The global aviation community has committed itself to sustainable aviation over the next 30-odd years. It aims to do so in three main ways: investing in technological innovation, adopting Sustainable Aviation Fuel (SAF), and improving operational and infrastructure efficiencies.
A key thrust in the effort towards sustainable aviation is to improve fuel burn by increasing aerodynamic efficiency through innovations in the structure of and materials used in airframes. OEMs need to design airframes that are more efficient to allow aircraft to move through the air more easily, and be as light as is safely practical in order to reduce fuel usage and the overall amount of CO2 generated per Revenue Passenger Kilometre.
In pursuit of this, OEMs have already begun installing in newer models wingtip devices (such as in the case of the A350) to increase aerodynamic efficiencies to reduce drag cause by airflow patterns. The result is a 3-5% reduction in fuel burn. OEMs are also using carbon composites to build aircraft and components to make airframes as light as possible. The B787’s primary structure is made up of nearly half carbon fibre reinforced plastic and other composites, which offers weight savings on average 20% compared to more conventional aluminium designs. As a result, the B787, which was first delivered in 2011, emits 20-30% less CO2 compared to its predecessors.
These aerodynamic changes, while not significant, are steps that have already been taken. There will most likely be more significant improvements in the next generation of aircraft, but this is still some time away – OEMs are still in he process of rendering and designing, and will still need time to build and conduct test flights before delivering improved airframes for wider use, possibly well into the 2030s.
In the meantime, the next significant step in the near term towards sustainable aviation is the widespread adoption of SAF, which can reduce CO2 emissions by up to 80%. SAF is produced from sustainable feedstock such as cooking oil and other non-palm waste oils, solid waste from homes and businesses, and food scraps that would otherwise go to landfill or incineration. SAF is a “drop in” fuel and can be blended at up to 50% with traditional jet fuel without any engine modification needed, making SAF easier to integrate into existing aviation operations.
Despite the fact that adoption of SAF will help bring the aviation industry closer to achieving its goal of net-zero carbon emissions, SAF only accounts for a minute amount of all jet fuel burned by the aviation industry today. Wider adoption of SAF is hampered by two things – the prohibitive cost (SAF is two to five times more costly), and lack of legislation to make the use of SAF mandatory.
Those two issues have now been partially addressed. To address the prohibitive cost, the Biden administration announced plan for a blenders’ tax credit in the US’ $1.2 trillion infrastructure bill which passed Congress in November 2021. To address the lack of legislation mandating the use of SAF, the EU proposed in July 2021 to force fuel suppliers to include SAF in aviation fuel supplied at EU airports, starting from 2025 to 2% SAF, and eventually increasing to 63% in 2050.
Over the longer term, both aircraft and engine manufacturers will need to look beyond SAF to alternative propulsion systems such as hydrogen, electricity or solar for their aircraft. Such technology has already developed substantially in the last five years, and some major manufacturers are concurrently exploring both the SAF route as well as alternative propulsion systems. For example, Airbus has publicly unveiled plans to commit for its next clean-sheet narrowbody design to be powered by a radical solution such as hydrogen. While Airbus’ commitment is a good first step, realistically, aircraft powered by alternative propulsion system systems are unlikely to be operating in significant numbers to serve commercial aviation until the 2040s at the earliest.
Both tracks of investing in technological innovation and wider adoption of more sustainable propulsion systems (be it through SAF or otherwise) are intertwined, and the aviation industry needs to commit and hold itself accountable to the goals laid out to allow its net-zero carbon emissions goal to take flight.