"The idea behind TerraPass is simple. TerraPass allows individual consumers to tap into the growing market for carbon emission credits traded by large companies such as DuPont and IBM. These markets are structured in the same way as as the markets for sulfur emissions that were so successful in reducing acid rain."I promptly read through their entire site — the concept is fascinating. Their FAQ sums it up nicely:
Isn't buying a TerraPass essentially just a donation to preserve the environment?
Let's put that question in another context. Is cleaning up after your dog essentially just a donation? Is picking up your trash in the woods essentially just a donation? Cars make a mess; even if not as visibly as your dog. Clean up after your car.
Does TerraPass physically modify my car?
No. TerraPass is a market mechanism that tips the economic balance in favor of efficiency and renewable energy. This mechanism results in exactly counterbalancing the carbon emissions of your driving, without modifying your car physically.