Deep Sea Mining part 2
part 2 on mineral processing and waste
Today’s Intercalation Station starts with a featured message from E-magy, Dutch silicon innovator currently running a free webinar series for all battery enthusiasts.
⚡️ Silicon anodes at scale - from lab innovation to industrial reality
Silicon anodes are the talk of 2025. But talk doesn’t scale - manufacturing does.
E-magy produces nanoporous silicon anode material, from pure silicon, in the Netherlands - delivering >350 Wh/kg and >3C Li-ion batteries without hazardous and costly silane gas or CVD processes.
Their proven, patented and proprietary manufacturing process turns standard cheap metallurgical-grade silicon into a unique nanoporous architecture, reducing silicon expansion when charging and discharging. It is a truly scalable, industrially viable solution for high-performance applications such as drones, consumer electronics, and solid-state battery technology.
🗓️ They’re running a free webinar series ‘The Future of Li-ion Batteries with Silicon Anodes‘, and the next live session airs Wednesday 5 November, diving into Challenges and Evolution of Silicon Anodes.
Join to explore what it really takes to move silicon from lab promise to production reality and what it means for the next generation of high-energy cells. The series outlines where scalable silicon is heading next in 2026, join live to learn and be part of that conversation.
🎥 Missed earlier episodes? Catch up on demand and get ready for what’s next.
Made in Europe. Built for scale. Don’t miss your last chance this year to see how it’s done.
Onto the Deep Sea Mining!
See Part I for an introduction by materials chemist Claire Cobley to deep sea mining as well as a discussion of how changing battery chemistries affects the demand for the metals extracted from polymetallic nodules.
In addition to arguing that demand will rise for the metals found in abundance under the sea, some also argue that harvesting metals from the seafloor will be gentler on the environment than mining on land. Part II of this series takes a closer look at several factors central to the discussion, including:
Mineral Processing
Location
Grinding
Waste
Biomass Density
Mineral Processing
Most investigations of deep sea mining understandably focus on the unconventional nodule collection stage. But the less-discussed processing that follows has an outsize impact on both the environmental impact and bottom line, making it critical to look at what happens after nodules are collected.
Efficiently transforming mined ore into purified metals is not a straightforward task. Mineral processors develop complex flowsheets for each deposit that detail the series of techniques that will convert a chunk of rock to a pure metal or marketable compound.
The mined material might be heated to extremely high temperatures, soaked in acid, isolated with soapy bubbles, extracted with organic solvents, dried, subjected to electrolysis, or undergo any other of a long list of techniques. Several such steps are usually needed in a typical flowsheet, each with their own corresponding energy needs and waste.
Although working with nodules instead of mined ores will require some modifications to existing workflows, completed pilots demonstrate that mixtures of established techniques can be used. The most appropriate sequence of steps is still being discussed and which techniques are ultimately selected will have a notable influence on the environmental impact.
One key question is what to do about manganese, which makes up roughly 30% of the nodule weight. In some flowsheets this is processed and sold, whereas in others Mn is considered a waste material. Although Mn is used extensively in steelmaking, extracting all the Mn in polymetallic nodules at scale could produce so much metal it would flood the market and drop the price.
Surprisingly, treating the Mn in polymetallic nodules as waste has some positive effects on the environmental impact, since it could drastically reduce the acid needed to process the ore (more on waste below). Which processing route is kinder to the environment overall is still a matter of debate.
Location, Location, Location
Metallurgical processing is extremely water and energy intensive, so the processing location is also critical. One study found that switching from a country whose grid had 15% hydropower to one with 85% hydropower reduced the overall global warming impact (GWP) of the entire nodule extraction process (including collection) by 25%.
In theory, nodules can be transported to processing facilities with better access to renewable energy, since they need to be shipped somewhere anyway. Ores extracted on land usually undergo initial processing on-site, even if the only energy source available is a diesel generator.
Ores extracted on land often undergo initial processing on-site, even if the only energy source available is a diesel generator. In theory, nodules can be transported to processing facilities with better access to renewable energy, since they need to be shipped somewhere anyway.
However, it is challenging to source large amounts of renewable energy in a way that is truly additional, that is, generating new renewable capacity rather than diverting existing supply. Selection of a processing site will also require balancing many factors, and pilot tests and early stage plans often mention Japan as a first location, a country with limited renewables in its energy mix.
The Energy Cost of Grinding
The sites on land with the highest concentration of metals have also already been extracted, which means that larger and larger amounts of rock are now moved and processed to produce the same amount of metal. Lower quality deposits require mining companies to dig deeper, drive further, grind finer, and generate more waste per ton of metal.
