Mantle-based Garbage Disposal: Would it work?

[Tex]

I just had one of those random, crazy ideas that make you stop and say whaaaaaaaa?

I propose a super-deep borehole that reaches all the way down to the mantle of the Earth. For the sake of the scenario, I would like you to assume that the drilling is unhindered by the super-hot temperatures of going just over two miles down, and the hole itself is large enough to dump the contents of dump trucks and the like into it.

First of all, would such a hole be possible to build, considering tectonic shifting? Would seeping groundwater flow down and cause large amounts of steam to escape the hole or condensation to rust the walls of the hole? Would constant garbage disposal raise the temperature of the mantle significantly enough to pose a problem?

What do you think? All answers are valid!

[Brotoro]

We've been unsuccessful in drilling a hole down to the mantle even for research purposes, so I don't think it's going to be practical to make a dump hole.

[Stargate525]

Why would you want to?

...I mean, you're just doing an elaborate burn job on the stuff. For metals, that's a waste. For everything else... I mean, why not just setup near a volcanic pocket and make an incinerator?

[jwenting]

just dump it in an ocean trench at the edge of a subduction zone. It'll slide down on its own over time.

[Tex]

We've been unsuccessful in drilling a hole down to the mantle even for research purposes, so I don't think it's going to be practical to make a dump hole.

True, but remember that we're assuming such a dump hole could work.

For everything else... I mean, why not just setup near a volcanic pocket and make an incinerator?

just dump it in an ocean trench at the edge of a subduction zone. It'll slide down on its own over time.

I've also thought of doing something like this. Perhaps controlled sinking to the subduction zones? Taking an inactive but lava-producing volcano and dumping there? How practical could this potentially be?

I actually have another question, too: Would the materials truly unite with the lava/magma, or would it still release polluting substances when the moisture of the items explodes into steam?

[lajoswinkler]

If you pierce a hole that deep, witho nothing than air in it, magma would start shooting out. It's a bad idea.

[vger]

If you pierce a hole that deep, witho nothing than air in it, magma would start shooting out. It's a bad idea.

And even if it didn't, wouldn't you more or less have a really expensive garbage incinerator? By drilling to the mantle, you more or less would have a chimney. Anything that gets dropped down there is going to ride the thermal vents right back up in the form of smoke and ash. Might as well burn the stuff on the surface. You'll get just as much pollution at a fraction of the cost.

On the other hand, if you could drill deep enough without reaching the mantle. you'd have an interesting concept for a vertical landfill.

Being that deep it's unlikely a lot of the poisons would get into our soil. It might even seep down into the mantle on its own.

Edited April 27, 2014 by vger

[lajoswinkler]

And even if it didn't, wouldn't you more or less have a really expensive garbage incinerator? By drilling to the mantle, you more or less would have a chimney. Anything that gets dropped down there is going to ride the thermal vents right back up in the form of smoke and ash. Might as well burn the stuff on the surface. You'll get just as much pollution at a fraction of the cost.

On the other hand, if you could drill deep enough without reaching the mantle. you'd have an interesting concept for a vertical landfill.

Being that deep it's unlikely a lot of the poisons would get into our soil. It might even seep down into the mantle on its own.

Exactly. Unless you fill it with water. The resulting pressure at the bottom of the hole is probably sufficient to stop the magma, and there'd be no boiling, either, though I still wouldn't play like that. Instabilities might form and magma might win in the near future.

In most places, anything deeper than 5 km is effectively out of the biosphere's reach at least for hundreds of thousands of years.

[Nibb31]

just dump it in an ocean trench at the edge of a subduction zone. It'll slide down on its own over time.

Most of our trash floats.

[Nibb31]

just dump it in an ocean trench at the edge of a subduction zone. It'll slide down on its own over time.

Most of our trash floats.

If you dump stuff deep enough, it gets crushed by the pressure and won't float back up. The difficulty is actually getting the trash to sink. You'd have to process it to weigh it down with tons of ballast, which, for the massive amounts we are talking about, would be prohibitavely expensive.

[jwenting]

Most of our trash floats.

so you pour it into a concrete block...

[rdfox]

One proposal for disposal of the meltdown debris at Fukushima Daiichi is to bury it in a vault in the subduction zone off Japan, so that it gets taken down into the mantle before it could pose a problem to future people. This might end up being the best solution for the "what the hell do we do with all this spent nuclear fuel?" problem, given that Yucca Mountain is now a dead issue...

[Nibb31]

so you pour it into a concrete block...

The US alone produces 2kg of waste per person per day. That's more that 200 million tons per year, about half of which is domestic waste. You'd need a whole lot of concrete to just make a dent in that much garbage.

[Nibb31]

One proposal for disposal of the meltdown debris at Fukushima Daiichi is to bury it in a vault in the subduction zone off Japan, so that it gets taken down into the mantle before it could pose a problem to future people. This might end up being the best solution for the "what the hell do we do with all this spent nuclear fuel?" problem, given that Yucca Mountain is now a dead issue...

I don't think Yucca Mountain would have had anything to do with Fukushima debris, not being on the same continent. One doesn't simply ship thousands of tons of radioactive material half way around the World.

[rdfox]

I don't think Yucca Mountain would have had anything to do with Fukushima debris, not being on the same continent. One doesn't simply ship thousands of tons of radioactive material half way around the World.

It wouldn't. I was suggesting it might end up being the alternative solution for the US's high-level nuclear waste disposal problem, since Yucca Mountain isn't going to happen. (Also, we *have* done that before; the US government shipped a whole BUNCH of fissile material from decommisioned Russian nuclear weapons to the US to be reprocessed into fuel elements for civilian power reactors, specifically to make sure it didn't end up in the hands of rogue states and/or terrorists...)

[Red Iron Crown]

Borehole disposal is a bad idea from a global warming perspective. All that heat from the borehole reaching the surface, plus all the fuel burned to bring the waste to the borehole site.

If we could bore to the mantle, we'd be much better off using the heat available there for geothermal power generation.