We're rounding out the week on a green note, inviting Adam Stein to share his thoughts on green travel and on the way his company Terrapass is providing options to make it even greener.

Green travel has become quite the buzz phrase lately. Unfortunately, it's also a bit of an oxymoron. Aviation is one of the swiftest growing and most intractable sources of the greenhouse gas emissions that are the primary cause of global warming.

Mile for mile, flying isn't so bad. On a per passenger basis, a plane actually gets slightly better mileage than a hybrid automobile. So what's the problem? Well, the sheer number of miles adds up quickly. A large jet burns about a gallon of fuel per second. On a round-trip cross-country flight, that equates to hundreds of tons of emissions.

My company, TerraPass, is focused on funding clean energy and efficiency projects that reduce greenhouse gas emissions. Naturally, we make an effort to reduce our own emissions as much as possible. But travel is a tough nut to crack, which occasionally leads to some creative thinking on our part.

For example, a colleague who recently got married decided to take his wedding on the road. Rather than having everyone fly to the ceremony (which would have created a ghastly amount of emissions), the bride and groom instead flew to the guests. They had one celebration in California and another in England. End result: fewer total emissions, twice the fun.

Businesses don't always have this sort of flexibility, which is why plane flights are the single biggest environmental impact for many companies. That's right -- unless your company has a smokestack or a huge number of computer servers (think Google), your single biggest impact is probably from flying.

What can you do? In addition to conserving, consider balancing those flight emissions by sponsoring emissions reductions elsewhere. Through a partnership with TerraPass, Expedia Corporate Travel makes it simple to balance your emissions from flying by funding clean energy and efficiency projects. Check out http://www.expediacorporategreen.com/ to learn more.

-Adam Stein