Coal Fueled Jet Aircraft: Could It Work?

Yes, a coal-fueled jet aircraft could technically work with modern materials and engines, but it would be impractical and inefficient. While you cannot simply pour coal into a jet engine, coal can be converted into a liquid fuel that is chemically similar to jet fuel, and modern metallurgy can handle the higher sulfur and ash content. However, the weight, cost, and complexity of the conversion process make it a non-starter for aviation.

Formula

The calculator above estimates the volume of fuel consumed during a flight. The formula is:

Fuel consumed (L) = (Flight time (min) × Fuel flow (kg/min)) / Fuel density (kg/L)

• Flight time (t) – duration of the flight in minutes.
• Fuel flow (f) – average fuel consumption rate in kilograms per minute.
• Fuel density (d) – density of the fuel in kilograms per liter (kerosene ~0.8, coal-derived jet fuel ~0.85).

The result is the total fuel volume in liters. This is useful for comparing different fuel types, since coal-derived fuels are denser than conventional kerosene.

Worked Example

Using the default values: a 120-minute flight, a fuel flow of 4.5 kg/min, and a fuel density of 0.8 kg/L (typical for Jet A-1).

1. Fuel mass consumed = 120 × 4.5 = 540 kg
2. Fuel volume = 540 / 0.8 = 675 L

The calculator returns 675 L.

Background: Why Coal for Jets?

The idea of powering jets with coal is not new. During World War II, Germany developed the Fischer-Tropsch process to produce synthetic fuel from coal because oil supplies were cut off. Today, coal-to-liquid (CTL) technology still exists, mainly in countries with large coal reserves and limited oil, like South Africa (using the Sasol process). The motivation is energy security, not economics. Coal is abundant and geographically widespread, but converting it to jet fuel is expensive and carbon-intensive.

How Coal Becomes Jet Fuel

Coal cannot be burned directly in a turbine. It must first be converted into a liquid hydrocarbon fuel. There are two main routes:

• Direct liquefaction – coal is dissolved in a solvent at high temperature and pressure, then hydrogenated to produce a synthetic crude oil.
• Indirect liquefaction (Fischer-Tropsch) – coal is first gasified into synthesis gas (carbon monoxide and hydrogen), then passed over a catalyst to form long-chain hydrocarbons, which are cracked and refined into jet fuel.

The resulting fuel is a blend of paraffins and is often called synthetic paraffinic kerosene (SPK). It can be blended with conventional jet fuel up to 50% under current certification standards (ASTM D7566).

Modern Materials and Engines

Modern jet engines are built to handle a wide range of fuels. Turbine blades are made of nickel-based superalloys with ceramic thermal barrier coatings, and combustion chambers are designed for high temperatures and corrosive byproducts. Coal-derived SPK burns cleaner than conventional jet fuel in terms of sulfur and aromatics, so it does not damage modern engines. The main issue is not the engine but the fuel production process. Coal contains ash, sulfur, and heavy metals that must be removed before conversion, and the process requires significant water and energy.

Practical Challenges

Even with modern materials, several obstacles remain:

• Weight and space – the gasification and liquefaction equipment is massive and heavy, impossible to carry on an aircraft. The fuel must be produced on the ground.
• Energy density – coal-derived jet fuel has a slightly lower energy density than conventional kerosene (about 42-44 MJ/kg vs 43-46 MJ/kg), meaning more fuel weight for the same range.
• Cost – building a CTL plant costs billions of dollars, and the resulting fuel is typically 2-3 times more expensive than petroleum-derived jet fuel.
• Carbon footprint – coal-to-liquid produces roughly double the CO2 emissions of conventional jet fuel on a well-to-wing basis, making it environmentally worse.

Comparisons: Coal vs. Biofuels vs. Hydrogen

Coal-derived jet fuel is not the only alternative. Sustainable aviation fuels (SAFs) from biomass (e.g., used cooking oil, agricultural waste) also use Fischer-Tropsch or hydroprocessed esters and fatty acids (HEFA) routes, but with a lower carbon footprint. Hydrogen, either as liquid or in fuel cells, offers zero CO2 at the point of use, but requires cryogenic storage and new aircraft designs. Coal-derived fuel has the advantage of using an existing fuel infrastructure and engines, but it fails on sustainability and cost.

Common Misconceptions

“Could you just grind coal into powder and burn it in a jet engine?� No. Coal powder is abrasive, has a high ignition temperature, and leaves ash that would erode turbine blades and clog fuel nozzles. Even in power plants, pulverized coal is burned in a boiler, not a gas turbine, because the ash content is too high.

“Did the Concorde run on coal?� No, the Concorde used conventional jet fuel (Avtur). Some early turbojet experiments in the 1940s and 1950s did test coal slurry fuels, but they were abandoned due to engine wear.

Frequently Asked Questions

Can a jet engine run on coal dust? No. Coal dust is a solid, and jet engines require a liquid or gaseous fuel that can be atomized and mixed with air. Coal dust would clog filters, erode components, and produce ash that damages the turbine.

Is coal-derived jet fuel currently used anywhere? Yes, South Africa has been producing synthetic jet fuel from coal using the Sasol process since the 1980s. It is blended with conventional fuel and used on commercial flights, but it represents a tiny fraction of global jet fuel.

Why don’t airlines use coal fuel if it works? Because it is not economically competitive. The capital cost of a coal-to-liquid plant is enormous, and the operating cost is high due to energy and water requirements. Airlines operate on thin margins and would not voluntarily pay 2-3 times more for fuel.

Does coal-derived jet fuel meet safety standards? Yes, synthetic paraffinic kerosene from coal has been certified for use in blends up to 50% with conventional jet fuel under ASTM D7566. It meets the same freezing point, flash point, and energy content specifications.

Could a coal-fueled jet ever be practical in the future? Only if oil prices rise dramatically and carbon capture becomes cheap and effective. Even then, the carbon footprint would be higher than biofuels or hydrogen, making it an unlikely choice for a climate-conscious industry.

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in t | Flight time | min | 120 | 1 | 1440
in f | Fuel flow (kg/min) | kg/min | 4.5 | 0.1 | 100
in d | Fuel density (kg/L) | kg/L | 0.8 | 0.5 | 1.2
out fuel | Fuel consumed | L | (t * f) / d | 0