#2 University of 
Colorado at Boulder 29,000 students Boulder, Colorado

Eight years ago the University of Colorado (CU) became the first U.S. university to buy renewable energy credits. Today the mile-high school supports local offset projects. CU does more than buy its way out of carbon guilt, however. The Buffaloes have also made strides in reducing emissions produced in the first place: Eighty percent of students

Transportation: Tuition covers city bus passes and loaner bikes. Most campus shuttles, or Buff Buses, run on biodiesel.
Curriculum: Students work at the forefront of climate and ocean studies through the Cooperative Institute for Research in Environmental Sciences (CIRES).

Energy: Only 7 percent of the school's energy comes from renewables; 85 percent comes from natural gas and the rest mostly from coal.

If you go Consider spending a semester studying ecology and conservation in Quito, Ecuador. You'll spend time in a cloud forest reserve and at a women's artisan cooperative

Score: 91.5

Photo by University of Colorado at Boulder/Casey A. Cass; used with permission.