SEQUESTERING CO2 IN ROCKS
“The Carbon Rocks of Oman” by Douglas Fox described the efforts of geologist Peter Kelemen and other scientists to possibly store carbon dioxide in mantle rock formations. As a physical chemist who took up the fundamentals of geology and geochemistry in environmental studies, I was intrigued by the article, which discussed various mechanisms that could be used to improve the process or reduce costs, including both in-situ and in-situ ex situ concepts.
Would it be possible to improve the permeability of the mantle rock using standard petroleum methods such as fracking with high pressure fluids? And there would be seawater – which would already be used for CO. Sequestration2 in Kelemen’s plan – be a candidate for such fracking?
Finally, calcium and magnesium in seawater also react with CO2, especially at the higher pressures and temperatures at depth? And if so, could this cause the natural or induced veins to “clog” before the solution can travel very far?
Gary McKown West Chester, PA.
Fox describes a natural process that CO. permanently petrified2 as magnesium carbonate (MgCO3) or calcite (CaCO3) in the mantle rock in Oman.
Every CO2 Molecule has two oxygen atoms, while in each molecule is MgCO. three are3 or CaCO3. If the process described has been intensified to remove the atmosphere from CO. to free2Is there a possibility that we will permanently “lose” too much oxygen? Would we exchange one evil for another?
URSULA GARDENMAN Zurich
FOX ANSWERS: In response to McKown’s letter, CO injection2 could actually be improved by artificial fracking with seawater. Pressurized “supercritical” CO2 could also be a possible fracking fluid.
The calcium and magnesium naturally contained in sea water should not increase the tendency of the pores in the rock to become clogged by precipitating carbonates. This is because liquids in the water below ground already contain calcium and magnesium. The natural carbonation reactions actually include a first step in which these elements in the rock form CO. dissolve2-rich water (which is acidic). Ions of calcium and magnesium then react with the CO2 and turn back into solid minerals.
Gartenmann asks an interesting question. Fortunately, the reactions that CO. convert,2 in CO3 do not consume oxygen gas (O2). Instead, they deplete oxygen atoms already in the water and in minerals like olivines (including Mg2SiO4th and Fe2SiO4th), Serpentine [Mg3Si2O5(OH)4] and brucite [Mg(OH)2]. Because of the oxygen content of such minerals, the earth’s crust and mantle roughly contain more than a million times more oxygen than the atmosphere!
But even if we assumed that all of the extra oxygen atoms needed to bind carbon in rocks came from the air, we would only lose a tiny amount: a billion tons of CO. mineralize2 would be about 0.00003 percent of the estimated 1.2 quadrillion tons of O. consume2 in the earth’s atmosphere. And mineralization of one trillion tons of CO2 would only use about 0.03 percent of that oxygen.
SCIENCE AND “TRUTH”
In “Is Science actually ‘Right’?” [Observatory], Naomi Oreskes argues that it offers a process of discovery rather than providing absolute truth.
Science isn’t really about “right”, “wrong”, “true” or “wrong”. My work in the interior of the earth, where observations are always incomplete and often not very precise, has led me to the idea of evaluating theories as more or less “useful in a certain context”. I find this avoids a lot of confusion about what science offers.
For example, Isaac Newton’s theory of gravity was replaced by Albert Einstein’s, but that didn’t make Newton’s theory “wrong” or make Einstein’s “right”. Newton’s theory is still extremely useful in many contexts. Einstein’s theory is useful in a much larger area: it can better explain the orbit of Mercury and the black holes. If one day a better idea than Einstein’s General Theory of Relativity emerges, or if observations are found that are incompatible with this theory, then Einstein will not have been “wrong” either.
A doctor with a good scientific background is likely to benefit your health more than a typical politician, no matter how prominent. And a climate scientist’s predictions about the future are likely more useful than those of an ill-informed coal manager. On the flip side, your average shopkeeper may have a better understanding of economies than most neoclassical economists, whose theories bear no useful resemblance to observable economies.
GEOFF DAVIES Retired Senior Fellow, Australian National University
BETTER WEAPON SECURITY
In “patient care must include a gun talk” [Forum], Chethan Sathya and Sandeep Kapoor argue that doctors should talk to their patients about the safety of firearms. Doctors are well equipped to have good discussions with their patients about exercise, smoking, drug and alcohol use, and diet-related health. But few of them, including my doctors, own firearms, and most of them know little about proper gun safety courses.
I own a firearm and have taken personal safety courses which have been invaluable. Doctors would be more effective and trustworthy on this issue if they were better informed about safe gun possession resources, including local safety courses. For the millions of citizens who own firearms, nothing improves gun safety better than a well-educated training course.
ANDREW GOLDSTEIN Portland, Ore.
NEW ERA OF PROTEINS
Your July issue was outstanding. I have never read so many articles in one issue of Scientific American. Everyone had important information.
I especially liked “Life, New and Improved”, Rowan Jacobsen’s contribution to the production of artificial proteins and the use of the technology in the development of a new COVID vaccine. I recommended it to my four granddaughters as required reading. One is a research biologist who works in neuroscience. Two have just finished their sophomore year of various colleges, and the fourth will be in high school next year.
JP UTTLEY by email
This is without a doubt the most fascinating article I have read in this magazine, and I have been a long-time subscriber. I look forward to sequels as this is obviously the beginning of a new era. I hate the overuse of hyperbolic descriptions, but the superlative works well here.
STUART TAYLOR Perth, Australia
“Switchgrass Cleaner” by Susan Cozier [Advances; August 2021], should have described other researchers who use plants to clean “PCBs”, not “PDBs”.