Text by Charitos Anastasiou

Cover image: Refuelling a German Pz IV medium tank from a railcar.

Lacking domestic petroleum reserves, the Germans began researching synthetic fuels immediately after World War I and the loss of their colonies in Africa and Oceania. The economic collapse significantly reduced energy needs, but the rapid economic growth and reindustrialization that followed—especially with the restart of the war industry under the Third Reich and the explosion of public works—brought the issue back into focus.

By the 1930s, the National Socialist regime began intensifying efforts toward energy self-sufficiency and the production of liquid fuels from domestic sources “at any cost.” Germany had abundant coal deposits, and as early as the 1920s, German researchers had discovered ways to produce liquid fuels from the gasification and pyrolysis of solids. Nobel laureate chemist Friedrich Bergius pioneered this technology; as early as 1913, he had proposed liquefaction or hydrogenative pyrolysis of coal, a process in which coal was treated with hydrogen at extremely high temperatures (400–600°C) and pressures (200–700 atm) in the presence of an inorganic solid catalyst. The large molecules in coal would break into smaller ones (pyrolysis), producing high-quality gasoline fractions. Although the method was economically and energetically inefficient, it offered relative self-sufficiency in liquid fuels—vital for wartime.

At the same time, Haber and Bosch achieved the production of valuable ammonia from nitrogen and hydrogen derived from coal. By 1921, Germany’s vast and pioneering chemical industry had significantly expanded the production of liquid fuels and ammonia directly from its rich deposits of anthracite, bituminous coal, and lignite.

In 1925, Franz Fischer and Hans Tropsch revolutionized the field with their namesake FT process: coal was gasified at 150–300°C and 20 atm, producing synthesis gas (also known as town gas—a mixture mainly of hydrogen and carbon monoxide), which was passed through a solid catalyst reactor. There, the two components reacted to form valuable long-chain hydrocarbons such as diesel and kerosene. This process was far more efficient and economical than Bergius’s, but it did not flourish initially because the world still ran on gasoline. Diesel engines and jet turbines, which would later rely on these fuels, had not yet been developed or widely adopted. A new era had begun in Germany—the era of ersatz (substitute) fuels and chemicals—reducing the country’s dependence on imported oil.

By 1936, the Germany accelerated these efforts with a Four-Year Fuel Plan. A growing number of industries, scientists, and chemical engineers worked actively to produce gasoline from a variety of coal grades and available catalysts. There was a vast fleet of vehicles, tanks, and aircraft requiring colossal quantities of gasoline to fight, but only limited access to petroleum reserves. Here, Germany’s excellent chemical industry stepped in. Millions of Reichsmarks were invested, and under the leadership of I.G. Farben, German industry massively improved both yield and quality. During the war, twelve major factories focused exclusively on synthetic fuel production.

Nevertheless, the overall process remained expensive and resource-intensive and could not match the output of oil refineries using crude petroleum. By late 1944, 25 synthetic fuel plants were producing 124,000 barrels per day (!), with ten located in the coal-rich, heavily industrialized Rhineland and many others in present-day Poland—especially Silesia, the industrial heart of Germany. Nearly 350,000 forced and enslaved laborers worked around the clock to meet the Wehrmacht’s insatiable need for gasoline. An additional seven underground plants were planned for construction by June 1944 but remained incomplete by the end of the war.

The failure to conquer the Caucasus oil fields meant that by 1945, nearly 75% of Germany’s fuel was of synthetic origin. Romania produced 100,000 barrels of crude oil per day, while Germany’s 25 synthetic fuel plants produced 125,000 barrels per day of clean, usable fuel from coal. For anyone who understands the complexity of such production, this represents a monumental feat—proof of Nazi Germany’s staggering scientific and technological power.

In contrast, the Western Allies had access to abundant reserves in the U.S., the Caribbean, Venezuela, and eventually Saudi Arabia, while the Soviets drew from enormous deposits in Azerbaijan. Iraq and Iran also supported the Allies. Japan, meanwhile, relied on the high-quality oil fields of the Dutch East Indies.

Studying World War II reveals something remarkable: all vehicles—from motorcycles and jeeps to tanks and aircraft—ran almost exclusively on gasoline. The only exception was the Soviet T-34, the first military vehicle to run on diesel fuel, setting a precedent for today’s use of diesel in nearly all military, industrial, and heavy-duty vehicles. During the war, the jet turbine engine was developed, running on kerosene (essentially light diesel), and although it changed aviation forever, it saw widespread use only after the war. Throughout the war, aircraft ran on high-octane aviation gasoline—hence the development of the octane rating still used today.

The above-mentioned methods—primarily the FT process—were used postwar, briefly in the U.S., but more extensively by apartheid-era South Africa. Isolated by international embargoes and lacking petroleum reserves, South Africa produced all its land and air fuels from coal for decades, employing many scientists and researchers from Germany.

The FT process flourished after the war, as diesel largely replaced gasoline in military, commercial, and heavy vehicles, as well as trains. Kerosene became the standard for aircraft, as jet engines became dominant in aviation worldwide. Today, the FT process offers hope for sustainable fuels by converting biomass or solid waste into high-quality liquid fuels—especially in the form of sustainable aviation fuels (SAF).