Fred Tennant thinks algae — those slimy little creatures from your biology textbook — will save the world. Here's how: the company PetroAlgae, where Tennant is vice president for business development, raises algae, which it then uses to make oil for biofuels. The benefit is twofold: first, algae provide a source for biofuels that, unlike corn or sugar cane, doesn't compete with food (unless you have a taste for algae sandwiches). Even better, the algae are capable of feeding off the carbon emissions from fossil fuels, and the pollutants in waste water. If the technology matures, you could have a perfect circle: the algae eat the carbon from a coal plant, then are used to make an environmentally friendly fuel that limits the need for petroleum. PetroAlgae is still a long way off from commercialization, but the technology has some greens salivating. "Algae consume a tremendous amount of CO2, and we're in a marketplace where getting rid of CO2 is a very good thing," says Tennant. "We're looking at a carbon-negative solution."