Let us now consider the plastic hanger.

Wal-Mart uses millions of them a year — uses them just once and then has to figure out what to do with them, along with the mountains of plastic film, shrink-wrap, shipping pallets, cardboard boxes, trailer tags and other behind-the-scenes detritus of the American shopping experience. Not too long ago, Wal-Mart employees just threw most of that stuff away.

And then along came Jeff Ashby, a hyperactive man who in the early 1990s drove a garbage truck and is now national accounts manager for Rocky Mountain Recycling in Salt Lake City.

Ashby has a neighbor who is a Wal-Mart employee whose job it is to take the filmy plastic wrap off each piece of clothing that comes into the store. One day a few years ago, the neighbor wondered aloud why all that plastic was thrown away rather than recycled. So Ashby came up with an idea he calls the "Super Sandwich Bale," a seemingly obvious innovation whose patent paperwork is a foot thick.

For nearly two years now, Wal-Marts everywhere in America have been using the Super Sandwich Bale — which means they now recycle more than 25 percent of what once was tossed into the trash compactor, Ashby said. Plastic clothes hangers currently account for a third of this volume.

The Super Sandwich Bale "has changed the recycling industry as we knew it," says Lesley Heikkila, a recycling specialist at Wal-Mart headquarters in Arkansas.

Now other retailers are also looking into using the process, as is the U.S. military. And 40 other material recovery facilities (MRFs or "murfs," in recycling lingo) in the country are under license from Rocky Mountain Recycling to use the Super Sandwich Bale technology. All of which means less junk ending up in the country's landfills, plus big money for Rocky Mountain Recycling. It also helps illuminate why the green mantra, "reduce-reuse-recycle" is often more complicated that it sounds.

For example: wouldn't it be better for the environment to reuse all those plastic clothes hangers? The problem, says Ashby, is not only the cost of labor to sort the different kinds of hangers once they've been used, but the cost in fuel to ship them back to the individual clothing manufacturers. It's better for the environment, he argues, to send the hangers in bulk to a facility that melts down the plastic into resin that gets turned into more hangers and other plastic objects. According to Ashby, it's actually almost twice as expensive to make a product like decking out of virgin polyethylene resin than from recycled plastic.

When you're trying to get to the bottom of what's green and what isn't, sometimes the solutions are counterintuitive. And often the answers are vague.