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Guest Post: Shale Gas - The Low Carbon Option?

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It may be surprising to hear that hydraulic fracturing is not the cause of water contamination, but what may be even more surprising is that shale gas produced using fracking may have lower life cycle greenhouse gas emissions than conventional gas.

According to a recent Environmental Science and Technology report, “shale gas life-cycle [greenhouse gas] emissions are 6% lower than conventional natural gas”

There are several reasons why shale gas could have lower greenhouse gas (GHG) emissions, but perhaps the most significant reason is that multiple horizontal wells (used when tapping shale gas) can be drilled from a single well pad. In conventional vertical drilling, there is one pad per well. In horizontal drilling, there are typically six to eight wells drilled from one pad. This means less equipment, less surface disruption, and fewer opportunities for leaks on the surface. As methane is a potent greenhouse gas, minimizing methane leaks is essential in reducing GHG emissions.

Shale gas is arguably one of the lowest carbon sources of natural gas, but all types of natural gas represent a huge opportunity to reduce greenhouse gas emissions. Now, there are environmental challenges associated with developing natural gas. Methane leaks and water management are two of the biggest issues, and everything possible should be done to protect the environment. But, even with all the environmental concerns, natural gas, with fracking, is still a clear winner. Especially when compared to its primary alternative, and biggest competitor.

But what is the primary alternative to natural gas? People tend to associate natural gas with oil, and this is sometimes a mistake. While it is true that the production techniques of the two are similar (they are often produced together out of the same well), the production stage is where the similarities between oil and natural gas end. Natural gas is not a substitute for oil. They are used for different purposes. But, natural gas is a substitute for coal.

That’s right, because natural gas is primarily used for power generation, the alternative to drilling for natural gas is mining for coal. As such, producing more gas, including using techniques like fracking, can mean using less coal, which is a big win for the environment.

Let’s take China for example. If China builds one new coal plant per week, that translates to about 450 million tons of added carbon emissions each year1. If China just built natural gas plants instead of coal plants, they would reduce added emissions by between 150 and 270 million tons per year (depending on the type of coal and power plant, natural gas typically has between 30% and 60% less GHG emissions than coal). That reduction in emissions would be like taking roughly 40 million cars off the road. Since building a coal plant is a major capital investment, they are usually run for more than 50 years to recover the initial cost, so switching to natural gas in China would be like taking 40 million cars off the road for over 50 years!

Likewise, as about 50% of our power here in the United States comes from coal, we have the opportunity to make significant GHG reductions by switching to natural gas. Now, we know that natural gas emits less carbon dioxide per unit of energy, but it also emits significantly less pollutants of almost every other type. Let’s look at a few other numbers:

There are challenges associated with drilling for natural gas, but even with the challenges, natural gas is our best chance to immediately make meaningful reductions in greenhouse gas, mercury, sulfur and other emissions. So we have a choice to make: Should we jump on the Gasland bandwagon, ban fracking, and continue to rely on coal? Or should we safely develop natural gas, replace coal and make meaningful carbon reductions? I vote for the environment, so I vote for gas.

Photo Credit:

1. Photo of natural gas rig in Shreveport, Louisiana by danielfoster437 and used under this Creative Commons License.

2. Photo of coal mine by ulrichkarljoho and used under this Creative Commons License.

Footnote:

1. 1 GW coal plant x 2lb CO2/kwh x 1,000,000 kwh/gwh x 8,760 hrs/year x 52 new plants per year

About the author:

Scott McNally has a B.S. in Chemical Engineering from the University of Texas. He has worked as an Environmental Engineer for Valero Energy Corporation, a Project Engineer for Shell Oil Company, and an energy and climate research intern for the White House Council on Environmental Quality. This is Scott's third guest blog post at Plugged In - he was invited to be a guest blogger by Plugged In's Melissa C. Lott. You can reach Scott via e-mail at scottmcnally at gmail dot com.

The views expressed are those of the author and are not necessarily those of Scientific American.

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