Natural gas is often labelled a ‘clean fuel’, at least compared to oil. In fact, natural gas has about 20% fewer greenhouse gas emissions than oil, for the same amount of energy, but, after leaks from natural gas distribution systems are taken into account the gap between gas and oil is narrowed to a figure closer to about 10% benefit in favour of gas.
Now a group of Cornell University scientists, Robert W. Howarth et al., have published the results of research that indicate that shale gas, the product of “fracking”, has a carbon footprint significantly worse than that of oil or coal. The article states that “3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the lifetime of a well. These methane emissions are at least 30% more than and perhaps more than twice as great as those from conventional gas.” The result, according to this research, is that the carbon “footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly so over 20 years. Compared to coal, the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.”
The research paper, which uses a lifecycle approach, is available in the peer-reviewed journal Climatic Change at http://www.springerlink.com/content/e384226wr4160653/fulltext.pdf
A response from other scientists at Cornell argues that leaks of gas from shale gas plants are not as large as the Howarth paper reports and that the carbon footprint of shale gas is therefore not as large or as bad as indicated. Their response is available at http://www.springerlink.com/content/x001g12t2332462p/fulltext.pdf