Aviation recommitted to its plan of reducing carbon emissions last year. It had first set itself a target in 2008 of halving the industry’s global emissions from the 2005 figure of 650 million tons by 2050. With the recommitment at the 2021 IATA Annual General Meeting, the goal is now aligned with the Paris Agreement of net-zero carbon emissions by 2050 to limit the increase in global temperature to less than 1.5°C by 2100.
In 2019, the global aviation industry was responsible for roughly 900 million tons of emissions. Commercial air traffic has increased nearly four times faster than fuel efficiency improvements over the last few years. And air traffic is expected to double every 20 years until 2050 even after accounting for the impact of COVID-19. This means that the challenges are massive and cannot be tackled through incremental technology improvements anymore.
While aviation has already achieved significant efficiencies over the last few decades – with each new generation of aircraft bringing 15-20% improvements approximately every 20 years – the ambitious target ahead demands a dramatic acceleration. This means pulling on all available levers – some already available, some emerging – and significant investments. The area is rich with unanswered questions. Which technologies will emerge as game changers? Will governments force a roadmap toward net-zero emissions? Who among airlines, consumers, and governments will pay for these new technologies, especially in a post-COVID era when balance sheets are severely weakened?
There are four areas that can contribute to a potential aviation decarbonization roadmap:
- Aircraft architecture and configuration
- Improved operations and infrastructure
- Sustainable Aviation Fuels
- Propulsion technology (with options ranging from next generation jet engines such as open rotor to full electric and hybrid electric propulsion)
Aircraft architecture and configuration: New aircraft architecture can significantly reduce CO2 emissions. Two design trends are most promising: blended wing-body configuration and use of sophisticated low-weight materials. The main hurdle against more widespread use of blended wing body is existing airport and traffic management infrastructure, which is designed for the classic configuration. Therefore, radical, new aircraft designs are only likely to be operational in the medium to long term. Further optimization of aircraft aerodynamics through new technologies – including laminar flow on wings, aeroelastic wing configurations, and active aerodynamic flow control – will likely only incrementally improve fuel consumption while adding to operational complexities.
Improved operations and infrastructure: Up to 12% reduction in CO2 emissions can be achieved through improved flight operations (for example, friendly routing through shorter flights, flying at lower altitudes, formation flying, or continuous descent approach) and a rigorous zero-emission approach for ground handling/taxying procedures (for example, using electricity and hydrogen as energy sources). Both can be realized in the medium term if there is alignment among relevant regulators, but pertinent projects such as (NextGen in the U.S. and Single European Sky) are extremely complex and have historically been slow to deploy.
Sustainable Aviation Fuel (SAF): SAF is not only the easiest available option but can be a real game-changer. For the most part, it is a drop-in solution: it can be used with existing airport infrastructure and with very limited modifications of aircraft/engines, which are already certified for 50% SAF blends. SAF comes in biofuel form, which is produced from biological or renewable sources such as waste oils or agricultural residuals, and synthetic form, which is better avoided.
Boeing aims to deliver planes capable of burning 100% SAF by 2030 even as it continues to study other carbon-reducing technologies. However, to be widely successful, SAF requires very substantial production increase as well as price reduction as its current price is about five times that of Jet A1 fuel. As it’s already certified for commercial use, SAF usage is growing. However, it accounts for less than 0.1% of total aviation fuel consumption. Policies mandating a minimum percentage of SAF blend are being voted in mainly in Europe that will soon force airlines’ hands and create demand for the massive industrial capacity investments required to bring unit cost down.
Next-generation jet engines: Performance-focused improvements in traditional jet engines as well as new architecture – including geared turbofan, higher pressure, higher by-pass ratio, advanced materials, and open rotor concepts – are being developed by engine OEMs. Almost 40% of new generation narrowbody engines that have come to market over the last five years use Pratt & Whitney’s geared turbofan technology. An open rotor program called RISE, which leverages hydrogen and promises fuel-burn reduction of 20% over present day turbofans, has just been launched by CFM International.
