Electricity from gas produced by hydraulic fracturing, or fracking, releases about half the greenhouse gas emissions as coal, Colorado researchers reported Monday.
In a study [.pdf] published in the prestigious journal Proceedings of the National Academy of Sciences, researchers from Golden's National Renewable Energy Laboratory and the Joint Institute for Strategic Energy Analysis compared electricity from coal, conventional natural gas (produced without fracking) and unconventional shale gas, which is produced by hydraulic fracturing.
The research team, led by NREL senior researcher Garvin Heath, wanted to see how the three different raw materials for electricity stacked up in terms of the greenhouse gas emissions they release.
Existing studies on the topic had come to very different conclusions; Heath's team used a technique called harmonization to compare the studies on what he called an "apples to apples" basis. After doing the comparison, he found that electricity from natural gas, whether produced conventionally or from hydraulically fractured shale gas, is a lot better for the climate than coal.
"We see that life cycle GHG emissions from electricity generated from shale gas are similar to those from conventionally-produced natural gas. Both energy sources, on average, emit approximately half the GHG emissions of coal-powered electricity when considering emissions from the smoke stack and those upstream through the supply chain," Heath said in a press release.
This doesn't mean the debate on whether shale gas is better for the environment is solved, the researchers noted in their paper.
There is still a lot of debate over how much methane leaksfrom unconventional natural gas wells, which would affect greenhouse gas emissions, because methane is a very powerful greenhouse gas. The researchers did not analyze methane leaks in their study.
Colorado has also recently passedregulations that limit the amount of methane that can leak from natural gas production sites. These regulations are widelyviewed as a modelfor other states with significant energy production.
They also pointed out that there may be a few processes or wells that contribute a lot to greenhouse gas emissions, and just how much those high emitters contribute to the total amount of greenhouse gases produced isn't well known yet.
The researchers also noted that they did not consider natural gas used for transportation and heating. Past studies have shown that natural gas used as a fuel for transportation is not necessarily better for the climate, although it can be cleaner burning and better for overall air quality.
