Trash disposal into lava

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gfd43tg
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With the news about the Hawaiian volcano eruption, it got me thinking: what if we just put our trash down an active volcano and let it incinerate? I know there is a logistical problem getting trash to lava / into a volcano, but would there be toxic emissions if we just threw our trash into flowing lava? I am curious in principle. Did I solve the global landfill problem?
 

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  • #2
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With the news about the Hawaiian volcano eruption, it got me thinking: what if we just put our trash down an active volcano and let it incinerate? I know there is a logistical problem getting trash to lava / into a volcano, but would there be toxic emissions if we just threw our trash into flowing lava? I am curious in principle. Did I solve the global landfill problem?
What would be the difference between this and using a waste incinerator?
Incinerators usually have legislation relating to environmental standards and emissions, which would be difficult to match with a volcano.
See here for example.
 
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  • #3
Bandersnatch
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but would there be toxic emissions if we just threw our trash into flowing lava?
Lava is still rocks. It's denser than most anything you would want to dump rather than recycle. So, you're asking if uncontrolled grilling of assorted rubbish in open air would produce toxic emissions.
 
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  • #4
gfd43tg
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What would be the difference between this and using a waste incinerator?
Incinerators usually have legislation relating to environmental standards and emissions, which would be difficult to match with a volcano.
See here for example.
I guess the difference is the volcano is already spewing out lava, and we don’t need to build an incinerator facility and burn additional gas just to burn the trash. The volcano is doing the work for us. How do we control emissions from a volcano right now?
 
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I guess the difference is the volcano is already spewing out lava, and we don’t need to build an incinerator facility and burn additional gas just to burn the trash. The volcano is doing the work for us. How do we control emissions from a volcano right now?
The point is the emissions from the burning waste are toxic or extremely potent greenhouse gases., which is why there are standards on emissions from incinerators.
Have a look at the literature review here, for an example of some of the compounds produced.
There's a similar article here about the emissions from burning PVC.
In an incinerator, these emissions can be controlled to a much greater extent by further treatments than would be possible at a volcano.
 
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  • #6
gfd43tg
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The point is the emissions from the burning waste are toxic or extremely potent greenhouse gases., which is why there are standards on emissions from incinerators.
Have a look at the literature review here, for an example of some of the compounds produced.
There's a similar article here about the emissions from burning PVC.
In an incinerator, these emissions can be controlled to a much greater extent by further treatments than would be possible at a volcano.
If the trash is submerged into the lava, can the gases get trapped inside and once the lava hardens to a rock the greenhouse gases will just be trapped inside the rock? Kind of like a tree absorbing and storing CO2
 
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Bandersnatch
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If the trash is submerged into the lava,
How would you achieve that?
 
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  • #8
Ryan_m_b
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If the trash is submerged into the lava, can the gases get trapped inside and once the lava hardens to a rock the greenhouse gases will just be trapped inside the rock? Kind of like a tree absorbing and storing CO2

If the idea is to use the lava to incinerate waste the issues are the toxic byproducts released into the atmosphere. If the idea is to submerge the waste in lava so that it is sealed away once the lava solidifies then you've basically invented a landfill with a crazy amount of extra danger.
 
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  • #9
gfd43tg
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If the idea is to use the lava to incinerate waste the issues are the toxic byproducts released into the atmosphere. If the idea is to submerge the waste in lava so that it is sealed away once the lava solidifies then you've basically invented a landfill with a crazy amount of extra danger.
Well in a landfill the trash is still physically present and piling up. In submerged lava the trash is reduced to ashes and the gas (hopefully) is trapped inside. So we would just have a growing island that has pockets of gas inside of it. It’s like a forest of trees holding CO2, it’s better than the CO2 accumulating in the atmosphere. Maybe the lava is hot enough to decompose the gases into base elements?
 
  • #11
gfd43tg
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I would advise you to pay attention to @Bandersnatch 's previous responses.
I get the density thing. Maybe we just have to push the garbage into the lava to get it under. Can I can get on a surfboard and go riding down lava and I won’t submerge into it?
 
