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What? I Can Use Iron as a Fuel?!

It may seem like I am joking. People put iron and steel pans on hot gas flames for cooking on a regular basis and they are not catching fire.

The idea that you can burn iron and produce excess heat seems ridiculous. In fact it isn’t, and if you ever read my story on how sugar can be used as rocket fuel, you may already have a clue.

Heat Conductivity

That is different from say wood or coal which does not conduct heat well.

Surface Area Exposed to Oxidizer

This process is what we typically refer to as burning. When the metal oxide is formed that produced a lot of heat. When something gets hot enough it will start emitting light. That is why we can see a flame.

For this burning to happen, we thus don’t only need to get to high enough temperature but we also need there to be oxygen for the metal to react with. The metal atoms below the surface of a piece of metal cannot come in contact with oxygen and thus cannot burn.

Thus by grinding down metal to fine powder or create fine strains as in steel wool, you get something that can more easily burn. This is because of two factors:

  1. You increase surface contact with oxygen.
  2. There is less other metal to conduct heat to, and potentially cooling down the metal before it ignites.

The trick is thus to suspend the metal in air to get maximum contact with oxygen. That is why air filled with coal dust, sugar dust or saw dust can be so explosive. It burns far more rapidly when suspended in air than when in a pile on the ground.

Steel Cutting Example

This high heat production is what makes iron suitable as a fuel. You get more heat out than you had to apply to ignite it.

Benefits of Metals as Fuel

Metal does not lie around in pure form ready to be burned and used for fuel. We have spend energy to make the metal. Thus it has never made economic sense to use metal as a fuel.

However the economic calculation changes dramatically when we look for possible compounds for storing energy. When you cannot use fossil fuels anymore due to concerns for global warming and need something to store the fluctuating power output from renewable energy sources such as wind and solar, then metals suddenly becomes an interesting alternative.

Metal unlike hydrocarbons, don’t release CO2 when burned, instead we get a metal-oxide which we can easily save and recycle for back to metal again using wind and solar power.

Geek dad, living in Oslo, Norway with passion for UX, Julia programming, science, teaching, reading and writing.

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