Green Bubble or Green Opportunity? Editor-in-Chief Amy Cosper talks about how going green can be a game-changer for all sectors.

The amount of money flowing into alternative energy is mind-blowing. Last year, VCs dropped $4.9 billion into the sector. Add to that the $79 billion allocated by the federal government's stimulus plan and . well, you get the picture.

The problem is that the sector is flush with greenbacks and tax credits but shy on profit and margin. Whether it's solar, wind, biofuel or geothermal technology, the question looms: Is the business of sustainable energy a sustainable business?

In this issue, we tackle that paradox by examining the business models of several alternative energy and cleantech companies. These well-funded companies are not only raking in the cash, they also are creating a new supply chain--which is where many entrepreneurs are finding real and profitable opportunities. (Be sure to read Julie Bennett's piece on the green bubble question.)