1 3 A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A R C H 2 0 2 3 Fig. 2 — Pathways to sustainable propulsion. Fig. 1 — Environmental impacts of climate change. The aviation industry, which accounts for approximately 2.5% of global CO2 emissions, could potentially contribute a greater fraction of global CO2 emissions due to the estimated increase in customer demand for air travel by 2050. Current and nearterm aircraft that will remain in the skies for decades are designed around the combustion of kerosene. Conventional jet fuels contain fossil-based carbon that is released during the aircraft engine combustion process as well as through the extraction, refining, and delivery of these fuels. However, sustainable aviation fuels (SAF) offer great potential as near carbon-neutral sources of energy over their carbon life cycle, contributing to goals to achieve net zero carbon emissions by 2050. Widespread deployment and use of sustainable aviation fuels would enable the preservation of the capital asset values of legacy engine products as customers drive toward a net zero carbon future. In addition to SAF, improvements to aircraft and engine technology, operations, and infrastructure are required for the aviation industry to meet its sustainability goals because the supply of sustainable aviation fuel is less than 0.1% of global aviation fuel demand. As the aviation industry continues to develop technologies that reduce fuel consumption per unit of thrust by 1-1.5% per year, a broad, sustained effort to ensure aircraft engine compatibility with sustainable aviation fuels, as well as increased production and adoption of these renewable liquid hydrocarbons will be required to achieve net zero carbon emissions in aviation by 2050. SUSTAINABLE AVIATION CHALLENGE Climate change impacts people and economies. The greater frequency and severity of inclement weather conditions caused by human activity since the pre-industrial age has increased the risk to human health, property, and global economic growth. As a result, mitigating the impacts of anthropogenic climate change to meet the goals of the United Nations Paris Agreement signed in 2016 is one of the most urgent challenges of our time. The shared goal of the Paris Agreement was to limit global warming to 1.5°C above pre-industrial levels. The aviation industry is one of six hard-to-abate sectors, along with cement, steel, plastics, trucking, and shipping. Together, these hard-to-abate sectors emit 30% of global annual CO2 emissions. As easier-to-abate sectors, such as automotive and power generation, decarbonize, and as global demand for air travel increases, the aviation industry’s contribution to global CO2 may rise substantially by 2050. The Air Transportation Action Group (ATAG) has produced a report called Waypoint 2050 that outlines the key technologies and strategies that would enable a net zero CO2 air transportation sector by 2050. The unmitigated growth of the aviation sector would more than double CO2 emissions by 2050 relative to 2022[1]. Advanced airframe and propulsion system technologies would enable a 30-35% reduction in CO2 emissions relative to the baseline unmitigated growth scenario. Strategies that improve aircraft operational efficiency, such as trajectory optimization, may yield an additional 5-10% reduction in CO2 emissions relative to the unmitigated growth scenario. Aggressive aircraft technology development and airline operational efficiency measures may only yield up to 45% reduction in CO2 emissions relative to the unmitigated growth scenario. Low carbon intensity fuels, such as sustainable aviation fuels and hydrogen, would be required at commercial scale to reduce aviation CO2 emissions by another 50-55%. The remaining gaps to achieve the net zero CO2 emissions goal by 2050 would be addressed through market-based measures such as CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation). PRATT & WHITNEY’S APPROACH TO SUSTAINABLE PROPULSION Pratt & Whitney (P&W) joined an industry-wide commitment to achieve net zero transport carbon emissions by 2050 in support of the Paris Agreement, and developed a technology strategy to support our customers’ commitments toward this goal. Pratt & Whitney’s approach to sustainable propulsion consists of: 1) continuing to develop the advanced gas turbine propulsion technologies that improve efficiency,
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