  • #12
TeethWhitener
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Can I can get on a surfboard and go riding down lava and I won’t submerge into it?
Are you less dense than lava?

Edit: ...ignoring the fact that you'd burst into flames or vaporize pretty quickly.
 
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  • #13
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If the trash is submerged into the lava, can the gases get trapped inside and once the lava hardens to a rock the greenhouse gases will just be trapped inside the rock? Kind of like a tree absorbing and storing CO2
What happens if the volcano erupts, as they are wont to do?
It is far easier and safer to simply recycle what waste is recyclable and incinerate the rest.
European countries are already doing this. Sweden, for instance, sends less than 1% of household waste to landfill. The percentage that can't go to landfill is because incinerating the byproducts are simply too toxic, which would still be too toxic to incinerate in a volcano.
 
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  • #14
Ryan_m_b
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Well in a landfill the trash is still physically present and piling up. In submerged lava the trash is reduced to ashes and the gas (hopefully) is trapped inside. So we would just have a growing island that has pockets of gas inside of it. It’s like a forest of trees holding CO2, it’s better than the CO2 accumulating in the atmosphere. Maybe the lava is hot enough to decompose the gases into base elements?

Why would the lava hold the gaseous byproducts? You can’t have it both ways, you can’t simumtaneously prevent physical pile up and somehow reduce the waste to ash.
 
  • #15
russ_watters
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Another angle here:
Did I solve the global landfill problem?
Without being able to speak for the more densely populated countries in Asia, landfill volume problems in the west are more political/NIMBY issues than anything else. Global warming concerns are changing how they are viewed though, since the greenhouse gas they emit - methane - is also a valuable resource. So towns can make money and generate electricity from them, while reducing GHG emissions.
 
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  • #16
TeethWhitener
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There's also this:
 
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  • #17
anorlunda
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You've got it a bit backward. You want to put the trash into a subduction zone rather than a volcano.

In a subduction zone, it gets carried deep into the Earth, mixes and reacts with what's down there, and doesn't reappear on the surface for a billion years or more.

subduction%20zone%20graphic.jpg
 

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  • #18
TeethWhitener
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You've got it a bit backward. You want to put the trash into a subduction zone rather than a volcano.

In a subduction zone, it gets carried deep into the Earth, mixes and reacts with what's down there, and doesn't reappear on the surface for a billion years or more.

View attachment 228148
I can’t put my finger on a source, but I seem to remember this being suggested as a solution for nuclear waste disposal some time back.
 
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  • #19
anorlunda
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I can’t put my finger on a source, but I seem to remember this being suggested as a solution for nuclear waste disposal some time back.

It sounds like that should work in principle. But the devil is in the details, and I don't think anyone knows enough about the details to be sure. The required level of how sure is sure enough would be higher for nuclear waste than ordinary trash.
 
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  • #23
berkeman
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Well in a landfill the trash is still physically present and piling up. In submerged lava the trash is reduced to ashes and the gas (hopefully) is trapped inside. So we would just have a growing island that has pockets of gas inside of it. It’s like a forest of trees holding CO2, it’s better than the CO2 accumulating in the atmosphere. Maybe the lava is hot enough to decompose the gases into base elements?
@Maylis -- Your Profile page says that you have a BS in Chemical Engineering. I'm a bit confused by some of your posts in this thread, given your technical background...
 
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  • #24
HAYAO
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For example, if you were to fall into a lava, you would simply land on top without submerging and burn on the spot until you vaporize. You probably wouldn't see anything like the terminator giving a thumbs up.

Stuff like plastics can easily produce environmentally hazardous emissions. Are you suggesting we should build some emission regulating facility on top of a lava? That sounds very costly and unrealistic. If you throw something large scale like wastes from a city, you risk uncontrollable small eruption that would probably damage the facility and quickly make them useless.
 
  • #25
gfd43tg
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You've got it a bit backward. You want to put the trash into a subduction zone rather than a volcano.

In a subduction zone, it gets carried deep into the Earth, mixes and reacts with what's down there, and doesn't reappear on the surface for a billion years or more.

