Todd Nelson, a Columbia sophomore, plans a double major in environmental science and history with a focus on industrialization and the rise of consumerism. He sleeps next to a worm bin where he composts food scraps.

He’s one of 13 students in Columbia’s GreenBorough dorm, where an experiment in sustainable living launched this semester is a competitive sport.

Showers are limited to five minutes (Nelson’s personal record is 1:50). A chart on the wall keeps track of offenders who forget to turn off lights and unplug appliances.

“We’re semi-paranoid about leaving on lights,” Nelson said. “We try to implement social pressure.”

The house won’t buy anything wasteful — like plastic cups — so its “off-the-grid” party two weeks ago had acoustic-only bands, flashlights, and was BYOC — Bring Your Own Cup.