Thirsty for change, Mark DiMassimo and Eric Yaverbaum decided to fight global warming one liter at a time.

"This country buys 28 billion bottles of bottled water a year. We use 17.5 million barrels of oil to make those 28 billion bottles," says Yaverbaum. "That's enough to fuel 1 million automobiles for an entire year. It's two-and-a-half tons of carbon dioxide into the air."

The two entrepreneurs, seen above, created Tappening.com to promote the earth-friendly benefits of tap water. And sold 400,000 reusable bottles, grossing $6 million. In a way, they capitalized on the eco-crisis, and they are perfectly okay with that.

"Okay? It's the best combination that there is," says Yaverbaum. "You can make an impact, an environmental impact with really simple changes and you can make money doing it."

Going green to make green is hardly a new formula. Thousands of companies are shading their advertising with what's proven to be an effective marketing tool. But buyer beware - consumers need to scratch below the advertising claims.

"There are companies that have very energy-efficient or environmentally-improved buildings and factories but they're making Hummers in those factories," says Dale Bryk of the National Resources Defense Council. "You want to say, what is the real impact of the company as a whole?"

Steve Strauss, the author of "The Small Business Bible," says green consumption is more than a trend. He believes customers will reward businesses that take even small steps toward having a smaller impact on the environment.

"There are consumers who actually will make their purchasing choices based on whether you are a green company or not," says Strauss. "There's absolutely a whole ethic about it that people will reward you for that."

Meanwhile, more and more companies are churning out new eco-products in the hopes of mining some of this green gold.

"They respond to customers when customers want to stay looking young. They respond to customers when customers want expensive cars that pollute," says DiMassimo. "So all the better when they respond to customers who want to the world to be a greener place."

While money is been a motivator, the founders of Tappening do not feel that undermines the message.