Sunday, December 02, 2007

Meet the Mother of All Greenhouse Gasses

A recent article at Slate looks at “Other Greenhouse Gases,” and it turns out CO2 is the weakest of the bunch. It’s so weak, the EPA uses CO2’s heat-trapping power (if you can call it that) to measure the real monsters of the greenhouse gas bunch.

The measurement is called “Global Warming Potential” (GWP). A molecule of CO2 has a GWP of 1. Methane, which accounts for 8 percent of the greenhouse gas America spews annually, has a GWP of 21. But it doesn’t last in the atmosphere as CO2. A methane molecule floats around for 12 years. CO2 on the other hand, sticks around for 50 to 200 years.

But its lifespan isn’t the only reason CO2 “gets most of the doomsday ink,” according to Slate. “In terms of sheer weight, it accounts for around 85 percent of America's greenhouse gas emissions, which amounted to 7.074 billion metric tons in 2004.” I don’t even know what a metric ton is but I’m pretty depressed by that number. (A metric ton is 1,000 kilograms or 2,204 pounds).

Methane is still a factor to beware of. While CO2 levels have jumped 35 percent since the mid-1700s, methane is up 150 percent. And as the so-called permafrost melts in the north as global temperatures rise, expect that to significantly boost methane levels.

(By the way, I haven’t gotten to the mother of all greenhouse gasses yet.)

What can we do about methane levels? Since reversing global warming (pretty much) isn’t an option, and the permafrost is (almost) sure to thaw (to some degree), anything we do is pretty much futile. But you could capture methane from landfills (the number one source of methane in this country) and recycle it as an energy source. Or you could mix cottonseed oil into cattle feed, which reduces their methane output (the number two source in this country) by 30 percent. (For more on how and why grazing animals like cows create methane,
check out this post.)

Of course, methane and CO2 aren’t the only greenhouse gasses. There’s also nitrous oxide, the stuff your dentist uses to mellow you out for an operation. The leading source of nitrous oxide is agricultural fertilizer. This stuff has a GWP of 310, stays in the atmosphere for 120 years, and accounts for 5 percent of all greenhouse gasses.

(Nope, nitrous oxide isn’t the mother of all greenhouse gasses either.)

Don’t let the fact that nitrous oxide comes third in this posting, and that less of it is produced than methane, fool you. Since its GPW is so high (15-times that of methane), it’s a bigger problem than methane.

But the biggest greenhouse monster of them all? A little something called sulfer hexafluoride (SF6), which is used for “preventing molten magnesium from oxidizing and for etching semiconductor wafers.” The Slate piece didn’t say how much of this we send quietly into the sky each year, but it’s bad stuff. SF6 carries a GWP of 23,900, “making it the most brutally effective greenhouse gas known to man.” Hoping for a short atmospheric lifespan on this stuff? Sorry. It lasts 3,200 years in the air.

Don't miss this terrific video of how much fun you can have with a tank of SF6...

Thanks to an anonymous friend of Pound360's for passing that vid along.

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I started pound360 to channel my obsession with vitamins, running and the five senses. Eventually, I got bored focusing on all that stuff, so I came back from a one month hiatus in May of 2007 (one year after launching Pound360) and broadened my mumblings here to include all science.