Which yoga pants are greener — Nike or Adidas? If you ask me, I’d advise greener shopping at Patagonia instead — but soon, an Eco Index clothing tag could help you make that decision.

According to the Wall Street Journal, Nike, Adidas and Patagonia are among about 100 companies working on this Eco Index — a “software tool to help them measure the environmental impact of their apparel and footwear, from raw material to garbage dump.” The index will debut at the Outdoor Retailer trade show in Salt Lake City next month — and on your clothes at an undetermined date.

The Eco Index is the kind of consumer tool that Daniel Goleman argued for in his book "Ecological Intelligence" — a tool that’ll help people make greener shopping decisions, thereby pushing companies towards more eco-friendly production practices. Instead of spending days researching different brands and trying to guesstimate which pair of jeans is greener, you could simply look at a clothing tag and pick up the pair with the lower score.

Of course, as you may expect, the Eco Index is not without controversy. The Wall Street Journal points out that the index is based on a series of questions a company answers about its products — broad questions that aren’t detailed, aren’t product-specific, and aren’t verified beyond the companies’ self-reported claims. Other discrepancies could also affect the accuracy of the index:

Some of the points are awarded for changes with very speculative impacts. Levi’s care tags ask consumers to wash in cold water, line-dry and donate to Goodwill. All of that earns Levi’s points on the Eco Index. But that doesn’t necessarily make Levi’s greener than a pair of Wranglers, which can just as easily be dropped off at the Salvation Army.
Still, an index like this sounds promising if done well — and widespread use of index tags could get the general public thinking about the environmental impact of their choices. (Though no one knows when those tags will actually show up on clothes.) In the meantime, would-be-green shoppers can get some help from the GoodGuide, which comes with a barcode-scanning iPhone app, when making decisions about food, toys, personal care products and some household items.

There’s an even simpler way to avoid these difficult comparison-shopping conundrums altogether: Buy less stuff, and shop pre-loved whenever possible! Do that, and you’ll save a lot of money while avoiding shopping headaches — unless what you need happens to be underwear or running shoes.

Also on MNN: The high cost of cheap T-shirts