Liquid hydrogen combustion: Hydrogen, which emits water vapor upon burning instead of CO2, can replace jet fuel in a conventional combustion engine with limited adaptations. While only 0.1% of global hydrogen production is currently carbon-free and not produced using coal or natural gas, “green” hydrogen is expected to become price-competitive in the next few years. But while it also has the added benefit of being much lighter than jet fuel, hydrogen takes up about four times more volume and requires bigger fuel tanks in what is a clear challenge for aircraft configuration. Other key hurdles include the vast engineering challenge of building a cryogenic fuel distribution system onboard the aircraft to take hydrogen from cryogenic tanks to the engine and the massive infrastructure required at airports globally to store and deliver hydrogen. Airbus is leading the industry on hydrogen, with plans for hydrogen-powered aircraft to enter service by 2035. Three concepts -- a regional turboprop, a narrowbody aircraft, and a blended wing body aircraft – have been presented to date.
Full electric propulsion: Converting electrical energy directly into mechanical energy to drive conventional propellers or small-ducted fan jets is highly efficient and emission-free. Electricity can be stored in batteries or get produced from hydrogen in a fuel cell, two very different options. In the fuel-cell version, however, the challenges of tank volume are the same as hydrogen combustion, limiting long-range applications. Batteries, on the other hand, have low energy density, which adds significant weight and sharply limits the range of application and missions. There have been several successful test flights and many new ventures covering commuter aircraft, including retrofitting existing platforms and launching new electric aircraft. Then there is the red-hot part of air mobility -- electric vertical take-off and landing (eVTOLs). The first aircraft have been certified (Pipistrel in 2020) and several small regional aircraft projects – typically fewer than 19 passengers -- are on the horizon.
Hybrid electric: Combining combustion and electric engines can reduce emissions by optimizing engine technology for certain segments. Electric engines can provide power during takeoff and climb, allowing combustion engines to be made smaller and lighter for cruise flying. Several approaches to hybridization are currently in development, which could bring electrification to larger commercial aircraft more realistically than full electric propulsion.
The automotive industry has been forced to embark on an accelerated and very expensive decarbonization transition because of strong government regulation and heavy fines driven by fleet emissions levels. A joint effort from the aviation industry, research institutions, governments, finance, and energy sectors is required urgently to avoid a similar situation. Sustainability targets are extremely ambitious and meeting them will demand substantial changes in mindset.
All players in the aviation ecosystem – legacy as well as new – must think ahead and articulate a clear strategy. For legacy aerospace players, OEMs, and suppliers, several key success factors need to be mastered to ride this new wave:
- Proactively prepare for what sustainable aviation means for your business and operating model
- Invest in the right technologies in a financially constrained post-COVID context and partner with agile startups to accelerate research and development
- Take a systematic approach – not only looking at the aircraft, the platform, and the engine, but at the overall aviation ecosystem (infrastructure, airport, fuel, etc.)
- Consider this an unmissable opportunity to play a new role in the value chain, receive funding from third-party investors, and as a business development initiative
- Manage and retain talent to deliver on this opportunity
For emerging and new aviation players, the success factors are quite different – although securing the right talent and expertise will be a key common theme with legacy players:
- Focus not only on the technology, but also the business model, the operating model, and choosing to make versus to partner versus to buy. First flight is not the end game
- Secure design-to-cost principles early on in development when degrees of freedom are still available, embedding modularization and production scale goals from the start. Digital design, manufacturing, and operations are competitive advantages to go to market at scale
- Secure funding. The road to certification and operation is a long and expensive one
Both airlines and airports need to build a similar view of how these new transportation modes can impact their business and operating models, identifying both threats and opportunities. The industry must establish a clear and focused roadmap and find the right mix of solutions as it cannot afford to waste resources and money on impractical or failed experimentation.