How can aviation take meaningful steps to cut both CO₂ and non-CO₂ emissions? The SESAR JU’s Green-GEAR project is testing one possible answer: the full green route charging (GRC) Solution. Check out this interview with Tatjana Bolic, Senior Research Fellow at the University of Westminster’s Centre for ATM Research, to learn how her work is helping shape this approach.
Tatjana, can you briefly introduce yourself and your role in the project?
Of course. My name is Tatjana Bolic, and I’m a Senior Research Fellow at the Centre for ATM Research at the University of Westminster. Within the Green-GEAR project, I work on the full GRC solution – a concept designed to explore how aviation can reduce its total climate impact, taking both CO₂ and non-CO₂ emissions into account.
So what is the main idea behind this solution?
The concept is actually quite straightforward: we’re looking at whether a new route charging mechanism could encourage more climate-friendly flight paths. The idea is to adjust route charges so that airlines are financially rewarded for avoiding parts of the atmosphere that have a high non-CO₂ climate impact.
Why focus on non-CO₂ emissions?
Aviation contributes around 5% to human-made climate change – and non-CO₂ effects make up roughly two-thirds of that. These effects include NOx emissions, water vapour, particulates, and the formation of contrails that can turn into contrail-cirrus clouds. While their climate impact is larger than CO₂, they’re much harder to assess because they depend on very specific atmospheric conditions – location, time, altitude – as well as engine type and fuel composition.
That sounds complex. What are the main hurdles to implementing your approach?
Right now, route charges finance air navigation service provision, and they’re regulated under the Performance and Charging Scheme. The latest SES2+ package does allow for environmental modulation of charges – but before that can happen, we need solid evidence from feasibility studies. And because this affects many different stakeholders, it’s crucial to reach consensus by showing clear benefits that outweigh the costs.
What challenges have you faced in your research so far?
The main challenge is that the portions of airspace to avoid for climate reasons are constantly shifting within the atmosphere. Creating a charging system that reflects all this complexity – but still stays as simple and practical as today’s – is not an easy task.
What have your tests shown?
We tested the full GRC solution on a medium-scale network – flights between the ten busiest European airports – while factoring in airspace capacity. The results are promising: although fuel use went up slightly (about 1%), the overall climate impact decreased by around 14% in a typical scenario. The biggest limitation is that available airspace capacity can cap the potential decrease in overall climate impact.
And what does this mean for the aviation sector?
A 14% reduction in climate impact is a big deal. It’s definitely worth scaling this up to cover the whole European network, and carrying out a detailed cost-benefit analysis for all stakeholders. That way, we can present clear evidence to both industry and regulators.
What’s next for your work?
This project is just the start. We’ve only scratched the surface when it comes to understanding non-CO₂ effects and finding practical ways to mitigate them. Further research is needed – especially as atmospheric science evolves – to refine the concept and make it ready for real-world application.
👉 Interested in learning more about the Green-GEAR project and Green Route Charging? Visit the project website: https://www.sesarju.eu/projects/GREEN-GEAR
