Natural gas is increasingly considered a cleaner alternative to coal when it comes to energy production--not to mention a greener alternative to gasoline when used in vehicles like the Honda Civic Natural Gas.

However, a new study suggests its green credentials may be damaged by methane leaks--negating any benefit from shifting to gas from dirtier coal-generated electricity.

As Nature reports, some plants are leaking significant amounts of methane into the atmosphere.

In a meeting with the National Oceanic and Atmospheric Administration, one research team suggested that a plant in the Uinta Basin of Utah was leaking up to 9 percent of its total production--nearly double that of the cumulative loss rates from industry data.

Another field near Denver, Colorado, was estimated to leak around 4 percent of its output.

Scientists at the Environmental Defense Fund (EDF) and Princeton University say that shifting to natural gas from coal has immediate climatic benefits--provided the cumulative leakage rate from natural gas production is below 3.2 percent.

Methane is a powerful greenhouse gas, estimated to be around 70 times stronger than carbon dioxide over a 20-year time frame. While its overall contribution to greenhouse gases is lower than CO2, large-scale leaks can offset the benefits of its use compared to coal.

Provided leaks are kept in check, the benefits of natural gas accumulate over time, particularly if methane plants replace coal stations.

Official figures for methane leaks are lower than recent studies. The Environmental Protection Agency estimated in 2009 that cumulative leaks totaled only 2.4 percent--below EDF and Princeton's safe limit.

The NOAA and the University of Texas are now launching a comprehensive study of natural gas emissions across the U.S, to determine whether leaks really are as big a problem as they're beginning to seem.

If plants nationwide are leaking methane at similar rates to those detected in Colorado--or worse, the plant in Utah--then the benefits of gas-generated electricity of CNG could be minimal.

[Hat tip: Brian Henderson]


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