Even as we green folk take steps to reduce our ecological impact – diverting waste through recycling and composting, energy-proofing our homes, buying local – environmentally minded travel is still a challenge.

In Boulder, Colorado, an extensive network of convenient bike paths" and solid bus service make it easy to leave the car in the driveway for days on end. To get out of Boulder, however – say, to a green building conference in San Jose – is more complicated. Denver International Airport is about 45 miles away; driving there releases 34 pounds of carbon dioxide into the atmosphere. The two-hour DEN-SJC flight will pump out another 1600 pounds; double that for your return trip.

One way to lessen your travel impact is to rent green. A number of alternative-fuel car rental options are available; you just have to know where to look.

• EV Rental, a small chain, rents only environmentally friendly cars. Pick up a Toyota Prius, Honda Civic hybrid or a Ford Escape hybrid from airports in Phoenix, Las Vegas, or around California.
• Bio-Beetle Eco Rentals started renting biodiesel-fueled Volkswagens in Maui three years ago; last month, they opened a Los Angeles branch. (They've also started renting biodiesel Jeep Liberties on Maui.)
• And just this week, Enterprise Rent-A-Car added five biodiesel vehicles – Jeep Liberties – to its rental fleet in Portland, Oregon.
• If you're not headed for any of these locations, one last option: Toyota rents available Prius models to prospective buyers. What better time to try one than between green conference meet-and-greets?