Energy Exchange

By: Steven Hamburg, EDF’s Chief Scientist

This week the National Oceanic and Atmospheric Administration (NOAA) released a study that estimates that natural gas producers in an area known as the Denver-Julesburg Basin are leaking roughly 4% of their gas – or methane – into the atmosphere.  Leaks of that magnitude could undermine natural gas’ role as a lower carbon alternative to coal and oil.  This is yet another contribution to the long running debate about exactly how much methane is vented or leaked during the production and distribution of natural gas.  The questions are: Why does this matter, and why is what NOAA saying an interesting and new contribution to this debate?

A recent paper in Science illustrates that reducing methane emissions and black carbon can have a positive near-term impact on the climate system.  It is becoming clearer that reducing methane emissions is key to reducing net radiative forcing (or the amount of energy reaching the surface of the earth), which – in turn – helps reduce the chances of a climate catastrophe.  The Environmental Protection Agency (EPA) inventory of U.S. greenhouse gas pollution shows that the oil and gas sector is the largest source of man-made methane, and most of those methane emissions are from leaks resulting from the production and transport of natural gas. 

As we’ve mentioned before, it is clear that the actual combustion of natural gas is cleaner than the combustion of gasoline or diesel, but there are other emissions associated with the production, delivery and use of those fuels.  Natural gas is largely methane, even when it comes out of the ground, and as a result is a potent greenhouse gas.  Over the first 2o years after it is emitted, a pound of methane is 72 times more potent than a pound of carbon dioxide when it comes to trapping heat.  As natural gas is produced and piped across the country, there are plenty of opportunities for it to leak into the atmosphere.  EPA estimates that leak rate to be somewhere between 2-3%, but the exact amount is the subject of much debate.

At a 2-3% leak rate, natural gas-produced energy has a net benefit to the climate system as compared to producing energy using coal.  If we want to reduce the risk of climate surprises and increasingly frequent extreme weather events, reducing leak rates from natural gas production is one of the most effective ways of doing so, at least in the short term.

Given that natural gas produced by un-conventional means already represents more than one third of US production, the key issue moving forward regarding leak rates is not whether they are high or low, but rather how to ensure that they are as low as technically possible.  The NOAA study provides an important new set of data, but only one snap shot of what is happening in natural gas production fields. 

Unfortunately, the news here is not good, in that it finds methane leak rates to be almost twice as high as the EPA estimates – which would mean that, in the short-term and absence of leak reductions, natural gas is unlikely to be better for the climate than is coal.  Though there are a few larger studies that are gearing up which plan to use a diverse array of techniques that add to the NOAA study to better define overall leak rates, scientifically sound and rigorous sampling and monitoring is still much-needed to quantify the average amount of methane emissions that result from natural gas production.  No matter what the data will show about leak rates, though, the next steps are clear – reduce leak rates!

One of the central questions that the forth coming research needs to answer is: Where are the leaks happening and, in turn, what needs to be done to minimize them? It is possible that a relatively small percentage of wells account for a large majority of emissions, meaning that getting practices right at just these high-emitting wells could reduce overall leak rates significantly.  

Getting practices right entails implementing the Department of Energy’s Shale Gas Production Subcommittee’s recommendations, which propose a focused set of steps for strengthening environmental management in the shale gas industry.  The Subcommitte’s report calls for measures to be taken to reduce emissions of air pollutants, ozone precursors, and methane as quickly as practicable and stresses the need for gathering the data necessary to determine whether, and to what degree, natural gas provides greenhouse gas benefits when substituted for coal or oil in energy production or transportation.

As EDF, and others, collect much-needed data the picture will quickly become clearer.  Stay tuned to the Energy Exchange for more information on this topic.