A growing medium made from Styrofoam could lead to lighter rooftop gardens, according to this piece. "Gaia soil," developed by biologist and plant scientist Paul Mankiewicz, consists of Styrofoam and pectin that is able to hold water. "[I]f you coat a cubic foot of Styrofoam, which weighs 10 pounds, with pectin, it will hold 20 pounds of water. And that’s the trick," Mankiewicz said. The "soil" has been used on several rooftop gardens at the New York City Department of Parks & Recreation, according to Artie Rollins, assistant commissioner of citywide services.