Could Magnesium Save the World?
Bruce Mulliken

It's a little offbeat, but in more ways than one it seems possible that one of Earth's most abundant metals could be used to save our little blue planet from boiling over.

Here's one way

Magnesium in powder or ribbon form burns really well. I mean REALLY well. So well, so hot, in fact, that it burns white hot underwater as well as in a pure carbon dioxide atmosphere. Burning in water or CO2 means a magnesium fire can't doused with a fire hose or a CO2 fire extinguisher. Why it burns in water is that water is, of course, part oxygen (required for combustion) and full of air bubbles (the same that fish breathe). Why it burns whilst surrounded by CO2 is even more interesting. Magnesium needs oxygen to burn, so with its heat of combustion so high it rips apart the oxygen from carbon then joins itself to the oxygen to make magnesium oxide. The carbon is then left alone, just pure carbon waiting to be collected.

The CO2 that magnesium burns so well in, is the same CO2 that nearly everyone in the scientific community accuses of warming the planet. So, if a magnesium fire can split apart carbon from two oxygens then why not give it a job: Put it to work saving the planet from global warming?

• Though it seems outlandish (and maybe it is) fossil-fueled power plants could capture carbon dioxide from their exhaust stream, and instead of stuffing it underground (as in carbon sequestration or storage methods) pump it into a big container along with some magnesium, where the magnesium is set afire. Soon, after a big bright white flame, and the magnesium would become magnesium oxide and carbon, just carbon. Filtering could capture the carbon and magnesium oxide dust floating in the air and keep both out of the atmosphere.
   
• Another simpler and equally nutty way may be to stuff burning magnesium flares down the smokestack of a fossil fueled power plant and let the magnesium do its magic of splitting carbon dioxide into its components, and eliminating it as a green house gas. (Don't try this without proper supervision.)

While the above two methods of saving the planet from evil CO2 might seem a little crazy, so does pumping exhaust from power plants into underground caverns for future generations to deal with.

However, a more tame way of using magnesium to save the planet is to use it to store energy from intermittent renewable energy sources. (Renewable energy needs to be stored cheaply if it is to compete with fossil fuels.)

The same robust oxidation that makes magnesium so good at burning, and thus oxidizing, also makes it a good component for a battery: Particularly primary (one time use) or recyclable rebuildable batteries.

Already magnesium is used as the sacrificial anode in salt water batteries in such diverse applications as operating lighted beacons on navigation buoys on waterways to providing electric power to torpedoes (like those used to sink ships in war.) In magnesium salt water electrochemistry, the batteries remain inert while in storage. When power is needed, salt water is added as an electrolyte, the battery powers up and runs until all the oxygen is gone out of the water or the magnesium is oxidized as much as it can. (In a torpedo salt water is injected into its battery when the device is launched from a ship or submarine into the ocean. Then off it goes until the battery runs out of power, or blows a hole in the side of ship.)

So how could magnesium salt water batteries save the world? By storing renewable energy and making it available at any time of the day or night.

This grand world-saving scheme goes something like this: Renewable energy, such as solar energy, is used as the energy source to make pure magnesium from sources like seawater. (Much of the "salt" in salt water in actually magnesium oxide.) It just takes energy and some chemicals to extract the magnesium from it.

The solar-powered process would make solid and pure magnesiumanodes to be installed in dry magnesium salt water batteries. Those batteries would be wired into the grid. When the sun goes down, the batteries whose sacrificial anodes are made with the power of the sun, would be flooded with salt water providing power to the grid or micro grid. When out of power, new fresh magnesium anodes would installed, with the old ones recycled using solar or other renewable energy.

Already the solar-to-magnesium process is in the works. The United States Department of Energy (DOE) has awarded Valparaiso University in Indiana $2.3 million in a cooperative agreement for Valpo's team of engineers and scientists to develop a novel electrochemical cell that produces magnesium using solar-thermal energy and electrochemical processes. The advanced hybrid cell uses concentrated solar power for heating, minimizing the electricity requirement for magnesium separation.

Once the magnesium is produced it could be used for anything from vehicle parts or anodes for batteries or magnesium flares to drop down the smokestack of fossil fuel power plants.

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