Understanding impact of deep-sea mining

Mining materials from the sea floor could help secure a low-carbon future, but researchers are racing to understand the environmental effects.

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While aboard the RV Sally Ride, Professor Thomas Peacock (center) speaks with Tom de Wachter of Global Sea Mineral Resources (left) and postdoc Cindy Dayang Wang SM '16, PhD '19 (right) in front of a CTD cage rigged with instrumentation to make measurements of the ocean water column.

While aboard the RV Sally Ride, Professor Thomas Peacock (center) speaks with Tom de Wachter of Global Sea Mineral Resources (left) and postdoc Cindy Dayang Wang SM ’16, PhD ’19 (right) in front of a CTD cage rigged with instrumentation to make measurements of the ocean water column.

Image: John Freidah

Resting atop Thomas Peacock’s desk is an ordinary-looking brown rock. Roughly the size of a potato, it has been at the center of decades of debate. Known as a polymetallic nodule, it spent 10 million years sitting on the deep seabed, 15,000 feet below sea level. The nodule contains nickel, cobalt, copper, and manganese – four minerals that are essential in energy storage.

“As society moves toward driving more electric vehicles and utilizing renewable energy, there will be an increased demand for these minerals, to manufacture the batteries necessary to decarbonize the economy,” says Peacock, a professor of mechanical engineering and the director of MIT’s Environmental Dynamics Lab (END Lab). He is part of an international team of researchers that has been trying to gain a better understanding the environmental impact of collecting polymetallic nodules, a process known as deep-sea mining.

The minerals found in the nodules, particularly cobalt and nickel, are key components of lithium-ion batteries. Currently, lithium-ion batteries offer the best energy density of any commercially available battery. This high energy density makes them ideal for use in everything from cellphones to electric vehicles, which require large amounts of energy within a compact space.

“Those two elements are expected to see a tremendous growth in demand due to energy storage,” says Richard Roth, director of MIT’s Materials Systems Laboratory.

While researchers are exploring alternative battery technologies such as sodium-ion batteries and flow batteries that utilize electrochemical cells, these technologies are far from commercialization.

“Few people expect any of these lithium-ion alternatives to be available in the next decade,” explains Roth. “Waiting for unknown future battery chemistries and technologies could significantly delay widespread adoption of electric vehicles.”

Vast amounts of specialty nickel will be also needed to build larger-scale batteries that will be required as societies look to shift from an electric grid powered by fossil fuels to one powered by renewable resources like solar, wind, wave, and thermal.

“The collection of nodules from the seabed is being considered as a new means for getting these materials, but before doing so it is imperative to fully understand the environmental impact of mining resources from the deep ocean and compare it to the environmental impact of mining resources on land,” explains Peacock.

After receiving seed funding from MIT’s Environmental Solutions Initiative (ESI), Peacock was able to apply his expertise in fluid dynamics to study how deep-sea mining could affect surrounding ecosystems.

Meeting the demand for energy storage

Currently, nickel and cobalt are extracted through land-based mining operations. Much of this mining occurs in the Democratic Republic of the Congo, which produces 60 percent of the world’s cobalt. These land-based mines often impact surrounding environments through the destruction of habitats, erosion, and soil and water contamination. There are also concerns that land-based mining, especially in politically unstable countries, might not be able to supply enough of these materials as the demand for batteries rises.

The swath of ocean located between Hawaii and the West Coast of the United States – also known as the Clarion Clipperton Fracture Zone – is estimated to possess six times more cobalt and three times more nickel than all known land-based stores, as well as vast deposits of manganese and a substantial amount of copper.

While the seabed is abundant with these materials, little is known about the short- and long-term environmental effects of mining 15,000 feet below sea level. Peacock and his collaborator Professor Matthew Alford from the Scripps Institution of Oceanography and the University of California at San Diego are leading the quest to understand how the sediment plumes generated by the collection of nodules from the seabed will be carried by water currents.

“The key question is, if we decide to make a plume at site A, how far does it spread before eventually raining down on the sea floor?” explains Alford. “That ability to map the geography of the impact of sea floor mining is a crucial unknown right now.”

The research Peacock and Alford are conducting will help inform stakeholders about the potential environmental effects of deep-sea mining. One pressing matter is that draft exploitation regulations for deep-sea mining in areas beyond national jurisdiction are currently being negotiated by the International Seabed Authority (ISA), an independent organization established by the United Nations that regulates all mining activities on the sea floor. Peacock and Alford’s research will help guide the development of environmental standards and guidelines to be issued under those regulations.

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