The impact of aircraft engine emissions and alternative fuels on contrail formation

Contrails are an important component of the climate impact of aircraft, with long lived contrails contributing 50% or more of the total radiative forcing from aviation. This is particularly true for long lived contrails, which can generate a considerable warming as they spread out over time. Contrails are a key target for reducing the climate impact of aviation. Alternative fuels have been proposed as a potential solution to aviation's climate impact, by reducing lifecycle CO2 emissions and reducing particulate emissions from aircraft engines. Even though alternative fuels currently account for a tiny percentage of overall aviation fuel burn, they are expected to become more prevalent in the coming years and some airlines are already routinely using them on commercial flights. Furthermore, different aircraft engines can have particle emissions which are different by an order of magnitude and the effect that this has on contrail properties has not yet been studied using satellite observations.

While different aircraft engine particle emissions have been shown to have an impact on the short-term contrail properties, their impact on the development of contrails is unclear and is currently assessed using models . These models are based on our theoretical understanding of ice crystal behaviour and cloud processes, but are subject to considerable uncertainty, particularly in the behaviour of the contrail over time.

To assess the impacts of alternative fuels through improved contrail modelling, new observations linking the contrail lifecycle to the properties of the generating aircraft are required. This will be based around the use and exploitation of satellite data. The overall aim of this project is to improve our simulations of impact of aircraft engine particle emissions and alternative fuels on contrail formation and development. This requires an understanding of which contrails should be visible to satellite (O1), identification and characterisation of contrails in satellite imagery (O2) before the use for constraining model simulations (O3).

EPSRC areas: particle technology and biophysics

Aerosol science has a significant impact on a broad range of disciplines, extending from inhaled drug delivery, to combustion science and its health impacts, aerosol assisted routes to materials, climate change, and the delivery of agricultural and consumer products. Estimates of the global aerosol market size suggest it will reach $84 billion/year by 2024 with products in the personal care, household, automotive, food, paints and medical sectors. Air pollution leads to an estimated 30-40,000 premature deaths each year in the UK, and aerosols transmit human and animal infections. More than 12 million people in the UK live with lung disease such as asthma, and the NHS spends ~£5 billion/year on respiratory therapies. Many of the technological, societal and health challenges central to these areas rely on core skills and knowledge of aerosol science. Despite this, an Industrial Workshop and online survey (held in preparation for this bid) highlighted the current doctoral skills gap in aerosol science in the UK. Participating industries reported that only 15% of their employees working with aerosol science at doctoral-level having received any formal training. A CDT in aerosol science, CAS, will fill this skills gap, impacting on all areas of science where core training in aerosol science is crucial.

Impact on the UK aerosol community: Aerosol scientists work across governmental policy, industrial research and innovation, and in academia. Despite the considerable overlap in training needs for researchers working in these diverse sectors, current doctoral training in aerosol science is fragmentary and ad hoc (e.g. the annual Fundamentals of Aerosol Science course delivered by the Aerosol Society). In addition, training occurs within the context of individual disciplines, reinforcing artificial subject boundaries. CAS will bring coherence to training in the core physical and engineering science of aerosols, catalysing new synergies in research, and providing a focal point for training a multidisciplinary community of researchers. Working with the Aerosol Society, we will establish a legacy by providing training resources for future researchers through an online training portal.

Impact on industry and public-sector partners: 45 organisations have indicated they will act as CAS partners with interests in respiratory therapies, public health, materials manufacturing, consumer and agricultural products, instrumentation, emissions and environment. Establishing CAS will deliver researchers with the necessary skills to ensure the UK establishes and sustains a scientific and technical lead in their sectors. Further, it will provide an ideal mechanism for delivering Continuing Professional Development for the existing workforce practitioners. The activity of CAS is aligned to the Industrial Strategy Challenge Fund (e.g. through developing new healthcare technologies and new materials) and the EPSRC Prosperity Outcomes of a productive, healthy (e.g. novel treatments for respiratory disease) and resilient (e.g. adaptations to climate change, air quality) nation, with both the skilled researchers and their science naturally translating to long-lasting impact. Additionally, rigorous training in responsible innovation and ethical standards will lead to aerosol researchers able to contribute to developing: regulatory standards for medicines; policy on air quality and climate geoengineering; and regulations on manufactured nano-materials.

Public engagement: CAS will provide a focal point for engaging the public on topics in aerosol science that affect our daily lives (consumer products, materials) through to our health (inhalation therapeutics, disease transmission and impacts of pollution) and the future of our planet (geoengineering). Supported by a rigorous doctoral level training in aerosol science, this next generation of researchers will be ideally positioned to lead debates on all of these societal and technological challenges.