Carbon Capture’s Other Dirty Secret: Nowhere To Put It (Part 2 of 2)

In Part 1 of this assessment, we saw that the magnitude of CO2 emissions were vastly larger than the largest and best sequestration facilities built to date, and further, that the majority were actually enhanced oil recovery facilities with significant net CO2 emissions end to end. We also saw that there’s significant competition for underground voids suitable to store gases that just want to escape. So much for problems one through three. In Part 2 we cover another geological issue, a basic physics problem with this entire scheme, an environmental problem and, of course, the reality about who is footing the bill. That’s problems 4 through 7.

The fourth problem is subsidence of underground areas where we’ve extracted fossil fuels and other substances. Nature abhors a vacuum, something obvious to Aristotle 24 centuries ago.

California’s great oil gusher image courtesy US Library of Congress

You might remember seeing images like this from the earlier days of oil exploration. Those underground caverns full of oil, gas, and even water were pressurized historically, until we poked holes in them, giving them a place to go. Now they aren’t pressurized in most parts of the world and we have to use increasing amounts of energy to extract the fluids we’ve become addicted to. Subsidence occurs globally wherever we extract things from underground, and subsidence is Nature abhorring that vacuum we’ve created and settling. You might also remember that Jakarta is sinking in large part due to subsidence due to ground water extraction.

When we make big holes in the ground, after a while they are much smaller holes in the ground. It’s as remarkable to think we have room for 2-3x the mass of what we extract underground as it is to think we’re going to put it back in places that are much smaller, or that we are going to create new voids underground sufficient for the scale of the concern.

The fifth problem is the amount of pressure required to accommodate vastly more mass of gas than of the liquids or solids we extracted. Gas is compressible, but you can’t compress it to the density of gas or solids. No matter how much we compress CO2, it will always take up a much larger volume than the gas, oil, coal, or water we extract, and a lot less than the salt in salt cavern we scrape out from underground. At 50 atmospheres of pressure, CO2 has a maximum density of about 157 kg per cubic meter, compared to light crude’s 875 kg per cubic meter or water’s almost a ton per cubic meter. So we’re supposed to put 2-3x the mass of CO2 into collapsing voids that used to contain solids or liquids that were much denser. You can’t make this math work.

But it gets worse. The deeper you go, the hotter things get, about 25 degrees Celsius per kilometer. That’s great for geothermal energy and hotsprings, but the hotter gas is, the less dense it is. Once again, physics. Two kilometers underground is much warmer than the surface, about 50 degrees Celsius on average, and the 157 kg drops to 125 kg at that temperature at 50 bar.

That’s why a massive K cylinder of hydrogen 1.5 meters long weighing 65 kg only contains 0.6 kg of hydrogen.

Gas isn’t dense, but we have created 2-3x the mass of all the fossil fuels we’ve extracted from the earth over the past 300 years, and it’s not like the Earth is some balloon with infinite space underground, unlike the atmosphere, which is a lot more elastic. More pressure equals more energy to compress the gas and an increase in the likelihood of the gas finding an escape route too, all too familiar who has ever filled up a balloon and then let it go to fly around the room. The Aliso Canyon leak didn’t occur because we pushed the “natural” gas out of underground storage, it was under pressure and just needed a path of escape.

The sixth problem is that making new underground caverns for storage usually involves flushing salt out of existing underground salt formations with massive amounts of water. Hundreds of cubic meters of water are pumped down into the ground each hour, often a couple of thousand meters, then hundreds of cubic meters of brine are pumped backed up and discarded. Where the geography allows it, this is done with sea water, but the number of accessible, near surface, and near sea water rock salt formations is diminishing, just as the number of places where you can stick a pipe in the ground and get pressurized crude shooting out has plummeted. In some places, they pump the waste brine back underground somewhere else (oh, look, another subsurface space demand). In others, they mix it with fresh water before discharging it back into freshwater rivers. The brines often contain rather toxic stews of chemicals in additional to what we think of as salt that we might put on our food, and salt is highly problematic in freshwater and on fertile soil regardless. There’s a reason the expression is to salt the earth, and it’s not because it makes things grow better.

All of this comes down to the final problem, which is that CO2 sequestration is very expensive and taxpayers are footing the bill. Drilling down two kilometers to a saline-capped region of rock to pump a measly 27 megatons of CO2 that was created by manufacturing hydrogen cost over a billion USD, 80% of that from the provincial and federal governments, along with over $30 million annually for operations. Equinor has graciously accepted what I estimate to be over a billion USD in tax breaks from Norway to put CO2 it pumped up from underground back underground at its Sleipner facility. The USA is giving enhanced oil operators who are extracting 2-3x the CO2 in the form of unburnt crude $12-$50 for each ton of CO2 that they “sequester” under the new oil and gas subsidy enacted in 2018, and under discussion to enhance it to $175 per ton. In discussion with a representative of Carbon Engineering a couple of years ago at a conference where I lost patience with the gaslighting going on and started questioning the narrative, the representative let slip that they will receive $250 per ton of CO2 from the USA and California for each ton of CO2 they pump underground for enhanced oil recovery at the Permian Basin facility that they are building with Oxy (née Occidental Petroleum).

The combination of failures to address the CO2 sequestration problems of magnitude of emissions, the physics of underground storage at scale, and the resultant costs is truly a policy failure of staggering proportions. It is willful blindness. And where there is willful blindness of this magnitude, it cannot be ascribed to benign ignorance.


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