Contrails, SAF, and Environmental Concerns

While for many years the focus of aviation emissions has been carbon, there are additional outputs from jet engines, including chemicals that form contrails, that have recently been shown to be harmful. Nitrous oxide (NOx) and other particulates all contribute to the overall environmental performance of aircraft. How to fix it is another question, as first we need to measure what is being produced, and then determine whether SAF could be a solution not only for reducing carbon but also for reducing persistent contrails. Researching Emissions and Contrails Gulfstream and Rolls-Royce have jointly just completed a high-altitude flight test campaign to research contrail reduction using Sustainable Aviation Fuel (SAF). During flight testing, a Gulfstream G800 powered by Rolls-Royce Pearl 700 engines demonstrated the potential to reduce particulate emissions that form contrails when operating on 100% neat SAF. During the testing campaign, a specially equipped G700 became a flying emissions laboratory, following the G800 in formation flight to measure environmental impacts and contrail formation. Flights were conducted at 50,000 feet, higher than most commercial aircraft but typical for intercontinental business jets. The team compared conventional Jet A, low-sulfur Jet A, and neat hydro-processed esters and fatty acids (HEFA) SAF without sulfur or aromatics. The good news is that preliminary results suggest a significant and measurable reduction in particulate emissions that contribute to contrails when using neat SAF. [caption id="attachment_195364" align="aligncenter" width="480"] image: Gulfstream[/caption] The research team included representatives from the FAA’s ASCENT center of excellence, NASA, DLR (the German Aerospace Center), the University of Science and Technology, Aerodyne Research, Montana Renewables, and World Fuel Services, joining Gulfstream and Rolls-Royce in the study. Which type of SAF will prove best? HEFA SAF is made from plant and animal oils and fats, and is sometimes called first-generation SAF. Fats have been used to make biodiesel for many years; this is the most efficient way to currently make SAF. But not all SAF techniques are effective or can be scaled similarly for mass production. The Fischer-Tropsch process uses agricultural and forest wastes, as well as energy crops such as corn or sugarcane. Alcohol-to-Jet uses cellulosic biomass or starch-based feedstocks. Power-to-Liquid (PtL) uses captured CO2, water, and renewable electricity. Catalytic hydrothermolysis uses clear free fatty acid oil and water, whereas HC-HEFA uses algal oil to produce SAF. Today, the production or collection of feedstocks across all methodologies combined falls well short of industry needs. Neat HEFA, which is being tested, is constrained by the availability and supply of low-emission waste feedstocks. Translated, that means the recycled grease from all the fast-food restaurants in existence still won’t make a huge dent compared with the potential demand for 100% SAF utilization. We now know that 100% use of the right type of SAF can reduce both carbon emissions and particulates, helping aviation, which accounts for about 4% of global climate change, achieve its goal of environmental neutrality by 2050. Positive Research Results The results of the study are promising, and could lead to new solutions for the industry. “As aviation continues its work in optimizing environmental efficiencies, Gulfstream is focused on advancing solutions that deliver measurable impact today while shaping a more sustainable future for flight,” said Mark Burns, president, Gulfstream. “This campaign reflects our strategy to lead with advanced technology, real-world testing and meaningful collaboration to better understand and reduce aviation’s environmental impact.” Gulfstream outfitted an instrumented cabin specifically to measure the emissions from a trailing aircraft in formation flight, and spent months ensuring that its measurement technologies could detect emissions and particulates. Alan Newby, Director of Research and Technology, Rolls-Royce, said: “Sustainable Aviation Fuels in combination with compatible, ultra-efficient aero engines will not only play a vital role in decarbonizing aviation but have also been shown to reduce certain non-CO2 emissions. The valuable insights we have gained from these latest tests at high altitudes, as well as the data from projects like QRITOS or ECLIF3, are driving real progress in understanding aviation’s non-CO2 climate impacts and potential mitigation options.” Industry-Wide Impact “This collaboration enabled these first-ever high-altitude 100% SAF emissions observations, allowing the team to operate safely and efficiently while maintaining the precision needed for accurate data collection,” said Rich Moore, research scientist, NASA. “This real-world data is essential to improving our models and understanding aviation’s broader environmental impact.” “Partnering with Gulfstream was an excellent opportunity that will help inform and quantify our efforts to mitigate the impacts of persistent contrails,” said Julie Marks, executive director of the FAA’s Office of Environment and Energy. “We appreciate the collaboration with industry as the FAA continues to evaluate how SAF may help reduce persistent contrails. The Bottom Line The industry has become aware of the benefits of SAF for emissions, and these measurements provide data on a range of chemicals and particulates emitted by jet engines. The data will be used in partnership with the broader aviation and atmospheric science communities to refine analytical models, inform future fuel standards, and support the development of operational strategies to reduce the environmental impact of air travel. With significant reductions recorded, this is positive for the industry and will confirm the need to build additional feedstock-gathering and production facilities. The industry has now shown that SAF works. Now the challenge is making enough of it for jet customers to run on 100% SAF.

US Flight Planner - US DoT On-Time Data	Airbus vs Boeing - Official OEM Data
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Researching Emissions and Contrails

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Researching Emissions and Contrails

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