The demand for critical minerals required to decarbonize energy technologies is outpacing supply, inspiring new research into novel ways to acquire valuable minerals. One transformative research area is using the natural hyperaccumulating ability of seaweed to naturally concentrate rare earth elements from seawater.

"If Algal Mining works, it would create a mining method that is environmentally restorative rather than introducing potentially adverse impacts,” said Dr. Simon Freeman, ARPA-E’s Algal Mining Exploratory Topic Program Director. 

What does algal mining have to do with energy?

Rare earth elements, a group of metals used in everything from wind turbines to electric vehicle batteries, could potentially be mined using macroalgae. Seaweeds hyperaccumulate rare earth elements at concentrations up to a million times higher than concentrations found in seawater. 

For over a decade, ARPA-E has been supporting research to bolster the supply of critical minerals to enhance the economic and energy security of the United States. 

How does algal mining work?

Seawater contains many valuable dissolved metals, but their concentrations are too low to extract directly in a commercially sustainable way. Ocean macroalgae, such as seaweeds, hyperaccumulate dissolved metals within their tissues in ways that are not completely understood. ARPA-E’s Algal Mining Exploratory Topic seeks to understand the environmental parameters that influence rare earth concentrations in these tissues and develop methods to remove them while retaining the value of the algae as a feedstock for other energy applications.

"The philosophy of using the entire plant is critical to future economic success, as the quantity of rare earths in seaweed is still very low,” said Freeman. “But the utility of algal mining, if successful, is also a strategic one.”

Does algal mining exist today?

No operations for extracting metals from macroalgae exist today. Some seaports remediate polluted waters using seaweeds that remove metals such as lead and tin. “Remediation of polluted harbors using seaweed has been done before,” said Freeman, “but these types of metals have always been pollutants, and never extremely valuable.”

What are the two most important research questions for the future of algal mining?

"First, the variability of environmental concentrations of rare earth elements and platinum group metals in the ocean and in seaweed are still unknown,” said Freeman. The University of Alaska Fairbanks, an ARPA-E awardee, is studying these questions in the coastal waters surrounding a natural rare earth deposit in Bokan Mountain in southeast Alaska.

"The second question concerns how to extract metals efficiently while retaining value for other products,” said Freeman. ARPA-E awardee Pacific Northwest National Laboratory is investigating special adsorbents to remove metals from seaweeds, and awardee Umaro Foods has partnered with a medical company to investigate a special molecule, called a metal chelator, to selectively extract metals from seaweed.

"Together, these projects support a nascent technology that one day could fuel an enormous industry for the blue economy,” said Freeman. “This program carries a lot of technical risk, but if it works, it could change mining forever.”

ARPA-E is featuring transformative work for securing a domestic supply of critical materials for energy in the coming weeks. Be sure to subscribe to the ARPA-E Newsletter and follow us on LinkedIn, X, and Facebook to get the latest updates.