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Scientists Link Methane Formation by Bacteria in Shale Rock to Increases in Atmospheric Methane During Deglaciation; Production of the Gas Was Relatively Rapid
29 January 2008
Researchers from the University of Massachusetts-Amherst and Amherst College have linked the methane production of a subsurface consortium of fermentative and methanogenic bacteria in shale rock to increases in concentrations of atmospheric methane associated with the retreat of the continental ice sheets. The study also concluded that these bacteria produced large amounts of methane in a relatively short time.
Steven Petsch, assistant professor Geosciences at U Mass-Amherst, and his colleagues studied natural gas reservoirs in Michigan’s Antrim Shale. Their results are published in the February issue of the journal Geology.
Bacteria digested the carbon in the rocks and made large amounts of natural gas in a relatively short time, tens of thousands of years instead of millions. This suggests that it may be possible to seed carbon-rich environments with bacteria to create natural gas reservoirs.
—Steven Petsch
The study also helps explain high levels of methane in the atmosphere that occurred between ice ages, a trend recorded in ice cores taken from Greenland and Antarctica.
When the ice sheets retreated, it was like uncapping a soda bottle. Natural gas, which is mostly methane, was released from the shale into the atmosphere.
—Steven Petsch
The research can help improve current climate change models to account for the effects of melting glaciers.
For most of its history, the Antrim Shale contained water that was too salty to allow bacteria to grow. But areas rich in natural gas showed an influx of fresh water that was chemically different from modern rainfall. The water, which is similar to meltwater from glaciers formed during the ice age, was injected into the rock by the pressure of the overlying ice sheets, according to Petsch.
Glacial meltwater diluted the salt water already present in the shale, allowing the bacteria to thrive and quickly digest available carbon. The natural gas they produced was chemically similar to the surrounding water and had a unique carbon chemistry that proved its bacterial origin. Petsch calculated that trillions of cubic feet of natural gas were eventually stored in the shale under pressure.
During glaciation, CH4 produced by this community accumulated in the shale at a rate of 1 Tg CH4 per 1000 yr as a result of ice coverage and increased hydrostatic pressure.
At least 75% of the gas was released into the atmosphere as the ice sheets retreated, adding to methane from other sources such as tropical wetlands. While methane from the Antrim Shale accounts for a small fraction of the rise in methane observed between ice ages, there are many natural gas deposits that were formed in the same geologic setting. The cumulative effect may have caused large emissions of methane to the atmosphere.
Klaus Nüsslein of the U Mass Microbiology Department analyzed DNA from water samples and identified bacteria capable of breaking down hydrocarbons in the rock. Other microbes were present that produced methane from the break-down products.
Additional members of the team include postdoctoral researcher Michael Formolo and undergraduate Jeffrey Salacup and Anna Martini, a professor of geology at Amherst College.
Resources
M.J. Formolo, J.M. Salacup, S.T. Petsch, A.M. Martini, and K. Nüsslein A new model linking atmospheric methane sources to Pleistocene glaciation via methanogenesis in sedimentary basins Geology, February, 2008; 36: 139 - 142.
January 29, 2008 in Climate Change, Natural Gas | Permalink | Comments (11) | TrackBack (0)
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Bacteria digested the carbon in the rocks and made large amounts of natural gas in a relatively short time, tens of thousands of years
During glaciation, CH4 produced by this community accumulated in the shale at a rate of 1 Tg CH4 per 1000 yr
Based on this information, only tens of megatons of methane were produced by these bacteria. That is hardly worth mentioning. I must be getting something wrong here.
Posted by: Anne | Jan 29, 2008 3:44:37 AM
From the paper:
"Given the estimated mass of CH4 stored under the ice sheet during glaciation (40–100 Tg C), CH4 release sustained over 100 yr following ice-sheet retreat would result in a flux of between 0.4 and 1.0 Tg yr–1 to the atmosphere."
"The estimated amount of microbial CH4 released from the Antrim Shale upon deglaciation is only a small portion of the global atmospheric CH4 budget, and, alone, it could only be responsible for <1% of the 140–200 Tg yr–1 global CH4 missions inferred during glacial-interglacial transition (Brook et al., 2000; Schaefer et al., 2006). However, the Antrim Shale is but one of a number of unconventional CH4 reserves from sedimentary basins overridden by or adjacent to Pleistocene ice sheets (McIntosh and Walter, 2005, and references therein) (Fig. 3). The cumulative effect of these may have been large emissions of CH4 to the atmosphere similar in isotopic composition to CH4 from wetlands, as glacial retreat from each basin resulted in releases of CH4 extending through much of the late Pleistocene."
