Lawmakers are growing increasingly critical of a proposed carbon emissions rule from the Environmental Protection Agency because they say the technology on which it relies isn't commercially viable.

The EPA rule essentially would prohibit construction of new coal-fired power plants unless they install "carbon capture and sequestration," or CCS, technology. CCS generally receives heavy government subsidies when tested at large-scale power plants.

"We've got to stop the EPA from passing regulations that can't be achieved. They're hurting our jobs all across America," Rep. David McKinley, R-W.Va., said at a coal-industry-sponsored rally in Washington.

The technology involves trapping carbon emissions and pumping them underground, and would be necessary to keep carbon emissions under the EPA's proposed cap to combat climate change.

Most experts don't believe the technology is close to being ready commercially, and certainly won't be by the time the EPA submits its rule in June. As a consequence, industry officials and lawmakers say the rule is a de facto ban on building new power plants.

"Affordable solutions may be decades away with the current level of funding and resultant R&D strategy," said Charles McConnell, who ran the Office of Fossil Energy in President Obama's Energy Department until February, during a House Science, Space and Technology Committee hearing.

The Energy Department has awarded nearly $5 billion to CCS demonstration projects and will offer another $8 billion in federal loan guarantees this fall. But that's probably not enough to get the technology to commercial scale.

The Mississippi Power-run facility in Kemper County, Miss., secured $245 million in Energy Department funding through the first round of grants. It also has taken advantage of nearby oil fields to strike contracts with drillers to use the emissions it captures to unlock oil in a process known as "enhanced oil recovery."

The added revenue from enhanced oil recovery is a plus, spokeswoman Jeannice Hall said. But she said the EPA "should not assume that [the strengths of the Kemper project] are replicable throughout America."

When asked whether the project would have been economically viable without federal assistance, Hall did not answer directly.

The possibility that the technology won't be ready could prove fodder for lawsuits against the EPA.

Oklahoma Attorney General Scott Pruitt, who heads the Republican Attorneys General Association, said the EPA "has an obligation to prove" that CCS can be installed economically.

While the power industry has few plans currently to build new coal-powered plants, overall interest in CCS has waned partly because of objections to the policy and partly because the domestic shale energy boom has provided power companies with an abundance of cheap natural in recent years, said Howard Herzog, senior research engineer with the Massachusetts Institute of Technology Energy Initiative.

Still, the Obama administration maintains coal will remain part of the nation's power profile, and that CCS will play a role.

Herzog noted that the private sector invested heavily in research and development in 2008 when Congress was discussing a cap-and-trade bill that would have created incentives for installing the technology. But that effort foundered in the Senate in 2010 after passing the House, and put a freeze on climate legislation, prompting Obama to rely on executive authority to tackle climate change.