Reply
Thread Tools Display Modes
#1
Old 04-12-2010, 02:12 PM
Guest
Join Date: Jul 2000
Location: Bama
Posts: 10,747
Plasma gasification - pros, cons, limitations? Discussion wanted.

My hometown, Montgomery, Alabama, is presently conducting feasibility studies on installing a plasma arc waste disposal unit. Several private facilities are using the technology, and quite a few municipalities are investigating (or actively installing) them.

Now, I must admit, I find the implications of the technology fascinating. For those not familiar, it uses a plasma arc, and the very high temperatures produced, to reduce garbage to elemental gases and a small amount of solid waste. The gases can be theoretically captured and refined, and reused. If you strap on a turbine, the production of the gases can be used to generate power, which can then be sold back to the electrical grid, for a cheap and substantial boost in power capacity. In addition, these disposal systems are considered to be net power generators. They produce more electrical energy than they consume.

OK, so, the advantages, from what I can tell:

Plasma arc disposal systems:

1) Can have a very high capacity. For most cities, they can actually dispose of more garbage than a city can produce. This enables the disposal unit to either accept garbage from other sources, such as outlying towns and communities as well, or actively reduce the existing landfills while eliminating all new waste. I understand that if the capacity is large enough, it can do both.

2) Generate cheap, plentiful power.

3) Produce useful materials, thus could be considered a rather extreme form of recycling.

The major drawbacks addressed in the Wiki article seem to be that:

1) There are significant transportation and infrastructure considerations to consider.

2) It's still a mostly unproven technology on very large scales.

3) The liner of the plasma chamber is a weak point, since most units use an expensive metal liner that usually has a life of about a year. I do note, however, that a workaround involving lower temperatures and a brick plasma chamber has been developed.

4) I have also heard that the slag generated is hazardous, and would have to be disposed of, though I note that it would involve very small volumes of slag, and could be considered a step up from enormous, multi-acre landfills.

5) I would guess there are some materials which can't be processed this way, such as radioactive materials.

So, discussion? How much promise does this technology hold? Will it ever be implemented on a large scale? What promise does it have of making up shortfalls in local energy grids? I note that, as opposed to some varieties of alternative energy, plasma gasification is localized by its very essence. It would be a decentralized source of energy, and if it stays that way, the electrical infrastructure cost might be minimal.

Last edited by Ogre; 04-12-2010 at 02:17 PM.
#2
Old 04-12-2010, 02:24 PM
Guest
Join Date: Nov 2000
Location: Montreal, QC
Posts: 57,243
For additional info on the technology, I recommend this 2007 article from Popular Science. I think it's kinda nifty, myself, and the transportation issue isn't any worse (and possibly much better) that what cities already pay for trucks to haul garbage to conventional landfills.
#3
Old 04-12-2010, 02:27 PM
Guest
Join Date: Jul 2000
Location: Bama
Posts: 10,747
Very nice. Thank you.
#4
Old 04-12-2010, 02:31 PM
XT XT is online now
Agnatheist
Charter Member
Join Date: Apr 2003
Location: The Great South West
Posts: 33,425
Just want to post to listen in on the discussion, but I find this a bit hard to swallow:

Quote:
They produce more electrical energy than they consume.
There isn't any free lunch, so even leaving aside the energy cost in the logistics aspects of getting the material there, plus the energy costs in the life cycle and maintenance of the system, I find it difficult to believe that even theoretically that such a system could possibly produce more energy than it consumes.

Other than that, I don't think there is anything fundamentally wrong with such a system, if the intent is to dispose of waste. If the intent is to generate loads of clean, cheap power, however, I don't believe that this thing is going to do that. I could be wrong of course, which is why I wanted to join the discussion...

-XT
#5
Old 04-12-2010, 02:37 PM
Guest
Join Date: Jul 2000
Location: Bama
Posts: 10,747
Quote:
Originally Posted by xtisme View Post
Just want to post to listen in on the discussion, but I find this a bit hard to swallow:



There isn't any free lunch, so even leaving aside the energy cost in the logistics aspects of getting the material there, plus the energy costs in the life cycle and maintenance of the system, I find it difficult to believe that even theoretically that such a system could possibly produce more energy than it consumes.

Other than that, I don't think there is anything fundamentally wrong with such a system, if the intent is to dispose of waste. If the intent is to generate loads of clean, cheap power, however, I don't believe that this thing is going to do that. I could be wrong of course, which is why I wanted to join the discussion...

-XT
According to the PopSci article Bryan posted, it takes about as much energy to start the unit as a police taser. After that, the unit's power (and temperature) level is maintained by tapping the power generated by the turbine. It uses about 2/3 of that generated power, with the excess potentially being transmittable to the power grid. It doesn't violate the laws of thermodynamics, if that's what you're suspecting.
#6
Old 04-12-2010, 02:39 PM
XT XT is online now
Agnatheist
Charter Member
Join Date: Apr 2003
Location: The Great South West
Posts: 33,425
That's what I was thinking, yes.

