Methane Leakage Emissions

Cornell professors Robert Howarth, Renee Santoro, and Anthony Ingraffea ignited a controversy in 2011 when they published a study claiming that, due to escaped methane, emissions from hydraulically fractured natural gas were worse than coal. Their study showed that the escaped gas amounted to four to eight percent of total gas production, more than twice the EPA’s estimate for the same figure.

Two different studies, one from Cornell and another from MIT, produced their own analyses criticizing Howarth et. al.’s claims on the grounds that their data set was too small, their assumptions incorrect. Both studies concluded that hydro fracturing leaked little gas. But both studies criticized Howarth et. al.’s assumptions by way of offering new assumptions, but no new data or measurements. Nothing was settled.

Carbon dioxide emissions—with the exception of emissions from transportation—come from large, industrial sources. By contrast, methane emissions leak out of hundreds of thousands of sources that include valves, pipes, landfills, and waste pools.  In oil and gas production, these emissions, known as ‘fugitive’, are just that; they steal out of the equipment and infrastructure and go uncounted into the atmosphere. The Environmental Protection Agency requires gas production, processing and transmission facilities to report fugitive emissions using emissions using estimates based on a predetermined calculation for leakage rates for each piece of equipment. But actual leakage rates can vary depending on the type of equipment, how it is maintained, the type and pressure of the gas that it conveys, and the geology of the formation from which it is withdrawn. The estimations are necessarily inexact. There are no direct measurements, and so much room for controversy.    

Recently, the Environmental Defense Fund attempted to fill the data gap by coordinating a study that took direct measurements of gas flow back from wells. Results showed that wells constructed using advanced technology leaked only 0.42 percent of production—much less than Howarth et. al.’s or EPA’s estimates. But the study settled nothing due to skepticism due to over sample bias—companies that voluntarily cooperate with fugitive emissions studies are likely to be the best actors.     

Then last month yet another study of fugitive methane emissions lead by Harvard claimed that emissions for the 2007-2008 period were 50 percent above the estimates used by the EPA for that year. The Harvard study is different to preceding studies in that it doesn’t rely on estimates or incomplete measurements, but rather uses to cell phone tower and airplane mounted instruments to detect the mass balance of methane in the air. The data is harder to quibble with.

The findings prompted Henry Waxman to call for hearings on methane emissions and global warming consequences of natural gas extraction. Given the current leadership of the House Energy and Commerce Committee, hearings are unlikely to happen. But methane emissions need more oversight. Uncertainties over methane leakage are just part its underreporting. New science on the global warming impacts of methane also point to it being a much larger portion of U.S. emissions than is currently reflected in U.S emissions inventories.

Methane emissions in the EPA inventory are not given in terms of tons of methane, but tons of carbon dioxide equivalent, or the potency of any gas a greenhouse forcer compared to carbon dioxide. Carbon dioxide equivalent is calculated through a conversion factor called Global Warming Potential (GWP). Estimation of the Global Warming Potential of a gas is complicated. The single number of Global Warming Potential is meant to capture the gas’s comparative power to absorb infrared radiation, its lifetime in the atmosphere and its indirect effects, including induced changes in tropospheric ozone, water vapor levels, and CO2 production. Most recently, the Intergovernmental Panel on Climate Change (IPCC), which sets the international standards recommended GWPs for gasses, has added climate feedback effects to the calculations.

The value of methane’s GWP has constantly changed as the science behind its derivation has evolved. In 1996 twenty-one was the IPCC’s recommended GWP for methane. Next year, the IPCC will revise its recommendations for methane’s GWP for the third time since 1996 from its current twenty-five to thirty-four. Methane numbers in the United States Inventories for Greenhouse Gasses and sinks, meanwhile, are still reported using the 1996 value of twenty-one. The EPA is in the process of updating the GWP for methane to twenty-five, the value recommended by the IPCC in 2007. The change will bring the United States emissions inventories up to the best available science of seven years ago, but leave methane emissions underreported by thirty-seven percent compared to the best available science of today.

