By Mark Alpert

(FORTUNE Magazine) – Cork Foster, the owner of Berry-Hill, a small mail-order firm in St. Thomas, Ontario, had a mind-popping idea. Instead of using styrofoam ''peanuts'' as a packing material -- customers complained that it hurt the environment -- he decided this year to try popcorn, which is cushiony like styrofoam but also biodegradable. So Foster, 49, brought a popcorn popper to work and started to use its end product in shipments of incubators, egg sorters, and other farm equipment. Since popcorn costs 75% less than styrofoam, Foster figures on saving about $10,000 a year. Not bad for an outfit with $850,000 in annual sales. Customers loved the idea, not least because they got something for free. Some fed popcorn to their chickens, some used it for compost, and some -- ignoring the ''not for human consumption'' warnings -- ate it right out of the box. The news of the popcorn packaging spread quickly, and Foster has had calls from General Motors, IBM, Xerox, and other companies. He now has six Proctor- Silex poppers running full tilt to make the 100 pounds of popcorn he needs each day. His one regret is that he can't get a patent: ''I don't know how I can make a buck out of this.'' - M.A.