How to Make Climate-Optimal Flying More Attractive?

NLR has completed the European research project on non-CO2 climate effects of aviation. This endeavor has yielded a large number of recommendations aimed at increasing the likelihood for stakeholders to implement operational improvements targeting the comprehensive climate impact of aviation. However, achieving voluntary implementation of these improvements by stakeholders presents challenges.

In the previous month, Royal NLR and its collaborative partners in the European ClimOP project successfully concluded an extensive research endeavor centered around operational improvements aimed at addressing the complete spectrum of aviation’s climate impact, including non-CO2 effects. While the non-CO2 impacts exhibit significant variability from one flight to another, they are responsible for two-thirds of aviation’s overall contribution on global warming. Consequently, the exploration of methods to mitigate these effects holds paramount importance in the pursuit of achieving a climate-neutral aviation.

With the project’s completion, the final report led by NLR has been released, presenting 20 valuable recommendations. Elisabeth van der Sman, the project leader representing NLR, expresses her satisfaction with the outcomes: ” With the publication of these results and recommendations, we’re one step further on our path to climate neutral aviation. Now it’s up to all parties involved to take up these recommendations and continue working on this topic.”

Regulations and policies
ClimOP, an acronym for ‘climate assessment of innovative mitigation strategies towards operational improvements in aviation,’ was launched four years ago, bringing together esteemed research institutions such as NLR and Delft University of Technology, along with industry representatives, to delve into this challenging subject matter. Commencing with an initial pool of over 50 operational improvements, the project meticulously examined these measures in a progressively detailed manner. “While other partners focused on detailed climate impact assessments, we mainly looked at the regulatory and policy implications of these improvements,” explains Van der Sman. “A key finding was that voluntary implementation of the operational improvements by stakeholders is unlikely, as in many cases the climate impact can only be decreased at the expense of increased costs.”

In light of this, the project assessed three mitigation strategies that could potentially catalyse implementation. The team defined a mitigation strategy as a combination of operational improvements, current regulations and policies, recent policy developments and implementation enablers. “For these three mitigation strategies, our analysis considered the impact on affected stakeholders and the level playing field.”

Three promising mitigation strategies
Upon pinpointing the most relevant implementation enablers within the existing and forthcoming policy context, the consortium ultimately delineated three mitigation strategies. Van der Sman elaborates, “The first was about charging climate sensitive areas and the second evaluated including non-CO2 effects in pricing schemes such as the EU Emissions Trading System (EU ETS) and CORSIA. A key element to both strategies is to put a financial incentive to increase the likelihood of airlines flying trajectories of reduced climate impact.” Presently, stimuli primarily revolve around reducing fuel burn and CO2 emissions. Van der Sman further explains, ” Because the non-CO2 climate effects are very dependent on time and location, it can sometimes be worthwhile to burn a little extra fuel and still reduce the overall climate impact.”

As a third mitigation strategy, the ClimOP initiative examined diverse alternatives for more sustainable taxiing practices. “We explored a spectrum of alternatives, ranging from electric towing to taxiing solutions such as onboard in-wheel electric engines.”

Recommendations to researchers, industry and policy makers
Earlier this month, the consortium unveiled a series of recommendations outlining the subsequent steps. Notably, the flight-related operational improvements cannot be implemented straightaway. ” A crucial step is to further improve weather models, as to accurately predict the location of climate sensitive areas. This can be done by installing humidity sensors onboard aircraft and by using satellite images for verification and validation purposes. Additionally, policymakers can assess the regulatory implementation options. Finally, airlines can integrate this information into their flight planning and decision making processes, to indeed ensure flight trajectories are as climate-friendly as possible.”

In the realm of sustainable taxiing, the report advocates, among other measures, for manufacturers of electric towing tractors to introduce heavy aircraft-compatible vehicles, and for onboard taxiing systems to bring to market lighter-weight solutions. Additionally, the report underscores the significance of considering air quality enhancements alongside climate-related benefits when making investment choices regarding eco-friendly taxiing solutions.

Supporting these developments, the ClimOP consortium underscores the necessity for ongoing research. “As airlines are the most affected in terms of costs, we need to better understand the implications on airline networks. This is particularly relevant when regional differences occur, for example between EU ETS and CORSIA,” emphasizes Van der Sman. Another avenue of exploration is the potential of increased adoption of sustainable aviation fuels (SAF) and, in the longer term, hydrogen as aircraft fuel, to mitigate non-CO2 climate impacts. Van der Sman clarifies, “Due to remaining scientific uncertainty, we have not taken this into account in our current assessments”, indicates Van der Sman. “Subsequently, this information can be used to update the models used to assess the economic impact of these mitigation strategies on airlines.”

Next steps by Royal NLR
” Whereas these recommendation are addressed at the entire research community, NLR is keen to play its part in these next steps,” asserts Bram Peerlings, lead of NLR’s ‘Climate Neutral Aviation’ programme, which was enriched by ClimOP’s contributions. “In the upcoming EU-project CICONIA, for example, we’re investigating a concept of operations for green air traffic management. This should bring climate-optimal routings one step closer to operational implementation.”