The Engine That Was Supposed to Run on Peanuts

It's Tuesday, September twenty-ninth. The diesel engine was designed to run on vegetable oil. Peanut oil, specifically. The inventor, a German engineer named Rudolf Diesel (ROO-dolf DEE-zel), unveiled it at the 1900 World's Fair in Paris running on fuel he pressed from peanuts so low-grade they couldn't be sold as food. He believed farmers should be able to grow their own fuel. He built the engine to give small craftsmen and rural towns a power source that didn't depend on big industry.

Exactly 113 years ago today, on September 29, 1913, Rudolf Diesel boarded a steamship in Antwerp, Belgium, bound for England. He ate dinner with his fellow passengers, said goodnight, went to his cabin, and was never seen alive again. His bed was untouched. His coat was folded neatly on the deck. Ten days later, a body was pulled from the North Sea.

Nobody knows what happened. And the reason the mystery still matters is that Diesel's original vision, an engine that ran on crops instead of crude oil, died in the water with him.

Rudolf Diesel was born in Paris in 1858 to German leatherworkers. His family was deported to England when the Franco-German War broke out, and he eventually landed in Augsburg, Germany, where he became a standout engineering student at Munich Polytechnic. He studied under Carl von Linde, the refrigeration pioneer whose name is still on industrial cooling systems, and joined Linde's firm in Paris as a refrigerator engineer.

But Diesel could not stop thinking about engines. Specifically, he wanted to build something better than the steam engine, which at the time converted something like 10 percent of its fuel's energy into actual work. The rest was wasted as heat. Diesel's goal was to design an engine that approached the theoretical maximum efficiency laid out by a French physicist named Sadi Carnot (car-NOH), a kind of ideal ceiling for how much energy you can extract from heat.

The insight that made the diesel engine work was compression. If you squeeze air hard enough inside a cylinder, it gets so hot that fuel injected into it ignites on its own. No spark plug needed. Diesel filed his patent in 1892, built a prototype in 1893 that nearly killed him when it exploded, and in 1897 produced a working 25 horsepower engine with a theoretical efficiency of 75 percent. The steam engine's 10 percent suddenly looked absurd.

Diesel was not just an engineer. He was a social theorist. He believed the industrial revolution was concentrating power in the hands of factory owners and city capitalists while leaving small craftsmen and farmers behind. His engine was supposed to fix that. It could run on vegetable oil, and it was simple enough to operate and repair locally. A farmer could literally grow fuel. Diesel said in 1911, "The use of plant oil as fuel may seem insignificant today, but such products can, in time, become just as important as kerosene."

At the 1900 Paris World's Fair, the French government asked Diesel to demonstrate his engine running on peanut oil. They were looking for energy sources that could be produced in their African colonies without importing petroleum. And it worked. The engine ran perfectly on oil pressed from peanuts that a friend had supplied, peanuts that were too low grade to sell as food.

Diesel became a millionaire. Royalties poured in from around the world. Ships, factories, power plants, all began adopting his engine. He was celebrated in the United States on tours in 1904 and 1912. He was elected an honorary member of the American Society of Mechanical Engineers.

And then everything fell apart.

Diesel was a brilliant inventor and a terrible businessman. He lost most of his fortune in bad investments and speculative deals. By 1913, he was essentially bankrupt. The New York Times reported that he owed roughly three hundred seventy-five thousand dollars, the equivalent of more than eleven million today, with tangible assets of about ten thousand.

He had also been through a nervous breakdown years earlier. Patent lawsuits had worn him down. His health was deteriorating. He had sold away rights to his own engine in a fit of despair, believing he was about to die, and when he recovered, he was locked out of improving his own invention.

On September 29, 1913, Diesel boarded the steamship Dresden in Antwerp, heading to Harwich, England. He had two appointments waiting for him. One was the opening of a new diesel engine factory. The other was a meeting with representatives of the British Royal Navy, who wanted to discuss powering submarines with diesel engines. This was eight months before World War I would begin, and Germany's relationship with Britain was deteriorating fast.

