Slashdot Mirror
Locking CO2 Away For Good
HobbySpacer writes: "The BBC
reports that waste CO2 from methane extraction in the North Sea has been succesfully
pumped back into the pourous sandstone beneath the ocean for the past 6 years without any
signs of leaking.
Carbon sequestration techniques like this are looking increasingly
practical. CO2 is being pumped
back into
depleted oil fields, where it also helps extract remaining oil deposits, and into
coalseams.
The ocean is the biggest natural bank of CO2 but tests of
ocean
sequestration in Hawaii and Norway have been blocked by environmentalists who hate this
kind of quick fix approach to the CO2 problem. But with developing countries like India and China certain to rely on their large coal reserves,
sequestration may be the only realistic approach to reducing their CO2 output.
An
Economist article discusses currently available steam reformation technology that could allow
a coal plant to output power and neatly separated CO2 and hydrogen. The non-polluting hydrogen is
then available for cars with fuel cells while the CO2 is stuffed away."
The CO2 would be in thousands or millions of old oil wells, coal seams, etc. and millions of square miles of deep ocean. Any one of those spots could have a problem & release some small fraction of 1% of the CO2.
If anything big enough to release a large fraction of the CO2 comes along (giant asteroid, Iraq's "Planet Buster" nuclear doomsday device, etc.), then we'll have *far* greater worries than the CO2 release.
It's easy to make up & spread cool- and credible-sounding stuff. Finding & checking hard facts is hard work.
Near surface natural CO2 deposits (dry ice) have been discovered and found to be a huge danger to anything that comes around. These deposits generally lie very shallow under the seafloor and can be meters in thickness. The biggest danger is not their sudden release and toxic effects of that, but lies in a totally different factor.
In several ocean slopes (offshore norway, east coast US) these deposits suddenly gave way in history, allowing the cover of these deposits to start sliding down the oceanic ramps. The gasses maybe killed some fish, but the Norway slide triggerd a tidal wave that reached elevations of over 100m in height when it crashed into the north of Scotland (that's 500-1000km further), destructing everything in it's path.
Another danger is to ships and constructions. The massive amount of gasses makes the sea like a giant bubblebath. Anyone that every played with a rubber duck that barely floats in a bubblebath knows what happens when you turn on the bubbles hard enough: it sinks. A massive gas pipe blowout just below an oil righ in the North Sea caused a complete oil/gas rig to sink like a rock a few decades ago.
That said CO2 looks like a dangerous thing to toy with, but that's not the case in the oil fields we are talking about here.
Most of these fields are at enormous depths, the typical North sea fields (in which these experiments have been done for quite a while) are at depths of over 500m. The rocks at that location are much more stable, and at 800m we're talking about serious tough rocks.
Using CO2 to extract the oil better (by pressurizing depleted oil fields) and returning the CO2 they are hitting the jackpot twice: First they can revive old fields relatively cheap and extract more oil, and secondly they can do something back for the environment in a very safe way.
The argument of cave-ins, earthquakes are however very serious ones. The typical example of a colorado experiment where fluids were injected into deep crustal fissures resulting in earthquakes occuring daily instead of yearly warn us against toying with the earth's structure.
That said one must conclude that CO2 injection must be evaluated before it is even tried. As a geologist from the Netherlands I can honestly say this news is not new. CO2 injection has been discussed for over a decade now and thes tests were done in several other fields in small scale before this larger experiment by statoil.
When you say "in general, you wouldnt want to live at the bottom of the sea" I can vough for that too, if you think the bottom of the sea is a safe place then you are wrong! But pumping some CO2 to fill up a hole you created again might be better than leaving the hole there. At least we should put a cover on the hole after we finished using it.
This approach is useful, but it always leaves the possibility of leaks, and has limited capacity.
The process of mineral carbonation exothermically reacts CO2 with certain silicate minerals (or materials derived from these minerals) to yield carbonates that are stable on a geological time scale. There are more than enough of the desirable silicates (serpentine, olivine) to react with all the CO2 that will ever be produced by fossil fuel combustion.