Nikhil Arora and Alejandro Velez were recent grads who were supposed to go into investment banking, but they became obsessed with the idea that mushrooms could be grown in old coffee grounds, reports Sarah Stankorb at GOOD. Faster than you can say “triple bottom line” they’d interested their local Whole Foods in their first batch of mushrooms — grown in a bucket in the basement of Velez’s fraternity.

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Fast forward to the present, and their company Back To The Roots is collecting, en masse, the used coffee grounds that were previously a nuisance to baristas everywhere. They grow gourmet mushrooms in the grounds, then turn the leftovers into an organic, chemical-free fertilizer that competes with Miracle Grow.

These guys are serious about reuse — they even build their store display cases out of old shipping palettes. “Our display units in Home Depot are now made from their own spent waste,” Arora told GOOD.

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Update: Hey, Grist is so cutting-edge we don’t even know how cutting-edge we are! Check out our interview with Arora and Velez from a whole year ago.