Comparison
between conventional and hydrogen-plasma-based reduction of deep-sea
polymetallic nodules. Credit: Science Advances (2025). DOI: 10.1126/sciadv.aea1223
The demand for metals will increase
significantly in the coming years, primarily because the climate-friendly
transformation of the economy is only possible through the electrification of
industrial processes, transport and heat generation. By 2050, around 60 million
tons of copper will be needed for electric motors and the expansion of the
electricity grid.
Moreover, depending on how battery
technology develops, a further 10 million tons of nickel and 1.4 million tons
of cobalt may also be required. Demand for copper and nickel would therefore
more than double by the middle of the century, while demand for cobalt could
increase fivefold.
The extraction of metals always has
a negative impact on the environment. Large areas of forest are repeatedly
cleared for nickel and cobalt mining. And the mining of cobalt in particular
often takes place under very questionable social conditions: according to
UNICEF, children are often sent to work in the mines.
The ores found on land also contain
only a very small proportion of the metals sought. For every ton of copper
mined from deposits on land, some 200 tons of waste are produced, and taken
together, the annual production of copper, nickel and cobalt generates between
4 and 5 billion tons of unusable rock and slag.
An alternative to land-based mining
is the extraction of deep-sea ore nodules, commonly known as manganese nodules,
which, besides large amounts of manganese, also contain a significant
proportion of copper, nickel and cobalt. They are found in large quantities in
the Clarion-Clipperton Zone in the Pacific.
A team from the Max Planck
Institute for Sustainable Materials has now presented an efficient and low-CO2 process in the journal Science Advances in which copper, nickel and cobalt can be
extracted from deep-sea ore by smelting and reducing it with hydrogen.
The method is significantly more
sustainable than the process used by the Canadian company TMC for the reduction
of deep-sea ores with carbon-based compounds in its Nori-D project. Using
hydrogen for reduction cuts CO2 emissions by more than 90% if
green hydrogen and renewable electricity are used. The Max Planck team's approach
also requires almost 20% less energy and fewer process steps.
No deforestation and significantly less waste in
deep-sea mining
"The
extraction of these nodules in the deep sea also leaves an environmental
footprint," says Dierk Raabe, Director at the Max Planck Institute for
Sustainable Materials. "That's why I was against exploiting these
resources just a few years ago, so we wouldn't repeat the same mistakes we made
on land."
In the
meantime, however, the materials scientist has become open to the idea of
deep-sea mining—at least if it is carried out in the most environmentally
responsible way possible. His view has changed for several reasons, not least
because the extraction of metals from deep-sea ores would not involve child
labor and would result in far less deforestation and far less waste.
For example,
the production of the metals for 1 billion electric car
batteries would generate 9 billion tons of rock waste if the
materials were extracted from deep-sea ores, while 63 billion tons of unusable
rock would have to be dumped if they were extracted from deposits on land. This
is what researchers at the University of Delaware have calculated.
The
environmental footprint of metal production from deep-sea ores would therefore
be significantly smaller using the Max Planck team's process. "We reduce
the dried ores with a hydrogen plasma directly
in an electrically operated arc furnace," explains Ubaid Manzoor, who
carried out the experiments as part of his doctoral research.
The
researchers are already able to recover almost all of the copper as pure metal
by melting the ore and then allowing the molten metal to cool slightly. As soon
as they allow hydrogen to flow into the furnace, an alloy of copper, nickel and
cobalt, among other elements, is produced alongside various manganese oxides,
some of which can be used in batteries. The proportions in the alloy vary
depending on the duration of the reduction.
"Because
we can separate copper first, it becomes easier to process the remaining
alloy," explains Manzoor.
In an earlier
study, Manzoor and his team of researchers had already presented a very similar
process that can be used to extract nickel from ores mined on land in a
climate-friendly way.
A contribution to the comprehensive life cycle
assessment of deep-sea mining
Whether
deep-sea mining will one day replace land-based mining remains the subject of
international negotiations. "With our work, we want to provide a
sustainable method for extracting critical metals from deep-sea nodules and the
data needed for informed decisions, considering the environmental impacts from
both mining of the ores and processing of the ores," says Manzoor.
And for Raabe, one thing is clear: "If we want to move away from a CO2-intensive economy, we will have to accept some bitter pills."
Provided by Max Planck Society
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