Press Release: Response to Howarth et al’s
Reply (February 29, 2012)
geo.cornell.edu
Lawrence M. Cathles (Department of Earth and Atmospheric Sciences, Cornell)
Larry Brown (Department of Earth and Atmospheric Sciences, Cornell)
Andrew Hunter (Department of Chemical and Biological Engineering, Cornell)
Milton Taam (Electronic Software Inc., Caroline)
In April of 2011 Howarth, Ingraffea and Santoro published online a letter in the journal
Climatic Change to essentially argue that coal is a “cleaner” fuel than natural gas in terms of
greenhouse gas emissions. We subsequentlyi submitted a commentary on that paper which
was published online by the same journal on January 3 of 2012. Howarth et al’s response
was published online on February 2, 2012.
In our commentary we pointed out a number of serious flaws in both their analysis and
presentation, which can be summarized as:
1) Unrealistically high estimates of fugitive emissions associated with unconventional gas
production based on a cryptic presentation of relatively few and poor primary sources
2) A dismissive discussion of new technologies now in use to reduce such emissions
3) An unsupported, and we feel inappropriate, choice of the time interval for estimating
greenhouse impacts of fugitive methane
4) Comparison of gas to coal on a basis (heat rather than electricity) which is basically
irrelevant to evaluation of the relative greenhouse effects of these two options.
In their reply Howarth, Santoro and Ingraffea (2012) reiterate their previous claims that
(1) the total methane emissions generated during the life of a shale gas well could be as
high as 7.85% of the well's lifetime production, (2) emissions during well completions are
far greater for shale gas wells than other types of gas wells, (3) 20 years is the appropriate
timeframe for comparing the greenhouse warming impacts of natural gas and coal, and (4)
this comparison should continue to consider their relative heat contents. Basically
speaking, they stand by their previous conclusion, citing new sources, that “shale gas has a
much larger GHG (greenhouse gas) footprint than conventional natural gas, oil, or coal when
used to generate heat and viewed over the time scale of 20 years (Howarth et al. 2011)”.
Here we reiterate and substantiate our charges that none of these conclusions are
warranted, especially in the light of new data and models. |
