At $100 a ton, feeding a landfill is pricey. But in the past two years, General Mills has turned its solid waste into profits. Take its oat hulls, a Cheerios by-product. The company used to pay to have them hauled off, but realized they could be burned as fuel. Now customers compete to buy the stuff. In 2006, General Mills recycled 86% of its solid waste, earning more from that than it spent on disposal.