Changing Jet Fuel: A Step-By-Step Guide To Refueling Safely

The aviation industry has been under pressure to move from jet fuel to more sustainable alternatives since before the 2016 Paris Agreement. Jet fuel is a mixture of various hydrocarbons, and the most commonly used fuels for commercial aviation are Jet A and Jet A-1. These are kerosene-type jet fuels, which are defined by their performance specifications rather than chemical compounds. The shift towards sustainable aviation fuel (SAF) is driven by the need to reduce the environmental impact of air travel, particularly for medium and long-haul flights, which generate the most emissions. While there are challenges to adopting SAF, such as feedstock constraints and higher production costs, it offers a promising solution to decarbonising the aviation industry.

Jet fuel is a mixture of various hydrocarbons

Jet fuel undergoes multiple refining processes and the addition of various additives to enhance its performance and suitability for specific aircraft and conditions. These additives can include fuel icing inhibitors, antioxidants, corrosion inhibitors, metal deactivators, and static dissipaters. The specific combination of hydrocarbons and additives gives jet fuel its characteristic properties, such as high energy density, elevated flash points, and precise viscosity, making it suitable for use in aircraft engines.

The properties of jet fuel are carefully tailored to meet the rigorous demands of aviation. The high energy density facilitates extended flights, while the elevated flash points improve safety during storage, handling, and fueling. The precise viscosity allows for effective pumping and combustion within engines, ensuring optimal overall engine efficiency. Additionally, the incorporation of corrosion inhibitors helps prevent damage to aircraft systems, enhancing safety and prolonging engine life.

The specific type of jet fuel used depends on various factors, including aircraft specifications, operational contexts, and fuel accessibility. For example, Jet A and Jet A-1 are commonly used for commercial aviation, while Jet B is often used for its enhanced cold-weather performance, and JP-4 and JP-5 are primarily used for military applications.

Jet A and Jet A-1 are the most commonly used jet fuels

Jet A and Jet A-1 are kerosene-type jet fuels. They are compatible with most jet aircraft, including civil and military planes, helicopter turbine engines, turboprops, and compression-ignition piston engines. These fuels are designed for aircraft powered by gas-turbine engines. Jet A and Jet A-1 have a flashpoint higher than 38°C (100°F) and an auto-ignition temperature of 210°C (410°F). The primary difference between the two fuels is their freezing point. Jet A has a freezing point of −40°C (−40°F), while Jet A-1 has a lower freezing point of −47°C (−53°F), making it better suited for colder climates. Additionally, Jet A-1 includes a mandatory antistatic additive.

The use of Jet A and Jet A-1 fuels ensures safety, efficiency, and consistency in aviation. These fuels adhere to stringent quality requirements, reducing the risk of incidents and malfunctions caused by fuel-related issues. The standardization of jet fuel also simplifies regulatory adherence and fosters international trade and cooperation in the aviation industry.

The availability and use of Jet A and Jet A-1 vary depending on the region and flight route. Jet A is typically employed in areas with milder or moderate climates, such as the USA. In contrast, Jet A-1 is favored for its ability to withstand colder temperatures and is commonly used in regions with cold weather and for international flights that encounter varying temperature conditions.

Jet fuel is defined by performance specifications

The most commonly used jet fuels for commercial aviation are Jet A and Jet A-1, which are produced to a standardized international specification. Jet A specification fuel has been used in the United States since the 1950s and is usually not available outside the US and a few Canadian airports. Jet A-1 is the standard specification fuel used in most of the rest of the world, except in Russia and CIS member countries, where TS-1 is the most common standard.

Jet A and Jet A-1 differ in two main ways: the freezing point and the addition of an antistatic additive. Jet A-1 has a lower freezing point of −47 °C (−53 °F) compared to Jet A's −40 °C (−40 °F). Jet A-1 also includes an antistatic additive, which is mandatory.

The typical physical properties of Jet A and Jet A-1 include an autoignition temperature of 210 °C (410 °F) and a maximum adiabatic burn temperature of 2,230 °C (4,050 °F). The density of Jet A is 0.804 kg/L (6.71 lb/US gal), while Jet A-1 has a slightly higher density of 0.820 kg/L (6.84 lb/US gal).

