Japanese sailor Kenichi Horie, who has sailed nonstop around the world and crossed the Pacific in a solar-powered boat made of recycled aluminum beer cans, is off on his next solo adventure at sea.

Horie set sail for Japan yesterday from the Hawaii Yacht Club on what he says will be the world's longest voyage in a wave-powered boat.

The 69-year-old mariner will travel nearly 4,000 miles (6,400 kilometers) aboard a 3-ton yacht called the Suntory Mermaid II at a speed of up to 5 knots. The journey, which would take a diesel-powered boat about 10 days to complete, is expected to take Horie about 2.5 months.

The boat made of recycled aluminum relies on the energy of waves to move two fins at its bow and propel it forward. Horie has described it as a sturdy vessel, designed to right itself if it capsizes. Still, it is equipped with an engine and 35-foot sail mast for emergencies.

His head full of leis, Horie waved to dozens of people who had gathered to see him off as the catamaran left Honolulu Sunday.

"So many people came to see me...I can leave with a very good spirit," he said through a translator.

Horie acknowledged he was a little bit scared.

Horie planned to carry rice, canned food, microwaveable meals and beer on the trip. Solar panels on top of the catamaran will allow him to power a microwave.

He will have a satellite phone and access to e-mail. He also planned to take books to read and listen to the radio.

Ken Dota, who is promoting Horie's voyage, says the sailor hopes the shipping industry will eventually adopt the clean wave technology.

The journey would not be Horie's first time traveling the seas using green technology. In 1992, he powered a boat by pedaling from Hawai'i to Okinawa. And in 1996, he sailed nearly 10,000 miles from Ecuador to Tokyo aboard a solar-powered boat made from recycled aluminum beer cans.