$25 million

Prize in the Virgin Earth Challenge, which will be awarded to the individual or team to come up with a commercially viable design that accomplishes or appears capable of achieving the net removal of significant volumes of man-made greenhouse gases annually for at least 10 years.

Sir Richard Branson, of the Virgin Group, and former Vice President Al Gore are two of the six judges for the competition, which was launched in February 2007. As of the end of September, 900 entries had been received. A review of entries that made the first cut will take place next February.—Kimberly Janeway | e-mail | Twitter | Forums | Facebook

Essential reading: Use less energy and save up to $1,500 on your annual utility bills. Read our reports on pellet stoves and solar water heaters and find out which compact fluorescent lightbulbs top our ratings (available to subscribers).