Working alongside migrant farm workers in California as a young man, Thomas Fricke developed an appreciation for organic agriculture firsthand, dodging the pesticides raining from the overhead crop dusters.

As the daughter of a State Department diplomat and social investment professional, Sylvia Blanchet grew up with an interest in international affairs and a tendency toward economic activism.

“Investors go gaga over green,” reported National Public Radio in July 2007. “Investors are pouring money into alternative energy and so-called clean-tech firms, touted as one of the biggest economic opportunities of the century.”

But to David Schoenwald, who manages the New Alternatives Fund, a socially responsible mutual fund, the idea that “clean tech” is a promising investment isn’t news. He’s been focused on the promise of renewable energy for more than two decades. When he founded New Alternatives with his father Maurice in 1982, the elder Schoenwald wanted to invest in technologies like solar panels, which were promising alternatives to nuclear power and fossil fuels.

In February 2006, college buddies Vaughan Lazar and Michael Gordon started throwing around ideas for starting a side business for fun. Lazar owned a printing and design firm, and Gordon worked for a real estate company.

“He was fed up with what he was doing, and I was bored with my business,” says Lazar, CEO of Pizza Fusion. The two decided to start a pizza restaurant because they liked pizza—eating and making it—and because it made good business sense; Americans eat approximately 100 acres of pizza each day, or about 350 slices per second. It didn’t take them long to start thinking of ways they could green their dream company.

When Greenmaker Supply won one of the 2006 Innovate Illinois prizes awarded to the state’s most innovative small businesses, the green home-improvement retail store was not even a year old yet.

The store was a perfect fit for Chicago, a city where the mayor’s very public commitment to green principles includes a 2004 executive order that Chicago’s new public buildings must be built with eco-friendly designs and materials. Greenmaker Supply helps homeowners make that commitment, too.

“Green building is something I’ve always been interested in,” says co-founder Ori Sivan, who has a master’s degree in environmental engineering. “Business is the biggest engine for innovation, and while I could have gone into engineering or academics, I thought the thing to do was start a green business.”

In Colonial America, most houses had their own cow to provide milk, and were situated near a community lime pit for agricultural and construction uses, says Anne Thibeau, president of the Old-Fashioned Milk Paint Co. Itinerant painters wandered the countryside, offering their services to homesteaders and shopkeepers. They carried rainbow sets of pigments, which, when mixed with a customer’s own milk and lime, would create a milk paint that added soft color to furniture and walls.

Jeff Lebesch was already a homebrewer of beer when he set off on a bike trip across Europe in 1986. Belgium’s famous beers inspired Jeff to duplicate their flavors once he returned home. He produced an amber ale and a brown dubbel (a darker “double ale”) named, respectively, Fat Tire and Abbey in honor of his trip, and won rave reviews from friends and relatives for their flavors.