Last year, the United States designated magnesium as one of the “electric 18” critical minerals essential to the energy transition. The metal is used in a variety of electronic devices and is lighter than aluminum, making it an attractive alternative for automakers.
But like many other minerals, China has grown to dominate the market. And it's not because there's a shortage of magnesium. In fact, it's the eighth most abundant mineral in the Earth's crust and the third most abundant dissolved mineral in the world's oceans. But at least in the United States, there's only one company that produces virgin metal; everything else is imported or recycled from scrap.
“What really matters is whether we can compete with the 90 percent of petroleum products that are currently produced in China,” said Howard Yu, co-founder and CEO of Tidal Metals.
Yu is confident his startup can do just that: Formerly known as GreenBlue, the company was working on desalination technology before realizing there was more value in the minerals left behind.
“At that time, the magnesium industry was already in turmoil in the U.S.,” he says. Sensing an opportunity, the company pivoted and rebranded to magnesium production in late 2023.
This lightweight metal has the potential to significantly reduce carbon emissions from transportation if it can be produced with minimal pollution. Motorsports fans will notice that magnesium is commonly used in race cars, especially in wheels. Every pound removed from a wheel improves acceleration and handling. In passenger cars, the widespread use of magnesium can improve fuel economy, reduce carbon emissions in fossil fuel vehicles, and extend the range of electric vehicles. Some battery companies are beginning to explore using this metal to improve energy density.
Magnesium is currently produced in two main ways: by heating the mineral dolomite, or by evaporating saltwater, usually in huge open-air ponds, and processing the residue. The former is widely used in China and accounts for the majority of production, but is highly polluting, especially when coal is used as the heat source.
Tidal Metals uses the latter evaporation method, but doesn't use ponds. Instead, it uses something called a temperature swing steam pump. Essentially, the company uses a moisture-wicking material to evaporate seawater, or the saltwater left over after desalination. The material, similar to the silica gel bags that come packed in overseas products, is placed inside a box that is exposed to seawater. Once the material becomes saturated, Tidal Metals closes the box, increases the temperature, and releases the water.
Meanwhile, a box full of another substance opens, and the seawater continues to evaporate. Once that box becomes saturated, Tidal Metals uses a heat pump to transfer heat from the first, dry box to the second, saturated box. Aside from the initial heat needed to heat the first box, Yu says the process is highly efficient. “We're basically recycling about 97 percent of the energy.”
Ultimately, the startup will evaporate one tonne of seawater to produce about four kilograms of magnesium salts.
Even when the water evaporates, some H2O molecules remain bound to the magnesium chloride. These also need to be removed, and Yu said the company has tweaked an existing process to make this easier, without providing details.
Tidal Metals is working on developing a pilot plant capable of producing 200 tonnes per year. The project was funded through a recent $8.5 million seed round led by DCVC, with participation from Vidra Innovation Ventures and First Spark Ventures. Once the plant's engineering is in place, the startup aims to build a larger facility capable of producing 10,000 tonnes per year as early as 2026, Yu said.
Overall, Tidal Metals' process is expected to be significantly less polluting than the methods used in China, especially when renewable electricity is used to power the heat pumps. What's more, the company can use seawater and brine waste from desalination plants, making it a nearly limitless resource, unlike magnesium obtained from mined dolomite.
“The desalination plant in San Diego pumps out 100 million gallons of seawater per day, enough magnesium to supply the entire United States, which equates to 180,000 tons per year,” Yu says. “Right now, all of it is going to waste.”