Wednesday, January 02, 2008

Arc Of The Somnambulant

So, I'd ended 2008 with a promise to post more frequently, and succeeded only in trolling for comments from My Hot Wife.

I've been lucky today, since along comes an interesting little article from that old dependable, Slate. In it, Mr. Brendan Koerner takes a look at plasma arc gasification (PAG).

So what is PAG? Well, the pat answer is that it's a cool-sounding big-ticket piece of kit designed to part a fast-growing county's tax-payers from their dollars. I am, though, being a mite unfair, since not a huge amount is known about the technology's limits. It could be the future, or it could be a less sensible use of precious tax-exempt bond capacity than just building a new prison.

The technology involves using electricity to heat up garbage to an enormously high temperature, creating synthetic gas, mostly inert slag, and a couple of nasty by-products, including heavy metals (no not the cool kind) and some other gases, of which probably the least malign is carbon monoxide.

It's fairly easy to filter out the nasty metals, and some of the gases, or at least it's possible. But the long-term performance of PAG equipments, given the temperatures at which they operate, is difficult to predict.

You also might have noticed I mentioned something called synthetic gas in the second to last paragraph. This is the key. The idea behind the PAG technology is that you burn this gas to generate the electricity used to heat the garbage, and so forth, in a virtuous circle.

But we have absolutely no idea how efficient this process is meant to be. This is a shame, because this is the only way we can judge what the total environmental benefits could be. If the technology is self-sustaining, there's no definitive statement I can find to this effect.

The Slate article gives us to understand that the biggest obstacles to the technology's adoption are the problems of disposing with the other byproducts of the process. I'm not convinced. It's telling that PAG has been extensively marketed to communities that for one reason or another are done with trying to plonk their garbage in landfills.

The environmental benefits may be there, although there's going to be some carbon emissions from PAG. But it's better - at least in environmental terms - than just burning trash, and is a quicker solution than trapping methane from landfills, which can take years.

It's sort of a mirror image to coal-to-liquids projects, which have gained some acceptance in the US as oil prices stayed high, and the US wakes up to the fact that it has much more coal than oil. The problem, though, is that the process, which takes coal, and turns it into something that can run in diesel petrol engines, emits hideous amounts of carbon, maybe 1.8x as much as ordinary petrol.

But in both cases the cost-benefit analysis is nowhere near advanced enough to justify a raid on the municipal kitty, no matter how connected the developers can be.


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