigating safety, environmental, and operational standards on a global scale. Aviation regulations have traditionally been built around fossil fuels and adapting them to hydrogen involves a complete overhaul of certification and safety protocols.

• International Collaboration for Safety Standards: Regulatory bodies such as the European Union Aviation Safety Agency (EASA) and the Federal Aviation Administration (FAA) are in the early stages of developing hydrogen-specific guidelines. Airbus’s collaboration with EASA to develop ‘Special Conditions’ for hydrogen is a positive step toward establishing consistent regulatory standards. However, full adoption requires coordination among international aviation authorities to avoid fragmentation, which could delay or limit hydrogen’s applicability across borders. As a first step, the International Civil Aviation Organization (ICAO) is forming task forces to create globally recognized safety protocols for hydrogen refuelling, handling, and storage. Given that hydrogen-powered aircraft will operate at major airports worldwide, international harmonization is critical to avoid logistical inconsistencies that could deter airlines from adopting hydrogen.
• Environmental Standards Beyond CO₂: While hydrogen-powered aviation emits no CO₂, combustion could produce trace amounts of NOx. This has led researchers to explore non-CO₂ emissions such as NOx and contrails, as these contribute significantly to global warming. Hydrogen-powered fuel cells, however, produce only water vapor, which could reduce contrail formation, depending on altitude and atmospheric conditions. Regulatory bodies are currently studying hydrogen’s overall impact, with findings expected over the next few years. Developing guidelines on NOx and contrail management will be crucial to ensure that hydrogen aviation does not inadvertently create new environmental issues while solving others. 

5. Timelines and Industry Milestones for Hydrogen Adoption

Hydrogen-powered aviation is still in the experimental phase, with ambitious targets set for 2030-2040. Airbus’s ZeroE concept aims to deliver hydrogen-powered commercial aircraft by 2035, but achieving this will require continuous technological advancements and an accelerated regulatory response. Key industry milestones are anticipated over the next two decades:

• 2025-2030: Large-scale pilot projects are expected to demonstrate the feasibility of hydrogen aviation on regional and short-haul routes. ZeroAvia’s smaller hydrogen fuel cell aircraft may begin commercial operations for flights under 500 kilometers, while industry players refine hybrid hydrogen-electric solutions for medium-haul routes.
• 2030-2040: Hydrogen-powered regional flights could become common, especially in Europe and North America, where infrastructure and regulatory frameworks are most developed. Longer-range flights may adopt hybrid solutions, with full hydrogen adoption contingent on technological breakthroughs and reduced hydrogen production costs.
• Beyond 2040: Hydrogen technology could expand to medium and long-haul flights as infrastructure, safety standards, and green hydrogen availability align to meet demand. Hydrogen’s role in aviation will depend heavily on collaborative global progress in green hydrogen production and distribution networks. 

6. Transforming the Passenger Experience: What Hydrogen Aviation Means for Flyers

The shift to hydrogen-powered aircraft isn’t just a matter of operational and environmental impact; it also holds potential for a fundamentally new passenger experience. With the right innovations, hydrogen aviation can deliver more than a sustainable travel option, potentially revolutionizing comfort, speed, and convenience. 

• Enhanced Cabin Designs: Due to the unique structural changes needed to accommodate hydrogen storage, aircraft interiors may be redesigned in ways that increase passenger space or optimize cabin layout for a more streamlined boarding process. Concepts by Airbus envision redesigned fuselages that could allow for modular cabins tailored to passenger preferences, with adaptable seating arrangements for families, business travellers, or those seeking a quiet workspace in-flight. 
• Potential for Quieter, Smoother Flights: Hydrogen fuel cell-powered aircraft promise a quieter experience than traditional jet engines. Fuel cells generate electricity without combustion, potentially eliminating the familiar engine hum and offering a smoother flight experience. This would particularly benefit long-haul travel, where reducing cabin noise and vibration could lead to more restful, enjoyable flights.
• Increased Public Awareness and Engagement: Hydrogen aviation could drive a new level of environmental awareness among travellers. Airlines might incorporate emissions-tracking features into ticketing, allowing passengers to see their carbon savings compared to conventional flights. As travellers become more climate-conscious, this transparency could reinforce hydrogen aviation as a responsible choice, fostering a stronger, more loyal customer base for pioneering airlines.
• Safety Perception and Education: Hydrogen's safety will likely be a top-of-mind concern for passengers. Although hydrogen technology is backed by rigorous testing and safety protocols, public perception may still skew towards scepticism due to hydrogen’s reputation for volatility. Airlines and manufacturers must therefore engage in open, educational campaigns that explain hydrogen’s safety features and reliability. Collaboration with regulatory authorities and high-profile safety endorsements will be essential in building traveller trust. 

