UPDATE II (8/24/2012, 11:02am ET): The U.S. Department of Energy’s National Energy Technology Laboratory has released yet another report showing that natural gas has roughly half the GHG emissions as coal, yet another nail in the coffin for the Howarth paper that tried to claim the complete opposite. Platts has a great story (subs. required) describing NETL’s findings, but here’s a key excerpt:
The large resource base of natural gas in the US can be used for cost-effective power generation, with environmental burdens coming primarily from burning the gas rather than producing it, the Department of Energy said in a report Thursday.
The global warming potential of “fugitive” methane released during the life cycle of gas from extraction to combustion is half that of coal as measured over both 20-year and 100-year periods, the study said.
The findings contradict previous studies, including one by Cornell University researchers Anthony Ingraffea and Robert Howarth that said the methane leaked over gas’ life cycle has a larger carbon footprint than coal over a 20-year span.
UPDATE (7/11/2012, 10:11am ET): Professor Cathles has released a new paper describing the climate benefits of utilizing natural gas, a paper that adds yet another nail in the coffin to the universally panned Howarth paper from last year. From the Cathles paper’s opening summary:
We show that substitution of natural gas reduces global warming by 40% of that which could be attained by the substitution of zero carbon energy sources. At methane leakage rates that are 1% of production, which is similar to today’s probable leakage rate of 1.5% of production, the 40% benefit is realized as gas substitution occurs.
Cathles also directly rebuts Howarth’s central claim that methane leaks constitute as much as 7.9 percent of production. “It’s just an impossible number,” Cathles told Bloomberg News. He added that “the story is quite clear that we would be very well advised to substitute natural gas” for coal and oil.
Interestingly, Cathles also found that even if the leakage rate were more than twice as high as Howarth’s upper end estimate of 7.9%, converting to natural gas would still provide climate benefits. “[S]ubstituting gas will be beneficial if the leakage rate is less than ~19% of production,” Cathles concludes.
—Original post, March 1, 2012—
We all know about the infamous (and universally panned) Cornell study from last year alleging high greenhouse gas emissions from shale development. But in case assessments by the U.S. Department of Energy, environmental groups, independent scientists, and even former state regulators weren’t enough to convince you that Howarth’s conclusions are fundamentally flawed, his own colleagues at Cornell are questioning Howarth’s findings. Again.
Some quick history: Last April, Professor Robert Howarth et. al. released their paper on GHG emissions from shale wells. But a few months ago, Dr. Lawrence M. Cathles (professor of Earth and Atmospheric Sciences at Cornell University) and a team of other scientists responded to the paper by noting, among other things, that it relies on unrealistic assumptions of emissions and improper time intervals to determine warming potential. (Andrew Revkin at the New York Times had a good write-up on the Cathles response.) Shortly after, Howarth et. al. responded to the Cathles et. al. response, essentially just regurgitating their previous talking points, without offering substantive response to virtually any of the conclusions reached by Cathles and his team. And now (bear with us here), Cathles et. al. have responded to Howarth’s response to Cathles’s response to the original Howarth paper. Got it?
What does the Cathles team say about the findings in the Howarth paper? From the release: “Here we reiterate and substantiate our charges that none of these conclusions are warranted, especially in the light of new data and models.”
The latest response is worth reading in its entirety, but here’s a sampling of some of the most noteworthy conclusions:
Howarth Study Overestimates Leakage and Venting Rates
- “This spectacular increase in the possible leakage is achieved by inflating leakages in (1) distribution, transportation and storage, and (2) routine on site leakage categories. In the first case the basis given for the inflation is (a) a leakage in Russian pipelines that occurred during the breakup of the Soviet Union which is irrelevant to gas pipelines in the U.S., and (b) a debate on the accounting of gas in Texas pipelines that is mainly a concern over royalties and tax returns (Percival, 2010). Howarth et al. claim the industry is seeking to hide methane losses of more than 5% of the gas transmitted, but the proponents in the article state ‘We don’t think they’re really losing the gas, we just think they’re not paying for it‘.” (Cathles response, p. 2-3)
- Howarth et. al. relied on data from a GAO study that is, among other things, an outlier. “The GAO data may deserve careful examination, but to adopt it’s [sic] estimates as representative of vented gas without making clear the assumptions involved and its outlier status is to distort its significance at the very least.” And as Cathles et. al. further note, “It is this large increase in venting that allows them to make their controversial charge” about high GHG emissions. (Cathles response, p. 3)
- “Howarth et al.(2011) do not treat shale gas venting as suggested by the EPA(2010) technical support document; instead they tacitly assume without any justification, that all gas was vented (not 50% as suggested by the EPA, or 85% as has become common practice by many others).” (Cathles response, p. 4)
- “[W]e can find no reason to suspect that it is current industry practice to vent gas during these periods at the extreme rates and quantities Howarth et al. suggest, and we find obvious economic and safety reasons that this would not be industry practice.” (Cathles response, p. 4-5)
- “The fundamental error of both Howarth and the EPA is to assume that evidence of capture is evidence of venting. Documenting that a small group of students are honest (capture gas) is not evidence that everyone else cheats (vents gas). This error is compounded by their adoption of venting magnitudes that are far too high.” (Cathles response, p. 5)
- “Thus only 3% of the 1578 wells studied vented methane into the atmosphere, a figure very much less than Howarth et al.’s presumption that all unconventional wells are 100% vented during well completion and workover.” (Cathles response, p. 5)
Howarth Study Uses Wrong Time Frame for Measuring GWP
- “Howarth et al. (2012) use a 20 year Global Warming Potential (GWP) for comparing coal and shale gas because of the supposed urgency of cutting emissions immediately, although they did not clearly provide any such justification in their original paper.” (Cathles response, p. 6)
- “Howarth et al. raise a completely false conundrum with their claim that substituting natural gas for coal has no value because some yet unknown climatic tipping point may [be] reached sometime over the next 20 years or so.” (Cathles response, p. 7)
Howarth Study Makes Improper Fuel Comparisons
- “We therefore find completely puzzling Howarth et al.’s continued insistence on citing other uses of natural gas, such as cooking and home heating, as a justification for comparing natural gas and coal on a heat content rather than electricity generation basis. Society is unlikely to reverse course and install coal‐fired heating and cooking systems in residential, commercial, or industrial facilities. No other life cycle analysis of which we are aware makes this irrelevant and misleading comparison.” (Cathles response, p. 7)
- “We feel that it is simply misleading to continue to cite comparisons between gas and coal on the basis of heat.” (Cathles response, p. 8 )
Howarth Response Mischaracterizes Industry and Uses It as ‘Evidence’
- “Howarth et al. state ‘While visiting Cornell, a Shell engineer stated Shell never flares gas during well completion in its Pennsylvania Marcellus operations (Bill Langin, Pers. Comm.).’ This evidence is used to bolster their claim that large quantities of gas are vented during shale gas well completion. We checked with Shell and they provided the statement … which states that Howarth’s above statement is a missrepresentation of the conversation that actually took place. According to Langin and Shell, Langin was asked whether ‘Shell routinely flares during flowback’, to which he replied no, Shell usually puts flowback gases into the pipeline for sales.” (Cathles response, p. 8 )