Aviation Decarbonization: Challenges and Opportunities Explained

The commercial aviation sector now has net zero targets for 2050. As aviation is both a hard-to-abate sector, and one that is also forecast for long-term growth, this is a tough ask.

To reach this target will likely require multiple gains from new technologies, policy incentives and behavioral change. It also creates several disruptive implications (and commercial opportunities) across the value chain, from aircraft manufacturers, regulators and operators to air traffic control, ground handlers and airports.

While decarbonization has become the talk of the day across aviation, the sector still needs to up its game, for example:

• On the scalability challenges of Sustainable Aviation Fuel (SAF);
• on the scale of the offsetting required to bridge what will remain a significant gap to net zero; and
• on tackling the (as of yet) largely ignored climate impact of contrails.

Fundamentally, I see a lack of context and creativity in this debate, which opens the sector to accusations of greenwashing and missed quick wins.

To outline this context, consider the impact of both in-flight and on-ground operations:

• In-flight operations account for approximately 3/4 of total CO2e emissions. Within this 3/4, contrails and other GHGs contribute more than tailpipe CO2.
• On-ground operations are responsible for the remaining 1/4 of CO2e emissions, with the major contributors including maintenance, repair and overhaul, aircraft taxiing to/from the runway, and terminal activities. 

At the Global Aviation conference in Dubai, I sought to emphasize some key points:

•  The focus on SAF as a silver bullet is problematic.
  • Fuel burn, taxiing on the ground and flying in the air, together contribute only around 40% of the total aviation footprint. Therefore, in an ideal world of sufficient SAF supply, it would only address approximately 40% of the total problem.
  • But we are a long way from having anywhere near a meaningful SAF supply. Biofuel SAF has a number of key constraints preventing them from scaling much beyond 5% of the total energy needed for the sector's fleet. The alternative is synthetic SAF, which does not have the same feedstock, food security, biodiversity or carbon accounting obstacles as biofuel, but instead requires an enormous investment in dedicated low carbon power.
  • Modelling suggests that even by 2050 there will be a significant shortfall in SAF supply, potentially reaching only 35% of the global fleet energy need. Demand-side mandates (such as the EU is adopting) will likely not be sufficient to get there - significant supply-side incentives are expected to be required.
• Electric, hybrid and hydrogen make only modest contributions by 2050.
  • It is predicted that hydrogen and electricity will each only contribute approximately 3% of the global fleet energy need by 2050. 
  • This is expected to continue to grow in importance beyond 2050, but with realistic assumptions around certification timelines and aircraft lifespan / fleet renewal rates, the contribution to 2050 targets will likely be limited to particular use cases. For example, smaller electric vehicles can begin to cannibalize traditional regional aviation. 
•  Contrail mitigation presents one of the best opportunities to get early momentum for the sector.
  • Contrails are clouds created when moisture condenses around tailpipe particulates in particular atmospheric conditions. Like naturally occurring clouds, they tend to trap heat at night, and can have either net cooling or warming effects during the day.
  • The current best estimates suggest contrails mean aviation is actually in worse shape than the sector wants to admit. Instead of aviation representing 2-3% of CO2 from human activity, in CO2e terms (i.e. including the net climate forcing impact of contrails) the sector is more like 5% of the problem.
  • However, unlike the scaling and investment challenge for SAF, or the long timelines needed to see hydrogen or electric aircrafts as major parts of the fleet, addressing contrails is low hanging fruit.
  • The majority of contrails are formed by a minority of (mainly long-haul) flights, and a growing body of real-world evidence suggests they can be avoided with relatively straightforward adjustments to flight plans, and without material cost implications.
  • This is essentially a weather data, climate modelling and flight planning challenge - one that could be addressed within the decade and at a fraction of the cost of the aforementioned approaches.
  • In theory, contrails could even be selectively formed to result in net cooling flights. But even the more modest goal of reducing their warming impact can be achieved now - by those long-haul airlines that don't need regulatory carrots and sticks to take action. 
• Contrails may be the most significant example, but the aviation sector has several other low hanging fruits, at least in comparison with SAF and hydrogen or electric flight.
  • Airspace and air traffic control can be highly inefficient for a number of reasons, not least where there are multiple State borders in close proximity like in Europe or the Gulf - but sovereignty concerns remain the bigger bottleneck to improvements than technical feasibility.
  • Likewise, technology already exists today that could help reduce emissions during taxiing or prompt pilots to make small adjustments in behavior that could have big impacts on annual fuel burn.
  • In short, on the airport tarmac, within the plane, or up the control tower, there are a number of quick wins that are not yet commonly realized.
•  Lastly, even when various incremental gains are considered, aviation may fall well short of zero emissions in 2050.
  • Aviation realistically needs quality offsets for 30-40% of its total net zero journey.
  • The quantum of this is greater than the volume of existing nature-based approaches available to any sector today.
  • This means that aviation will likely need to be a significant investor in approaches outside of its own industry, such as afforestation and direct air carbon capture.

Aviation brings friends and families together, it bridges cultures, it boosts economic standards. However, to get off the back foot, the sector needs more realism in its communications, and more creativity in building and realizing momentum with the quicker wins. Lastly, those that are proposing SAF mandates for the sector can also look towards airspace improvements, incentivizing synthetic fuel production, and integrating contrail science.

Guest Author: Chris Brown is partner, global strategy group at KPMG. Read more KPMG blogs here. Read all guest blogs here. More: Read all guest blogs here.