Methane and the greenhouse-gas footprint of natural gas from shale formations

In the quest to find solutions to the problem of greenhouse gas (GHG) emissions and climate change, many have pointed to natural gas as a cleaner burning fuel that could displace dirtier fuels such as coal or oil and help the world transition to alternative sources of energy. However, recent research has focused on the more intensive, “unconventional” industrial process that is being used to extract natural gas from shale formations — called hydraulic fracturing, or “hydrofracking” — and the waste gas that seeps out.

A 2011 study by Cornell University published in Climatic Change, “Methane and the Greenhouse-gas Footprint of Natural Gas from Shale Formations,” calculates the climate impact of unconventional natural gas extraction. Though carbon dioxide is the best known of the GHG that trap heat in the Earth’s atmosphere, methane gas can have an even more powerful effect.

The study’s findings include:

• Between 3.6 and 7.9% of the methane escapes into the atmosphere during shale-gas production due to venting and well leaks; this level is at least 30% higher than that released during conventional natural gas production.
• On a 20-year time horizon, the GHG footprint for shale gas is up to 43% higher than conventional natural gas, 50% greater than oil and 20% higher than coal for the same amount of energy produced by each of those other sources.

The researchers conclude that the “large GHG footprint of shale gas undercuts the logic of its use as a bridging fuel over coming decades, if the goal is to reduce global warming.” The study’s authors encourage policymakers to account for the full GHG footprint of unconventional gas as they chart the energy future and urge carbon trading markets, which currently have outdated models, to modify their valuations accordingly.

Tags: carbon, coal, fossil fuels, global warming, greenhouse gases, fracking