Is the idea of using a big hole for garbage disposal that we would dump the garbage into the molten core and let it burn? Or is it more about using the hole as a really deep landfill?

Do you know what a hole from the surface to the molten core is called?

An active volcano.

Scary thought but you’d (have to) stop digging way above the molten part.

It heats up way above 100C long before you get there, which should be plenty for geothermal energy.

I wonder if sustained high temperature exposure would gradually decompose plastic / toxic waste / other bad things into less harmful components.

Of course, heavy elements came from down there, so it’s probably not an issue to dump them back down. Just stay well clear of the water table!

I am of course not a geologist, and it’d be interesting if one could give a perspective on this.

I'm not sure how tall a column of water you need to trigger supercritical water oxidation, but the problem would be getting the oxygen down there.

Better to do that stuff at the surface, I think.

Yeah, I realized that after I commented, and when I googled it, the Quora answer I got basically boiled down to "you don't know what will come back out."

I always thought that was the scary part of a nuclear plant meltdown until I watch Chernobyl and realized poisoning the aquifer for a million years is a much more likely scenario.