Heap-Leaching Copper
Remind Me Again How Much Carbon those Windmills Are "Saving"?
I worked as General Counsel for about 8 years at Lisbon Valley Copper Mine in San Juan County, Utah. It’s known for some of the best cathode in the nation. That’s Grade A 99.9% virgin cathode prized by rod mills to make electric motor windings. More likely than not, this cathode is blowing somewhere in the wind near you.
LVM provides an excellent comparison to KUC. Not all copper mining operations are as fossil intensive as KUC. And that's primarily due to the ore type. KUC is copper porphyry ore that has varied widely over time.
LVM's ore is associated with shallow marine deposition involving copper oxides such as malachite and azurite, but with a good share of sulfide compounds. It's a sandstone host rock. Unfortunately for its owners (not me), LVM's ore contains no other metals. It was deposited in a shallow marine environment through means that are not fully understood.
One man's trash is another man's treasure.
The best thing about oxide ore (compared to sulfate porphyry) is that it readily dissolves in sulfuric acid. By contrast, KUC's ore requires a lot of processing to release sulfur as a waste. LVM's ore requires H2SO4 (sulfuric acid). "Let's make a deal!" KUC's acid plant is the biggest in the Western USA.
Acid solubility means the LVM process can cut to the chase - almost straight to electrowinning (plating). But they've still got to strip waste and mine ore first. Drill. Blast. Haul. Repeat. Same as KUC but tiny scale in comparison.
Centennial Pit pictured. Source
But here's where the process is vastly different. Heap Leach: No Crushing. No Grinding. No Flotation. No Tailings Impoundment. No Smelter No Slag. No Coal. Waste is dumped. Ore is dumped on the pad. Apply acid-->directly to the EW plant.
Now if you think the heap leach pad consumes a lot of acid, you'd be right. The ore grades are low. Not milling the ore has trade-offs - it means you've got to apply acid to 100% of the ore mass. Depending on the source rock, the ore consumes (neutralizes) lots of acid.
While KUC consumes a lot of energy crushing, milling, smelting, etc., LVM consumes lots of acid. And 94% H2SO4 is heavy. Depending on weather conditions, the distance between KUC and LVM is around 288 or 339 miles. The shorter haul involves a lot of mountain climbing in full trucks.
During the KUC slide, LVM had its own existential experience. No acid. No copper. No copper, no money. No money, no bond. No bond, no mine. Shipping in acid from Texas by rail still required trucking a great distance.
Catastrophe was avoided thanks in part to LVM's very savvy lawyer😉 but that's a different story. Heap Leach mining involves astronomical volumes of fluids that are constantly being pumped. Solution grades are "stacked" and eventually the PLS is sent to the EW plant (tan).
All of this leads me to a simple question for the Lifecycle Assessment Experts (because Excel is not my strong point). Please tell us how many pounds of "embedded carbon" are found in 1 pound of high-grade copper cathode from KUC? LVM?
Because if I were in a court of law trying to prove the efficacy of my client's petroleum & coal "saving" machine to investors, I sure wouldn't want to be representing the party with the burden of proof.
Years ago I spent almost a year doing life cycle cost analysis of RFP responses. I was working for a subcontractor of TRW on a DOE contract. It requires a lot of data, and where data isn't available doing one's best to work out what some part would be. Let's just say this is a "bigger than a breadbox" project. I would guesstimate at least a year of work. With access to data on operations of the two mines, it could probably be done. But I have to finish my current project first.
My model Y may have a lot of copper, but its energy usage is crazy efficient. 20% of what a ICE car uses. That should get me some green credit don’t you think?