CONCORD, N.H. — At the end of his freshman year, Alex Freid was disgusted by all the furniture, electronics, and other belongings his fellow University of New Hampshire students were tossing into the trash as they moved out for summer break. Three years later, he is leading a nonprofit that aims to help other campuses start waste-reduction programs like the one he created at UNH. The nonprofit group called PLAN: The Post-Landfill Action Network, builds on the success of the three-year-old student-led Trash 2 Treasure program at UNH, which involves collecting usable goods that otherwise would be discarded, cleaning and organizing them, and then selling them at a massive yard sale when students return to campus in the fall.That program has diverted more than 100 tons of materials, saved the university more than $10,000 in disposal fees, and generated more than $30,000 in revenue, which has been reinvested in other sustainability initiatives, such as a bike sharing service. And it led Freid, a double major in political science and philosophy who graduated in May, to a full-time job focused on spreading such programs to other schools.‘‘We’ve always had people come up to us and say, ‘Oh, man, this is such a great idea, why don’t other campuses do this?’ So it kind of got to a point where it was inevitable,’’ he said Friday.The network has approached 77 schools across New England so far, and more than two dozen have expressed interest. At least six have committed to applying for what the network calls Phase 1, including Plymouth State University in New Hampshire and the University of Massachusetts Amherst. At that level, PLAN provides start-up funding to student groups.