For 25 years, Gary Hirshberg, the co-founder and "CE-Yo" of Stonyfield Farms, has shown that making yogurt doesn't necessarily require the same old culture. From the get-go, this environmental activist has used his decided capitalist venture as a laboratory to promote green business practices. Along the way, he's harnessed his idealism and iconoclasm to build one of the leading brands in the dairy case. All the while, he's demonstrated that getting bigger doesn't necessarily mean having to lose one's passion or values. GreenBiz executive editor Joel Makower talked with Hirshberg recently on the occasion of the publication of his new book, Stirring it Up: How to Make Money and Save the World.