When it comes to energy, natural gas is posited as the greatest thing since ... well, natural gas. For starters, it's billed as being cleaner than coal and oil and safer than nuclear energy. What's more, it's cheap right now because of its abundant supply. And considering the U.S. is loaded with the product, it's seen as vital in making the country more energy independent.

But natural gas is like the George Harrison of commodities--a quiet and often overlooked, yet vital, player overshadowed by stronger personalities. As the prices of many commodities have soared and grabbed headlines, natural gas prices have languished, and there aren't many people who can quote you the latest price per million British thermal units of the stuff.

The profile of natural gas is changing, however, in part because of the Marcellus Shale, a massive formation of dense black shale about one mile deep in the Appalachian belt of West Virginia, Pennsylvania and New York. Some estimates put the Marcellus gas reserves at almost 500 trillion cubic feet, an amount topped only by the South Pars gas field in Qatar and Iran. Not all of that is recoverable, but it's expected that enough will be tapped to create a bonanza.

In a report last year to the American Petroleum Institute, Timothy Considine, an energy economics professor at the University of Wyoming, said the forecast for Marcellus drilling and production in 2020 (18 billion cubic feet per day) could generate almost $25 billion in value-added economic activity and more than 280,000 jobs.

The hubbub surrounding the Marcellus' potential has given investors a reason to take a closer look at the commodity. "Natural gas has gone from being a sunset industry to a sunrise industry," says Tim Guinness, the manager of the Guinness Atkinson Global Energy Fund. "It's gone from looking to peter out to having a huge new lease on life, and it will be profitable for the next 30 to 50 years. Companies that are reasonably positioned in new shale acreage will do pretty nicely."

At the same time, the Marcellus has created a bull market for lawyers, regulators and shareholder activists because of the concerns about potential environmental impacts caused by hydraulic fracturing, the chief drilling method used to extract the region's vast natural gas reserves. Hydraulic fracturing, also known as fracking (or fraccing), injects huge amounts of water, chemicals and sand into subterranean rock formations to extract oil or natural gas.

The high pressure fluid of water and chemicals fractures the rocks, and then sand and other materials are pumped into the fractures to keep them open after the pressure is released to enable trapped hydrocarbons to flow out. The fracturing fluids are diverted into storage tanks to be recycled or disposed of, and wells capture the oil or natural gas.

The chemicals used in high-pressure drilling fluids are a proprietary mix that companies guard as trade secrets. They are used to dissolve minerals, prevent corrosive bacterial buildup and maintain fluid viscosity, among other things. These chemicals can vary depending on the drilling area, and many are toxic. Fears of drinking water contamination have led to numerous regulatory actions and fines against drillers. And in December, New York state put a moratorium on the fracking of horizontally drilled wells (but not vertically drilled ones) until at least July 1, while it finishes an environmental impact review of the process.

Shareholder activists say investors should pay attention to the environmental issues in the Marcellus. "There are environmental hazards involved in every step of the process, and these hazards can result in substantial business risks that could potentially harm shareholder value," says Larisa Ruoff, the director of shareholder advocacy at Green Century Capital Management in Boston, which operates two environmentally responsible mutual funds.

Liquid Market
Natural gas is a multifaceted industry involving onshore and offshore drillers, pipelines and liquid natural gas (LNG), along with ancillary businesses. Most U.S. production goes toward domestic consumption, and increased drilling--aided by hydraulic fracturing, which has opened up previously hard-to-tap fields and extended the life of older wells--has flooded the market. According to the U.S. Energy Information Administration, American natural gas reserves are at their highest level in 40 years.