Trying to limit your environmental impact? Buying "eco-friendly" stuff doesn't help.Before attending trade shows flogging "green" products, I set my B.S. detector to 11. That habit was reinforced recently, when I attended a small show in New York, featuring the big boys of consumer electronics-Nokia, Sony, Samsung, and the like. I came to a stand offering green credit cards, which award one ton of carbon offsets for every $1000 you spend. That may sound good, but I had to ask: How does that conversion rate compare to regular cards that give you cash or frequently flier miles? How much value are you getting for your money?"1 ton."But what's that ton worth? How much does it cost?"Carbon offsets range in price, from $8 to $12."But doesn't that get to how much money you guys are taking for commission?"The value is probably comparable to what you'd get otherwise. And it doesn't really matter what it costs, for people that care about green."On her first point, the woman was wrong: Frequent flier miles are worth about $20 for every $1000; cash back programs range as high as $50. On her second point, though, she was right. "Green" consumers probably don't care. And one symptom is the ubiquity of worthless green products-from solar-powered doodads to green furniture. Very few of these "sustainable" products actually reduce your carbon footprint-and carbon is really the absolutely chief issue we should care about, not some nebulous idea of eco-friendliness.The green credit card really exemplifies the problem. It encourages you to buy more, and salves your conscience with the promise that every purchase is helping the planet. It feeds the pernicious idea that we'll be okay if we just buy new stuff.But being "green" is chiefly about your behavior and daily habits, not what a given product is made from. A LEED-certified house in the suburbs isn't green. You'd probably do better with a smaller place, closer to work-if you cut your commute in half, you've basically done the same thing as doubling your gas mileage and staying put. A sofa made from sustainable woods? It's still better to buy antiques. Green computer? That's a starting point, but not if you just end up replacing it in two years. Buy a better one that'll last you longer and take care of it-in time, computers can run 40 percent slower; there's software that will clean one up like new, making it last longer. The list could go on.Granted, greenwashing isn't necessarily malicious. It's an unavoidable fact, which stems from how much uncertainty there is in the market today. We're just now figuring out what exactly a "carbon footprint" means. For example: 90 to 95 percent of the carbon emitted while making a computer is indirect-that is, it doesn't come from the materials themselves, but rather the supply chain that produced the parts. That has radical implications for how we consume, which the market doesn't acknowledge because there's really no way to sell a product aimed at keeping you from buying less crap.I'm not advocating that everyone become a miserly shut-in. But there is another approach, as we wait for clearer guidelines about the carbon costs attached to what we consume, on a day-to-day basis. Of course, check off the big boys on your list of carbon sources: How efficient is your car? How weather-tight is your home? Is it close to work? There are solutions to each of these problems that don't involve ditching what you already have. For other big purchases, don't be afraid of spending more, if it means something that will last longer or retain some resale value. The merits of a green product should be the last thing you consider, and only when what you already have is truly spent.