Monday, February 25, 2013

Fracking's Impact on Climate Change

by Duncan Gromko

Although the enviro community is currently arguing over the Keystone XL pipeline (my take on this disagreement), I think the biggest fight on the horizon is over fracking. On the one hand, burning natural gas is cleaner than burning coal, both in terms of local impacts and global greenhouse gas emissions. Natural gas has been billed as a "bridge fuel" that will reduce emissions in the near term while renewables slowly replace fossil fuels. Per unit of energy, burning natural gas emits about half the carbon dioxide as coal. On the other hand, extracting the natural gas through fracking could endanger local water supply.

Source: Flickr.
While that is an important tradeoff that I will address at some point (and I think the ecosystem services framework is a great way to look at the issue), in this post I'm just going to stick to the global impacts of fracking and increased natural gas supply.

What is the impact of natural gas on climate change?

Well, unfortunately, this issue is complicated as shit. In the long term, the low cost of natural gas might be making renewables less competitive, ultimately undermining efforts to reduce GHG emissions in the power sector. There's already evidence that natural gas is undermining nuclear and wind power. Also, by investing in natural gas infrastructure, we may be locking ourselves into natural gas. Those issues are longer term and harder to predict.

Setting that argument aside, natural gas has been billed as a bridge fuel because energy produced from natural gas emits less carbon dixoide. Think Progress estimated that 6% of the recent CO2 emissions drop was due to the switch from coal to natural gas. The idea is that, while we're undergoing a long-term transition from fossil fuels to renewables, natural gas can help us reduce greenhouse gas emissions in a cost-effective way. If we're talking about reducing emissions by about 20% of 1990 levels by 2020, natural gas could play an important role.

However, there is a climate problem with fracking: methane leakage. Basically, while natural gas is being captured via fracking (let's be clear here, methane = natural gas), methane is released into the atmosphere. And methane has about 20 times the greenhouse gas effect as carbon dixoide. Even if natural gas production reduced CO2 emissions, it could have a negative impact on the climate if methane emissions offset this gain.

A PNAS/EDF paper says that as long as leakage is below 3.2%, the CO2 benefits of natural gas will offset the methane negatives. 3.2% leakage is kind of the climate tipping point for natural gas. If leakage is greater than 3.2%, the climate negative of the leaked methane will be greater than the climate benefit from lower CO2 emissions.

While everyone is getting excited about the US drop in CO2 emissions, my big question is: what has happened to methane emissions over the same time period? Have methane emissions (from fracking) been offset CO2 emissions?

It's tough to measure the leakage rate for the natural gas industry as a whole. Using EPA data, Richard Meyer estimated a leakage rate for the entire natural gas sector of about 1.2%. Using older data, Ramon Alvarez et al estimated 2.4%. Howarth et al estimated 3.85%. So there is significant disagreement. But the interesting question here is: what are the additional methane emissions from fracking? Howarth estimated that fracking leads to an additional 1.9% of leakage, but they used data from five gas formations, not the entire country. O'Sullivan estimated fracking leakage at 0.4-1.0%. As a new industry, I'm sure that leakage varies widely operation to operation. There is potential to reduce leakage with new technology and regulation.

Overall, US methane emissions have fallen by about 10% since 1990 because of improved technology; leakage during fracking isn't the only place for improvement.

And the situation in the US is different from Europe, China, Mexico, and Argentina, which also have large shale gas reserves. There might be more climate benefits in China, for instance, where 80% of electricity comes from coal and hundreds more coal plants are being built. However, China has greater problems with water scarcity, so watershed protection would be a greater concern.'s complicated and I don't think there is a straightforward answer. I hope that methane emissions are better understood before we commit to natural gas and fracking as a climate solution. Fortunately, the EPA has resolved to do just that and the Department of the Interior is looking into regulation possibilities.

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