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25.1.04

Modern Day Alchemy

Killing Germs, Reducing Waste, Making Oil: TDP Might Be The Next Big Thing

... TDP [thermal depolymerization] turns just about anything into oil and fertilizer. And when I say "anything," I mean that: animal waste, medical waste, human waste. Used diapers, used computers, used tires. Anything that's not radioactive can be tossed into the hopper.

... Dioxins and PCBs are two particularly nasty kinds of chemical. Right now, we don't really dispose of what we make; we burn or bury it, which means it ends up forgotten but not gone. More specifically, it ends up in the grass and water, and thus back in the food chain.

... But thermal depolymerization is good news. It breaks down industrial and medical wastes and poisons. So instead of burning that stuff and introducing nasties like PCBs and dioxins into the environment, you can run them through a TDP system where they get broken down into their components, which include — lest we forget — oil.


The industrial waste destruction part is what really struck me, since I've been reading a lot of summaries of Superfund cleanup plans. The most depressing part was the fact that the contaminants usually couldn't really be fixed -- they could just be sealed away or hauled off-site. I'm sure there's a downside (given my general skepticism about technical fixes), but I haven't been able to figure out exactly what it would be. This is one of those times when I wish I had more than a handful of readers, so that I could hope for a lively comment section with input from someone who knows more about this than I do after reading a couple of popular press articles.

The author's website includes a pdf of a photocopy of a recent Discover magazine article on TDP, which goes into more detail about how the process works. A box at the end of the article discusses the question of global warming. According to TDP's proponents, the box says, the technology could reduce global warming. The main contributor to global warming is carbon dioxide, and the main source of carbon dioxide is the burning of fossil fuels. Thus, we're taking a stock of carbon that was taken out of circulation millions of years ago and putting it back into circulation. But wide use of TDP would allow us to stop drawing on that underground reserve of carbon, instead only recycling the carbon that's already at the surface. This prognosis misses two things. One is that fossil fuel extraction probably won't halt for a while. TDP looks like the elusive coal-to-oil process that has been pursued so long, since less efficient fossil fuels like coal and oil shale are far more abundant than petroleum and natural gas. So in the search for feedstocks, coal seems like an obvious choice -- though perhaps the economics of it will alter things. Second, there's the issue of the carbon getting "stuck" in the atmosphere. If we take things like sewage sludge and garbage, which at present keep carbon sitting here on the surface, and convert them into oil, that oil will be burned and the carbon will wind up in the atmosphere. The crucial question is whether we can take that carbon back out of the atmosphere as fast, or faster, than it's put in. Even without the re-introduction of fossil carbon, global warming could be caused by an increase in the proportion of available carbon that exists as atmospheric carbon dioxide at any given moment.

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