Is natural gas a transition fuel? Natural gas is viewed as a transition fuel to allow further development of low carbon alternatives. Natural gas releases less CO2, SO2, NOx and particulate than coal. This makes natural gas a better choice than coal. However, as Stephenson et al point out, there are some unintended environmental impacts that may weigh against using natural gas as a transition fuel.
Natural gas provides a relatively inexpensive energy source that in many cases releases less CO2 than coal or oil. Natural gas combustion, unlike a coal fire which burns for a longer duration, is easy to start and stop. This makes natural gas a convenient fit with renewable energy sources such as wind and solar which exhibit a variable electricity production. A natural gas fired plant can be relatively easily started up to compensate for the drops in electric power when the wind stops blowing or clouds or night reduce solar output. Natural gas is an abundant US energy source in our shale formations. This will allow us control over some of our energy future vice being reliant on external energy sources. These two properties are strong drivers to use natural gas as a transition fuel.
According to Cathles, natural gas is a good transition fuel. Natural gas could reduce CO2 by 40% if substituted for coal. This benefit will remain regardless of the duration of the transition. He refutes the methane fugitive leakage rates that have been estimated as high as 8 percent and believes they are closer to 1.5 percent for both conventional and hydraulic fractured wells. Even if a higher leakage rate exist, he argues that natural gas is a better substitute due to the different decay rate of methane released by natural gas extraction and the greater amounts of CO2 released by burning coal and oil. Finally, he validates the “surge capacity” of natural gas to buffer solar and wind farms (Cathles, 2012).
According to Stephenson et al, natural gas from British Columbia (BC) shale gas has additional greenhouse gas (GHG) emissions that should be investigated. There are several sources of higher GHG emissions from BC shale formations. The gas in the Horn River BC shale formation has a higher CO2 level that other natural gas sources with a concentration of about 12%. This CO2 is likely vented to the atmosphere make the gas suitable for pipeline use which requires a CO2 concentration less than 1%. There is evidence the hydraulic fracturing process may release methane as a fugitive emission. Methane is a more harmful GHG than CO2 and could drastically sway the environmental benefits of natural gas when compared to coal or oil. However, the fugitive emission problem requires additional study to adequately quantify. The end use of natural gas due to its low price could offset low carbon emission sources such as nuclear power. BC intends to open a liquid natural gas (LNG) terminal to ship gas overseas. The liquefaction process has been a traditional source of CO2 emissions since the process requires energy that is usually provided by burning a fraction of the gas. Additionally, ships burn fossil fuels to transport LNG. Finally, the regasification process releases some CO2 (Stephenson et al, 2012). With all of these additional GHG sources, natural gas from BC may not be the best transition fuel from an environmental lens.
There are other environmental issues with shale gas. As noted by the Energy Information Administration, there are several negative consequences of hydraulic fracturing for shale gas. The hydraulic fracturing process requires a lot of water. This demand on water resources could negatively impact some regions. The hydraulic fracturing fluid (a mixture of chemicals, water and sand) may contain potentially hazardous chemicals that can spill, leak or find other ways to contaminate the environment. The hydraulic fracturing process produces large amounts of waste water. This water contains the potentially hazardous chemicals added for the process and other contaminants that could be brought up from deep underground. This water requires treatment which may not remove all of the impurities. These impurities may be released to the environment from the treatment facility or spills. The waste water may also be disposed of in deep wells or non-potable salt-water aquifers. Finally, the hydraulic fracturing process can cause small earthquakes (EIA, 2012).
Let’s bring this problem a little closer to home. Pennsylvania is no stranger to hydraulic fracturing. According to the NRDC, hydraulic fracturing is suspected of contaminating drinking water in Pennsylvania. Additionally, three spills of more than 8,000 gallons of fracturing fluid near Dimock Township, Pennsylvania in 2009 contaminated wetlands and caused a fish kill (NRDC, 2013). Shale sediment near Blacklick Creek in Pennsylvania contains more than 200 times the normal level of radium. The radium is brought to the surface along with salts such as sodium, calcium, magnesium, chlorine, bromide. The radium and salts have resulted in surface contamination and appear to have been detected in the creek (Efstathiou, 2013). These examples show the environmental impact on Pennsylvania beyond the GHG benefits over coal.
It is evident that not all shale formations are created equal. The formation near Blacklick Creek Pennsylvania contains high levels of radium and the Horn River BC formation contains high levels of CO2. The lesson is that each well needs to be individually evaluated to determine its unique features. Some wells may be abandoned due to high CO2 levels or other contaminants such as radium. The variation between formations will challenge regulators to ensure the proper regulations are in place on a region to region basis. These regulations are necessary to ensure the proper price is placed on the natural gas to account for the varied environmental impacts. The hydraulic fracturing process appears to be ahead of regulators and is spurred on by a drive for cheap energy.
In conclusion, natural gas is a transition fuel. Natural gas has some great properties that will allow it to be a good transition fuel such as “surge capacity” to enable better near term use of wind and solar, lower CO2 emission when compared to coal and oil. Additionally natural gas is a domestic energy source. However, with the different properties of shale formations, the environmental impacts from hydraulic fracturing to obtain shale gas may vary based on the formation and uses of the natural gas. Each well or region should be evaluated to determine the local and global impacts. These environmental impacts need to be accounted for to ensure the proper price is placed on natural gas.
References:
Cathles, L. Assessing the greenhouse impact of natural gas. Geochemistry, Geophysics, and Geosystems, Volume 13, Issue 6, 19 June 2012.
Efstathiou, J. Radiation in a Pennsylvania Creek Seen as a Legacy of Fracking. Bloomberg.com, 2 October 2013.
Energy Information Administration. What is shale gas and why is it important? www.eia.gov, 5 December 2012.
Natural Resources Defense Council. The rapid expansion of natural gas drilling across the nation endangers human health and the environment. Nrdc.org, 2013.
Stephenson, E., Doukas, A., and Shaw, K. Greenwashing gas: Might a ‘transition fuel’ label legitimize carbon-intensive natural gas development? Energy Policy 46, 8 April 2012.