(Bloomberg News) On the eastern bank of the Mississippi River, about an hour upstream from New Orleans, the outline of Nucor Corp.'s new $750 million iron-processing plant is rising between fields of sugar cane and sweet gum trees.

Surveying the facility from the road, Michael Eades, president of Ascension Economic Development Corp., says it's part of a wave of investment lured by low natural gas prices to this stretch of Louisiana's industrial riverfront. Companies such as Westlake Chemical Corp., Potash Corp. of Saskatchewan Inc. and Methanex Corp. have projects in the works. Ormet Corp. reopened an alumina refinery last year, bringing back 250 jobs.

"We're just seeing an incredible amount of activity," said Eades, who tallied $1.1 billion in new projects last year in Ascension Parish alone, where his private, nonprofit group promotes development. He expects twice that this year.

It's a harbinger of a nationwide investment boom spreading from the oil fields of North Dakota and the Marcellus gas shale in Pennsylvania to power plants in California and chemical refiners in Texas. A surge in U.S. natural gas development has spurred $226 billion in spending plans on pipelines, storage, processing facilities and power plants, most slated for the next five years, according to Industrial Info Resources, a market- intelligence provider in Sugar Land, Texas.

U.S. energy supplies have been transformed in less than a decade, driven by advances in technology, and the economic implications are only beginning to be understood. U.S. natural gas production will expand to a record this year and oil output swelled in July to its highest point since 1999. Citigroup Inc. estimated in a March report that a "reindustrialization" of America could add as many as 3.6 million jobs by 2020 and increase the gross domestic product by as much as 3 percent.

Narrow Gains

So far, the economic benefits have been confined to states such as Louisiana, Texas and North Dakota, while the national jobless rate has stayed above 8 percent for 42 straight months in the wake of the worst recession in seven decades.

"It is definitely a positive for the economy, but one can overstate how much of a positive," said Michael Feroli, chief U.S. economist for JPMorgan Chase & Co. Oil and gas production account for about 1 percent of gross domestic product, and will have a limited impact on the country's unemployment, he said.

Even so, there are signs the economic gains have begun to expand beyond the oil and gas fields and that the promise of abundant, low-cost fuels will give a competitive edge to industries from steel, aluminum and automobiles to fertilizers and chemicals.

Jobs Debate

That would provide a boost to a U.S. manufacturing sector that has lost 5.12 million jobs since 2001 and become the focus of a national debate over how to revive factory employment. Manufacturers have added 532,000 jobs since January 2010 as the economy started to recover, Bureau of Labor Statistics data show.

The expansion of fossil-fuel production -- coupled with a weak economy and increased energy efficiency -- has helped the U.S. pare its crude oil imports by 17 percent since the 2005 peak, Energy Department data show. Imports in 2011 accounted for 45 percent of U.S. consumption of crude and refined products. The department predicts the share will fall to 39 percent next year, which would be the first time since 1991 that imports dropped below 40 percent of demand.

"The impact on the global petroleum market and the natural gas markets is really palpable and wildly underestimated," said Ed Morse, head of commodities research at Citigroup Global Markets Inc. who led the team that wrote the March report. The economic activity that comes with higher energy production will boost incomes, increase consumption and create wealth, he said.

Cheaper Energy

Increased production and swelling domestic stockpiles have helped make U.S. energy cheaper than in other countries. U.S. oil futures have slid to a $20 a barrel discount to London- traded Brent, a benchmark for more than half the world's oil. Natural gas in the U.S. fell to $1.902 per million British thermal units in April, the lowest in a decade. The fuel costs almost three times as much in the U.K. and more than five times as much in Japan.

"This is one of those rare opportunities that every country looks for and few ever get," said Philip Verleger, a former director of the office of energy policy at the U.S. Treasury Department and founder of PKVerleger LLC, a consulting firm in Carbondale, Colorado. "This abundance of energy gives us an opportunity to rebuild our economy."

Cycle of Growth

Verleger envisages a virtuous cycle of economic growth as producers, flush with cash from oil and gas sales, will buy more equipment and put more people to work, while low-cost energy puts cash back in consumers' pockets, stimulating spending.

Companies plan to invest $138 billion in more than 700 natural gas storage, pipeline and processing plants in the U.S., and another $88 billion in more than 500 gas-fired power generation units, according to Joseph Govreau, vice president and editor-in-chief of Industrial Info Resources. The firm tracks projects from planning stages through construction.

The IIR estimates don't include petrochemical and fertilizer projects, which are undergoing a revival because of the low cost of natural gas feedstock.

