Two weeks ago, the Explainer released a list of questions we were either unable or unwilling to answer in 2007. This included topics like "Why do men almost never win on ABC's Wheel of Fortune?" and "Is it possible I have the softest cat in the world?" We then invited you, Slate's readers, to let us know which of these questions was most deserving of a response.
Some of you wrote in with quick answers to the questions on the list. Many pointed out, for example, that our No. 3 vote-getter—"When a fly lands on a ceiling, does it execute a barrel roll or an inside loop?"—has already been covered by the Straight Dope. (Answer: The fly grabs the ceiling with its forward legs, and then does a reverse somersault.) As for the inquiry about a movie featuring a devil in red pajamas: That's the 1959 classic Santa Claus (later sent up in an episode of Mystery Science Theater 3000). Readers also attempted to crowdsource our questions, with varying degrees of success, on Yahoo! Answers.
Meanwhile, we received about 30,000 votes for our reader-selected favorite. Which brings us to our official Explainer Question of the Year for 2007:
Why don't we drop medical waste and nuclear waste into active volcanoes, the "ultimate high-temperature incinerators"?
The answer: Because the hazardous parts would come right back out.
We do incinerate more than 90 percent of the medical waste in the United States, both to reduce its total volume and to kill off infectious agents. But burning up blood-soaked bandages, discarded needles, and stray organs like tonsils and appendices creates many dangerous byproducts, including dioxins and carbon monoxide, as well as fly ash laced with heavy metals. While an onsite incinerator at a hospital would be equipped with scrubbers and filters to capture these byproducts for landfill, any gases or ash produced in a volcano would be emitted straight into the atmosphere.
It's also not clear that volcanic incineration would be hot enough to sterilize garbage. According to the Environmental Protection Agency, medical waste should be burned at more than 1,600 degrees Fahrenheit, with some states demanding temperatures of 1,800 or 2,000 degrees to reduce volatile organic emissions. Molten lava can be hot enough to do the trick, measuring about 1,800 or 1,900 degrees on average. But the exact temperature varies widely depending on the volcano. The unusual black lava at Tanzania's Ol Doinyo Lengai, for example, can be as cool as 930 degrees. *
It's an even worse idea to toss nuclear waste into a volcano. Combustion won't have any effect on spent nuclear fuel, nor will it reduce the radioactivity of low-level waste like contaminated clothing and equipment. The only reason to incinerate miscellaneous radioactive garbage would be to reduce its overall volume, so it's easier to sequester. As with the incineration of medical waste, this produces dangerous emissions that would pop right out of a volcano.
Even without medical or radioactive waste, volcanoes already release dangerous gases into the environment. In Cameroon, carbon-dioxide pollution from a volcanic crater lake asphyxiated several thousand valley-dwelling people when it displaced the available oxygen. Active volcanoes in Hawaii have caused problems with acid rain and "vog," a combination of volcanic gases and fog.
It would also be dangerous and impractical to transport large quantities of garbage to the top of an active volcano. At best, you might drop small items through "skylight" openings on the tops of lava domes.
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Explainer thanks Robert Benedict of the American Nuclear Society and Robert Trombley of the International Volcano Research Centre.