How long does it take for petroleum-based plastics to break down? Some say 500 years, but no one knows for sure. The scary truth is that they never completely disappear. But if you must consume plastic, you might as well put it to good use and grow some mushrooms. Huh?! That’s the theory behind Philips’s "paternoster." The conceptual contraption takes advantage of a remarkable feature of mycelium fungi: They can actually digest plastic. To work the gadget, the user feeds plastic containers into the top of what looks like a giant, old-fashioned coffee mill; turning the hand crank on the side moves the ground-up pieces of plastic along a dark conveyor circuit. Each week, the plastic grounds are mixed with mycelium; only after the fungi has had several weeks to metabolize the waste is it exposed to daylight (via an aperture) and allowed to sprout edible mushrooms. [figure=inline-large][caption][/caption][/figure] The plywood and copper and parts are made for self-assembly, and the exposed inner workings make the slow process of decomposition understandable to children. Now, if only it were available for purchase. For now, it remains a concept, Philips says, "intended to raise awareness about waste and natural methods of regeneration." The paternoster is part of Philips's Microbial Home, a domestic ecosystem that harnesses biological processes to break down waste and convert it into energy. To read about its urban beehive, go here; for the kitchen island, here.