Metso sold more than 20 Vertimill stirred grinding mills across global mine sites during 2025, installing a combined 67 MW of power and marking the company’s strongest year yet for the energy-saving technology, according to trade filings published in January 2026. By replacing conventional ball mills, the new equipment is expected to cut electricity use by up to 35 percent—roughly 36,550 kW in total—reducing operating costs and carbon emissions for customers spread from the Andes to the Outback.
The record order book underscores how quickly miners are rewriting comminution strategies to lower both energy bills and greenhouse-gas footprints. Grinding can consume more than half of a concentrator’s power budget; incremental efficiency gains therefore translate directly into cash savings and lower Scope 2 emissions. Metso’s 2025 sales figures, confirmed by industry outlets IM Mining and Geomechanics, suggest that energy-efficient, multi-stage circuits are moving from niche pilot projects to mainstream design criteria for both new and brownfield plants.
Metso’s flagship Vertimill®, first commercialised more than two decades ago, uses low-speed, gravity-induced stirred media to grind ore particles more efficiently than the high-speed impacts inside a traditional ball mill. When deployed in secondary, tertiary or regrind duty, the units can deliver finer product sizes with less power, water and steel consumption, offering operators a rare triple win on cost, throughput and sustainability.
Early Adopters Double Down
The latest batch of sales pushes the company’s installed stirred-mill base close to 1,000 units worldwide, Metso says, with 2025 orders coming from copper, gold, and iron-ore producers seeking to debottleneck existing circuits or design greener greenfield plants. “We’re observing an expanding adoption of stirred milling technology across established and emerging markets,” noted Alan Boylston, vice-president of stirred mills at Metso. “Mining operations are increasingly integrating these solutions into secondary and tertiary grinding applications.”
Company data indicate that the 36,550 kW of annual power savings achieved by last year’s Vertimill deliveries equate to avoiding about 135,000 t of carbon-dioxide emissions, assuming a typical grid mix. That is roughly the yearly footprint of 20,200 Finnish residents, based on Finland’s per-capita average of 6.7 t CO₂. With electricity costs often representing a mine’s second-largest operating expense after labour, the financial incentive to cut megawatt-hours is almost as compelling as the environmental one.
Portfolio Expands Beyond Vertimill
While Vertimills made the headlines in 2025, Metso’s stirred-milling family also includes HIGmill™, Stirred Media Detritor (SMD) mills and Vertical Power Mills (VPM). Each design targets specific particle-size ranges, ore characteristics, and plant layouts. For fine and ultra-fine grinding—sometimes down to 10 microns—HIGmills deploy a fluidised, high-intensity approach, whereas the SMD series uses open-ended chambers to handle higher flowrates. All models fall under the Metso Plus suite of products, services, and digital tools aimed at improving environmental performance across the full asset life cycle.
Complementing the hardware are more than 50 service and repair centres that support remote sites with liner changes, gearbox rebuilds and process optimisation. These aftermarket revenues provide Metso with an annuity-style income stream while helping customers sustain energy savings over the long term.
Drivers Behind the Demand Spike
Several converging trends explain why 2025 became a breakout year for stirred milling:
• Net-zero commitments: Major miners have pledged absolute or intensity-based carbon reductions, often tied to executive remuneration. Because milling is so power-hungry, electrification or efficiency projects yield outsized emissions cuts.
• Ore complexity: As head grades decline, finer grind sizes are needed to liberate valuable minerals, amplifying the energy advantage of stirred mills.
• Power prices: Volatile electricity tariffs—exacerbated by gas-supply shocks and carbon pricing in some jurisdictions—make kWh savings more valuable.
• Process design philosophy: Engineering firms increasingly design flowsheets around multi-stage crushing and HPGRs feeding Vertimills, rather than the historical SAG-and-ball paradigm.
Several brownfield sites retrofitted Vertimills in 2025 to create secondary regrind stages, freeing up capacity in overworked ball-mill lines and postponing costly plant expansions. In greenfield projects, engineers opted for “SAG-plus-stirred” or all-stirred circuits that combine HPGRs with Vertimills to maximise energy efficiency from the outset.
