Study proposes making EV batteries from deep-sea rocks

Researchers from the University of Delaware in the US and Canadian deep-sea mining specialist DeepGreen claim that metal rocks found on the deep-ocean floor could represent a far less environmentally damaging source of EV battery metals than conventional approaches

The peer-reviewed study, published in the Journal of Cleaner Production, is a comparative life cycle assessment of EV battery metal sources, quantifying the direct and indirect emissions and disruptions to carbon sequestration services realized in the mining, processing and refining of battery metals.

In depth: The Engineering challenges of deep-sea mining

Entitled ‘Life Cycle Climate Change Impacts of Producing Battery Metals from Land Ores versus Deep-Sea Polymetallic Nodules’, the paper starts with a demand scenario of producing four metals (nickel, cobalt, manganese, copper) to supply one billion 75KWh EV batteries with a cathode chemistry of NMC 811 (80% nickel, 10% manganese, 10% cobalt). It then compares the climate change impacts of supplying these four metals from two sources: conventional ores found on land and polymetallic rocks with high concentrations of four metals in a single ore, found unattached on the seafloor at 4-6 km depth.

deep-sea metal
A hydrothermal vent on the deep ocean floor. Image: marius hepp/EyeEm via

“We wanted to assess how metal production using either land ores or polymetallic nodules can contribute to climate change. Looking from mining to processing and refining, we quantified three indicators for each ore type: direct and indirect carbon-dioxide-equivalent emissions, disturbance of existing sequestered-carbon stores, and disruption of future carbon-sequestration services. These three indicators directly impact the remaining global carbon budget to stay below 1.5C warming,” said the study’s lead author Daina Paulikas of the University of Delaware’s Center for Minerals, Materials and Society.

The study found that producing battery metals from nodules can reduce active human emissions of CO2e by 70-75%, stored carbon at risk by 94% and disruption of carbon sequestration services by 88%. “Terrestrial miners are handicapped by challenges like falling ore grades, as lower concentrations of metal lead to greater requirements of energy, materials, and land area to produce the same amount of metal. Furthermore, nodule collection has a relatively low energy, land, and waste footprint compared to mining on land. When it comes to emissions, even when we assume a complete phase-out of coal use from electric grids powering terrestrial mines and plants, our model shows that metal production from high-grade polymetallic nodules can still retain a 70% advantage,” said Paulikas.

deep-sea rocks

“What happens to carbon sinks on land and on the seafloor used for metal production is another big part of the climate impact story,” said Dr Steven Katona, marine biologist and co-founder of the Ocean Health Index who contributed to the study. “On land, carbon is stored in vegetation, soil and detritus. On the seafloor, carbon is stored in sediments and seawater. Producing metals for one billion EVs from land ores would disrupt 156,000 km2 of land and 2,100 km2 of seabed for deep-sea tailings disposal. Producing the same amount from nodules would disrupt 508,000 km2 of the seafloor during nodule collection and 9,800 km2 of land during metallurgical processing. Despite disturbing a larger area of the seafloor, metal production from nodules would cause much less carbon disruption. This is because seafloor sediments store 15 times less carbon per km2 than an average terrestrial biome and there is no known mechanism for disturbed seafloor sediment to rise to the surface and impact atmospheric carbon. In contrast, mining on land requires removal of forests, other vegetation and topsoil to access the ore, store waste and build infrastructure. In the process, we lose stored carbon and disrupt carbon sequestration services for as long as land remains in use, which can be as long as 30-100 years.”

The researchers found that polymetallic nodules could deliver metals for one billion EV batteries with up to 11.6 Gt less of CO2e compared to terrestrial sources. This represents a significant potential saving given the remaining carbon budget of just 235 Gt for a 66% probability of staying at 1.5°C global warming.

“This peer-reviewed study shows the intrinsic benefits of seafloor rocks when it comes to climate change impacts. The resource itself gives us a significant head start on land miners, but being low carbon is not enough. We are working on taking carbon out of the atmosphere, not adding it,” said Gerard Barron, Chairman and CEO of DeepGreen Metals. “We’ll use hydropower onshore; we are exploring electrofuels to power offshore operations and using electric equipment and carbon-negative reductants in metallurgical processing. Put it all together, and we have a shot at bringing carbon-negative metals to the market.”