PORTLAND – Two mountain climbers from Maine have set their sights on the world’s tallest peak.

Bill Yeo, 40, of Durham and John Bagnulo, 35, of New Vineyard will set out next month for Mount Everest, ascending from the less-traveled north side, out of China. They are preparing to climb without Himalayan mountain guides and without the use of supplemental oxygen.

Yeo, a hiker and climbing guide, will be conducting a soil study while climbing the 29,035-foot peak. He will collect samples every 1,000 feet, and later test them at the University of Southern Maine for metal deposits from utility and factory smokestacks in China.

Bagnulo, a former professor of nutrition and exercise physiology at the University of Maine at Farmington, will also do some field work during the climb, looking at the use of natural supplements for high-altitude climbers.

Before the climb, Yeo and Bagnulo will spend weeks becoming acclimated to the thin air of the Himalayas and getting their bodies tuned for an assault on Everest’s summit.

Bagnulo and Yeo have climbed Aconcagau, the 22,831-foot peak in the Andes and the Western Hemisphere’s highest land mass. In 2001, Bagnulo attempted, then halted, an ascent on Lhotse, a 27,890-foot Himalayan mountain.

Yeo, who works at L.L. Bean, has made four ascents of 20,320-foot Mount McKinley, North America’s highest peak.

Climbing from the northern side of the mountain has its advantages, Bagnulo said.

“There’ll be less people, and it’s a fraction of the cost to climb from China,” he said. Some say the north side presents a harder, more technical climb, as well. “There’s a lot of rock and not nearly as much snow,” Bagnulo said.

Once they get settled at their base camp, they will begin to portage more than 500 pounds of food plus another 300 or so pounds of gear up the mountain, first to an advanced base camp, then in stages to the point where they’ll be near enough to the summit to attempt the final push. They’ll stay at each camp level for several days, adjusting to the air.

The actual assault on Everest won’t happen until near the end of April, or perhaps even in early May.

The adventure is costing each man a minimum of $15,000, a sum they regard as money well spent.

“I like to expose myself to new places and experience new things,” said Yeo, who also enjoys the culture of mountaineers.

Bagnulo said he thrives on adventure, adding that it’s far more dangerous to live without risk. That kind of life “kills your spirit – your soul,” he said.