PHILADELPHIA - Big players in the Marcellus Shale industry met in a city far from Pennsylvania's drilling boom towns for the second year in a row on Thursday to project a future for abundant shale gas as a low-cost energy source and savior of the manufacturing sector that will benefit all corners of the commonwealth.

Several years into the development of the state's shale gas resources, speakers at the Marcellus Shale Coalition's Shale Gas Insight conference talked less about getting the gas than using it: as a cleaner-burning transportation fuel, a feedstock for petrochemicals and an energy source for electricity and manufacturing.

"I'm convinced that we are at the beginning of a new industrial revolution and that you are at the tip of the spear," Gov. Tom Corbett said in a morning speech, in which he aligned himself with the industry almost from his first words.

"We, you, are creating jobs," he said. "We are building our future."

Corbett characterized critics of the industry, who held a rally and protest march outside the Pennsylvania Convention Center, as the "unreasoning opposition."

"Our opponents agree that we can land a rover on Mars," he said, "but they can't bring themselves to think that we can safely drill a mile into our own soil.

"After all the predictions of disaster and the fearful warnings from people who have no understanding of the industry, Pennsylvania is reaping a bounty."

Across the street from the convention center, critics of the industry gathered to highlight homeowners who say they have been harmed by nearby natural gas drilling. They argued that natural gas has only a limited potential to reduce the production of greenhouse gasses and championed investment in renewable energy sources, like wind and solar.

In a cramped room at the Arch Street Methodist Church, activists said the industry can afford to try to buy influence and a "green" image.

"They get to spin every little piece of information until it's unrecognizable," said Tracy Carluccio, deputy director of the Delaware Riverkeeper Network. "It is being called clean, when actually it's the opposite. It's the same old fossil fuel."

"Gasland" director Josh Fox reiterated the David and Goliath theme. "Gasland" chronicles the effects of natural gas drilling on the American landscape.

"What we're talking about today is big business, across the street," he said. "The 1 percent of the 1 percent of the world coming to Pennsylvania and saying, we own it."

In keynote addresses and small workshop sessions, the big businesses inside the conference center said they take seriously the need to inspire public confidence in their operations.

Jack Williams, president of XTO Energy, a subsidiary of Exxon Mobil, told the nearly 2,000 attendees during his keynote speech that they need to be publicly engaged.

"We need to acknowledge that for all the success of shale development, public confidence is not as strong as it could be," he said. "Some Americans continue to demonstrate a high level of concern about the impact of shale development activity. Our industry must take steps to strengthen public confidence."

He noted that many oil and gas companies now publicly disclose the components of the additives they use to hydraulically fracture, or frack, their wells on FracFocus.org. The fracking process involves injecting chemically treated water and sand underground at high pressure to release gas trapped in rock.

He also pointed to an industry effort in Pennsylvania to create a pre-drilling water quality database that offers rural residents more information about the quality of their water than ever before.

Williams endorsed the idea of exporting liquefied natural gas, or LNG, to energy-hungry markets in Europe and Asia. He said LNG exports, like those of grain, cars and other products, would bring money back to the U.S.

"The question of exporting some of this North American bounty is not a question of either/or," he said. "We can do both - fueling U.S. competitiveness and global growth."

The conference also featured a discussion, moderated by famous newsman Ted Koppel, of how shale gas figures into the November election.

Representatives from the presidential campaigns of President Barack Obama and Republican Mitt Romney traded barbs over energy policy, but both backed expanded use of natural gas in the nation's energy landscape.

The heavily drilled Susquehanna County community of Dimock emerged in a political salvo between the presidential campaign operatives. Current state Department of Environmental Protection Secretary Michael Krancer, stumping for the Romney campaign, described the federal Environmental Protection Agency as "rogue and out-of-control," in part for its recent groundwater investigation in the township.

"No one called the EPA into Dimock. The EPA called the EPA into Dimock," Krancer said of what he perceived as an overreach of authority.

"They spent millions of dollars of Superfund response money to show us exactly what we already knew in Pennsylvania - that drilling wasn't contaminating water."

Former DEP secretary Kathleen McGinty, speaking for the Obama campaign, said while the EPA found "no evidence" of contamination in Dimock, the industry and regulators should continue their focus on cementing and casing of wells and safety and environmental issues.

Obama has an "all of the above" energy policy, Ms. McGinty said. She noted that under the president, the U.S. has reached record natural gas production, a 14-year high in domestic oil production and a 20-year low in oil imports.

"We have moved aggressively on alternative energy," she said, noting a doubling in renewable power. Two new nuclear plants are in the works and employment in coal mining is up. Romney's plan is all about oil, she said.

Krancer didn't see it that way, criticizing the president's policy as "nothing but what's above ground: wind, water, and Solyndra," alluding to a failed solar cell company with millions of government loans.

The conference continues today.