Middlebury College hasn't divested, but it has empowered a student group to try to show administrators how. (Bgblogging/Flickr CC).

At Harvard Tuesday morning, environmentalists and student activists expanded their blockade of Massachusetts Hall, blocking University Hall. The protesters are demanding Harvard sell off fossil fuel stocks in its $36 billion endowment. Today, WGBH's Kirk Carapezza explains why divestment is not so easy and how colleges are trying to foster a sensible conversation about climate change.

Middlebury College, tucked between Vermont’s Green Mountains and Lake Champlain, is known as environmentally friendly. So it’s not surprising that students there, like thousands of others across the country, want their college to stop investing in fossil fuel stocks.

What Middlebury did to address students’ concerns, though, is surprising. The school gave a group of students the chance to manage a small portfolio of the school's endowment.

Over the past year, RISE, or the Research and Investment in Sustainable Equity student club, has invested $150,000 of Middlebury's $1 billion endowment in 12 different holdings – companies ranging from healthcare, biotech and even solar energy.

But what they haven't invested in is fossil fuel stocks.

As students across the country urge their universities to divest their endowments from fossil fuels, RISE is trying to prove it's possible.

Over the past year, they've gotten a 3.5 percent return on their investment. That's compared to the 15 percent average for college endowments.

“It’s been a learning process for all of us,” said junior Marie Henneburg, a member of the student investment group. “Being pragmatic people, we are aware that investors are not willing to give up returns.”

Related: Amid Calls to Divest, Schools Explore Green Revolving Funds

But it's not just about giving up returns, it can be logistically challenging for a school to divest. Middlebury pools its endowment with other schools and foundations. Those funds are a complicated mix of stocks that are challenging to dissect.

It all makes the divestment move pretty daunting. Still, there’s a groundswell of students trying to force change. Two hundred miles south of Middlebury, on the campus of Tufts University, students are still rallying for divestment.

In January, Tufts President Tony Monaco told student activists that it wasn’t possible.

“The students are still asking us to divest even though we looked at it hard with student representatives in the room,” Monaco said. “It doesn't mean we can’t come back and revisit it. We did leave the door open.”

But Tufts also opened a new door by agreeing to invest in green technology. This spring, the school is breaking ground on a new central energy plant, plus it’s increasing solar panels on campus.

“That’s a direct investment in a green effort which will have payback to this university,” said Monaco.

Listen: WGBH's Science Editor Heather Goldstone explains what effect divestment would have.

For students who are passionate about the issue, it's not enough. Sophomore Mary Lipscomb said she’s frustrated with the administration.

“Climate change is the biggest problem facing our generation,” Lipscomb said. “And it is a social justice issue, even though it is not frequently talked about as one.”

Lipscomb is from Bow, New Hampshire, and she directs the university’s sustainability group. She wants Tufts to fully divest.

“The administration is very slow to change and they market themselves as progressive and as open to change but it’s a business and you have to put enough pressure on them to get them to be willing to do anything,” said Lipscomb.

Right now, Mary understands it might not be financially possible, and she says that disruptive stunts -- like blocking administrative buildings -- have given the divestment movement a bad name on campus.

But she and other students say that without a little disruption, nothing is going to change.

This is the second story from WGBH's On Campus in a week-long series, The Cost of Divestment. The series was done in partnership with WCAI's Living Lab, a forum for the stories behind science headlines.