-XT
#7
Old 04-12-2010, 02:50 PM
Guest
Join Date: Jul 2000
Location: Bama
Posts: 10,747
The process just uses a particularly energy-rich fuel source, and is efficient, allowing it to recycle some of the energy produced to operate it.
#8
Old 04-12-2010, 02:52 PM
Guest
Join Date: Oct 2004
Posts: 7,672
Quote:
Originally Posted by xtisme View Post
That's what I was thinking, yes.

-XT
It's not a closed system. You're throwing garbage (fuel) into it. It's like saying you can't get energy out of a coal power plant because of thermodynamics.
#9
Old 04-12-2010, 02:58 PM
Guest
Join Date: Dec 2003
Location: Vermont
Posts: 11,805
Yea, its basically the same from a thermodynamic standpoint as burning the garbage and using the heat to spin a turbine, it generates electrical energy by combusting the garbage.

The main concern I'd have would be the greenhouse gas emissions caused by burning the resulting gas for fuel.
#10
Old 04-12-2010, 03:00 PM
Guest
Join Date: Jul 2000
Location: Bama
Posts: 10,747
Quote:
Originally Posted by Simplicio View Post
Yea, its basically the same from a thermodynamic standpoint as burning the garbage and using the heat to spin a turbine, it generates electrical energy by combusting the garbage.

The main concern I'd have would be the greenhouse gas emissions caused by burning the resulting gas for fuel.
That's a fair point.
#11
Old 04-12-2010, 03:11 PM
Guest
Join Date: May 2003
Location: Dallas, TX
Posts: 6,847
Thanks for posting this thread. I was going to attempt to point something out, but the more reasonable voices were being drowned out.

I've posted on this board before about strides in fusion/fission hybrid technology. The article is from a year ago, but here is the statement from UT at Austin:

Quote:
Physicists at The University of Texas at Austin have designed a new system that, when fully developed, would use fusion to eliminate most of the transuranic waste produced by nuclear power plants.

The invention could help combat global warming by making nuclear power cleaner and thus a more viable replacement of carbon-heavy energy sources, such as coal.
Fusion-Fission Hybrid
The idea behind the compact Fusion-Fission Hybrid is that fusion can be used to burn nuclear waste, producing energy and getting rid of much of the long-lived waste generated by nuclear reactors.

"We have created a way to use fusion to relatively inexpensively destroy the waste from nuclear fission," says Mike Kotschenreuther, senior research scientist with the Institute for Fusion Studies (IFS) and Department of Physics. "Our waste destruction system, we believe, will allow nuclear power—a low carbon source of energy—to take its place in helping us combat global warming."
While I agree that we need to be looking at every viable clean energy source including wind, with this technology available, there's no reason to think that nuclear energy can't be a viable option.
#12
Old 04-12-2010, 03:36 PM
Guest
Join Date: Dec 2003
Location: Vermont
Posts: 11,805
Err...I don't think that has much to do with the OP, we has little to do with nuclear power generation or waste. The Plasma gasification thing is just a really fancy way of burning (in the non-nuclear, everyday combustion sense) trash.

Last edited by Simplicio; 04-12-2010 at 03:37 PM.
#13
Old 04-12-2010, 03:46 PM
Charter Member
Moderator
Join Date: Jan 2000
Location: The Land of Cleves
Posts: 77,448
I'm sure there are some scenarios where this is a good idea, but the truth is, landfills are still a perfectly good waste disposal method for most of the US. We have plenty of space, the land is cheap, and it's a form of carbon sequestration, which frankly we need. I could maybe buy that this is a good idea for, say, New York and LA, where land is much more profitably spent on more people (who in turn produce more waste), but outside of the most populated cities? Probably not.
#14
Old 04-12-2010, 03:55 PM
Guest
Join Date: May 2003
Location: Dallas, TX
Posts: 6,847
Quote:
Originally Posted by Simplicio View Post
Err...I don't think that has much to do with the OP, we has little to do with nuclear power generation or waste. The Plasma gasification thing is just a really fancy way of burning (in the non-nuclear, everyday combustion sense) trash.
I know. I just wanted to get the point out without the howler monkeys in the other thread turning it into some kind of political feces flinging contest. Personally, I find it as sustainable as using landfill waste and think we should pursue both.
#15
Old 04-12-2010, 04:09 PM
Guest
Join Date: Dec 2003
Location: Vermont
Posts: 11,805
Quote:
Originally Posted by Chronos View Post
I'm sure there are some scenarios where this is a good idea, but the truth is, landfills are still a perfectly good waste disposal method for most of the US. We have plenty of space, the land is cheap, and it's a form of carbon sequestration, which frankly we need. I could maybe buy that this is a good idea for, say, New York and LA, where land is much more profitably spent on more people (who in turn produce more waste), but outside of the most populated cities? Probably not.
I believe a lot of organic waste that ends up in landfills ends up releasing methane gas, so conceivably one of these plants could be a net positive in terms of greenhouse gas reduction if most of the trash was organic and it was destined to end up in a landfill if it didn't get gasified.