Another type of jet fuel is Jet B, which is used for its enhanced cold-weather performance. Jet B is a naphtha-kerosene fuel blend that is rarely used due to its dangerous nature. It has a low freezing point of −60 °C (−76 °F) and is primarily used in extremely cold climates like northern Canada and Alaska.

Aviation biofuel is used to decarbonise air travel

Aviation biofuel is a crucial step in the journey to decarbonising air travel. However, it is not a panacea and comes with its own set of challenges.

The aviation industry has been under pressure to move from jet fuel to sustainable aviation fuel (SAF), also known as aviation biofuel, since before the 2016 Paris Agreement. This shift is essential to reduce the carbon footprint of the industry, which has quadrupled since the 1960s and could triple again by mid-century if no action is taken.

Biofuels can be blended with jet fuel to reduce emissions, much like how biofuel is blended with gasoline for motorists. The EU's ReFuelEU Aviation proposal, for example, mandates that aviation fuel suppliers provide a blend of 2% SAF from 2025, increasing to 70% by 2050. While this is a positive step, it is important to note that even if biofuel were to power the entire global fleet, the climate effect of CO2, NOx, and water vapour emissions, as well as fuel production, would still be around three times higher than hydrogen-powered fuel cells.

One of the main challenges of aviation biofuel is the amount of land required to produce it. The world could need four to five times as much land for biofuels as it uses today, which could lead to deforestation and a reduction in carbon sequestration. Additionally, energy crops that involve a change in land use can have harmful ecological consequences, and in a warmer world, energy crops will compete with food crops for increasingly scarce water resources.

Another issue is the cost of biofuel, which is about twice that of jet fuel. While a high carbon price could reduce this differential, it would also increase the cost of carbon offsets, which the aviation industry relies on.

Furthermore, the environmental benefits of biofuel are not as far-reaching as is ultimately needed. Energy crops that involve a change in land use can have harmful ecological consequences, including deforestation and wetlands loss. Additionally, the production of biofuels often involves the use of fertilisers, which have their own carbon costs.

While aviation biofuel is an important step in the right direction, it is not a long-term solution for the aviation industry's climate impact reduction. The future of aviation fuel lies in hydrogen-electric powertrains, which are zero-carbon, have greater energy density than lithium-ion batteries, and produce far less noise pollution.

Synthetic paraffinic kerosene (SPK) is a non-petroleum-based jet fuel

SPK refers to any non-petroleum-based fuel designed to replace kerosene jet fuel, which is the most common type of jet fuel used in commercial aviation. Kerosene-type jet fuels include Jet A, Jet A-1, JP-5, and JP-8. While most jet fuels are kerosene-based, SPK is made from alternative sources such as biomass, plants, or animals.

SPK can be produced from plant or animal sources such as jatropha, algae, tallows, waste oils, babassu, and camelina (bio-SPK). It can also be produced from solid biomass using pyrolysis processed with a Fischer-Tropsch (FT) process (FT-SPK) or with an alcohol-to-jet (ATJ) process from waste fermentation. Additionally, small piston engines can be modified to burn ethanol.

The use of SPK as a jet fuel has several benefits. Firstly, it helps to reduce carbon emissions from the aviation industry, which is responsible for at least 2% of anthropogenic greenhouse gas emissions. Secondly, SPK is a "drop-in" biofuel, which means it is interchangeable with conventional jet fuels. ASTM International, the organization that certifies the safety and performance of jet fuels, has found it safe to blend in up to 50% SPK into regular jet fuels. This allows for a gradual transition to more sustainable aviation fuel without requiring significant changes to aircraft engines or infrastructure.

SPK also has a positive environmental impact. Biofuels are derived from plants, animals, or waste, and depending on the type of biomass used, they can lower CO2 emissions by 20-98% compared to conventional jet fuel. For example, Jatropha oil, a non-food oil used as a biofuel, can lower CO2 emissions by 50-80% compared to Jet-A1, a kerosene-based fuel.

In addition to its environmental benefits, SPK has economic advantages. The production and use of SPK can reduce the cost of jet fuel by providing an alternative to petroleum-based fuels, which are subject to fluctuations in oil prices. SPK can be produced from a variety of sources, including waste products, which can help reduce the cost of feedstock and make the fuel more economically competitive.

Overall, Synthetic paraffinic kerosene (SPK) is a promising alternative to conventional jet fuel that has the potential to reduce carbon emissions, improve environmental sustainability, and provide economic benefits to the aviation industry.

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