There could be hidden environmental impacts of replacing coal with natural gas, a new report says.

While burning shale gas instead of coal in power plants releases less than half the greenhouse gas emissions than coal, the shale boom also has set into motion additional sources of pollution, the report says.

The Environmental Integrity Project report points to the abundance of cheap natural gas as the catalyst for the construction or expansion of 95 facilities in three major sectors — oil and gas, chemical manufacturing and petroleum refineries.

These new plants would increase greenhouse gas emissions by about 91 million tons annually — 41 million tons from the oil and gas sector; 45.8 million tons from the chemical manufacturing sector; and 4.3 million tons from petroleum refineries — releasing roughly the same amount as 20 large coal-fired power plants.

Not factored into the emissions estimate are those from proposed natural gas-fired power plants, compressor stations and flares that support the shale boom, the report says.

“It’s important that we understand the full climate change picture when it comes to America’s shale gas boom and the related tradeoffs,” said EIP Director Eric Schaeffer. “As natural gas replaces coal as the fuel of choice for electric power plants, greenhouse gas emissions from that sector will decline, since gas releases less than half as much carbon as coal per kilowatt of electricity generated.

“But the data suggest that declining CO2 emissions from the electric power sector will be partially offset by higher emissions from other industries cashing in on cheap and abundant supplies of oil and gas from shale deposits,” he said.

The report also calls on the U.S. Environmental Protection Agency to set a national greenhouse gas standard for every industrial category, including natural gas — an action required by the 2007 case Massachusetts v. EPA.

While most of these new projects are located in Texas and Louisiana, two are in Pennsylvania: A proposed compressor station in Huntingdon County and proposed refinery in Philadelphia County.