By JIM MOTAVALLI

AS horizontal drilling and the controversial extraction technique known as fracking have made domestically produced natural gas more available and sharply cheaper, that gas has been widely embraced by industry, electric utilities and trucking fleets.

The rapid development of shale gas technology has helped reduce energy imports and, in some cases, encouraged companies producing petrochemicals, steel, fertilizers and other products to return to the United States after relocating overseas. Natural gas exports are growing and terminals built to hold imported supplies are being repurposed for international sales.

The American petrochemical industry, for example, uses natural gas as both its primary raw material, in the form of liquid ethane, and as an energy fuel. And cheaper prices have led to a major expansion of capacity in the United States.

The hydrocarbon molecules in natural gas are split apart and then recombined as building blocks for many products, including bulk chemicals and fertilizers. The chemical ethylene, which is largely derived from natural gas, is used to make things like pool liners, building insulation and food packaging.

According to Kevin Swift, chief economist at the American Chemistry Council, European producers mostly use oil-derived raw materials for making these same products. “The U.S. has a competitive advantage when oil is seven times as expensive as natural gas, but now we have more like a 50-to-1 advantage,” he said. “The ‘shale gale’ is really driving this. A million B.T.U.’s of natural gas that might cost $11 in Europe and $14 in South Korea is $2.25 in the U.S. Partly because of that, chemical producers have plans to expand ethylene capacity in the U.S. by more than 25 percent between now and 2017.”

A 2011 PricewaterhouseCoopers study estimates that high rates of shale gas recovery could result in a million new manufacturing jobs by 2025. Robert McCutcheon, United States industrial products leader at PricewaterhouseCoopers, said in a statement that the revived natural gas industry “has the potential to spark a manufacturing renaissance in the U.S., including billions in cost savings, a significant number of new jobs and a greater investment in U.S. plants.”

The growing commitment to natural gas faces some headwinds because of continuing concern over the safety of fracking, which involves forcing pressurized fluids into shale formations to fracture the rock and release the gas deposits.

Some environmentalists say that fracking can cause drinking water to become contaminated with chemicals and released methane, which is a powerful naturally occurring greenhouse gas and the primary ingredient in natural gas. Other complaints tie the disposal of fracking wastewater to a series of small earthquakes. Some states and municipalities with questions about fracking have imposed temporary moratoriums on the extraction technique.

Despite these issues, natural gas is expanding its reach in manufacturing. The Nucor Corporation, which makes direct-reduced iron in a process heavily reliant on natural gas, said in 2010 that it would build a $750 million facility in Louisiana. In 2004, the company dismantled a similar Louisiana plant and shipped it to Trinidad.

According to Nucor, affordable domestic natural gas means its made-in-Louisiana direct-reduced iron, which is sold in pellet or briquette form as a raw material for steel mills, can be delivered at the same price as the product shipped from Trinidad. “Affordable American shale gas has completely changed the economics for us,” said Katherine Miller, a Nucor spokeswoman.

Methanex, a Canadian company that makes methanol from natural gas is planning to move a plant from Chile to Louisiana, with production to begin in 2014. Gary Rowan, a Methanex vice president, said that his company had also shut down a Louisiana plant in the early 2000s. “Certainly, the outlook for low North American natural gas prices is one of the reasons we selected Louisiana as a new location for our methanol plant,” he said.

Electric utilities see a significant natural gas price advantage over other fuels, but because of pending and potential environmental regulations they are also motivated by its status as the fossil fuel with the lowest carbon emissions. On March 27, the Obama administration proposed the first-ever rule to limit greenhouse gas emissions from new power plants. Natural gas plants are expected to meet the standard, but coal burners will have a much harder time. “The electricity sector is the principal growth area for natural gas under carbon dioxide emission constraints,” said an M.I.T. study titled “The Future of Natural Gas.”

Another advantage, according to Richard McMahon, a vice president of finance and energy supply at the Edison Electric Institute, is that natural gas plants are cheaper to build than coal plants.

“Natural gas generally has a smaller footprint,” he said. “Coal plants need to store coal, but natural gas plants get their fuel from a pipeline and don’t need physical storage.” The Obama greenhouse rules would widen the price gap by requiring new coal plants to include carbon capture technology.

The United States still has a big investment in coal plants, and a transition will be gradual. The federal Energy Information Administration estimates that electricity generation from natural gas will increase about 9 percent in 2012, at the same time that coal production declines almost 5 percent. If there is a constraint on utility commitment to natural gas, it is the fuel’s history of large price fluctuations.

Thomas Farrell, chairman and chief executive of Dominion Resources, a utility that delivers electric power and natural gas to four states, describes natural gas as “very volatile in its pricing. We’re a utility whose customers rely on us to think through 60-year power plant investments, and we’ve found that the best approach is to have diverse sources and not depend on one predominant source of fuel.”

But he added that the company was definitely benefiting from low natural gas prices now. Dominion Virginia Power’s 13 percent natural gas electricity production in 2010 jumped to 17 percent in 2011. The company recently completed a natural gas plant and is constructing another, but it also has large nuclear and coal investments.

The share of natural gas as a transportation fuel has never been large, but it is growing rapidly. Refueling is an issue, because there are about 1,000 natural gas stations in the United States (compared with nearly 160,000 gasoline stations) and only half of those are open to the public. Only one automaker, Honda, sells a natural gas passenger car on the American market, and consumers are unlikely to buy them in large numbers any time soon. But the opportunities for truck fleets are quite different.

Almost 40 percent of new garbage trucks and 25 percent of new transit buses can run on natural gas, said the trade organization Natural Gas Vehicles for America. Dan Ustian, chief executive of the truck maker Navistar, said that garbage truck number could grow to 50 percent by the end of next year. Navistar is also building long-range trucks.

Although natural gas cars and small trucks usually run on compressed natural gas, known as C.N.G., to avoid frequent refueling, the larger trucks will mostly use the liquefied form, L.N.G., which has much greater energy density per volume (but must be kept at very cold “cryogenic” temperatures).

Mr. Ustian estimates that, because of quick paybacks with a $1.50 a gallon equivalent price advantage, natural gas could capture 10 percent to 20 percent of the new tractor-trailer vehicle market within a year.

Chrysler, Ford and General Motors have all recently introduced “bifuel” pickup trucks that can run on both natural gas and gasoline. To ensure that such trucks have a place to fill up, Navistar has joined with a natural gas provider, Clean Energy Fuels, and Pilot-Flying J Travel Centers to locate stations 250 miles apart along Interstates. By the end of the year, Clean Energy hopes to have 75 stations open in 33 states.

Andrew Littlefair, president and chief executive of Clean Energy, said that the aim was to make natural gas refueling available on the major trucking corridors. “You don’t need 23,000 truck stops with natural gas,” he said. “You need hundreds in the right places and you can move a lot of fuel. These stations will be where the trucks go now, and the economics look very good.”

In March, Chesapeake Energy, a major natural gas producer, and General Electric said they would collaborate on developing natural gas infrastructure for vehicles, including construction of more than 250 C.N.G. stations beginning this fall.

The prospects exist for American producers to become significant natural gas exporters. In 2011, Dominion won approval from the Energy Department to export L.N.G. from its Cove Point terminal in the Chesapeake Bay to about 20 countries that have free trade agreements with the United States. It has applied for a permit to service the rest of the world. Dominion said that its terminal work force — initially intended to handle imports before the United States became a powerhouse producer — could nearly double with the added workload.

“It’s definitely ironic,” Mr. Farrell said. “Ten years ago, even the futurists wouldn’t have predicted that we’d be exporting natural gas today.”