Adam Morton • 01.08.24 • 6 min read

From 1st January 2025, the European Commission is planning to introduce a Monitoring, Reporting and Verification (MRV) requirement for aviation non-CO2 effects. Adam Morton, Head of Technology – Sustainability & Strategy, considers technical pre-requisites necessary to make MRV workable and how work undertaken in the UK can help to deliver this initiative. 

Requiring airlines to report a wider set of emissions from individual flights is now considered a key part of addressing aviation’s total climate impact. Recognising aircraft climate effects are broader than carbon dioxide (CO2) emissions, the European Union’s Climate Transition Plan will require aircraft operators to monitor and report aircraft non-CO2 effects from January 1, 2025. 

This pilot scheme follows industry consultation and is part of a wider initiative which will ultimately see MRV results published annually from 2026. This would then be closely followed by legislation to cover non-CO2 effects through a revised EU Emissions Trading Scheme (ETS).  

Under current plans this market-based measure (MBM) to incentivise sector decarbonisation, would be expanded to monitor contrails and oxides of nitrogen (NOx), together with reporting of aircraft data and fuel properties. In this way, the ETS could eventually allow for pricing incentives to drive mitigation of all the major aircraft emission types linked to climate change. 

The aviation sector remains committed to achieving Net Zero carbon emissions by 2050. 

Addressing aviation’s wider climate impact is also key and starts with reliable monitoring and reporting to inform technology development, underlining the importance of this MRV initiative. The ATI’s Non-CO2 Technologies Roadmap published in March of this year set out the priority areas for the associated Non-CO2 Programme to address. This followed the Natural Environment Research Council (NERC) launching, in partnership with the Department for Transport (DfT) and the Department for Business and Trade (DBT), a parallel programme of fundamental research into how aircraft non-CO2 emissions react with the climate over time. 

This reflects alignment in addressing the challenges facing a rapid introduction of MRV which include the difficulties in collecting the necessary underlying data. Compliance with the proposals will need four-dimensional (4D) trajectory inputs including latitude, longitude and altitude, all as a function of time. While such 4D data is already collected, its accuracy for MRV purposes may be insufficient and alternative solutions such as post-flight downloads are likely to raise logistical and confidentiality concerns. 

Full compliance with current proposals would also require all aircraft to collect data on humidity with on-board humidity sensors being the leading option. However, at present very few aircraft have such systems installed and recent work by IATA concludes existing technologies are focused on weather forecasting applications. The available units do not have the accuracy or response times necessary to detect Ice Super Saturated Regions (ISSRs) in way that supports either MRV or tactical re-routing decisions. While post-flight interpolation of humidity and trajectory has been identified as an interim solution, developing sensor technologies represents a market opportunity for UK aerospace. 

Further complicating compliance is the greater need to better understand fuel characteristics and engine exhaust conditions. Predicting CO2 emissions is relatively straightforward based on mass-balance calculations and fuel burn. In contrast, for a clear understanding of non-CO2 impacts, NOx and soot emissions must be modelled based on flight specific data and a good understanding of the actual fuel in the tanks on the day. As the industry moves to new fuels including different varieties of sustainable aviation fuels (SAF), it will be essential to grow our understanding of how these change emission characteristics and climate impact. As our appreciation of engine/fuel interaction grows, this may drive reporting of sulphur and aromatic content for each delivery or flight. . 

Once the necessary data has been collected, this must be input into robust models able to predict the corresponding climate effects with high confidence. However, at present quantifying the impact of non-CO2 emissions is widely recognised as immature, with insufficient confidence in the models that already exist. 

Work is already underway in Europe and North America to close this understanding gap but in most cases these early research projects run until after the planned EU MRV reporting start date. As a result the results may not be ready for informing how the MRV debate evolves in Europe. 

The challenge is exacerbated by the need to align weather prediction and impact models to fulfil a number of different and complex functions. These include underpinning future MRV requirements but also supporting non-CO2 mitigation strategies by airlines, airframers and equipment manufacturers. 

At a time when the whole industry is asking how the necessary gaps in understanding can be closed in time to meet an ambitious EU timeline, work funded by the ATI and NERC is expected to make a major contribution over the longer term. It is only by investing in sensor technologies, data collection and modelling that aerospace can achieve the necessary confidence in future non-CO2 MRV initiatives.