This startup aims to produce more eco-friendly metal in the U.S.

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The star of Magrathea’s process is an electrolyzer, a device that uses electricity to split a material into its constituent elements. While using an electrolyzer in magnesium production isn't new, 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 obtain a solid magnesium chloride salt. Magrathea takes that salt, currently sourced from a leading supplier, 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 separate the magnesium from the chlorine, forming magnesium metal.

Typically, running an electrolyzer in this process requires a steady source of electricity. The temperature is generally maintained just high enough to keep the salt in a molten state. Allowing it to cool down too much would allow it to solidify, disrupting the process and potentially damaging the equipment. Heating it more than necessary leads to wasted energy. Magrathea’s approach builds in flexibility. The company operates its electrolyzer about 100 °C higher than is necessary to maintain the molten salt's liquidity. It then utilizes the extra heat in innovative ways, including to dry out the magnesium salt that eventually goes into the reactor. This preparation can be done intermittently, allowing the company to draw electricity when it's cheaper or when more renewable sources are available, thereby cutting costs and emissions. Additionally, the process will produce a co-product, called magnesium oxide, which can be used to capture carbon dioxide from the atmosphere, contributing to offsetting residual carbon pollution.

The result could be a production process with net-zero emissions, according to an independent life cycle assessment completed in January. While it may not reach this target immediately, there is significant potential for a much more climate-friendly process than what is currently used in the industry, Grant notes. Breaking into magnesium production won't be simple, says Simon Jowitt, director of the Nevada Bureau of Mines and of the Center for Research in Economic Geology at the University of Nevada, Reno.