Aluminum might seem like an odd choice for a fuel. When you think of aluminum, you probably think of aluminum cans and foil. But this dependable metal has a few tricks up its sleeve.
One of those tricks is the thermite reaction, a chemical reaction between aluminum and iron oxide (rust). If you haven’t heard of the thermite reaction, watch this video right away.
Seriously. Go ahead, I’ll wait.
A company called Trolysis has an idea to put this capacity to use by reacting aluminum with water to create hydrogen gas, effectively turning aluminum into a fuel. (Disclaimer: This article is not an endorsement of Trolysis. Neither the author nor the Illinois Science Council has received any form of compensation from Trolysis in relation to this article.)
There’s a puzzle here. Consider the thermite reaction for a second. If something as mundane as rust can cause aluminum to release so much energy, why doesn’t it blow up in our faces all the time? Should we be afraid of our aluminum foil suddenly burning up and destroying our refrigerators?
Don’t worry. When aluminum is exposed to air, it gets coated with a thin layer of aluminum oxide. This coat protects the inside from reacting with oxygen enough to catch fire.
So, aluminum has the capacity to release a lot of energy, but it can only do so under special conditions.
The thermite reaction is one way to create those conditions. This reaction starts with ground-up aluminum metal and ground-up iron oxide (rust). A spark gets things started, shaking things up enough to break through the protective aluminum oxide layer. This allows a bit of the aluminum to react with the rust. Then, the energy released from this reaction motivates more of the material to move and shake, and before you know it, the stuff is blazing intensely.
The products of this reaction are aluminum oxide and iron. First, it seems we’ve discovered a dramatic method for producing iron, even if it’s not very practical. What’s more useful is the energy released. In industry, this energy is sometimes used for cutting or welding metal.
Where does all of this energy come from? It comes from how we produce aluminum metal.
Aluminum metal comes from aluminum ore, rocks that contain aluminum. First, a chemical process extracts the aluminum from the ore and stores it as aluminum oxide. Next, manufacturers pump a large amount of electricity through the aluminum oxide, pulling the oxygen out and leaving the aluminum in a pure metal state.
You can almost think of this almost like charging a battery. You can’t attach wires to aluminum to light a lightbulb, but, like a battery, this aluminum stores useful energy.
How is aluminum turned into a fuel?
Some of the details on how to convert aluminum into fuel are available to the public, but don’t think you can go out and do this yourself. A lot of the process is a trade secret.
Basically, Trolysis combines aluminum with water to create a chemical reaction that forms hydrogen and aluminum oxide. They throw away the aluminum oxide, but the hydrogen is valuable: it can be used in a fuel cell to generate electricity. So, aluminum effectively becomes a portable electricity source.
Why We Won’t See Aluminum-Powered Cars Anytime Soon
While a fascinating prospect, there are some limitations to this technology that makes it hard to use as fuel in the real world. One limitation is that it relies on recycled aluminum. (New aluminum is not cost-effective.) The price of recycled aluminum fluctuates just like gold, which means means the process of making hydrogen from aluminum fluctuates in cost. If the cost of recycled aluminum rises too high, this process might no longer be cost-effective. And, ironically, if this technology becomes popular, demand will go up and push up the cost of recycled aluminum, thereby diminishing its own market potential.
Aluminum as a fuel seemed like a far-fetched idea to me when I first heard of it. Because it relies on recycled aluminum, there’s a limit to how far it can go. One thing is clear: it’s a clever and inspiring idea. It makes me wonder…What other everyday material might secretly hold the power of fuel?
Erik Kristofer Anderson is a freelance science writer from Chicago. He holds a Master of Science in Chemistry from the University of California Berkeley, where he studied photosynthesis using ultrafast laser spectroscopy. His interests include renewable energy and sustainability. He can be found at www.erikand.com.