View attachment 228148
Brilliant! So I’m not totally off base here. Just need to figure out how to get it on the plate that is sliding into the earth. My guess is the pressure is so high down there that the gas will stay dissolved in the mantle. Also need to make sure we don’t get back pressure pushing the flaming trash back out.
 
  • #26
TeethWhitener
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Brilliant! So I’m not totally off base here. Just need to figure out how to get it on the plate that is sliding into the earth. My guess is the pressure is so high down there that the gas will stay dissolved in the mantle. Also need to make sure we don’t get back pressure pushing the flaming trash back out.
As @russ_watters said, the main issue with properly maintained landfills in developed countries is NIMBY-ism. Treating the waste and storing it isn't a particularly pressing logistical problem. Plus, the cost of engineering a subduction zone disposal scheme for regular waste would be astronomical compared to current waste management costs.

From the google search that @Bystander provided, I'm gathering that the main objection to storing nuclear waste in a subduction zone is that those areas tend to be earthquake-prone and otherwise geologically unstable. Plus you have to worry about high-pressure salt water corroding whatever container you've put your nuclear waste in.
 
  • #27
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to make sure we don’t get back pressure pushing the flaming trash back out.
The relevant usual speed is around a few centimeter for a year. So you need to contain that 'trash' for some hundred thousand years.
Also, to put the containers in place you need to work some kilometers underwater.
We can't do that even for nuclear waste.

If you want to 'burn' trash then it would be better to use some biology instead. Less of a firework, but you might get more usable material.
 
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  • #28
If the trash is submerged into the lava, can the gases get trapped inside and once the lava hardens to a rock the greenhouse gases will just be trapped inside the rock? Kind of like a tree absorbing and storing CO2
Denser the fluid, more is the buoyancy and the gas won't just remain 'trapped' in the lava... At least not long enough for the lava to solidify
 
  • #29
fresh_42
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My first thought has been the creation of TCDD by an uncontrolled burning. Bad idea, cp. Seveso.
 
  • #30
Bandersnatch
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You probably wouldn't see anything like the terminator giving a thumbs up.
I think the more pertinent example here would be poor Smeagol (not) sinking into the lava river of Mount Doom ;)
Speaking of Terminator 2 - the lore has the T-800 made of some sort of titanium alloy. So it'd not only not sink gracefully down the molten steel as depicted, it likely wouldn't even melt. It'd just lie there awkwardly, with the Connors standing above in the haze of burnt flesh, pondering if perhaps not paying attention in science classes wasn't such a good idea after all.
 
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  • #31
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Steel melts somewhere around 2700F, and titanium melts around 3000F, so it's not unreasonable to assume that titanium would melt in a container of molten steel if the steel isn't right at the melting point. From some quick googling, temperatures above the melting point of titanium are pretty common in steelmaking.
 
  • #32
Bandersnatch
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From some quick googling, temperatures above the melting point of titanium are pretty common in steelmaking.
From what I understood, foundries are designed to not get much above the melting point, and that temperature depends on the alloy. But yeah, it's possible. Hence the 'likely' qualifier.
I also wondered how alloying of titanium can change the melting temp, but couldn't find anything - not to mention the movies weren't precise enough about their made-up lore to specify the details of alloy composition.
 
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Ti-6Al-4V is pretty common, and starts melting about 100F below pure Ti, so the number I used above is probably pretty representative.
 
  • #34
CWatters
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How would you recover energy from it if you just put it into a volcano or subduction zone? Most modern incinerators use it to generate electricity.
 
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  • #35
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Not to mention that subduction zones are often underwater and that they move at rates of centimeters per year.

https://en.wikipedia.org/wiki/Subduction

https://www.livescience.com/43220-subduction-zone-definition.html

This would mean burying the trash in the subduction zone manually in order to get it to subduct and realizing that should the zone snap the trash could be sent everywhere via tsunami action.

Here's an article on the subducting of nuclear waste:

https://www.thenakedscientists.com/...ld-nuclear-waste-be-disposed-subduction-zones

I think its time now to close this thread as we have pretty much exhausted all the reasons for why this won't work and is likely an interesting but bad idea for getting rid of our trash.

I'd like to thank everyone for contributing here and now formally close this thread.
 
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