Posted by: marcus | Jan 29, 2008 4:48:11 AM
Yet more confirmation of the vast amount of life, living in rock, that only recently was discovered in the past half decade. The prodigious amount of bacterial life estimated to aggregate to almost one third of the Earth's entire biota by weight, was totally unknown until the last decade, since lots dwell under the deep seabeds. These organisms live as far down as six miles beneath it, at comparable pressures to these bacteria discussed by the UMASS scientists.
These largely archaic anaerobic bacteria, retreated there to avoid the corrosive effects of oxygen poisoning. Free oxygen that was released by plant "pollution". These organisms, working over long time frames, have altered the Earth on vast scales, and may even be partially responsible in creating the petroleum that we use every day.
Posted by: Stan Peterson | Jan 29, 2008 9:45:53 AM
Global warming is causing the permafrost to melt. When it melts enough, a LOT methane may be released causing a 10x increase in the effect of GHGs. This is a feedback loop that we do not want to see happen.
Posted by: sjc | Jan 29, 2008 10:56:38 AM
I've read one theory gaining some support today is that life originated inside the earth and moved out to the surface, whereas scientists have long considered the opposite
So the end of the last ice age, they speculate, triggered a release of glacially trapped methane. Today's warming its theorized, will release methane from permafrost and, in a worst case scenario, from the seabed. And we know methane is a GHG. Yikes
Posted by: Jim G. | Jan 29, 2008 11:08:04 AM
That's like the CO2 / temperature records of the past which show a close correlation as ice ages end ..... meaning that it indeed is a positive feedback cycle. The fact that CO2 always lags temperature increase by a milennium was hijacked by the movie "The Great Global Warming Swindle" to discredit global warming science, but in actual fact only confirms the opposite - that it is a positive feedback relationship.
I am afraid to say it, but I think we are in deep trouble. Our CO2 emissions have committed us to a certain amount of warming for many decades to come, we have barely begun to see the effects of what we have already released because of the inertia of the oceans.
Posted by: MarkMC | Jan 29, 2008 12:43:02 PM
i would love to get my hands on some of those bugs. do some selective breeding, and create a hyper efficient strain that makes methane from coal. lots of carbon in coal. I would rather see us burn methane than coal. to be clear, i would rather we not use any carbon based fuels if possible (go solar, gethermal, wind, tidal etc), but in the interim as we transition, it would be great to gasify the coal via this biological process and reduce the net emmissions drastically. sounds plausible.
Posted by: | Jan 29, 2008 1:40:27 PM
@ nameless -
2C + 2H2O -> CO2 + CH4
ergo, you'd still have to strip out the CO2 of the gas produced in order to get high-grade methane. It would be easier and cheaper - not to mention carbon-neutral - to use regular anaerobic digesters that can take a wide range non-woody cellulosic feedstocks as inputs.
Posted by: Rafael Seidl | Jan 30, 2008 7:42:17 AM
I read that landfill methane has to be processed to get a lot of the nasty stuff out of it before it is used. The less processing the better from a cost standpoint. That is why I favor synthesis. You end up with methane...period.
Posted by: sjc | Jan 30, 2008 9:42:22 AM
@ Mark MC,
You have stated a total non sequitor.
As the world warms due to whatever source, (and its only marginally from increased GHG0, plants begin to flourish and respire. When they die, they rot, and they release CO2 and perhaps CH4 so that it is availble to be taken up by the next geenration of organisms. As others point out if the Permafrost melts, the frozen remains warm and rot, release CH4 and CO2 to feed the next generation now able to live. As the seas warm, they hold less CO2 by Henry's Lawa non organic solubility relationship. That is now available in a form readily consumable by non aquatic life.
I fail to see the supposed "correlation" that you are making. Warming begets life. Life begats and lives on the previosu generation's life. And converts inorganic elements into forms consumable by life. So what?
Using your lack of logic I could both postulate and "prove" that a stupid proposition is true, such as:
Chewing gum kills you.
For example:
Only live people chew gum.
Dead people do not chew gum.
All live people die, eventually.
Therefore chewing gum kills living people, like you.
Drivel and Nonsense!
Posted by: Stan Peterson | Jan 31, 2008 2:23:19 PM
I understand how the introduction of fresh water from the glacial melt diluted the salt water in the Antrim shale thus allowing healthy micro organism to create methane gas. My question is the same possible in the southern Michigan Antrim formation.
Posted by: J Munn | Mar 29, 2008 9:30:47 AM
