Last week was a big one for the assessment of higher education in America — U.S. News and World Report released its 2011 rankings, and Washington Monthly rolled out a new rankings system that flips traditional lists upside down and "asks not what colleges can do for you, but what colleges are doing for your country." And Sierra magazine, the publication of the Sierra Club, published a list called "Coolest Schools," which ranks institutions of higher education based on how green, or environmentally friendly they are.

Sierra created its 162-school list after collecting surveys from participating colleges made up of a grueling 10 categories: Energy, Supply, Efficiency, Food, Academics, Purchasing, Transportation, Waste Management, Administration, Financial Investments and Other Initiatives, and then evaluated each school that responded based on the criteria. Sierra admits that the rankings are not comprehensive: "There are more than 2,000 four-year colleges and universities in the United States, meaning that the schools on the ‘Coolest Schools’ index are in the top 10 percent when it comes to the environment," the magazine says. But the Sierra Club is hopeful that the list will give schools and students the opportunity to build on their environmental accomplishments in the coming years. Sierra says that for many schools looking to take a more environmentally friendly path or hoping to expand what they’ve already done, purchasing cleaner sources of energy is a crucial step.

Below, we give you Sierra‘s 20 greenest schools. Green Mountain College in Poultney, VT, which uses power from the heat and biomass of cows and plans to be carbon neutral by next year, tops the list.

1. Green Mountain College in Poultney, VT

2. Dickinson College in Carlisle, PA

3. Evergreen State College in Olympia, WA

4. University of Washington in Seattle, WA

5. Stanford University in Stanford, CA

6. University of California, Irvine in Irvine, CA

7. Northland College in Ashland, WI

8. Harvard University in Cambridge, MA 

9. College of the Atlantic in Bay Harbor, ME

10. Hampshire College in Amherst, MA

11. [TIE] University of California, Santa Cruz in Santa Cruz, CA

11. [TIE] Middlebury College in Middlebury, VT

13. University of Colorado, Boulder in Boulder, CO

14. Warren Wilson College in Asheville, NC

15. University of California, San Diego in San Diego, CA

16. [TIE] University of California, Davis in Davis, CA

16. [TIE] University of Vermont in Burlington, VT

18. Georgia Institute of Technology in Atlanta, GA

19. University of Pennsylvania in Philadelphia, PA

20. New York University in New York, NY

Get the complete rankings here. Your school not on the list? Get in touch with the Sierra Club about how you can participate in the next green schools survey.