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Comment by jofer | Hacker News Reader

You physically can't remove the overburden for this. The Smackover is at a depth of multiple kilometers in most of these areas.

It's mining brine. I.e. the "mines" are basically deep water wells.

The limestone itself doesn't have any lithium. It's the water in the pores in the limestone that is relatively concentrated in lithium.

In most of these cases, you're already producing brines from the smackover formation as a part of existing oil and gas production, but the brine is being re-injecting after oil is separated from it. The idea is that it's better to keep those and evaporate them down for lithium production.

That does require large evaporation ponds, generally speaking, but it's not strip mining.

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Extremely helpful, thanks for the extra detail here. I have a background in the oil industry and live in a region strip mined for coal (I actually can't tap a useful ground well because of it), but I don't know much about how lithium is actually extracted.

As far as evap ponds go, are there usually chemicals or elements in the same brine water as lithium that is important when evaporating into the atmosphere?

There are a lot of things in deep subsurface brine. It really varies.

First and foremost, here are definitely lots of other salts. It is brine, after all. You produce a lot of halite (salt), gypsum, calcite, and all kinds of other evaporite minerals.

There are all kinds of things in smaller concentrations, though.

What comes out of a oil/water separator would need lots of additional processing before going to something like an evap pond. It's relatively hazardous stuff for a lot of reasons other than oil (e.g. it can be rather radioactive). It typically goes through quite a bit of additional processing unless it's being immediately reinjected.

Yeah, underground brine is rarely nice to be around, especially when concentrated, but does often have a lot of useful minerals. Related facts, I’m guessing.

I think they're using better processes than evaporation these days. For example, concentrating the brine using reverse osmosis first.

Those are expensive and are avoided when possible. Brine ponds are cheap if you can use them. But with that said, yeah, evaporation ponds don't work especially well on the Gulf Coast.

The process for here, I was reading, would involve concentration of the lithium with resin absorbers (to separate it from other alkali elements, I imagine), followed by elution into water, reverse osmosis, and only then evaporation. This is called "DLE": Direct Lithium Extraction.

Yes, but that's among the most expensive ways of approaching the problem. In regions where it's feasible, evaporation approaches are far cheaper, which is why they're still the most widely used approach. In humid regions with a lot of precipitation like the gulf coast, though, you have to take more expensive and energy-intensive approaches to concentrate things.

A serious issue with pond evaporation is that it wastes all the waster. The DLE approach evaporates 98% less water. It's increasingly being used even in places like Chile where evaporation can be used.

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