The EPA decided to update to 2007 values in part to standardize with the recommendations of the United Nations Framework Convention on Climate Change (UNFCCC), which sets guidelines for international reporting. While it is valuable to be able to accurately compare the United States’ emissions to the rest of the world, it is arguably more important to have a realistic assessment of the comparative size and impact of different sources on a national level. Abatement decisions are not made on an international level, but driven by domestic energy interests and domestic regulatory assessments of significance, harm, and abatement costs within national borders. When numbers are skewed, there is a danger that decision-making will be skewed as well.

According to the EPA, total net emissions in the United States in 2011 were 5.75 billion tons of carbon dioxide equivalent. Of those emissions, methane constitutes 580 million tons, accounting for ten percent of total U.S emissions. If methane emissions in the United States are indeed underestimated by 50 percent, that would make them just over fourteen percent of total emissions. Incorporating the most accurate GWP—thirty-four—into the upward revised number for leakage, total methane emissions become 1.4 billion tons of carbon dioxide equivalent, or 2.4 times higher than emissions listed in the current national inventories, and twenty-one percent of total emissions. Even in the most conservative case where EPAs leakage rates are entirely accurate, if thirty-four were used as a conversion factor, methane would be reported as fourteen percent of total emissions.  

Control of fugitive methane emissions is simpler than the control of carbon dioxide emissions. Halting carbon dioxide emissions in the United States will require that trillions of dollars infrastructure currently locked into fossil fuels be retired and further trillions of dollars be invested in development and construction of non-emitting energy technologies. By contrast, controlling fugitive methane emissions requires that simple and already existing technologies be installed at a profit to the companies that install them. 

The failure to control fugitive methane despite the obvious benefits is a typical failure of energy efficiency to be effected. There are many reasons why large industries waste energy—and therefore money—including poor incentive structures, higher rates of return on an investment in the company’s main line of business than on investment in efficiency improvement, or poor understanding of where and how the gains are to be made.    

But in addition to wasting private money, energy inefficiency imposes a cost on the public through higher emissions and climate change. In the case of methane emissions through natural gas losses, the cost is thirty-four times higher than that of carbon dioxide for every ton of emissions wasted.  

Given the high cost to the public of methane emissions, the low cost of regulation to the emitters, and the continued failure of the market to stimulate action, there is a clear case for controlling emissions through regulation. President Obama has highlighted methane as a problem, saying a June 2013 speech, “We'll keep working with the industry to make drilling safer and cleaner, to make sure that we're not seeing methane emissions…” But the President’s Climate Action Plan has no specific plans for controlling methane. It calls in general terms for interagency partnerships to reduce methane emissions in agriculture, oil and gas. Concrete plans for controls are yet unarticulated.   

In referencing cleaner drilling, President Obama was referring to the EPA’s promulgation of New Source Performance Standards for the oil and gas production. The new regulation puts controls on certain wells, compressors, valves, and storage tanks upstream of processing. Gas wells with ‘green completions’ are the type of infrastructure that the Environmental Defense Fund monitored in its study showing a loss rate of 0.42 percent. The study is also the reason why many companies are claiming that Harvard study showing high leakage from the 2007-2008 period is outdated. The EPA’s New Source Performance Standards are not designed to control methane. They are designed for the control of hazardous and toxic pollutants such as benzene and xylene that are components of natural gas when it is extracted, but are removed during processing. Some methane is controlled as an ancillary benefit, but it is not the principal intent of the regulation. Thus, upstream of processing only very specific installations with high air toxics emissions are targeted. Installations downstream of processing are not affected by the regulation at all.  But about half of methane leaks from oil and gas production occur downstream of production. But EPA’s own estimate, this regulation will prevent between 1 and 1.7 million tons of methane emissions in the future, or between 3 and 5 percent of present day volume as reported by the EPA.

The EPA reports that emissions have dropped 12 percent since 2005. But even through conflicting reports, it is clear that the real magnitude of reductions remains unknown. Information increasingly points to methane emissions being a more serious component of the U.S. emissions than previously believed. The government needs to start taking the problem seriously, first through accurately reporting the emissions, and then through promulgating methane-targeted policy that controls emissions, rather than relying on regulations that were written without methane in mind.

Photo Credit: Methane Measurment/shutterstock