In August 2015, the U.S. Environmental Protection Agency (EPA) proposed new regulations for the oil and gas industries to cut emissions of methane into the atmosphere. These new regulations would have oil and gas drillers and operators:
- Finding and repairing leaks;
- Capturing natural gas from the completion of hydraulically fractured oil wells;
- Limiting emissions from new and modified pneumatic pumps; and
- Limiting emissions from several types of equipment used at natural gas transmission compressor stations, including compressors and pneumatic controllers.
This proposal was followed up in January 2016 by the Department of Interior proposing regulations to limit methane emissions from oil and gas drilling on public and tribal lands. Similar to EPA’s proposed regulations, it is aimed at eliminating any leaks from drilling equipment but goes further by requiring equipment to capture any flared or vented natural gas.
A third initiative, the EPA’s Natural Gas STAR Methane Challenge Program, which was already in place on a voluntary basis, will be officially launched at the end of March at the Global Methane Forum in Washington, DC. This program provides the mechanisms by which oil and gas companies can “reduce methane emissions, improve air quality, and capture and monetize this valuable energy resource.”
According to data collected by the National Oceanic & Atmosphere Administration (NOAA) Earth Systems Research Laboratory (ESRL), atmospheric methane concentration has been increasing over the last three decades similar to the concentration of carbon dioxide in the atmosphere. See the charts below from the ESRL’s website. Note the differences in the vertical scales.
The current atmospheric concentration of methane at 1,850 parts per billion (ppb) or 1.85 parts per million (ppm) is less than 0.5% of the current 400 ppm carbon dioxide concentration. But concentration alone does not tell the whole story. Methane actually has 25 times the Global Warming Potential (GWP) of carbon dioxide. GWP is defined as the amount of warming a greenhouse gas will cause over a given period of time.
Most climate change institutions use 100 years as the time horizon for estimating the GWP of methane as well as other greenhouse gases, such as nitrous oxide (N2O) and the various hydrofluorocarbons. The latter are generally lumped together and identified as fluorinated gases. Multiplying the actual amount of greenhouse gas emissions by its GWP gives what is known as its carbon dioxide equivalent (CO2eq). Expressing all greenhouse gases in terms of their CO2 equivalents is the technique used to show what impact each greenhouse gas has on global warming.
According to data collected by the U.S. Environmental Protection Agency (EPA), carbon dioxide accounted for 82% of greenhouse gas emissions in the United States in 2013. Based on their CO2 equivalents, methane is the next highest at 10%, followed by N2O at 5% and fluorinated gases at 3%.
However, based on data from the Intergovernmental Panel on Climate Change (IPCC), methane emissions on a global basis are much greater than what the EPA has inventoried for the United States. Again, based on CO2 equivalents, methane accounts for 16% of all global greenhouse gas emissions.
Interestingly, according to the EPA’s U.S. Greenhouse Gas Inventory Report 1990-2013, methane emissions declined from 745.49 tons of CO2eq in 1990 to 636.31 tons of CO2eq in 2013; a 15% decrease. Over the same time period, CO2 emissions increased by 7.5%.
Now you might rightly ask: if the methane concentration in the atmosphere has increased over the 1990 to 2013 time period, as shown above, how is it that the quantity of methane emissions in the U.S. has decreased over the same time period. I asked the EPA this question and received the following reply:
“EPA produces the annual Inventory of U.S. Greenhouse Gas Emissions and Sinks report on behalf of the U.S. Government to submit to the Secretariat of the United Nations Framework Convention on Climate Change (UNFCCC). It is an annual report required of the United States per its obligations as a Party to the UNFCCC. The report summarizes the latest information on total U.S. anthropogenic emissions of greenhouse gases across all sectors of the U.S. economy.
To meet the requirements of reporting greenhouse gas inventories to the UNFCCC, the annual Inventory of U.S. Greenhouse Gas Emissions and Sinks report focuses only on anthropogenic, or human-made, sources of emissions. This is based on inventory calculation guidance published by the Intergovernmental Panel on Climate Change (IPCC) (www.ipcc-nggip.iges.or.jp/). Additionally, the annual Inventory of U.S. Greenhouse Gas Emissions and Sinks report only focuses on greenhouse gas emissions produced from human-made activities in the U.S.
The measurements you reference include methane emissions from all countries across the world and these countries could have very different emissions trends than the U.S. alone. I welcome you to look at the research compiled by the IPCC in its periodic assessment reports which reflect the latest science on climate change (www.ipcc.ch/report/ar5/wg1/). Additionally there are useful tools produced by external organizations that publish greenhouse gas emissions data from all countries and which show the global methane emissions trends (cait.wri.org/historical/).”
Based on this response and the data shown above, the U.S. appears to be doing a much better job in reducing methane emissions than the rest of the world.
The proposed regulations by the EPA, the Department of Interior, and EPA’s voluntary Methane Challenge Program should do even more to help the U.S. in achieving its 2025 goal of reducing methane emissions by 40 to 45% from 2012 levels.