Today's "clean economy" comprises about 2.7 million jobs, according to new research, but relatively few of these contribute major carbon cuts.

In a wide-ranging count of "green jobs," the Brookings Institution and Battelle identified hundreds of thousands of jobs in public transportation, waste collection and management, and organic food.

Jobs in renewable energy, electric cars and other low-carbon technologies played a small role. Businesses involved in renewable energy made up 5 percent of all clean economy jobs; nuclear energy contributed 3 percent.

"The vast majority of clean economy jobs produce goods or services that protect the environment or reduce pollution in ways that have little to do with energy or energy efficiency," the report says.

Nevertheless, it said, clean-energy jobs are following the larger trend in the clean economy. They are fast-growing, are manufacturing- and export-intensive, and offer better-than-average pay to workers with modest education.

The 2.7 million jobs also rank the sector among major U.S. employers. The fossil fuel industry employs about 2.4 million, and information technology employs almost 5 million, according to the report.

Brookings considered a business part of the "clean economy" if its product has "an environmental benefit or adds value to such products."

A spike in 'regulation' jobs

Nevertheless, the results left Matthew Stepp, a clean-energy policy analyst at the Information Technology and Innovation Foundation, unsure what to conclude.

He didn't mind seeing the large employment numbers in sectors such as conservation and regulatory compliance, and waste management.

"All those jobs in some aspect reduce emissions. But what number of those jobs are drastically reducing emissions ... those are a small part," he said. "I don't think that waste management can get us to 80 percent reductions by 2050, for example. I think batteries could."

By Brookings' count, "waste management and treatment" employs 386,000. "Battery technologies" employs about 16,000.

The report found almost 142,000 jobs in "regulation and compliance," a point that may cause Republican eyes to roll.

Freshman Rep. James Lankford (R-Okla.) recently scoffed at remarks by U.S. EPA Administrator Lisa Jackson, for example.

"She said a new rule was 'expected to create jobs,' because it will 'increase demand for pollution control technology,'" Lankford wrote at Townhall.com. "Apparently, government regulators and compliance officers are 'green jobs.'"

Do green jobs translate into votes?

Quotes like that cause advocates like Kyle Ash, senior legislative representative for Greenpeace, to wince.

Once, "green jobs" was the term that was going to power a climate bill through Congress. Now, some feel, it's a punch line. The low-carbon energy "advocacy community is struggling with the usefulness of that term in hindsight," Ash said.

"It's unclear that it worked," and supporters are unsure why, he said.

All the same, Ash believes members of Congress can still be converted to believe in clean energy as a real economic force.

Next week, Greenpeace will release a study targeting 15 congressional districts whose members, from both parties, are "voting the wrong way" on EPA regulations on coal pollution.

Fourteen of the 15 districts, Ash said, employ more people in renewable energy than in coal. The difference is acute in Michigan, Illinois and Ohio, he said.