Independence National Historical Park, the cradle of American liberty, has become the epicenter of a 21st-century conflict, this one revolving around fossil fuels and climate change.

An environmental group, the Clean Air Council, is pressuring the Biden administration to block the National Park Service’s plan to disconnect from the Philadelphia district steam-heating system and to install natural gas boilers on park property. The Clean Air Council says the conversion will commit the park to fossil-fuel heating for years to come at a time when President Joe Biden has ordered federal agencies to reduce climate emissions.

“Choosing to finance additional fossil fuel infrastructure would set an unfavorable precedent and potentially undermine the administration’s climate goals,” said Joseph Otis Minott, executive director of the Clean Air Council, in an August letter to Deb Haaland, the secretary of the Department of Interior, which oversees national parks. Minott took his complaint public on Thursday in an opinion piece posted on WHYY’s website.

Minott said the energy conversion project was undertaken with little public scrutiny, and the Park Service’s estimates on savings and climate impact are suspicious because they were produced by Philadelphia Gas Works, which would benefit from the switch to natural gas.

“They should have been able to find someone that wasn’t selling anything to make an assessment of what was best for such an iconic establishment in Philadelphia,” Minott said in an interview with The Inquirer.

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Details of the Park Service’s plans are unclear, including when the conversion might occur, and how many boilers would be installed, and where.

“The amount of energy and cost savings that will be achieved by the National Park Service project is considerable, because many of the park’s buildings will be served by the new, highly efficient systems, including Independence Hall, Liberty Bell Center, Old City Hall, Congress Hall, the First and Second Banks of the United States, and the Merchants’ Exchange Building,” Cynthia MacLeod, the park’s superintendent, said in an email Friday.

Vicinity Energy, which produces steam at its Grays Ferry Cogeneration plant along the Schuylkill and distributes it by underground pipes to more than 300 buildings in Center City and University City, said that it now heats 34 of 46 National Park Service buildings. The Park Service buildings total about 350,000 square feet, and take about 0.7% of the steam system’s load.

Vicinity said it was never asked to bid on the Park Service project or to present an alternative. “It was never out there in public, and then we got wind of them planning to leave the system,” said Bill DiCroce, chief executive of Vicinity Energy, a French-owned company that owns 19 district energy systems in America, the largest of which is in Philadelphia.

The Park Service’s conversion plan thrusts the federal government into an ongoing commercial squabble between Vicinity Energy and Philadelphia Gas Works, the city-owned gas utility.

PGW, which is under pressure from climate activists to reduce its carbon footprint, has been aggressively courting steam loop customers to convert to natural gas. It is also seeking a 1,000% increase in the fee it charges Vicinity to supply natural gas through a pipeline to Vicinity’s steam plant at 2600 Christian St. Vicinity last month filed a formal complaint with state regulators, alleging that PGW was engaged in predatory, anticompetitive practices.

» READ MORE: Philly steam-loop owner accuses city’s gas utility of ‘predatory, anti-competitive’ conduct

The battle over the park’s fuel source is symbolic of the tug-of-war underway over how quickly the nation should move away from using such fossil fuels as gas, oil, and coal to cleaner fuel sources that emit little to no greenhouse gases, principally carbon dioxide.

Vicinity’s steam system and PGW both use fossil fuels. Vicinity says its system is more efficient and climate-friendly because its steam plant simultaneously produces electricity, getting more total output per unit of energy. PGW argues that onsite natural gas boilers are more efficient and cost less to operate than the district steam system.

“Natural gas is an important source of clean energy,” PGW spokesperson Richard Barnes said in a statement Friday, while declining to address specifics about the Park Service arrangement. “The direct use of natural gas onsite, in almost every case, is more efficient and produces less emissions than energy produced remotely.”

MacLeod, the park superintendent, told the Clean Air Council in July that converting to natural gas boilers would reduce carbon dioxide emissions by 1,685 tons a year. PGW’s engineering study also said that “steam service costs 190% of equivalent thermal unit of gas.”

Vicinity says the Park Service calculations do not include the efficiency of the steam system’s cogeneration of electricity, nor the leakage of methane from PGW’s aging gas mains, which account for a loss of about 2.6% of the system’s gas every year.

“It’s going to be three times more carbon intensive for them to do what they’re doing,” DiCroce said.

The Vicinity steam system also has a greater potential for incorporating low-carbon fuels in the future, DiCroce said. The company has already replaced some fuel oil with biofuel produced from vegetable oil. It is also exploring replacing some natural gas with renewable gas produced from landfills or farm waste (an option that would also be available to PGW).

Vicinity also could eventually replace its fossil-fuel boilers with electric boilers, powered from renewable solar or wind energy, as it is doing in Boston, said DiCroce, essentially electrifying multiple skyscrapers and institutions now heated with fossil fuels.

» READ MORE: Can Philadelphia’s gas utility survive in a climate where fossil fuels are shunned?

“We have the ability over time to change fuels to reduce carbon as a district energy system,” said DiCroce. “Let’s say you put a natural gas boiler in your building. Guess what? They are forever natural gas boilers, so your carbon profile is locked.”

MacLeod, in an email, said the Park Service project is being undertaken as a utility energy service contract, under which an energy provider and the customer share cost-reduction benefits of any improvements. Constellation Energy has partnered with PGW to convert the park’s buildings to gas.

MacLeod said the National Park Service contracting officer “followed the relevant procedures as far as offering opportunities” to the four utilities that serve the park — PGW, Vicinity, Peco Energy, and the Philadelphia Water Department.

“In 2017 all of the park’s publicly regulated servicing utilities were approached about participating in an energy-saving project,” MacLeod wrote to the Clean Air Council in July. “Philadelphia Gas Works was the only utility that was interested and eligible.”

Vicinity said it was never consulted. “We have no record of them ever reaching out to us,” said DiCroce. “We asked them to produce any record that they reached out to us. No response. Crickets.”

Minott said his protest to the Biden administration is not intended as an endorsement of the Vicinity steam loop system. He said the process should have been more open and transparent, and allowed a more thorough evaluation of the alternatives, including the use of renewable power.

“Even if they say, `Listen, we can’t do any of the things that you tree-huggers are pushing on the world like solar, wind, and energy efficiency,’ given that we should be moving away from natural gas, I would want to know does it make sense to build new infrastructure vs. keeping what’s already there?”

“I don’t know the answer to that. I’m just saying, was that looked at?”