A new study has found that government estimates of total methane emissions in the United States may be inaccurate. In fact, they may be underestimating the actual amount by as much as 50 percent, casting doubt on a recent decision by the Environmental Protection Agency (EPA) to reduce its emissions estimate.
A team of researchers – consisting of Anna Michalak of the Carnegie Institution for Science; Scot Miller and Steven Wofsy, both from Harvard University; and other colleagues – used measurements of methane in the atmosphere taken across North American in 2007 and 2008 in order to create a better estimate of methane emissions from a variety of sources, such as fossil fuel drilling, refining and agriculture.
However, these new estimates varied greatly from governmental estimates in certain regions of the country, especially in the south-central part of the country. In this area, total methane emissions were 2.7 times larger than those in most reports. Emissions from gas and oil drilling and processing could account for about half of this total, representing a methane source which is about five times more than what is in the most commonly used emissions database.
According the EPA, methane is the second most common greenhouse gas being emitted by human activity in the U.S. Carbon dioxide is the first. In 2011, methane made up about nine percent of all greenhouse gas emissions related to human activity. It is also emitted by natural sources, such as the raising of livestock and wetlands. Leakage from natural gas systems also add methane to the atmosphere.
Methane, however, does not remain in the atmosphere quite as long as carbon dioxide does. Natural processes, such as chemical reactions in the atmosphere and natural processes in the soil help to remove it.
Unfortunately, methane is better at trapping solar radiation than carbon dioxide is. Pound for pound, it has 20 times more impact on climate change than carbon dioxide does.
Some ways in which scientists say that methane emissions can be reduced include:
- Upgrading equipment used in producing, storing and transporting oil and gas in order to cut down on leaks
- Capturing methane emissions from coal mines and using it for energy
- Reducing and capturing methane given off by agriculture by changing feeding practices and manure management strategies
- Capturing methane emissions given off by landfills
The state of Colorado recently revealed that it had a proposal on the table for reducing its own methane emissions from oil and gas drilling. If the proposal becomes law, it would make Colorado the first state to enact such a law. It has been estimated that the proposed measures would reduce volatile organic compound (VOC) emissions by about 92,000 tons a year. When VOCs are reduced, methane emissions go down as well.
The study results were published during the week of November 25, 2013 in the online version of the scientific journal the Proceedings of the National Academy of Sciences.
By Nancy Schimelpfening
Overview of Greenhouse Gases – U.S Environmental Protection Agency