Does Shale Gas Benefit or Add To Greenhouse Gas Emissions?

There have been several studies of the impact of natural gas produced from shale on air pollution and greenhouse gas (GHG) emissions. Selected critics believe that methane and other emissions from shale production are greater than commonly thought, but the majority of experts find the emissions associated with shale gas-fueled electric power generation to be significantly lower than those using coal or oil as a fuel source.


Studies/Experts Citing Higher Emissions Impacts for Shale Gas Studies/Experts Finding Lower Emissions Impacts for Shale Gas
   
Methane and the greenhouse-gas footprint of natural gas from shale formations – Howarth and Ingraffea (2011)Cornell professors ignited controversy when they said emissions from natural gas produced from shale rock are worse than coal production and combustion. Clearing the Air: Reducing Upstream Greenhouse Gas Emissions from U.S. Natural Gas Systems – World Resources Institute (2013)Key findings include: “Cutting methane leakage rates from natural gas systems to less than 1 percent of total production would ensure that the climate impacts of natural gas are lower than coal or diesel fuel over any time horizon. This goal can be achieved by reducing emissions by one-half to two-thirds below current levels through the widespread use of proven, cost-effective technologies.”
Inventory of Greenhouse Gas Emissions and Sinks  1990–2009 – Environmental Protection Agency (2011)In 2011, EPA introduced a new calculation method that doubled the agency’s previous estimates of emissions from natural gas production based on an extrapolation from small sample. Surprise Side Effect Of Shale Gas Boom: A Plunge In U.S. Greenhouse Gas Emissions – Julie Carey/Navigant Economics via Forbes (2012)“One of the primary factors for much of the improvement in the U.S. environmental picture includes the shale gas revolution … the country’s increased reliance on natural gas (and displacement of some coal-fired generation) has already benefited the environment, and will continue to do so in the future.”
Characterizing Pivotal Sources of Methane
Emissions from Natural Gas Production
 – URS Corp./LEVON Group (2012)Survey of 91,000 wells in producing formations across the U.S. (October 2012) found that methane emissions from natural gas production are 53 percent below what the Environmental Protection Agency had estimated in 2011. URS collected data for 26% of all US gas wells in 19 of the 21 most significant producing basins. The survey sample employed was 10 times greater than EPA’s. Methane emissions tracked through different stages of production.
Commentary on Methane and the greenhouse-gas footprint of natural gas from shale formations – Cathles et al, Cornell University (2011)Review of widely-publicized Howarth/Ingraffea disputes their findings in several areas.
Life Cycle Greenhouse Gas Analysis of Natural Gas Extraction & Delivery in the U.S. – DOE/National Energy Technology Laboratory (2011)Life cycle analysis: natural gas combined cycle power plant has a 54% lower long-term global warming potential than a comparable coal fueled plant.
Life cycle greenhouse gas emissions of Marcellus shale gas – Carnegie Mellon University (2011)Study finds that natural gas from the Marcellus shale has generally lower life cycle GHG emissions than coal for production of electricity by 20–50% margin.
The greenhouse impact of unconventional
gas for electricity generation
 – University of Maryland October (2011)Study argues that arguments that natural gas is dirtier than coal are unjustified
Comparing Life Cycle Greenhouse Gas Emissions from Natural Gas & Coal – Worldwatch Institute/Deutsche Bank Climate Change Advisors (2011) See also related press release.On average, U.S. natural gas fired electricity generation still emitted 47 less greenhouse gases than coal from source to use, even with adjustments for increased global warming potential for methane.
Some Thoughts in the Howarth Shale Gas Paper– Michael Levi, Council on Foreign Relations (2011)“[Howarth’s] analysis is based on extremely weak data, and also has a severe methodological flaw (plus some other questionable decisions), all of which means that his bottom line conclusions shouldn’t carry weight.”
Mis-measuring Methane: Estimating Greenhouse Gas Emissions from Upstream Natural Gas Development – IHS/CERA (2011) – see also related press release.“Estimates [of methane emissions] are being used that are not supported by data, do not reflect current industry practice and would be unreliable to use as a base for decision-making.”
Characterizing Pivotal Sources of Methane
Emissions from Natural Gas Production
 – URS Corp./LEVON Group (2012)Survey of 91,000 wells in producing formations across the U.S. (October 2012) found that methane emissions from natural gas production are 53 percent below what the Environmental Protection Agency had estimated in 2011. URS collected data for 26% of all US gas wells in 19 of the 21 most significant producing basins. The survey sample employed was 10 times greater than EPA’s. Methane emissions tracked through different stages of production.
Commentary on Methane and the greenhouse-gas footprint of natural gas from shale formations – Cathles et al, Cornell University (2011)Review of widely-publicized Howarth/Ingraffea disputes their findings in several areas.
Life Cycle Greenhouse Gas Analysis of Natural Gas Extraction & Delivery in the U.S. – DOE/National Energy Technology Laboratory (2011)Life cycle analysis: natural gas combined cycle power plant has a 54% lower long-term global warming potential than a comparable coal fueled plant
Life cycle greenhouse gas emissions of Marcellus shale gas – Carnegie Mellon University (2011)Study finds that natural gas from the Marcellus shale has generally lower life cycle GHG emissions than coal for production of electricity by 20–50% margin.
The greenhouse impact of unconventional
gas for electricity generation
 – University of Maryland October (2011)Study argues that arguments that natural gas is dirtier than coal are unjustified
Comparing Life Cycle Greenhouse Gas Emissions from Natural Gas & Coal – Worldwatch Institute/Deutsche Bank Climate Change Advisors (2011) See also related press release.On average, U.S. natural gas fired electricity generation still emitted 47 less greenhouse gases than coal from source to use, even with adjustments for increased global warming potential for methane.
Some Thoughts in the Howarth Shale Gas Paper– Michael Levi, Council on Foreign Relations (2011)“[Howarth’s] analysis is based on extremely weak data, and also has a severe methodological flaw (plus some other questionable decisions), all of which means that his bottom line conclusions shouldn’t carry weight.”
Mis-measuring Methane: Estimating Greenhouse Gas Emissions from Upstream Natural Gas Development – IHS/CERA (2011) – see also related press release.“Estimates [of methane emissions] are being used that are not supported by data, do not reflect current industry practice and would be unreliable to use as a base for decision-making.”
Still Not Worse than Coal – Geoffrey Styles, GSW Strategy Group via the Energy Collective(2011)Calls into question many of the assumptions underlying the Howarth study.
Gas Is Cleaner Than Coal: What Cornell Prof Gets Right and Wrong – John Hangar, former Secretary, Pennsylvania Dept. of Environmental Protection (2011)Horwath’s conclusion that gas emits more heat trapping gas than carbon flies in the face of numerous life cycle studies done around the world.
Shale gas production: potential versus actual greenhouse gas emissions – O’Sullivan & Paltsev, MIT (2012) – see also Study finds methane emissions at wells to be lower than EPA or Howarth study estimates
Additional reactions to Howarth paper collected by Energy in Depth (2011)