In recent years, with the rapid development of global technology, various advanced weapons have emerged constantly, and the forms of warfare are changing rapidly. Many countries have launched military energy strategic transformations. Among them, exploring the development and use of sustainable aviation fuel (hereinafter referred to as "SAF fuel") has become an important development direction for many countries. Currently, military forces from multiple countries are collaborating with commercial sectors to attempt the use of SAF fuel. However, due to factors such as technological level and price, there is still a long way to go for SAF fuel to be widely promoted and used in the military of various countries. The current armed conflicts in many parts of the world have made many countries increasingly aware of the risks of relying on a single energy source, and the development of SAF fuel can help achieve military energy independence. To ensure effective operation within the mission scope, military aircraft need to have reliable fuel sources at all times. SAF fuel is mainly made from renewable raw materials with diverse sources, including used cooking oil, household waste, energy crops and other biofuels, as well as synthetic fuels made from carbon dioxide captured from air or industrial emissions. Compared with traditional aviation fuels, SAF fuel can reduce carbon emissions by about 80% throughout its entire lifecycle and is considered a good solution to ensure continuous fuel supply. Multiple countries are increasing their investment in the research and development of SAF fuel and attempting to use it on military aircraft. At present, the developed SAF fuel can be completely mixed with kerosene, with a maximum ratio of up to 50%, without the need for aircraft or engine modification, and without adverse effects on aircraft operation and maintenance. The UK is accelerating testing to verify that it is at the forefront of military SAF fuel development. The UK Ministry of Defence updated its aviation fuel standards in 2020, allowing the use of SAF fuel on military aircraft. Subsequently, the UK launched the "Zero Emissions in Aviation" strategy, planning to build five SAF fuel factories and achieve a 10% share of SAF fuel in aviation fuel by around 2030. In recent years, the British Air Force has been experimenting with SAF fuel, attempting to mix it with traditional aviation fuel and test it on military aircraft. In November 2022, the British Air Force collaborated with companies such as Airbus to conduct the first military aircraft flight test entirely using SAF fuel. The aircraft is named "Voyager" and is an improved version of the Airbus A330 aircraft, powered entirely by SAF fuel. During the flight, the Voyager also conducted an air-to-air refueling operation. During the 2024 Royal International Air Show in the UK, the Typhoon fighter jet was showcased for an 8-minute flight using a blend of sustainable aviation fuel at a ratio of approximately 35%. At the military parade held by the British Air Force in June this year, the "Red Arrows" flight demonstration team used SAF fuel for the first time, mainly renewable biofuels. The chemical structure of this fuel is very similar to the regular diesel used by the "Red Arrow" flight demonstration team for smoking. During the Royal International Air Show in the UK from July 18th to 20th this year, the British Air Force's "Red Arrows" and "Typhoon" flight demonstration teams once again used SAF fuel for flight demonstrations and organized formation flights. France is increasing its production investment and continuously accelerating its investment in military SAF fuel. In February 2023, a French NH-90 helicopter completed its first test flight using SAF fuel. This test flight was conducted in collaboration between the French armed forces and aircraft equipment manufacturers Safran, Total Energy, and Airbus, without modifying the NH-90 helicopter engine. The NH-90 helicopter is a medium-sized twin engine general-purpose helicopter, equipped with two RTM322 turboshaft engines. In this test, one of the engines used SAF fuel. This fuel is produced by Total Energy using a hydroprocessing process of esters and fatty acids from waste edible oils. Previously, French President Macron announced during a visit to Safran Group's factory in Vilarosh that he would invest 200 million euros (approximately 230 million US dollars) to build a SAF fuel plant to promote the production of SAF fuel. At present, several French defense companies, including Safran Group, are verifying the relevant situation of 100% operation using SAF fuel and evaluating the operation results. The United States promotes research and development progress, and spends a large amount of money every year to purchase aviation fuel, with transportation and delivery costs reaching billions of dollars. In the view of the US military, excessive reliance on foreign fuel during overseas missions will threaten US economic security and affect its mission execution efficiency. Moreover, fluctuations in fuel prices will cause fluctuations in the US military budget, thereby increasing operating costs, requiring additional funding to be sought from Congress or forced to squeeze out funds from training and weapons procurement projects. Therefore, the US military is also attempting to reduce its dependence on traditional fuels. The United States proposed in the 2023 National Defense Authorization Act that by 2028, the Pentagon must establish at least one refinery to produce a 10% blend of SAF fuel. The US military has sponsored an energy company called "Twelve" to produce jet fuel using carbon dioxide. The US military is also collaborating with an airline based in Brooklyn, New York City to develop carbon conversion technology and manufacture commercial and military aviation fuels. At present, these two companies are attempting to expand their technological scale and increase the proportion of SAF fuel in blended fuels to 50%. In January of this year, Lockheed Martin decided to test the use of synthetic fuel on the F-35 fighter jet. The company stated that the proportion of new fuels in synthetic fuels can reach up to 50%, depending on the type of raw materials and production methods. It is reported that the biofuels used by the US military have evolved from the first generation represented by biodiesel and bioethanol, the second generation represented by cellulose biofuels, to the third generation using algae as raw materials, and have been used in fighter jets, helicopters, and other aircraft models. The future development is highly concerned. Cooperation between military and commercial sectors of various countries to accelerate the development of SAF fuel can reduce dependence on fossil fuels such as oil to a certain extent, improve energy efficiency, and help achieve the commitment made by many countries at the 26th United Nations Climate Change Conference to achieve net zero carbon emissions by 2050. However, SAF fuel still needs to overcome many difficulties in order to be widely used in the military of various countries. Production issue. According to the International Energy Agency's statistics, the current usage of SAF fuel still accounts for a relatively low proportion of global aviation fuel. The current production of SAF fuel is around several hundred thousand tons, and to be widely used in military aviation, it would require hundreds of millions of tons. Based on current production estimates, there is still a huge gap that needs to be filled. How to achieve large-scale production of SAF fuel is an important issue faced by countries around the world. Cost issue. It is estimated that the price of SAF fuel is about 2.5 times that of traditional aviation fuel. The large-scale use of SAF fuel by multiple countries will require very high costs for fuel research and development, procurement, and renovation of storage facilities. The outside world is also concerned about whether countries are willing to pay for such high prices. In addition, the increase in SAF fuel production involves significant adjustments by refineries and may encounter resistance from relevant stakeholders. Whether this industry can attract more investment is also unknown. (New Society)