Air travel’s climate footprint has made sustainable aviation fuel one of the most urgent engineering challenges in modern transportation. Researchers at Osaka Metropolitan University have now reported a coconut oil-derived fuel that can be blended with conventional Jet A-1 without causing a major loss of engine performance. In experiments with a small turbojet engine, the new fuel maintained thermal efficiency comparable to that of standard aviation fuel, while reducing hydrocarbon emissions. The results suggest that discarded or substandard coconuts could become a locally available feedstock for aviation biofuel, particularly in Southeast Asia, where large quantities of coconuts are rejected each year for failing to meet commercial appearance or quality standards.
The fuel was produced using a co-solvent method that combines extracts from coconut oil with acetone and an alcohol. Unlike many biofuel production routes that require substantial heating, pressurization, or multiple purification stages, the Osaka Metropolitan University process operates at ambient temperature and pressure. This can reduce energy consumption during manufacturing and may also help preserve the chemical purity of the resulting fuel. The researchers prepared two types of coconut-derived aviation biofuel: fatty acid methyl ester, or FAME, made using methanol, and fatty acid ethyl ester, or FAEE, made using ethanol. Both belong to the broader family of fatty acid esters commonly associated with biodiesel, but their properties can be adjusted for use in aviation fuel blends.
Coconut oil is considered an attractive source for this purpose because its fatty acids contain relatively short carbon chains compared with many other vegetable oils. Jet fuel, including Jet A-1, consists primarily of hydrocarbons within a particular range of molecular sizes, and the chain lengths found in coconut-derived compounds are closer to this range than those in oils dominated by longer fatty acids. That chemical similarity does not automatically make untreated coconut oil suitable for a turbine engine. Raw vegetable oils are too viscous, thermally unstable, and chemically different from aviation kerosene to be used directly in most aircraft engines. Converting the oil into FAME or FAEE changes its physical and combustion properties, producing a fuel that can be mixed with conventional jet fuel and evaluated under controlled engine conditions.
To determine how the coconut-based fuels behaved, the research team created blends containing different proportions of FAME or FAEE and Jet A-1. They then tested the mixtures in a small turbojet engine, examining fuel consumption, thermal efficiency, and emissions. Thermal efficiency describes how effectively the engine converts the chemical energy in fuel into useful mechanical or propulsive output. Fuel consumption, meanwhile, depends not only on how efficiently the engine operates but also on the energy content of the fuel itself. The researchers expected the coconut-derived blends to consume more fuel because their heating values—the amount of energy released during combustion—differ from those of conventional Jet A-1.
The experiments confirmed that fuel consumption generally increased as the proportion of biofuel rose. This result was attributed primarily to differences in heating value rather than to a dramatic deterioration in engine operation. Even though the engine needed more of the blend to produce a comparable amount of energy, its thermal efficiency remained broadly similar to that observed with Jet A-1. In practical terms, the findings indicate that the engine was still converting the available fuel energy effectively. The result is important because a sustainable aviation fuel must do more than burn: it must deliver reliable energy without causing unacceptable changes in engine behavior, operating stability, or performance.
The emissions results were particularly significant. As the proportion of coconut-derived fuel increased, hydrocarbon emissions declined. Unburned hydrocarbons are released when fuel does not combust completely, and lowering them can indicate more complete combustion under the tested conditions. The researchers observed no significant changes in carbon dioxide or nitrogen oxide emissions compared with conventional Jet A-1. Carbon dioxide is the principal greenhouse gas associated with the combustion of aviation fuel, while nitrogen oxides contribute to air pollution and can affect atmospheric chemistry at cruising altitude. The absence of a significant increase in these pollutants suggests that the coconut-based blends did not create a new emissions penalty in the tested microturbine system.
“Our experiments showed that our fuel blend can operate in existing gas turbine engines without major loss of efficiency or engine performance, and without increasing emissions,” said Dr. Huynh Phuong Uyen Nguyen of Osaka Metropolitan University’s Graduate School of Sustainable System Sciences. The statement reflects the central appeal of drop-in or near-drop-in sustainable aviation fuels: they can potentially be introduced into existing engines and fuel infrastructure without requiring an entirely new generation of aircraft. However, the experiments were conducted in a small turbojet engine, not in a commercial airliner, and the findings should therefore be viewed as an early technical demonstration rather than proof of immediate large-scale aviation readiness.
The researchers also emphasize that combustion performance is only one part of the qualification process. Before a coconut-based fuel could be used widely in aviation, it would need to meet demanding requirements for long-term storage stability, cold-weather behavior, energy density, material compatibility, and safety. Jet fuel must remain stable during storage and transport, resist unwanted chemical reactions, and perform reliably across the extreme temperature range encountered in aviation. The compatibility of FAME and FAEE with seals, pumps, tanks, and fuel-control systems would also require extensive testing. In addition, a full life-cycle assessment would be necessary to determine whether the environmental benefits remain substantial after accounting for cultivation, harvesting, processing, transport, land use, and possible competition with food production.
The opportunity may be especially relevant in Southeast Asia, where approximately 30 percent of harvested coconuts are reportedly discarded because they do not satisfy commercial standards. These coconuts may not be suitable for conventional retail markets, yet they still contain oil that could serve as a chemical feedstock. Converting agricultural waste or rejected crops into fuel could provide an additional revenue stream for producers while reducing dependence on imported petroleum. The region’s vulnerability to fuel-price shocks further strengthens the appeal of locally sourced alternatives. At the same time, using waste coconuts rather than expanding plantations would be essential if the fuel is to avoid creating new environmental pressures through deforestation, excessive water use, or competition with food supplies.
The Osaka Metropolitan University team now plans to improve fuel-consumption performance and investigate technologies capable of operating engines on 100 percent coconut-derived biofuel. The researchers also intend to examine storage stability, material compatibility, and broader environmental impacts before pursuing practical deployment. Their study, published in the journal Fuel, provides evidence that coconut oil converted through a co-solvent process can function as a promising component of aviation fuel blends. It does not yet solve aviation’s emissions problem, but it points toward a potentially scalable pathway in which agricultural by-products become cleaner-burning energy sources for turbine engines. As airlines search for alternatives that can work with existing propulsion technology, an ingredient as familiar as coconut oil may be entering the conversation in a surprisingly technical new form.
Subject of Research: Aviation biofuel derived from coconut oil and its combustion and emission characteristics in a micro jet engine
Article Title: Combustion and emission characteristics of aviation biofuel derived from coconut oil using the co-solvent method: toward eco-friendly micro jet engines
News Publication Date: 8 June 2026
Web References: https://doi.org/10.1016/j.fuel.2026.140208
References: Fuel, DOI: 10.1016/j.fuel.2026.140208
Image Credits: Osaka Metropolitan University
Keywords: sustainable aviation fuel, coconut oil biofuel, FAME, FAEE, Jet A-1, co-solvent method, turbojet engine, aviation emissions, hydrocarbon emissions, renewable fuel
