This may be a long-shot, but it's an exciting possibility:
A microscopic green algae -- known to scientists as Chlamydomonas reinhardtii, and to regular folk as pond scum -- was discovered more than 60 years ago to split water into hydrogen and oxygen under controlled conditions. A recent breakthrough in controlling the algae's hydrogen yield has prompted a Berkeley, California, company to try to be first to commercialize production . . .
Melis found that algae must eventually be supplied sulfur to survive, but he was able to repeatedly switch hydrogen production on and off by changing the algae's environment.
Melis launched a company, Melis Energy, in 2001 to try to commercialize a technique that harnesses algae's ability to turn sunlight into hydrogen. In the fall of 2001, the company built a bioreactor containing 500 liters of water and algae that can produce up to 1 liter of hydrogen per hour. A siphoning system extracts the hydrogen, which is stored in its gaseous state.
The company is continuing to refine the process and improve its reliability, while also searching for investors so that it can increase production volume . . .
He said that his team of researchers at Berkeley has thus far only been able to achieve 10 percent of the algae's theoretical production capacity, but in the near future he will publish an advancement for peer review. Once the process reaches a 50 percent yield, Melis said it would be cost-competitive with fossil-fuel energy . . .