Environmentally conscious rental car drivers guilty about their role in releasing harmful greenhouse gases can now avail themselves of a program to purchase carbon offset credits.

Customers at Enterprise Rent-A-Car, Alamo Rent A Car, and National Car Rental now have the option of spending an additional $1.25 per rental, an amount that will be matched by all three companies up to a combined $1 million, for carbon offset programs.

The money raised will fund such projects as alternative electrical production by facilities like wind farms that reduce the release of damaging carbon dioxide into the atmosphere.

The carbon credits are provided in partnership with TerraPass, a company based in San Francisco, that both sells the credits and certifies that they are used in meaningful greenhouse gas reduction.

According to estimates generated by TerraPass, more than 300 million pounds of carbon dioxide will be offset per 100,000 participating rental customers.

In a pilot program to test customer reaction during the month of October, the three rent a car companies had approximately a thousand customers per day opt for the carbon credit.

The $1.25 fee was arrived at by TerraPass figuring an average fuel economy of 28 miles per gallon on the highway at a daily distance of 71 miles per day.

In a press release the CEO of Enterprise, Andrew Taylor, said, "The future success of our business requires us to have an abundant supply of vehicles and the fuel to power them. And both the vehicles and fuel must remain acceptable to society."