Cairo-based Orascom Construction Industries is investing $250 million restarting an ammonia and methanol plant in Beaumont, Texas. Another Orascom subsidiary may build a $1.3 billion fertilizer plant in Iowa that would create as many as 2,000 construction jobs and 165 permanent positions, according to Tina Hoffman, a spokeswoman for the Iowa Economic Development Authority.

'Massive' Investment

"The amount of petrochemical investment that the U.S. will have in the next 10 to 15 years is massive," said Omar Darwazah, head of investor relations for Orascom. "Given the shale gas boom, gas prices in the U.S. are arguably more competitive than the Middle East, because you don't have the political risk."

Increased U.S. production has already wrought significant shifts across the energy industry. Plans for gas-import terminals, thought indispensable five years ago, have been shelved in favor of export facilities such as Cheniere Energy Inc.'s $10 billion plant in Louisiana's Sabine Pass.

Enterprise Product Partners LP and Enbridge Inc. this year reversed the Seaway pipeline that once carried oil imports from the Gulf Coast to a storage hub in Oklahoma. Now, it carries crude produced in states such as North Dakota and Colorado to refiners in Texas and Louisiana, which process and, increasingly, export it. East Coast refiners, dependent on more expensive tankers of foreign crude, are working to develop rail links and pipelines to bring oil east.

Environmental Concern

Environmentalists say cheap fossil fuels come with a high price, including air pollution that can cause respiratory difficulties, and drinking water contamination from hydrofracturing, or fracking, in which a high-pressure stream of fluid is shot underground to crack rock and release hydrocarbons. Lower gas and oil costs have also undermined investment in power sources that produce less carbon dioxide, including wind, solar and nuclear, raising concern that climate change will accelerate.

"The state is just overjoyed at all the jobs that will be coming to Louisiana without looking at the health side effects and environmental side effects," said Darryl Malek-Wiley, a community organizer at the Sierra Club in New Orleans.

The report from Citigroup -- "North America, the New Middle East?" -- estimated that the U.S. could become the world's largest producer of crude and natural gas liquids such as propane by 2020, overtaking Russia and Saudi Arabia.

China Consumption

U.S. natural gas prices may eventually rise if planned export terminals increase demand for the fuel, putting domestic consumers in competition with foreign markets willing to pay more. China will drive global gas consumption higher by 2.7 percent a year through 2017, the International Energy Agency said in a June report. The U.S. already competes with global consumers for refined products such as gasoline and diesel.

Still, the promised bounty from lower prices can be seen along the highways and back roads of Ascension Parish, in the heart of Louisiana's plantation country.

In November, cheap natural gas prices convinced Hannibal, Ohio-based Ormet to reopen the refinery that makes alumina, used in aluminum production. The facility was shuttered in 2006, said Chief Financial Officer James Riley.

In nearby St. James Parish, Nucor has begun construction on the plant that will process iron using natural gas. The product will supply its steel mills, said Katherine Miller, a spokeswoman for Charlotte, North Carolina-based Nucor. Five hundred people will be needed to build the plant and 150 will be employed there once completed, she said.

Doubling Workforce

Eades gestures toward construction trailers parked on the site where Vancouver-based Methanex said in July that it will reconstruct a plant moved from Chile, white, football field- sized domes that will store Nucor's iron ore, and chutes that carry bauxite over the Mississippi River levy into Ormet's rust- colored plant.

All this construction means new jobs. MMR Group, a Baton Rouge-based industry contractor, will double its workforce of 2,800 in the next two years, said Grady Saucier, vice president of marketing.

A five-minute drive from MMR's offices in Ascension Parish, Associated Builders & Contractors, a trade group, can't keep up with demand for its training program for would-be electricians, pipefitters and welders. Steven Allen graduated from the school's pipefitting certification program this year. Now, he earns as much as $28 an hour working in petrochemical plants, up from the $9 an hour he made as a construction laborer.

Family Struggle

"Being a laborer and a helper isn't going to cut it when you've got a family to support," said Allen, 30, a father of 6- year-old twins.

Smaller businesses, including valve manufacturers, electric-motor companies and rental lots packed with heavy equipment, also feed off the boom, Eades says. One company, Rain for Rent, provides fake downpours seen on movie sets -- as well as storage tanks and water pumps to the petrochemical industry.

Closer to Interstate 10, which connects New Orleans to Baton Rouge, a TownePlace Suites by Marriott and a Holiday Inn Express have opened in the past year next to an outlet mall and a Cabela's outfitters store, all benefiting from the influx of new workers to the region, Eades said.

"If you have gas prices in the U.S. that are substantially cheaper than Europe or Asia, it has to have a substantial impact," said James Brick, an analyst in Houston with Wood Mackenzie, an energy and metals researcher. "The question we're now asking is, 'Is this the tip of the iceberg?'"