Bridge Fuel

As we recognize the need for energy independence and alternative sources to power our nation, natural gas is an important economic driver and a critical bridge fuel.

Rep. Dianne DeGette, D-CO

When the total emissions of greenhouse gases are considered, Greenhouse gas emissions from HVSWHF-obtained natural gas are estimated to be 60% more than for diesel fuel and gasoline. HVSWHF-obtained natural gas and coal from mountain-top removal probably have similar releases. These numbers should be treated with caution. Nonetheless, until better estimates are generated and rigorously reviewed, society should be wary of claims that natural gas is a desirable fuel in terms of the consequences on global warming.

Robert Howarth, David R. Atkinson Professor of Ecology & Environmental Biology, Cornell University.

One frequently reads and hears reports on scientific papers in the mainstream press. Whether it is some interesting tidbit about astronomy, the discovery of a planet perhaps, or something from medical biology such as new data on the effects of certain vitamins on general health, science news is either interesting or important. Yet, journalists aren't scientists (and most will admit that under pressure) and sometimes, in the desire to provide timely information they make mistakes. There is nothing wrong with this, and the errors are of the kind that most folks, including many scientists, make, such as confusing correlation and causality.

When there is an issue freighted with so much political, financial, economic, and environmental baggage as a report on the greenhouse gas footprint of fossil fuels, however, the itch to sensationalize may seem overwhelming. In April, Robert Howarth of Cornell University and some colleagues published a paper on the net total effect of natural gas extraction and combustion, comparing it to the extraction and combustion of coal. While admitting up front they had limited data, and revising their estimates based upon misstating the rate of capture of methane within coal veins and mines, they discovered that, far from being a "clean alternative" or "bridge fuel" from dirty coal, the entire process for getting natural gas out of the ground, getting it to municipal generating stations and underground storage tanks where it can be sent through pipelines to residential gas users has a similar overall potential impact to coal.

If you Google "Robert Howarth", among the links provided at the top of the list of 1.9 million include such stories as these: "Natural Gas May Be Worse for the Planet than Coal", in the April 16, 2010 edition of Technology Review; "BBC News – Shale gas ‘worse than coal’ for climate", on the homepage of Gas Drilling Awareness for Cortland County[, NY]; "The Clean Fossil Fuel? Natural Gas Under Fire", from May 9 of this year on the website The Txchnologist, a site sponsored by GE; "Shale gas worse than coal: study", an April 27 report from the Canadian Broadcasting Corporation.

All this breathless reporting has been met by equally breathless retorts from the industry. America's Natural Gas Alliance, the industry umbrella organization, was quick to make clear the limitations of Howarth's study.

News of the National Energy Technology Laboratory's (NETL) presentation supporting the fact that natural gas produces half the greenhouse gas emissions of coal came out last week just as debunked professor Robert Howarth went to Washington to trot out his baseless claim that somehow natural gas is actually a less clean fuel.

News of the National Energy Technology Laboratory's (NETL) presentation supporting the fact that natural gas produces half the greenhouse gas emissions of coal came out last week just as debunked professor Robert Howarth went to Washington to trot out his baseless claim that somehow natural gas is actually a less clean fuel.

The NETL, according to its website, is "part of DOE’s national laboratory system, ... owned and operated by the U.S. Department of Energy (DOE). NETL supports DOE’s mission to advance the national, economic, and energy security of the United States." The report in question is a detailed analysis of the overall greenhouse gas (GHG in the linked report) footprint of natural gas, from cradle to grace, as it were, and it contradicts Howarth's study. In a summary on the website Marcellus Drilling News, the NETL study is summarized as follows:

…the Department of Energy’s National Energy Technology Laboratory (NETL) has applied ISO standard methodology, and a substantial understanding of industry operations, to do the calculation itself… Its conclusion? Used to generate electricity, natural gas – conventional or not – results in far less emissions than coal.

Using a 100-year global warming potential and assuming an average power plant, unconventional gas results in 54% less lifecycle greenhouse gas emissions than coal does. Even using a 20-year global warming potential, as Howarth controversially argues one should, the savings from substituting unconventional gas for coal are almost 50%. The NETL study acknowledges – and explores – a range of uncertainties. But it finds nothing close to the problems that Howarth claims.

Howarth found a large fraction of produced gas from unconventional wells never made it to end users, assumed that all of that gas was vented as methane, and thus concluded that the global warming impacts were huge. As the NETL work explains, though, 62% of that gas isn’t lost at all – it’s “used to power equipment”.

No less an institution than the Council on Foreign Relations has weighed in.

The NETL documents don’t address the Howarth study explicitly, but if you flip to page 25, you’ll see a big part of the discrepancy explained. Some readers will recall that Howarth found a large fraction of produced gas from unconventional wells never made it to end users, assumed that all of that gas was vented as methane, and thus concluded that the global warming impacts were huge. As the NETL work explains, though, 62% of that gas isn’t lost at all – it’s “used to power equipment”.

The NETL work also does a much more careful job looking at things like losses from long distance transmission. In addition, it doesn’t include losses from local distribution, since there’s no local distribution involved in using gas for power generation.

Bottom line: Those who were skeptical of the Howarth study were reacting correctly. There’s still much useful work to be done, but for now, the NETL work is a far more useful guide for thinking through the gas emissions issue.

Since this is science, even as it is laced with politics - big politics, big money, big stakes - the argument, I believe, will go on, but I would offer a couple thoughts on the controversy. First, the issue of the greenhouse has footprint of natural gas is, overall, less urgent than the potential for long-term environmental damage from the process used to extract it, what the NETL report calls "unconventional wells", hydraulic fracturing. Trying to taint natural gas with culpability in global warming misses the point. The threat from hydraulic fracturing is very real, very immediate, yet also long-term, and (perhaps) only tangentially related to matters of global warming.

This is not to suggest that continued study of the question of the cleanliness of natural gas is unwarranted. Given the highly-charged atmosphere (no pun intended), any study will become fodder for whichever side feels their ox is being gored. The question of whether or not considering natural gas a "bridge fuel" to cleaner energy production and use should be continually evaluated. For now, however, the question is not gas's status as a bridge. Instead, studies of the impact of hydraulic fracturing on ground water and soil health should be conducted, and attention should focus on the already-existing questions and problems surrounding the life-cycle of natural gas.