HARRISBURG - Pennsylvania has made more than a half-billion dollars from logging and oil and gas exploration on state forest land since 1935. Now, the state's parks and forests department is considering using its land to harvest another natural resource, the wind, as a way to promote clean energy.

Officials have been discussing the idea for a few months and say they are still studying whether wind farms on state land will be feasible.

But with 2.1 million acres of state forest land blanketing some of Pennsylvania's highest ridge lines, forestry officials say there is plenty of possibility. The wind-power industry has noticed and approached the department in recent months, said Michael DiBerardinis, the secretary for the Department of Conservation and Natural Resources.

"I think we're attractive by the sheer size of what we own, but then where we own it," DiBerardinis said in a recent interview.

Plus, he said, wind energy can help reduce reliance on coal-fired power plants, a source of the acid rain that damages forests.

In this pursuit, Pennsylvania has plenty of company: At least a dozen other states are engaged in or discussing putting wind farms on public land. Most are in the western United States, where a handful of wind farms already dot state lands.

Plus, the federal Bureau of Land Management is hoping to multiply the 500 megawatts of wind power already generated on its land to more than 3,200 megawatts by 2025.

On private land, Pennsylvania has five wind farms producing 129 megawatts - enough to power almost 40,000 households - the most of any state east of the Mississippi River, with two more set to open this year.

For now, the department legally cannot authorize a wind farm on state land, so it would have to obtain the right from the Legislature.

And pinpointing a suitable location for a wind farm could take a while.

Officials have a long list of factors to consider, including the impact on animals and forests, the location of transmission lines, and the massive turbines' wind exposure and visibility.

They expect only a small fraction of state forest land will be suitable.

"Right now our gut is that we're talking a few percent," said John Quigley, the department's newly hired director of operations. "Probably a single digit percent of all state forest land might - might - be appropriate."

Quigley and others also cannot predict how big any wind farm on state land would be. For instance, the turbines could generate money for the state by pouring electricity into the regional grid, or they could simply generate electricity for forestry offices.

Environmental advocates say they favor wind-farm development as long as the department makes the planning process open to the public and ensures that builders meet strict environmental guidelines.

Lowell Graybill, the past president of the Pennsylvania Federation of Sportsmen's Clubs, said his members have reservations. They recognize the value of clean energy, but don't want public land to be fenced off, he said.

Brent Alderfer, president of Community Energy Inc., a wind-farm developer and marketer based in Wayne, said he believes the rural character of state lands can create opportunities for wind farms that can be tough to find in the eastern United States.

"When you look at the state and the region and you say, 'Where is a good place to properly site wind farms?' it turns out that the state-owned lands and state game lands probably have some of the best sites," Alderfer said.