That’s right: You may soon be able to use coal to make your car more fuel-efficient. Not by running it on coal — gross! — but building it out of metal mixed with structures found in coal ash.
Fly ash, a byproduct of burning coal, contains microscopic bubbles called cenospheres. They sound like Clive Barker creatures, but they’re actually really useful — because when you mix them with metal, they make the metal lighter without compromising its strength. Even regular gas-powered cars could be at least 10 percent lighter, and thus more fuel-efficient, if they were made out of cenosphere-infused metal. The savings are even greater for electric cars, because the battery also could be made at least 20 or 30 percent lighter.
Will the Car of the Future Be Made from Coal Ash?, Scientific American.