Winding down coal plants could account for a multibillion-dollar global business by the end of the decade, according to new research.

Analysts at Navigant Research, a division of the consulting firm by the same name, believe the coming wave of coal plant retirements creates a market opportunity for cleanup firms.

Between now and 2020, they said in a report released yesterday, companies that smash buildings, haul away debris and salvage polluted land could rake in more than $5 billion. Nearly all of that would be in Western Europe and North America, where coal has faced regulatory and market head winds.

“There was a time in the ’70s or ’80s when you could put up a fence, shut the thing down and essentially walk away,” said Richard Martin, editorial director at Navigant Research and author of the report. “These days, the regulations have evolved to the point you can’t really do that and it’s kind of a ‘pay me now’ or ‘pay me later’ situation.”

Coal is on track to retain a major role in the U.S. power mix, albeit a smaller one than its historical half-share. Cheap shale gas and tougher air pollution rules are called the main culprits.

But even when a coal unit pushes 50 or 60, it’s not always clear what to do. For some, retrofitting with pollution controls may pencil out. Others may see a chance to convert to natural gas units.

Martin forecast that through 2020, the majority of coal plants will wave the white flag: decommissioning.

This choice could have various business aims. A utility may obliterate the coal plant but keep the land for a future generator. Or, with sufficient cleaning, the land could be converted to public space.

Sometimes, investors try to capitalize on the real estate – with condominium or retail projects – as a very old coal plant may sit in the urban core.

It doesn’t always work. Martin described one abortive campaign to rejuvenate London’s Battersea Power Station. Multiple efforts have spun out over the decades, and last month, officials joined a Malaysian investor to roll out a multiuse plan they say will succeed.

Before redevelopment, though, comes the dirty work – and paychecks for companies that swing wrecking balls, clean pollution and remove junk.

Martin said demolition is actually the cheapest stage because scrap metal has such high resale value that it can cover most of the cost.

“The more expensive part of the process is almost always environmental remediation,” he said – particularly for the ponds holding coal ash, the byproduct of coal burning. “The cost of disposing of the coal ash itself in a lot of cases is going to be at least as much as the whole rest of the decommissioning process combined.”

Martin, a journalist by training, said there’s no single price tag for coal decommissioning; plants are too different. But his rough median was $18.9 million for a coal plant between 350 and 500 megawatts in size.

Revis James, director of fossil generation research and development at the Electric Power Research Institute, agreed the coal ash issue is likely to prove the knottiest in the coming surge of coal retirements.

The ash reservoirs are likely to contain a large, cumbersome amount, he said. There may be techniques to move or dilute it, but if not, power companies may find themselves in permanent care of the facility to keep it from leaking.

James said that’s just one of many issues that will need to get worked out in this unprecedented chapter of coal’s history.

“We haven’t had a lot of decommission of coal plants, historically, so there isn’t a huge body of experience or regulatory basis to go by,” he said.