Universities are dense with passionate, creative idealists. There's time to care about the world and energy to act. Young people are willing to be bold and take chances.

This is why colleges are at the forefront of sustainability. Their clientele demands it. Resolute students insist that their schools offer vegan food, divest from fossil fuel companies, shut down coal-fired power plants, and—not least—offer courses that enrich their understanding of the planet they hope to make their mark on.

When administrators and professors comply, they take what might have been a spurt of idealism and stretch it out immeasurably. They solidify the impulse to make the world a better place. The outcome can be the last sputter of an on-campus smokestack or a sculpture lamenting climate change's tragic fallout.

To celebrate the schools that honor their students' idealism by committing to the planet's big issues, Sierra has, for eight years now, tallied America's greenest universities. Our ranking is the result of an extensive survey, created in partnership with the Association for the Advancement of Sustainability in Higher Education. This year, 173 qualified schools spent a lot of time and effort responding. Click here to see who won—and perhaps to reawaken your inner activist.