21st January, 2011 - Posted by admin - Comments Off
Geoffrey Styles writes a piece, Worse than coal?, in the Energy Outlook blog noting that gas leakage has probably been underestimated:
The EPA estimated the total CO2-equivalent methane leakage from the production, processing, transportation, storage and distribution of natural gas in the US in 2006 at 261 million tons per year. That amounts to more than 4% of total net US emissions for that year, so it is hardly insignificant. It’s also about 2.5 times the figure reported in the agency’s latest GHG inventory.
He does back-of-the-envelope calculations which conclude:
As a result, although the emissions advantage of natural gas over coal is less than it would be without such a high rate of leakage, gas still emits 35% less CO2 equivalent per BTU over its lifecycle than coal, on average.
One problem is that his calculations use an old estimate for the power of methane (21 times CO2). This was updated by a later IPCC report (to 25 times CO2). Schindell et al. update this figure (33 times CO2). In addition Geoffrey uses the 100 year measure of the warming power of methane. If methane is measured over 20 years and the work of Schindell is applied, methane’s effect rises considerably (105 times CO2).
It would be interesting to see these back of the envelope calculations done for a GWP of methane of 105 (i.e. five times larger).
Wikipedia’s Global Warming Potential gives some history of assessments of methane’s power.
CCQ’s Soot makes methane even worse references Shindell et. al.
BrusselsBlog Cooling and Supercooling argues for stopping the warming quicklyto avoid climate feedbacks. This means methane’s GWP should be nearer 100 than 20. Ramanathan et. al. do this more authoritively.