The governor of Colorado is expected to sign a bill later this month that encourages a major power company to switch from coal to natural gas as a way to slash harmful air pollutants and begin the process of addressing climate change.

Gov. Bill Ritter's (D) April 19 bill-signing will be the culmination of a monthlong slugfest pitting Colorado's coal industry against big gas producers drilling in the state's sparsely populated west.

Tension in the energy sector about the extent to which state and federal policies should incentivize utilities to retire coal plants and instead use gas is palpable on a national level. Gas burns cleaner than coal, emitting half the amount of greenhouse gases as well as far less ozone and haze-causing nitrogen oxide. Yet on the national stage, coal is still king.

Colorado Gov. Bill Ritter (D) helped negotiate the coalition that turned his state's largest utility from coal to natural gas.

In the more self-contained political dimension of Colorado, though, coal lost its latest battle. Xcel Energy Inc., the state's largest utility, approached the governor's office and lawmakers about a rapidly approaching January deadline for the state to submit cleanup plans with U.S. EPA.

Quietly, the lame-duck governor, Xcel executives, gas producers and environmental groups negotiated and built a coalition of support that attracted a Democratic majority and the Senate's Republican leader. In another political twist, two members of the Legislature slated to run against each other co-sponsored the bill.

In early March, bipartisan co-sponsors from the state's urban center and gas-producing areas on the Western Slope introduced a bill that requires Xcel Energy to cut nitrogen oxide emissions nearly 80 percent by 2017 at aging coal-fired power plants in the Denver and Boulder region. To get there, Xcel will have to pull together a list of options later in the year for retrofitting those plants or switching to cleaner sources, putting some emphasis on natural gas. The bill also includes regulatory fixes for concerns about gas price volatility.

This coalition of strange bedfellows rushed it through committee and passed it out of the state House and Senate in a span of three weeks.

"The argument was, 'Get ahead of the big, bad dog coming after us, and that dog is coming out of Washington,'" said John Straayer, a Colorado State University political science professor.

Coal industry predicts 'energy poverty' for Colo.

The coal industry and its mostly Republican supporters in the Senate blasted the bill as a jobs killer, a recipe for skyrocketing electricity prices and a disaster for declining coal producers operating in the northwestern corner. The debate heated up quickly as television and newspaper ads illuminated the coal-versus-gas fight.

Once the bill passed, the Colorado Mining Association condemned the legislation.

"It makes no sense to ignore coal as an energy source," said CMA President Stuart Sanderson, who according to sources was a ubiquitous figure in the Capitol during the heady debate. The mining group said in a release after passage that it is considering ways to limit the impact of a resource plan to be submitted to the Colorado Public Utilities Commission in August.

"Meanwhile, the industry will continue to demand that Xcel Energy include emissions control technologies in its resource planning, in lieu of the path currently chosen that will lead to energy poverty in Colorado," said the mining organization.

Xcel spokesman Mark Stutz insisted that the company doesn't necessarily have a preference with regard to coal or gas, but he said Ritter pushed hard for gas to be emphasized in the bill -- and that helped build consensus around a path forward to meet U.S. EPA standards. "We're going to need some assurances and protections from the gas industry," Stutz said, referring to price volatility.

The gas industry has said the ups and downs in gas prices that have scared off regulators and policymakers for a decade won't be nearly as bad in the future. Growing and long-term supply growth in tight-sand and gas shale basins will keep prices in check, and ultimately keep electricity prices down.

Straayer says gas has an edge in Colorado. Gas is drilled on both ends of the state, those jobs don't appear to be going away, and gas development still has broad support from a political standpoint in a state where politicians tout environmental stewardship.

The Sierra Club joined other environmental groups in supporting the measure. The Colorado Legislature this month also adopted a 30 percent by 2020 renewable energy standard for utilities, and Sierra Club regional representative Roger Singer said that also upped the ante for Xcel to begin the slow turn toward burning more natural gas.

Gas is the "bridge fuel" and backup fuel for intermittent wind and solar power, Singer said, but he said there continues to be concern about the impact that developing the fossil fuel has on the land.

"It's cleaner at the power plants," he said, "but we just need to make sure we don't lose what gains we have here during the development stage."