7. Government and Industry Collaboration in Accelerating Hydrogen Adoption

No single player can drive the hydrogen revolution in aviation on its own. Government policies, regulatory incentives, industry collaboration, and private investments must converge to create the necessary conditions for hydrogen aviation to thrive.

• Government Subsidies and Policy Support: Financial backing from governments will be indispensable in offsetting initial costs for research, development, and infrastructure. The EU’s Hydrogen Strategy, for example, includes a pledge to invest up to €470 billion EUR by 2050, primarily focused on industrial hydrogen applications but with significant implications for aviation. Policies that encourage the use of green hydrogen, subsidize airport retrofits, or offer tax incentives for airlines investing in hydrogen technology would likely spur faster adoption and make hydrogen-fuelled flights more economically viable.
• Industry Partnerships and Research Collaboration: Collaboration across sectors is essential, bringing together aerospace companies, fuel providers, airport authorities, and research institutions. Partnerships, such as the one between Rolls-Royce and easyJet to develop hydrogen combustion engines, exemplify the type of joint effort needed to surmount technical challenges and produce scalable solutions. Research institutions play a crucial role in advancing electrolyser efficiency, fuel cell technology, and safe storage materials, all of which are central to making hydrogen aviation feasible at scale.
• Public-Private Partnerships and International Consortia: National policies alone may be insufficient to bring about rapid change. International consortia like the Hydrogen Council, comprising 120 member companies from multiple industries, are working to align policies and investments globally. Such coalitions aim to share knowledge, establish common standards, and streamline international regulatory processes. Public-private partnerships can leverage government funding with private-sector expertise, accelerating research and enabling large-scale demonstrations of hydrogen technology in real-world settings.
• Carbon Pricing and Regulatory Incentives: As governments intensify efforts to limit greenhouse gas emissions, carbon pricing is emerging as a critical regulatory tool. Higher carbon costs for traditional aviation fuel could make hydrogen more economically attractive. By implementing carbon pricing on fossil fuel emissions, policymakers can drive demand for low-carbon alternatives like hydrogen, making the economics of hydrogen-powered aviation more competitive in the long term. 

8. Potential Economic Impacts: Jobs, Innovation, and Industry Evolution 

The shift to hydrogen-based aviation has far-reaching economic implications. Beyond creating a new market within the aerospace sector, hydrogen aviation stands to generate employment opportunities across numerous industries, from renewable energy to aircraft manufacturing and hydrogen infrastructure. 

• Job Creation in the Green Economy: Building the hydrogen economy could create hundreds of thousands of jobs, especially in hydrogen production, infrastructure, and maintenance. Electrolyser manufacturing, fuel cell production, and cryogenic storage facilities will require skilled workers, prompting a shift in workforce training and education to meet the demand. With investments directed at retraining workers from traditional energy sectors, hydrogen aviation could emerge as a major pillar of the green economy.
• Economic Growth Through Innovation: Hydrogen aviation is poised to spark innovation across industries, leading to breakthroughs in hydrogen production, fuel cell technology, and sustainable materials. Companies involved in hydrogen technology could see increased funding opportunities and international collaborations, accelerating technology transfers across borders. For example, Japan's leading hydrogen efforts in the automotive sector may inspire parallel developments in aviation, while hydrogen-powered transport across Europe could drive regional cooperation in research and development. 
• Airline Profitability and Market Differentiation: As hydrogen technology matures, airlines that adopt hydrogen-powered aircraft may gain a competitive edge, especially among eco-conscious passengers. Offering lower-emission flights could create new revenue streams and enable airlines to charge a premium for sustainable travel options, enhancing profitability in a carbon-constrained world. Early adopters could benefit from government incentives and tax credits, while enhancing brand loyalty by promoting climate-conscious choices. 

9. Blue Sky : The 2050 Vision for Hydrogen-Powered Aviation

Despite its challenges, hydrogen-powered aviation remains a pursuit of net-zero emissions by 2050. Realizing this vision will require rapid technological advancements, unparalleled industry coordination, and strong regulatory support. But if all of these pieces miraculously fall into place, the benefits could be transformative. 

