Gas Engine Turned Into a Hydrogen Generator: Engineers Show the Impossible

Mazda has once again proved it can surprise the automotive industry. The automaker has patented an engine that, while running on gasoline, can independently produce hydrogen and release pure carbon in powder form. The idea sounds like science fiction: the engine takes in fuel and generates power, while the driver receives a byproduct that can be stored or even sold. But how realistic is this concept?

The Essence of Mazda’s Six-Stroke Engine

A conventional internal combustion engine operates in four strokes: intake, compression, power, and exhaust. Mazda’s new patent adds two more steps.

On the fourth stroke, part of the exhaust gases is diverted not to the tailpipe but to a reformer—a special unit where, at high temperatures, gasoline is injected and split into hydrogen and carbon powder.

The fifth and sixth strokes handle reverse expansion and exhaust.

In this way, the engine creates its own hydrogen fuel, which is then reused for combustion.

Why It Matters

The main goal is to sidestep the challenge of hydrogen storage. Transporting and storing hydrogen is notoriously difficult due to high pressures and potential leaks. Mazda’s system produces hydrogen on the fly, eliminating the need for storage tanks.

Instead of releasing CO₂ into the atmosphere, the process leaves behind solid carbon, which can be collected in a dedicated tank. In theory, this carbon could be recycled—for example, in metallurgy, tire manufacturing, or pigment production.

The Catch

As exciting as the idea is, there are serious drawbacks. The engine design would be extremely complex, requiring an extra valve, a secondary exhaust circuit, and a reformer. It’s unclear whether the components could endure constant exposure to scorching gases. Fuel efficiency is also in question—CarBuzz estimates the driving range on a tank of gas could be roughly half that of a conventional engine.

There’s also a practical issue: every tank of gas could produce up to 35 kg (77 lb) of carbon powder that would need to be removed. Auto shops would need entirely new procedures to handle this “fuel.”

Pros and Cons of the Idea

The advantages include producing hydrogen directly inside the engine, eliminating CO₂ emissions in favor of solid carbon, and the potential to reuse that carbon. The downsides are a complicated and expensive design, lower efficiency compared to traditional internal combustion engines, and the need to regularly remove large quantities of carbon powder.

What If a Gas Engine Became a Hydrogen Factory?

If Mazda were to bring this concept to production, it could be the first engine in history to combine the principles of a classic combustion engine with hydrogen energy. For now, however, it remains more of an engineering experiment than a ready-to-market technology.

Three Quick Facts

One liter of gasoline contains about 700 g of carbon. A 50-liter tank would produce around 35 kg (77 lb) of carbon powder. Mazda has long experimented with unconventional engines—from rotary Wankels to gasoline units with compression ignition.