Green Plains Renewable Energy's first ethanol-producing plant came online in Iowa in 2007, producing 15 million gallons that year. Now the company's nine plants produce 740 million gallons of the fuel annually, making Green Plains the fourth-largest ethanol producer in North America. In the last 12 months, the company posted $37 million in net income, $2.9 billion in revenue, and saw its ninth consecutive quarter of profitability.

Green Plains's rapid growth comes mainly from acquisitions. The company built its first four ethanol plants itself, and then bought the following five (including one earlier this year). But only 58% of the company's profits come from ethanol. Green Plains also has a large presence in agribusiness, buying, storing, and selling corn, soybeans, wheat and oats. Its next great experiment: using ethanol production byproducts carbon dioxide and warm water to grow algae for use in food and fuel.