How the Technology Works
Instead of tumbling a full load of steel balls and ore, a Vertimill uses a vertical screw to stir a shallow bed of grinding media, usually ceramic or worn-media scats. The slower tip speed—typically 10–12 m/s versus 20+ m/s in a ball mill—reduces frictional losses. Gravity assists the media’s downward motion, and slurry density can be optimised to minimise turbulence. The result is a lower specific energy (kWh/t) for the same or finer product size. Process engineers also note reduced liner wear and less media consumption, which further cuts indirect emissions tied to steel manufacture.
Operational data from early installations show 25–35 percent energy savings, consistent with the headline figures reported for the 2025 deliveries. In some cases, the finer grind achieved in a Vertimill allows downstream flotation or leaching circuits to recover additional metal, improving overall plant economics.
Regional Uptake
Latin America and Australia accounted for a majority of 2025 orders, particularly in copper, where the push toward lower-grade porphyry deposits demands finer grinding. African and North American miners followed, with several feasibility studies incorporating stirred mills for battery-metal projects such as nickel sulphides and lithium pegmatites.
Regulators have taken note. Chile’s Comisión Nacional de Energía has flagged comminution efficiency as a key lever for reducing the mining sector’s 21 TWh annual electricity demand, while Australia’s Safeguard Mechanism now penalises high emitters, nudging mine planners toward best-available technologies.
Financial Implications
A single large Vertimill can cost US$5–7 million installed, but payback periods can be less than two years when electricity unit costs exceed US$0.10/kWh. The 36,550 kW saved by 2025 deliveries translate to roughly 320 GWh over an average 25-year life, avoiding tens of millions of dollars in energy spend at today’s prices.
Investors are rewarding suppliers able to quantify such savings. Metso’s shares outperformed the OMX Helsinki 25 index through most of 2025, buoyed by recurring service revenue and a growing order backlog for sustainable technologies.
Engineering Lessons
Process-design mistakes can blunt the energy benefits of stirred mills. Metso and independent consultants caution that Vertimills require careful sizing of cyclone clusters, pump upgrades to handle higher slurry densities, and control loops that maintain optimal media fill. A 2025 audit of several early installations found that plants operating outside design parameters forfeited up to 10 percent of expected savings.
Training and digital twins are therefore becoming standard scope in new contracts. Metso Plus includes cloud-based modelling tools that allow metallurgists to test circuit changes virtually before making physical modifications.
Industry Outlook
While comminution efficiency dominated the 2025 narrative, the broader decarbonisation challenge looms large. Mine operators still face the uphill task of electrifying mobile fleets and securing renewable power contracts. Nevertheless, the rapid uptake of stirred mills demonstrates that pragmatic, commercially attractive technologies can gain traction without regulatory mandates.
If commodity prices soften, capital spending may tighten, but the structural drivers—rising energy prices, carbon pricing, ore complexity—are unlikely to reverse. Analysts therefore expect the share of stirred milling in global grinding capacity to continue climbing through the decade, gradually displacing legacy ball-mill lines much as HPGRs have eroded SAG dominance in certain commodities.
For Metso, the key will be retaining its technological edge as competitors roll out rival designs. The company’s 50-year head start is significant, but incremental gains in liner metallurgy, digital predictive maintenance and process automation will determine whether it can defend its market lead.
Bottom Line
Metso’s record Vertimill sales in 2025 provide concrete evidence that miners are moving beyond pledges to practical implementation of energy-efficient technologies. With documented power savings, lower carbon outputs and attractive payback periods, stirred milling is no longer an experimental option—it is rapidly becoming the new industry baseline for fine and ultra-fine grinding.
Sources
- https://im-mining.com/2026/01/13/metso-books-record-stirred-mill-sales-in-2025/
- https://www.geomechanics.io/news/article/metsos-record-2025-stirred-mill-sales-circuit-design-lessons-for-process-engineers