The key measure of quality is grade, the mass percentage of the desired mineral in the overall mined ore. How big of an effect does grade have on energy use? More than you might think.
Grinding, crushing, and the initial separation of rock, collectively known as comminution, typically accounts for 35-50% of the energy use of a mine. That energy use is often dirty and always substantial. In Australia, comminution accounts for 1.3% of the entire country’s electricity usage.
The grade of the ore is the most important factor determining how much energy is required. In 1900, miners were working with deposits with grades of 4% Cu, but the average grade is now close to 0.5%.
Deep sea nodules in the Clarion-Clipperton Zone (CCZ) contain around 1.1% Cu, which means less energy should be required to process and refine than recently discovered Cu deposits. As can be seen in the graph above, energy consumption increases rapidly at low grades. The porous nodule structure will likely also reduce the amount of energy needed to prepare the nodules for processing.
And the other metals? The grades for Ni and Mn in nodules are similar to land-based deposits. The Co grade is somewhat higher, but Co is often produced as a byproduct of Ni or Cu mining. However, even if Mn is treated as waste (see above), the high combined Cu/Ni/Co grade could potentially reduce the environmental impact of processing compared to typical land deposits if suitable flowsheets can be found.
What about Waste?
Another important factor to consider is the amount and type of waste generated. There are several different types of mining waste, but they generally fall into two broad categories: waste generated during the mining itself (e.g., low-value rock that is dug up to get to metal-containing ores beneath), and waste generated during processing (e.g., what is left of mined ores after the metal and any other products have been extracted).
Mining for metal resulted in over 150 billion metric tons of waste in 2023, so this is no small problem. For comparison, combined global municipal solid waste is close to 2.1 billion metric tons per year.
Unlike most land-based mining, deep sea mining of nodules does not involve removing the first type of waste, since the nodules are loose on the seabed and no nearby rock needs to be removed. This substantially reduces waste generation and is a notable advantage.
On the other hand, collecting nodules does stir up sediment, which will be pumped back to the seafloor. The effects of the resulting sediment clouds and the re-deposition on the seafloor are still being studied, but have the potential to disrupt underwater ecosystems.
How much waste is generated by land and sea-based mining during processing depends on several factors including grade (discussed above), which processing flowcharts are chosen (still being finalized), and whether the excess material can be transformed into marketable byproducts instead.
There are many initiatives searching for ways to reuse mining waste. However, repurposing waste into other products is only possible if (1) purchasers exist in accessible locations and (2) the concentration of undesirable elements is sufficiently low for the desired application. In addition to leftover traces of the metals being mined, heavy metals (e.g., Pb, Cr, As) and radioactive elements (e.g., U, Th) are sometimes found in low concentrations in mine waste, and are particularly relevant when considering reuse options.
One major player in the space, The Metals Company, claims that by using nodules as a feedstock it is possible to produce almost no solid waste due to the low heavy metals content in nodules. The company hopes to sell byproducts from processing as construction material and fertilizer.
However, the overall volume of waste isn’t the only important metric - it is also critical to consider how hazardous the waste is. Different processing techniques generate different types of chemical waste, and some are more harmful to the environment than others. In addition to potential contamination with heavy and radioactive metals mentioned above, another common environmental challenge from mining waste is acid mine drainage, which occurs when S-containing mineral waste reacts with water to create sulfuric acid.
Roughly half of land-based Ni and Cu mines are based on S-containing ores, making this a common (though not universal) concern. Polymetallic nodules are based on metal hydroxides instead of sulfides, so this route to acid mine drainage is eliminated.
Biomass Density
While the seafloor supports more life than once thought, the number of plants and animals in a given area is still low. Land-based mines, on the other hand, are located in a variety of landscapes, including some with rich and dense ecosystems. A notable example is the nickel mines in Indonesia’s rainforests.
Although not all land-based mining occurs in such biodiverse regions, Indonesia produces about half of the world’s nickel, and its mining industry is expanding rapidly. Far more biomass is destroyed when mining nickel in these rainforests than when extracting the same amount from the seafloor.
Closing Thoughts
If the right choices are made during setup, it is plausible that deep sea mining will have a lower global warming potential than existing land-based mines. But this is not an automatic win - it is an opportunity to build something better.
However, our incomplete knowledge of the deep sea complicates the analysis. Will mining the sea floor disrupt the ocean’s role as a carbon sink? This could negate positive effects, but is difficult to answer with small-scale tests. We are unfortunately unlikely to fully understand the impact of deep sea mining operations until they are executed at scale.
Part III will conclude the series and cover financial and strategic considerations.
🌞 Thanks for reading!
📧 For tips, feedback, or inquiries - reach out
📣 For newsletter sponsorships - click here