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Tech Review reports on a US startup that claims to have modernized and cleaned up the magnesium refining process, https://www.technologyreview.com/2025/05/28/1117481/metal-magrathea/ [technologyreview.com] The light weight metal has many applications.

The star of Magrathea’s process is an electrolyzer, a device that uses electricity to split a material into its constituent elements. Using an electrolyzer in magnesium production isn’t new, but Magrathea’s approach represents an update. “We really modernized it and brought it into the 21st century,” says Alex Grant, Magrathea’s cofounder and CEO.

The whole process starts with salty water. There are small amounts of magnesium in seawater, as well as in salt lakes and groundwater. (In seawater, the concentration is about 1,300 parts per million, so magnesium makes up about 0.1% of seawater by weight.) If you take that seawater or brine and clean it up, concentrate it, and dry it out, you get a solid magnesium chloride salt.

Magrathea takes that salt (which it currently buys from Cargill) and puts it into the electrolyzer. The device reaches temperatures of about 700 °C (almost 1,300 °F) and runs electricity through the molten salt to split the magnesium from the chlorine, forming magnesium metal.

Typically, running an electrolyzer in this process would require a steady source of electricity. The temperature is generally kept just high enough to maintain the salt in a molten state. Allowing it to cool down too much would allow it to solidify, messing up the process and potentially damaging the equipment. Heating it up more than necessary would just waste energy.

Magrathea’s approach builds in flexibility. Basically, the company runs its electrolyzer about 100 °C higher than is necessary to keep the molten salt a liquid. It then uses the extra heat in inventive ways, including to dry out the magnesium salt that eventually goes into the reactor. This preparation can be done intermittently, so the company can take in electricity when it’s cheaper or when more renewables are available, cutting costs and emissions. In addition, the process will make a co-product, called magnesium oxide, that can be used to trap carbon dioxide from the atmosphere, helping to cancel out the remaining carbon pollution.

The company site, at https://www.magratheametals.com/ [magratheametals.com] doesn't pull any punches--from their home page:

Magnesium supply underpins trillions of dollars of trade and national security is impossible without it. Today there is 0 production in all of NATO. The US cannot manufacture cars, planes, and other critical assets without magnesium metal. This is a national security emergency.

Magrathea is the US Department of Defense backed category leader in solving this problem with the most sophisticated backers, the most talented technologists, and the most commercial traction of any Western magnesium project in 2 decades.

The Tech Review article ends with a mention that currently, 95% of magnesium is from China...and like any monopolist, they would be likely to cut prices (short term) to attack competitors in other parts of the world.

Personally, I thought that Magrathea built luxury planets, and has been on holiday during the current galactic recession...

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