Diesel ate dinner with two business associates that night. He seemed in good spirits. He asked about the weather for the next morning, went to his cabin around ten, and told the steward to wake him at quarter past six. His nightclothes were laid out on the bed.

The next morning, the steward knocked and got no answer. Diesel's cabin was empty. His bed had not been slept in. His hat and overcoat were found neatly folded on the deck, near a railing. He was gone.

Ten days later, on October 10, a Belgian sailor spotted a body floating near the mouth of the Scheldt River. The body was too decomposed to identify visually, but the personal items recovered, including a pill case, wallet, and pocket knife, were confirmed by Diesel's son as belonging to his father. The body was not brought aboard. Custom at the time, when a sailor recovered a corpse at sea, was to remove anything valuable and return the body to the water. It was never examined.

The official ruling was suicide. But almost nobody accepted it.

The suicide theory has evidence behind it. Diesel's wife Martha opened a bag he had left behind. Inside were financial documents revealing his debts and a sum of cash. He had also drawn a small cross in his diary next to September 29. The cross, combined with the untouched bed and the folded coat, is hard to ignore.

But there are also reasons to doubt it. Diesel had just booked a new home for his family. He had written excitedly to his wife about the trip to England. He had been making concrete plans. And the two things he was traveling for, the factory opening and the submarine meeting, were real opportunities to turn his fortunes around.

The murder theories are harder to prove but have more suspects.

Theory one: the German secret service. Diesel was about to share his submarine engine expertise with the British navy on the eve of war. Germany was already developing its U-boat fleet. The Germans had a clear motive to stop him. One newspaper headline at the time read: "Inventor Thrown Into the Sea to Stop Sale of Patents to British Government."

Theory two: Big Oil. Diesel's engine could run on vegetable oil, and he was openly saying farmers should grow their own fuel. Standard Oil, led by John D. Rockefeller, had a near-monopoly on petroleum refining in the United States and a massive interest in making sure the world's engines burned oil, not crops. Another headline from 1913: "Murdered by Agents from Big Oil Trusts."

Theory three: he wasn't dead at all. In the spring of 1914, a Munich newspaper reported that Diesel was alive and living in Canada, working at the Vickers shipyard in Montreal. The story claimed the British government had helped him fake his own death so he could develop submarine engines for the Royal Navy without German interference. No follow-up reporting ever confirmed it.

None of these theories have ever been proven. The mystery is 113 years old and no closer to being solved.

What we do know is that the engine Diesel built did not follow his vision. By the 1920s, the petroleum industry had made diesel fuel from crude oil so cheap and widely available that vegetable oil made no economic sense. The engine designed to give farmers independence became the engine of industrial globalization, powering the ships and trucks and trains that move goods across the world on a single, petroleum-based fuel.

The peanut oil engine became a fossil fuel engine, and that is where we are today, with billions of diesel engines burning billions of barrels of crude.

There is a version of the twentieth century where diesel engines ran on crops and fuel was distributed across millions of farms. We did not get that version. The diesel engine became a crude oil engine, engineered to burn petroleum because it was cheaper, and Diesel's vision of farmers growing their own fuel was largely forgotten.

But here is what makes this more than a what-if story. Right now, the global biodiesel and renewable diesel market is worth roughly seventy billion dollars a year, and it is on track to nearly double by 2030. Governments, oil companies, and startups are spending billions deploying advanced chemical engineering to make engines run on vegetable oil again. They are trying to get back to what Rudolf Diesel did with a peanut press at the Paris World's Fair in 1900.

One of the most important inventions of the industrial age was not designed for oil companies. It was designed for farmers. And a hundred and thirteen years later, we are spending seventy billion dollars a year trying to get back to peanut oil.

Stay informed, stay curious, and we'll see you tomorrow.