HARRISBURG -- An environmental coalition is at odds with natural gas drillers over whether the state should slap a "severance tax" on natural gas that is extracted from the vast area of underground Marcellus shale in Pennsylvania.

Penn Future, Audubon Pennsylvania, the Nature Conservancy, the Pennsylvania Land Trust Association and more than 30 other "green" groups said yesterday the state could reap at least $100 million in new revenue from a natural gas severance tax, also called an extraction tax.

They said other mineral and oil-rich states, such as Texas, Oklahoma, West Virginia and Louisiana, impose a tax on such natural resources.

But the oil and gas industry quickly objected. Natural gas companies are just now deciding "where their manpower, equipment and resources should be committed" to take advantage of the Marcellus shale resources, said Oil and Gas Association President Stephen Rhoads.

Pennsylvania is in tough competition against other states for the industry's investment and attention, he said. Putting a severance tax on this new energy resource "just as the industry is getting a foothold on this important shale development, will have a considerable negative impact on the state's ability to compete with those states," he said

The environmental groups claim the $100 million could boost the state's environmental stewardship fund, which pays for cleaning up streams and protecting state forests, and could help the state Fish and Boat Commission, the state Game Commission and county and municipal governments. The latter often face added costs, such as repairs to roads and bridges, and damage to the environment caused by drilling equipment.

The environmental groups estimated that Pennsylvania could have as much as 363 trillion cubic feet of natural gas deep underground, in the three-fourths of the state that is covered by Marcellus shale deposits. That could be worth as much as $1 trillion.

This severance tax would be in addition to natural gas leasing fees that the state already imposes on drillers. Gov. Ed Rendell wants to use $174 million from those lease fees to help erase the estimated $2.3 billion budget deficit for 2008-09.