As decarbonization targets tighten and energy costs climb, mineral processing’s biggest power hog — comminution — is under the microscope. And the question dividing engineers, investors, and ESG committees alike: are High Pressure Grinding Rolls (HPGR) actually better than the SAG mills that have dominated hard-rock circuits for 40+ years?
Below is a clear break down:
1️⃣ Energy Consumption & Carbon Footprint
Comminution can account for the majority of a mine site’s total energy draw, so small efficiency gains scale into real emissions reductions. Reported HPGR energy savings versus SAG circuits vary by ore type and target grind size, with trade-off studies citing reductions roughly in the 10–35% range (von Michaelis, 2013). One frequently cited case study found an HPGR-ball mill circuit cut energy use by 21% at a coarser grind, rising toward 34% at a finer target size (Wang et al., 2013).
2️⃣ Ore Hardness & Micro-fracturing
HPGR’s confined-bed compression generates micro-cracks along grain boundaries — weak points that improve liberation in downstream flotation or leaching, and reduce the workload on ball mills further down the circuit. This is a genuine metallurgical edge, not just a marketing point (Wills & Finch, 2016).
3️⃣ Operating Costs & Wear
SAG mills consume large volumes of steel grinding media and liner plate — a major, ongoing operating cost, especially with competent (hard, abrasive) ore. HPGR trades that for wear on tungsten-carbide-studded roller tires, which for many operations translates into lower overall media/wear cost, though tire wear can escalate sharply with sticky, abrasive, or moist feed.
4️⃣ Operational Flexibility
SAG mills handle a wide range of feed sizes and are far more tolerant of moisture and clay content. HPGR needs a more tightly controlled, pre-crushed feed and struggles with wet, sticky ore that can pack and bridge in the feed chute — a real constraint in tropical or high-clay orebodies.
As a matter of facts, HPGR isn’t a universal upgrade — it’s a trade-off. The energy and downstream liberation benefits are well documented, but they come with more sensitivity to moisture, ore stickiness, and feed-size control, plus different capital and material-handling requirements. The right crusher depends on ore characteristics and site conditions, not on which technology is “newer.”. For many hard, dry, competent ores, the business case is increasingly strong; for sticky, high-clay, or highly variable feeds, SAG still often wins on operability.
How much weight should comminution energy efficiency carry in a project’s overall ESG score?
References
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Von Michaelis, H. (2013). How energy efficient is HPGR? CEEC (Coalition for Eco-Efficient Comminution). https://www.ceecthefuture.org/resources/how-energy-efficient-is-hpgr
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Wang, C., Nadolski, S., Mejia, O., Drozdiak, J., & Klein, B. (2013). Energy and cost comparisons of HPGR-based circuits. Proceedings of the 45th Annual Canadian Mineral Processors Operators Conference. CEEC. https://www.ceecthefuture.org
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Wills, B. A., & Finch, J. A. (2016). Wills’ mineral processing technology: An introduction to the practical aspects of ore treatment and mineral recovery (8th ed.). Butterworth-Heinemann.
