Natural Gas - Not as Green as it Used to Be

Oil and gas prices have diverged dramatically in the past few years. Graph: New York Times. Click on image to enlarge.

Natural gas has been in the news a lot recently.

On the economics side, we are seeing a fascinating divergence of petroleum and natural gas prices. For decades, oil and gas prices have tracked pretty closely--natural gas prices rising and falling as international political events boosted or depressed oil prices. Today, for the first time, as oil prices are surging, natural gas prices are still falling. In the last few weeks, natural gas prices have fallen to historic lows, compared with oil.

A little over a week ago, the New York Times reportedthat on an apples-to-apples comparison (in which natural gas prices were converted to barrel-of-oil-equivalents), oil was four times as expensive as natural gas. And the price of oil has risen nearly $10 per barrel since then. That difference in price between these two energy sources has never been so great. One significant implication is a significant regional disparity in hardship with home heating. About 55% of the country heats with natural gas, and those homeowners and renters have seen their heating costs go down. The 7% of Americans who heat with heating oil, however, have seen heating costs rise dramatically. In New England, heating oil prices have risen to over $3.60 per gallon.

Huge new reserves of natural gas have been found in the Marcellus Shale formation. Image: From ReelFacts; adapted from USGS. Click on image to enlarge.

The drop in price of natural gas has been driven by oversupply. We're finding and producing more natural gas, and that has depressed prices. And we're discovering huge new deposits of this energy source--most prominently with the vast Marcellus Shale deposits in Pennsylvania, New York, Ohio, and West Virginia.

Named for the village of Marcellus, New York, this black shale formation was believed in 2002 to contain 1.9 trillion cubic feet (TCF) of natural gas (the U.S. uses about 23 TCF of natural gas per year), but by 2009, that estimate by the U.S. Department of Energy (DOE) had increased to 269 TCF!

Environmental benefits of natural gas

We have long looked to natural gas as the cleanest of fossil fuels. Burning it emits little nitrogen or sulfur pollution. Natural gas is mostly methane (a molecule comprised of one carbon atoms and four hydrogen atoms); it has the lowest carbon-to-hydrogen ratio of any hydrocarbon. That means burning natural gas releases more water vapor and less carbon dioxide than burning oil or coal (which have higher carbon-to-hydrogen ratios).

How "Fracking" works. Image: Clean Water for North Carolina. Click on image to enlarge.

This is significant, because carbon dioxide is our most significant greenhouse gas--the leading culprit in global climate change. Burning natural gas instead of coal or oil will reduce the pace of climate change, proponents argue. The combustion of natural gas releases 117 pounds of CO2 per million Btus of heat produced, while burning the same heat content of gasoline emits 156 pounds, fuel oil 161 pounds, and coal 205 to 227 pounds, according to DOE.

Environmental concerns

Even as we tout the environmental benefits of natural gas, it has come under greater environmental scrutiny recently. For starters, the extraction and processing of natural gas releases some methane directly into the atmosphere, and methane is about 20 times as potent a greenhouse gas as CO2. Some estimate that while burning natural gas instead of coal to generate electricity results in only about half the CO2 emissions, when you factor in the direct emissions of methane, the greenhouse gas reduction is only about 25% (considering CO2-equivalents).

In addition, with Marcellus Shale natural gas production, there is significant potential for groundwater and drinking water contamination. This is because a practice called hydraulic fracturing or "fracking" involves injecting a mixture of water, sand, and various chemicals deep underground at extremely high pressure (as much as 10,000 psi) to fracture the underlying rock and free trapped pockets of natural gas.

The process is very water-intensive--with each fracking operation requiring as much as 5 million gallons of water, according to FracTracker, a project of the Center for Healthy Environments & Communities at the University of Pittsburgh. A single well may generate 1,000 tons of drilling waste that can include not only water and mud but also a range of salts, heavy metals, and naturally occurring radioactive material; much of that waste is held in surface impoundments. Leakage from those impoundments and the fracturing of rock sediments deep underground is contaminating groundwater throughout the region--the subject of a 2010 documentary film, Gasland.

Fracking wells in the Pennsylvania countryside. Photo: PhillyWorkersVoice. Click on image to enlarge.

Currently, fracking is exempt from the Safe Drinking Water Act--through a special provision in the 2005 Energy Policy Act passed during the George W. Bush Administration. That provision is known as the Halliburton Loophole; according to the New York Times it was added to the bill at the insistence of Vice President Dick Cheney to strip the U.S. Environmental Protection Agency of the authority to regulate this practice.

Clearly, natural gas can--and should--play a role in a shift to cleaner, lower-carbon energy sources, but there's no free lunch with this energy source. By understanding the impacts of natural gas extraction, we are reminded of the need to improve efficiency--no matter what the energy source. The less we use the better.

In addition to this Energy Solutions blog, Alex contributes to the weekly blog BuildingGreen's Product of the Week, which profiles an interesting new green building product each week--most recently a new cotton insulation. You can sign up to receive notices of these blogs by e-mail--enter your e-mail address in the upper right corner of any blog page.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. To keep up with his latest articles and musings, you can sign up for his Twitter feed.