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:
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.
Generate cheap, plentiful power.
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:
There are significant transportation and infrastructure considerations to consider.
It’s still a mostly unproven technology on very large scales.
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.
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.
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.
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.
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…
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.
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.
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.
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.
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’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 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.
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.
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:
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).
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?
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)
Personally, I find it as sustainable as using landfill waste and think we should pursue both.
