Natural Gas: The Newest Danger for Global Warming
June 18, 2012
Now that the atmosphere over the Arctic contains 400 parts per million of carbon dioxide and the world hasn’t significantly reduced its greenhouse gas emissions, we should be gravely concerned about the push for more natural gas, a potent greenhouse gas.
Fossil fuels come from drilling or mining deep underground to access stored energy sources from bygone millennia. We bring them to the surface and burn them for heat or electricity or to run our cars and buses. Burning fossil fuels creates carbon pollution. It doesn’t matter if it is coal, oil, propane, kerosene, gasoline or natural gas—it all contains carbon, which gets released as a greenhouse gas.
Methane or natural gas, however, is 72 times more potent at capturing heat in the atmosphere than carbon dioxide over the first 20 years after release. Methane gradually converts to carbon dioxide, so it’s worst in the short term; the global warming potential over 100 years is about 25 times that of carbon dioxide.[i]
So why did we think that natural gas could be a bridge fuel until non-carbon sources of energy are fully developed? Because gas-fired electricity plants emit only half as much carbon dioxide per kilowatt-hour generated as do coal-burning plants. New reports, however, point out that we haven’t taken into consideration the leakage of methane during mining or transport. Leaks occur when the well is drilled, during transport in pipelines, at storage sites, or when methane is pumped into the fancy new natural gas-powered buses.
Where are these leaks and how big are they?
When drilling occurs for oil, gas or even coal mining, it taps a potential natural gas field. Because it’s a gas, it mixes with the air and disburses unless it gets captured and securely funneled into a pipe to be delivered to the gas plant or your furnace.
New hydraulic fracturing technology is tapping deeper sources of gas. The well is drilled straight down, then horizontal drilling takes place—part of the new technology. Water mixed with sand and many types of chemicals are forced into the well to fracture the rocks or tight sand to allow for more release of the natural gas.
The fracking fluid is then pumped out, but along with it comes natural gas and other deeply buried volatile chemicals which create significant air pollution around the well sites. In some wells, this early recovery or “burping” is not captured. However an estimated 90% can be captured by a process called “green completion” that involves capping the well and separating the methane and other valuable petrochemical products. The gas can be sold along with chemical products from the well. However, in new fields the pipeline may not be built yet, nor are other storage facilities available, making it impossible to store the escaping methane.
There has not been adequate overall testing to determine the exact amount of leakage of methane, but to better calculate greenhouse gas emissions, the EPA recently (2011) doubled its estimate of natural gas leakage to 2.4% from development, production and delivery of natural gas.[ii] This is still felt to be a very conservative number. Geologists and the EPA have noted that hydraulic fracturing increases the leakage rate compared to standard mining of natural gas. One study by Petron, based on air sampling in the natural gas fields of Colorado, showed a leakage rate in the field of 4.1% (range of 2.3-7.7%).[iii] This is only in the field, at the well sites and in storage tanks on- site, and doesn’t count pipeline and end storage leaks. Another analysis by Howarth estimates fracturing in shale to have a leakage rate of 3.6% to 7.9% from venting at the time of drilling, back flow and leaks over the lifetime of the well.[iv] Despite the cost of losing natural gas, the industry minimizes its leakage rates or won’t report them.
How much leakage is too much? An elegant new analysis by Alvarez, Pacala, and others in the Proceedings of the National Academy of Sciences[v] looks at the amount of global warming produced by various uses or technologies of natural gas. For electricity production, as expected, fuel switching to natural gas from coal reduces the global warming potential by about 25% in the first forty years using the EPA’s leakage rate of 2.4%. If that leakage rate is higher than 3.6% then fuel switching provides no benefit at all. If the leakage rate is as high as measured in Colorado at 4.1% even without pipeline leakage then natural gas is worse than coal from a global warming perspective.
Pacala’s surprising analysis also reveals that fuel switching from diesel to natural gas for heavy-duty vehicles at the EPA rate of leaks of 2.4% never provides a benefit to greenhouse gas emissions even when averaged over 100 years. For smaller gasoline vehicles, it takes forty years of averaging before there is a break-even point showing lower greenhouse gas effect by switching to natural gas from gasoline.
Several actions can be taken to reduce methane leaks that endanger our climate and our planet’s livability. First and foremost is to uphold the EPA’s cost-effective regulations to reduce not only methane leaks, but harmful air pollution at the well head of more than 11,000 new hydraulically fractured gas wells each year, using a process called green completion.[vi] This is already required in Colorado, Wyoming and other jurisdictions so we know the technology is available and it appears to be cost-effective.
The most important action though is to reduce all fossil fuel use and markedly increase efficiencies, wind and solar. The prospects for doing so are strongly outlined in the new report by the International Energy Agency, Energy Technology Perspectives 2012[vii]. The executive summary explains that “every additional dollar invested can generate three dollars in future fuel savings by 2050.” The report lays out the needed steps to achieve a maximum of 2 degrees C increase which at the minimum holds the potential to save human lives from the threat of runaway climate change.
[i] Intergovernmental Panel on Climate Change. IPCC Third Assessment Report, Climate Change 2001.
[ii] U.S. Environmental Protection Agency (2011) Inventory of US Greenhouse Gas Emissions and Sinks: 1990-2009 (EPA Publication 430-R-11-005) http://epa.gov/climatechange/emissions/downloads11/US-GHG-Inventory-2011-Complete_Report.pdf
[iii] Tollefson, Jeff. Air Sampling Reveals High Emissions from Gas Field. Nature. 482, 139–140. (09 February 2012)
[iv] Howarth, RW, Santoro, Methane and the greenhouse-gas footprint of natural gas from shale formations. A Letter, Climatic Change. DOI 10.1007/s 10584-011-0061-5.
[vi] Www.epa.gov/airquality/oilandgas Overview of final Amendments to Air Regulations for the Oil and Natural Gas Industry.
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