Presumably someone could actually (or already has) crunched the numbers regarding the ratio of plastics to organics in the Montgomery waste-stream and figured out if the plant would be a net greenhouse gas producer or whether it would actually reduce gases relative to a landfill. But it isn't obvious to me one way or the other.
#16
Old 04-12-2010, 04:19 PM
Straight Dope Science Advisory Board
Join Date: Mar 2000
Location: With Candy Darling
Posts: 15,989
I posted this in the Pit, and then saw your link here. Just so you know I did not ignore you or your post, I'll repost the very little I had to say here:
Quote:
I apologize, but I do not have any real experience with this at all - in fact, I found that Wiki page you linked to to be quite interesting, and I e-mailed my librarian to get some articles on it tomorrow when he comes in. Although I am somewhat ignorant of the process, I am proud that I guessed halogens released in the plasma (especially chlorine from plastics) would be a potential design problem before I read that far on the Wiki page.
#17
Old 04-12-2010, 04:22 PM
Guest
Join Date: Jul 2000
Location: Bama
Posts: 10,747
Quote:
Originally Posted by Una Persson View Post
I posted this in the Pit, and then saw your link here. Just so you know I did not ignore you or your post, I'll repost the very little I had to say here:
Ha! Thanks! Ignore my private message to you, then.
#18
Old 04-12-2010, 04:38 PM
Guest
Join Date: Jul 2000
Location: Bama
Posts: 10,747
Quote:
Originally Posted by Chronos View Post
I'm sure there are some scenarios where this is a good idea, but the truth is, landfills are still a perfectly good waste disposal method for most of the US. We have plenty of space, the land is cheap, and it's a form of carbon sequestration, which frankly we need. I could maybe buy that this is a good idea for, say, New York and LA, where land is much more profitably spent on more people (who in turn produce more waste), but outside of the most populated cities? Probably not.
I would argue, being an ecologist, that outside of the problem of CO2 generation from burning the syngas, that landfills are an inferior choice. The carbon sequestration provided by landfills is leaky, at best. Methane is generated in large quantities by the breakdown of organics, and methane is a more powerful greenhouse gas than carbon dioxide. In addition, landfills are constant threats to the water table, even with clay liners. The loss of habitat and natural lands is also unacceptable (IMHO), although I do appreciate the free plant digs every year, as my local dump expands.

One other potential benefit: plasma disposals can apparently handle hazardous waste, and even chemical weapons. No more dedicated facilities to sequester the nasty stuff (apart from nuclear waste).
#19
Old 04-23-2010, 06:05 AM
Guest
Join Date: Apr 2010
Posts: 1
Questions

Orge, I am in the state something like you. (On the other side of the Atlantic)
So lucky me, I found this thread.

PWM sounds great and viable but I have some questions ...

Technical Questions:
Every brochure I've read states that there is some waste coming out of the technology:
- one waste output is from gasifier bottom. As I understand it is still fed to the plasma chamber, but on another route. (?)
- now the tricky part the syngas cleaning, trapping sulfuric dust particles.
- third the alkali-tower for trapping acidic elements.

Anyway what happens to these hazardous wastes?
Will they be trapped in the artificial obsidian? (first probably)
Will they be transferred to waste depos? How?

After plasmafication (before cooling), we can only talk about elements, so what about hazardous metals still found in municipal wastes as well (mercury, gallium, etc)?


Business Perspective:
If the technology is sound, because of the high investment needs, I think the
business side is only viable if used as a waste treatment plant, e.G money flows in not only according to the outputs (heat, electricity and obsidian) but also, less traditionally, from the input side (waste removal).

Also the running cost must be very high: If the process is self sustainable - from energy perspective - the extreme stress to the machinery (raw heat, mechanical) must wear them off quickly (like the tiles of the space shuttle), and the plasma chambers coal lining and coupling would cost some peanuts as well.

Have anybody seen a business plan that was sound? That's of course a yes/no question, hence every BP has to be adapted to market.

Or my other idea is that this forward-thinking investment must be (co)funded by the government, like in case of BA-Concord in 1960'.

Waste perspective:
What type of wastes does PWM handles? I know it handles municipal, does it handles hazardous wastes as well? Waste waters?
#20
Old 04-23-2010, 02:18 PM
Guest
Join Date: Mar 2006
Posts: 2,405
Quote:
Originally Posted by gkoves View Post
Waste perspective:
What type of wastes does PWM handles? I know it handles municipal, does it handles hazardous wastes as well? Waste waters?
It will handle any non-radioactive waste from what I have read. In fact, apparently a niche application of the technology is disposing of medical waste. (Sorry, no cites)

FWIW,
Rob
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 10:07 AM.

Send questions for Cecil Adams to: [email protected]

Send comments about this website to:

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Copyright © 2018 STM Reader, LLC.

Copyright © 2017
Best Topics: graphic equalizer wallpaper most populous mammal centrifuge urine wet willy crywolf show cat trill sound female canine anatomy worst shakespeare plays frog smoking cfm shoes zebra jumper pt cruiser reviews laptop with 9 pin serial port bouncy ball that you sit on me falta in english what comes after 999 billion peeing on feet for athletes foot is it illegal to destroy money tylenol arthritis vs tylenol can i store dry ice in my freezer the higher your iq the more forgetful you are definity hp 100 tire what temp does wine freeze how to print amazon receipt