The 300-student College of the Atlantic, has become the United State’s first and only carbon-neutral college campus. Grist, an environmental magazine, now considers the campus and school to be the greenest in the country.

With only one major, human ecology, the private institution spent $25,000 over the last 15 months to offset 2,488 tons of emissions. The school bought carbon offsets through The Climate Trust of Oregon, which reduces carbon dioxide emissions through the optimization of traffic signals and the management of traffic flow in the state’s city of Portland. Essentially, the organization aims to reduce the amount of time that cars spend idling at traffic lights.

The College of the Atlantic, located in Bar Harbor, Maine and voted one of the 222 Best Northeastern Colleges by The Princeton Review, is the first to achieve its goal among more than 450 universities to take the net-zero pledge through the American College and University Presidents Climate Commitment program.