Houston (Tex.) -- Environmentally-minded coalitions are working overtime to block construction of all new coal-fired power plants in the United States after a "watershed" year in 2007 when plans for dozens of coal units were delayed or scrapped, said one environmentalist.

After years of limited success against power-plant construction, concerned groups were buoyed last year by action in California and Florida to restrict imports of power produced from coal. Coal generators release about 40 percent of U.S. emissions of carbon dioxide, a gas blamed for global warming.

Even more supportive was a Kansas ruling that denied permits to build new coal units by Sunflower Electric.

"Kansas was a major, major victory," said Bruce Nilles, director of the Sierra Club's national effort to block coal plants. "In 2008, we will really begin to act on stopping the majority of these coal plants."

State regulators in Montana Friday rejected a request from environmentalists to require a cooperative to install the same controls on CO2 -- which is not regulated in the U.S. -- as it plans To use on regulated pollutants at a new coal plant, but the fight is far from over, said Abigail Dillen, an attorney with Earthjustice.

Dillen said the group will appeal a decision by the Montana Board of Environmental Review in favor of the 250-megawatt Highwood plant proposed by Southern Montana Electric. Highwood is also being challenged in federal court over its long-term funding source, the U.S. Rural Utilities Service, Dillen said.

In Georgia, an environmental group said it would appeal last week's ruling to uphold issuance of an air permit for Dynegy's 1,200-MW Longleaf coal plant.

While opponents said developers did not thoroughly evaluate the plant's impact on air quality, Dynegy spokesman David Byford said its joint venture with LS Power builds generation based on the needs of utilities that will buy the power.

"We're going with the technology that we believe our customers are asking us for," said Byford.

In Arkansas, local landowners plan to appeal last month's regulatory ruling to grant a certificate of need to a unit of American Electric Power Co to build a 600-MW coal plant in Hempstead County. An appeal will be filed this month at the Arkansas Court of Appeals, said Little Rock attorney Chuck Nestrud.

In Kentucky, a coalition, including the Sierra Club, the National Parks Conservation Association and others, has notified the U.S. Environmental Protection Agency that it may file a lawsuit after that agency failed to act on a petition opposing Peabody Energy's 1,500-MW Thoroughbred coal plant in Muhlenberg County.

While the strategy differs from state to state, the groundswell of opposition to coal projects grew steadily in 2007, said the Sierra Club's Nilles.

"We're seeing a lot of action on the state level on a scale we've never seen before that is really taking the market away from the coal industry by requiring a certain amount of generation to be from renewables," such as wind and solar power, Nilles said.

New coalitions combine traditional environmentalists, local landowners, religious groups and elected officials.

"It is now a broad cross-section of people who say we need urgent action on global warming," Nilles said. "The first thing we need to do is not dig the hole any deeper" with new coal plants.

Building new coal plants locks the country into a supply of carbon- intensive power and may hurt investment in renewable technology and efforts to increase efficient use of power which can slow the growth in demand for new generation, he said.

Utilities and the coal industry argue that new coal plants can operate with lower emissions than are needed to guarantee a reliable source of future power generation.

(Editing by Marguerita Choy)