The rapid expansion of natural gas development in the United States has been a double-edged sword. While natural gas supporters are quick to point out its economic benefits and green attributes—natural gas produces roughly half the carbon dioxide emissions of coal during combustion—this isn’t the whole story. Natural gas comes with environmental consequences, including risks to air and water quality.
One risk is “fugitive methane emissions,” potent greenhouse gases that escape into the atmosphere throughout the natural gas development process. This methane—which is 25 times more potent than carbon dioxide over a 100-year timeframe—contributes to global warming and undercuts the climate advantage that cleaner-burning natural gas has over coal and diesel. (Learn more about fugitive methane emissions in our recent blog post.)
Despite the controversy surrounding natural gas development, energy forecasts suggest that natural gas is here to stay. Fortunately, several pathways are available to limit the climate impacts associated with its development. WRI just released a working paper, Clearing the Air: Reducing Upstream Greenhouse Gas Emissions from U.S. Natural Gas Systems, which outlines a number of state and federal policies and industry best practices to cost-effectively reduce fugitive methane emissions. We find that with the right amount of reductions, natural gas does offer advantages from a greenhouse gas (GHG) emissions perspective over coal and diesel.
Reining in Fugitive Methane Emissions
While reports vary on the extent of the fugitive methane emission problem, recent studies estimate U.S. leakage rates in the range of 2 – 3 percent of total production, with some published estimates as high as 7 percent. To put that in perspective, at a 2 percent leakage rate, more than 6 million metric tons of methane escape into the atmosphere in one year--an amount equivalent to the annual emissions of roughly 120 million cars. Our research shows that reducing the current methane leakage rate by two-thirds--i.e., down to 1 percent or less of total production--ensures that switching from diesel or coal to natural gas provides a net climate benefit over any time horizon. Furthermore, we find that we can reach the 1 percent target through existing state and federal policies and the widespread use of cost-effective technologies.
Start with “Green Completions”
The U.S. Environmental Protection Agency (EPA) recently took significant steps toward addressing emissions from new gas development sites. The EPA’s New Source Performance Standards (NSPS), finalized in April 2012, aim to reduce volatile organic compounds (VOCs) and air toxics, but have the co-benefit of reducing fugitive methane. The rule requires “green completions” for all hydraulic fracturing operations, ensuring that methane emissions are no longer intentionally vented from shale gas wells. (The rule does not address methane accidentally leaked throughout the natural gas lifecycle). Our analysis finds that the rule will reduce total upstream methane emissions by 17 percent by 2015 and 29 percent by 2035 (see gold line in the figure below).
Apply 3 Technologies
EPA’s recent policy can get the United States closer to the 1 percent leakage target, but a lot of work remains to be done. Widespread implementation of three additional emissions-control technologies on new and existing wells and equipment can help significantly. Using plunger lift systems, switching the existing stock of high-bleed pneumatic devices to low-bleed equivalents, and using methane leak detection and repair technologies at processing plants and compressor stations can reduce emissions by another 30 percent, bringing the overall leakage rate down to just over 1 percent (see purple line in the figure below). These technologies are extremely cost-effective, paying for themselves in three years or sooner.
Use Existing Authorities to Address GHG Emissions Directly
To meet and surpass the 1 percent leakage target, it will be important to address methane directly rather than relying on co-benefits of rules that address VOCs or other pollutants, which miss significant sources of fugitive methane emissions. Fortunately, many policy pathways exist at the state and federal levels that, with the appropriate level of ambition and combined with NSPS and policies that encourage use of the aforementioned technologies, can get us below the 1 percent target (see the green “Go Getter” scenario in the above infographic).
The federal Clean Air Act, for example, is an appropriate tool for setting national standards for pollutants, including GHGs like methane. The EPA could establish new performance standards for both methane and carbon dioxide to reduce new and existing sources of these harmful pollutants throughout the natural gas supply chain.
Moving Forward with Emissions Reductions
Climate change is happening faster than scientists were predicting just a few years ago, and we know that methane emissions are partly responsible for fueling this warming. Cutting methane leakage from natural gas systems is a key step in meeting the United States’ stated goal of reducing its greenhouse gas emissions 17 percent below 2005 levels by 2020.
We have the technology and we know the policies. Now, it’s up to the industry and government to ensure that fugitive methane emissions are kept as low as possible.