• Hydrogen’s Role in Achieving Net-Zero Targets: If hydrogen aviation can be effectively scaled, it could prevent up to 1 gigaton of CO₂ emissions annually by mid-century, a major contribution toward achieving the Paris Agreement’s climate targets. With additional infrastructure, renewable energy expansion, and continued cost reductions in electrolyser technology, hydrogen could become a viable option for most short to medium-haul flights globally, with potential applications in long-haul routes by 2050. 
• Ecosystem Transformation and Broader Societal Impacts: Hydrogen aviation is not just a shift in fuel, it represents an evolution of how society approaches energy, mobility, and environmental responsibility. If successful, it could serve as a model for decarbonizing other sectors, including maritime shipping and heavy industry. A thriving hydrogen ecosystem in aviation would ripple across other industries, from agriculture to manufacturing, creating a more resilient, sustainable economy and a healthier planet. 
• Realigning Public Expectations: With government support, public awareness campaigns, and visible industry leadership, hydrogen-powered aviation could redefine societal expectations around sustainable travel. Future generations may come to expect hydrogen or similarly green options as a standard rather than a premium offering, marking a profound shift in how we perceive transportation’s role in climate action. 

The Promise and Challenge of Hydrogen Aviation

Hydrogen aviation represents a powerful vision for a climate-friendly future, with the potential to significantly reduce the carbon footprint of the aviation sector. However, the transition to hydrogen-powered flight is complex and resource-intensive, requiring extraordinary advances in technology, infrastructure, regulatory frameworks, and public acceptance. Achieving such a transformation could span decades and demand unparalleled global investment and coordination, potentially surpassing even the most ambitious engineering achievements of the past century.

 Amid this challenge, Sustainable Aviation Fuel (SAF) has emerged as a practical, high-impact bridge to a more sustainable aviation future. SAF enables meaningful emissions reductions right now by integrating seamlessly with existing aviation technology and infrastructure. Unlike hydrogen, which would necessitate a complete redesign of fuel systems and aircraft, SAF can be used in today’s aircraft with minimal modifications. For the near to medium term, SAF stands as an economically viable and logistically sound solution to address the pressing need for emissions reduction.

Avena Fuels has risen as a compelling startup in the SAF field, and has proven business executives needed to drive the company forward within the aviation sector toward a sustainable future. With their innovative SAF-FIAB (Sustainable Aviation Fuel - Factory in A Box) technology, Avena Fuels has developed a modular, scalable approach to SAF production that reduces setup time and costs compared to traditional fuel production. Their ‘Factory in A Box’ concept allows for rapid deployment and integration within existing infrastructure, including airports and remote or underserved regions enabling SAF production exactly where it is needed most.

The benefits of SAF are both substantial and far-reaching, as it can cut life-cycle greenhouse gas emissions by up to 80% compared to traditional fossil jet fuel, offering a critical means of reducing emissions while new technologies continue to evolve. Avena Fuels’ approach further expands SAF’s potential, as its technology transforms a diverse array of feedstocks, including sewage sludge, waste oils, and agricultural residues into high-quality, sustainable fuels. This adaptability not only bolsters the supply chain but also supports waste reduction and provides additional economic opportunities for renewable industries.

SAF production is accelerating globally, driven by government incentives, industry demand, and innovations like those from Avena Fuels. Facilities around the world are scaling up, making SAF more affordable and widely available. The regulatory landscape is also evolving in the U.S., with the Inflation Reduction Act of 2022 offering considerable tax credits to SAF producers, while the EU’s ‘Fit for 55’ package promotes SAF adoption through blending mandates that encourage further investment and innovation.

Given the present landscape, SAF is the ‘smart money’ choice for impactful, immediate investment, with SAF projects like Avena’s offering some of the highest returns in terms of emission reductions, scalability, and near-term feasibility.

Here in late 2024, SAF stands out as the most effective solution to reduce aviation emissions in the short to medium term, offering a compelling pathway for sustainable progress without requiring a complete industry overhaul.

As a seriously compelling startup, Avena exemplifies the SAF sector’s promise. Through practical, adaptable technology, Avena is helping drive the aviation industry’s ongoing transition to sustainability supporting global climate targets today while allowing time for future innovations like hydrogen to mature.

While hydrogen aviation remains a long-term aspiration, the immediate scalability and practicality of SAF render it an indispensable tool for reducing emissions.

Carl Cagliarini