Clean Enough to Wash Your Hands

Global warming moved another notch up the worry scale last week when the National Academy of Sciences reported that human pollution might not just be causing a gradual rise in the earth's temperature but could also lead to "large, abrupt, and unwelcome" climate change. So it was a particularly good week for DaimlerChrysler to introduce a new fuel-efficient minivan called the Natrium. It runs on a common compound called sodium borohydride. A chemical reaction inside the engine produces hydrogen to power the car's fuel cell, leaving behind not carbon dioxide (the primary culprit in global warming) but borax, a standard ingredient in many household soaps.

Sure, it's clean, but can you get fries with it? Last month the U.S. government began fueling certain military vehicles and post office trucks with "biodiesel," an alternative to diesel fuel derived from vegetable oil. The fuel, which can reduce greenhouse emissions in diesel cars by as much as 78%, is nontoxic and can be made from surplus soybeans or leftover oil from the fryers of fast-food restaurants.

--By Andrew Goldstein