GRIM-SAF: Ground and Inflight Measurements involving SAF

Aviation is estimated to grow by 4.3% p.a. over the next 20-years. Any changes in emissions must be consistent with national, international and industrial climate strategies, which require civil aviation to be carbon neutral by 2050. Sustainable Aviation Fuel (SAF) will play a significant role in meeting these targets, reducing the sector's consumption of fossil fuels.

However, the burning of SAF still leads to non-CO2 climate and pollution effects. To quantify these effects requires the full characterisation of particle and gaseous emissions across the whole flight envelope, including ice nuclei (IN) forming potential, and the time evolution of those emissions characterised from a few seconds after released to several days.

In addition to non-CO2 SAF climate effects three other key environment uncertainties exist;

Emissions from aircraft-engines detrimentally impact local air quality (LAQ), resulting in health effects in areas surrounding airports. Does SAF adoption change LAQ and are there disparities in those communities?

Emissions of lubrication oil occur independent of fuel type, but this is not currently regulated or included in models, despite contemporary research indicating potential climate and LAQ impacts.

As most SAF testing is ground-based, there is an urgent need to confirm whether use of ground-based emission measurements on tethered engine test-stands adequately represent real-world emissions in-flight.

GRIM-SAF (GRound and Inflight Measurements involving SAF) builds upon several existing academic-industrial collaborations, using a unique UK emission engine-test-cell facility. The project will generate contemporary total-emission data from two engine types for a range of conventional & SAFs, both on-ground and during in-flight 'chase' experiments.

The project will deliver data essential to improve emission inventories, atmospheric models of climate and weather and LAQ effects, and reduce uncertainties in predicting the impacts of industry-wide adoption of SAF. The objectives are:

Comprehensively quantify combustion and lubrication oil emissions, including gases (CO, CO2, NOx, VOC) as well as particulate chemical and physical properties from both conventional and SAFs measured at engine-exit and within the evolving plume.

Elucidate the interactions between combustion and lubrication oil emissions and IN forming potential, developing new knowledge of the impact of SAF and lubrication oil on contrail formation.

Evaluate the effects of aging and interaction of combustion and oil emissions on LAQ, simulating effects "beyond the airport fence" informing local communities now and in the future.

Perform a UK-first in-flight 'chase' emissions experiment to quantify 'real-world' gas and particle emissions at altitude from aircraft using SAF in-flight.

Develop empirically validated correlations between ground-based measurements and emissions observed at altitude for conventional and SAFs, enabling the existing International Civil Aviation Organisation (ICAO) emissions data bank to be more accurately used to predict 'cruise' emissions. Outputs and benefits of GRIM-SAF include:

The most comprehensive, publicly available, total-emissions database to-date, inclusive of, SAF blend ratio, lubrication oil contribution and engine conditions across full power range of two engine technologies.

Key information for policy makers, e.g. local councils and governments when considering town planning and airport expansion applications, to understand the likely impacts of SAF-enabled aviation and oil on LAQ moving toward 2050 and identify possible mitigation strategies. Understanding the relative impacts of different oil venting strategies towards future design of low emissions engines.

Insight into whether existing regulatory emissions standards are appropriate for a SAF-fuelled future aviation fleet. Recommendations on whether climate-aviation models should include oil emissions.