Car rental firms join carbon-offset bandwagon

With green issues dominating the headlines at this week's Detroit auto show, you may find yourself wondering how much it costs to assuage the gas-guzzling guilt you feel when picking up your next rental car. The convenient answer is $1.25 (plus applicable taxes). That is the price at which Enterprise, National, and Alamo are selling carbon offsets to their customers in a carbon-offset program launching today. According to the companies, the $1.25 offset charge represents the cost of offsetting the CO2 impact of the average rental vehicle operating in the company's fleet. TerraPass, the company responsible for delivering the offsets through planting trees and other carbon-reduction projects, claims that 13,500 metrics tons of CO2 will be offset for every 100,000 customers that participate in the scheme. The three rental companies, which describe the program as a "simple but meaningful way to address the environmental impact of renting a car," have also pledged to match up $1 million of offset purchases.

However, amid all the green intentions and backslapping, the environmental benefits of carbon offsetting have come under increasing scrutiny as the market for offsetting expands. With more than $54 million spent in 2007 on CO2 offsets on everything from airplane tickets to laptop computers, the FTC is starting to look into green marketing claims made by companies that are suspected of trying to "greenwash" their images. Don't get me wrong--I'm all for any initiative that makes some impact on CO2 reduction. But turning down your free upgrade to a Chevy Suburban next time you're in a rental car center might be just as environmentally beneficial.