By Graham Templeton –
The US Geological Survey claims that the rate of earthquakes stronger than magnitude 3.0 in the central and eastern US is roughly five times what it used to be. From 2010 to 2012, that area experienced an average of 100 such earthquakes per year; from 1967 to 2000, the annual average was 21. That could be an aberration since the former number is averaged over so few years, but that’s just the beginning of the story.
A gas injection rig.
It’s been known for a whilethat there is at least a correlation between certain waste disposal methods and increased numbers of small earthquakes — but actually we’ve been causing earthquakes for much longer than that. Particularly large dams can cause them by suddenly putting a lake’s worth of mass on top of a previously unencumbered bit of the Earth’scrust. Even conventional coal mining and oil extraction can do it, hollowing out formerly sturdy areas and honeycombing large areas with structural weaknesses.
Still, the practice of pumping things down into the earth seems to be much more damaging than the process of bringing other things back up. A new study has linked a series of small earthquakes near Snyder, Texas to the underground injection of CO2 gas. When injected far enough underground the gas will freeze into tiny cracks in the rock — it’s essentially the reverse of hydraulic fracturing.
Between the physical pressure exerted by the gas and the chemical changes it can cause in the rock, it seems gas injection can cause earthquakes of a decent size; though nobody was hurt in the Snyder quakes, the town experienced 93 of them, three of which were powerful enough to be dangerous. Even larger earthquakes have been linked to gas injection as well, like a 4.4 magnitude quake in 2011. Past research has uncovered a more general correlation between many kinds of injection storage (including, importantly, the fluid runoff from the fracking process).
The Hoover Dam, which put enormous stress on the surrounding landscape.
Keep in mind through all of this that while the scientists claim to have evidence that injection directly caused these earthquakes, they also point out that equal amounts of gas and fluid injection elsewhere has not caused earthquakes. The ability of these techniques to shake the ground is likely a product of both the injection and the injection site; while many view this sort of research as an implicit attack on the energy industry or on natural gas in particular, the answer here may be as simple as learning to survey a candidate injection site to avoid quake-prone formations.
Some of what we pump underground are wastes, others products of the carbon capture process. Whether it’s gaseous CO2 or radioactive water, thick hydrocarbon sludge purified out of power planet emissions or sulfuric acid produced in an industrial process, it all has to go somewhere. Carbon capture is just the first in the two-step process of protecting the environment; the second is carbon storage, and up until now storage underground has been the go-to option.
These concerns will have to be taken into account when evaluating any proposed carbon capture technology. Pulling CO2 out of the air is one thing. Just what to do with it then is becoming an equally pressing concern.