Meet the companies tackling nine of humanity's biggest problems -- and making millions saving us from ourselves.
Problem #4: Dirty Air
Problem #4: Dirty Air
The background: Three billion households worldwide depend on wood and charcoal to prepare food, but a person cooking over an open fire that's burning wood or kerosene inhales the equivalent of the smoke from two packs of cigarettes a day. Respiratory infections are the leading cause of death in children under the age of 5 and kill 1.6 million people overall each year.

The solution: Sun Ovens International, based in Elburn, Ill., sells a family-size solar oven for $259 that's used in 130 countries. A much larger solar cooker, including a trailer and a set of pots and pans, sells for $10,500 and is designed for schools, hospitals, and orphanages. The solar oven uses mirrors to redirect the sun's rays into an insulated box.

The ovens have been popular in Haiti; the United States and Canadian militaries will use them for humanitarian projects in Afghanistan, and they'll soon be available in Uganda and Nepal.

The payoff: Sun Ovens has sold about 32,000 of its family-size ovens and 260 institutional units. Last year it generated $720,000 in revenue.

The opportunity: Sun's CEO estimates there's a worldwide market for more than 300 million family-size solar ovens, which would generate at least $75 million in revenue annually.

Global Warming

Oil Dependency

Hunger and Malnutrition

Dirty Air

Dirty Water

Overfishing

Epidemics

Drug-Resistant Infections

Waste Disposal
8 technologies to save the world These futuristic projects promise to make the world greener, while making entrepreneurs some green. (more)
Blog: Can tech save the planet? Are green entrepreneurs the answer to our problems? Tell us what you think by posting a comment on the Green Wombat blog. (more)
101 Dumbest Moments in Business Business 2.0 Magazine's 7th annual look at the year in bungled layoffs, customer-service snafus, executive follies, and other madness. See all 101. (more)