New research reveals that polymetallic rocks located on the deep-sea floor can supply hundreds of millions of tons of heavy-duty battery metals to store energy and power electric vehicles (EVs) with much less effect on the atmosphere than to extract the same metals from the earth.
The peer-reviewed research, published in the ‘Journal of Cleaner Production’, is a comparative life-cycle assessment of EV battery metal sources, quantifying direct and indirect emissions and destruction of carbon sequestration services performed in the mining, processing and refining of battery metals.
The carbon intensity of manufacturing metals such as nickel has led to increased interest in low-carbon metal sources and a recent plea by Tesla’s Elon Musk promising “a giant deal” for nickel extracted “efficiently and in an environmentally sensitive manner”.
The new study goes beyond only considering carbon emissions from human activities to look at the disruption of ecosystem carbon sequestration services caused by changes in land and seabed usage to produce battery metals, as EV manufacturers such as Tesla and Polestar spearhead a campaign for accountability in the automotive industry and report the lifetime carbon footprints of their vehicles.
The paper, titled ‘Life Cycle Climate Change Impacts of Land Ores Battery Metals versus Deep-Sea Polymetallic Nodules,’ begins with a demand scenario for the production of four metals (nickel, cobalt, manganese, copper) to supply one billion 75KWh EV batteries with NMC 811 cathode chemistry (80% nickel, 10% manganese, 10% cobalt).
The results of supplying these four metals from two sources are then compared to climate change: traditional ores found on land and polymetallic rocks with large concentrations of four metals in a single ore found unattached on the seafloor at a depth of 4-6 kilometers.
“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.
“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, the actual collection of nodules entails a relatively low energy, land, and waste footprint compared to a conventional mine. When it comes to emissions, even when we assume a complete phase-out of coal use from background electric grids for process inputs, our model shows that metal production from high-grade polymetallic nodules can still produce a 70% advantage.”
Daina Paulikas, study’s lead author, University of Delaware’s Center for Minerals, Materials and Society.
“What happens to carbon sinks on land and on the seafloor used for metal production is another big part of the climate impact story. 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.”
Dr. Steven Katona, marine biologist and co-founder of the Ocean Health Index who contributed to the study.
The researchers found that polymetallic nodules could deliver metals with up to 11.6 Gt less CO2e compared with terrestrial sources for a billion EV batteries. This reflects substantial potential savings due to the remaining carbon budget of just 235 Gt with a 66 percent chance of remaining at 1.5C global warming.
“We hope this work motivates others to dive deeper into supply chain analysis for the clean energy transition, and specifically to pay attention to the impacts of producing critical minerals like the ones we studied. Given the expected 500% increase in mineral requirements for clean technologies, I think we have a shared responsibility to take a planetary view and think through all aspects of mineral production to ensure that this resource-intensive transition does not exacerbate climate change.”
Daina Paulikas, study’s lead author, University of Delaware’s Center for Minerals, Materials and Society.
The researchers’ emphasis on impacts of climate change builds on a larger analysis, ‘Where Should Metals For the Green Transition Come From?’, That compares a number of social and environmental impacts and was commissioned by DeepGreen Metals, a company that seeks to collect polymetallic rocks under a blockchain-enabled system to rent and reuse battery materials to supply electric vehicles.
“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. 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.”
Gerard Barron, chairman and CEO of DeepGreen Metals.
