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Sinking Carbon

January 30, 2013

In the last few decades, the common man has received a free course in economic principles through life experiences. Although I took a course in economics as an undergraduate based on the venerable book by Paul Samuelson, the way economics really happens didn't hit home until the Reagan presidency.

A part of Reagan's legacy is Reaganomics, a version of a very old economic idea called supply-side economics. The idea of supply-side economics is that lower taxes and less regulation allow businesses to flourish, thereby bringing economic benefit to everyone. Such benefits would be manifest in lower unemployment and a greater supply of low cost goods and services.

The interesting thing is that the converse principle is also reasonable, that giving consumers lower taxes will leave them more money to buy goods and services. This would benefit the consumers, and also the businesses with which they deal.

Chemists will find an analogy of these competing ideas in Le Chatelier's principle. According to Le Chatelier's principle, you can influence the product yield of an equilibrium reaction by changing the concentrations on either side of the chemical reaction. You can either push more product or pull more product.

Reducing the concentration of carbon dioxide (CO2) in the atmosphere can be done in two ways. We can strive to reduce CO2 emissions, which appears to be too difficult for our technological civilization; or, we can remove the CO2 from the atmosphere. Carbon capture is the easiest means of carbon sequestration, since we get the carbon before it's diluted in the atmosphere, but there are other means of global CO2 removal.

In a previous article (Ordovician Carbon Sinks, February 28, 2012), I wrote how 460 million years ago atmospheric carbon dioxide was about twenty times the present level, and the average global temperature was 5°C (9°F) higher than it is now.[1-3] Shortly thereafter, geologically speaking, in the Late Ordovician, there was a tremendous cooling of the Earth leading to glaciation.

According to climate models, glaciation during that period was only possible if the atmospheric CO2 level had dropped to about eight times its present value. The cause of this CO2 drop was the initial dispersal of plants on land masses, but not just for the reason you might think.

Although plants do fix carbon from the atmosphere, this early vegetation caused weathering of the Earth's crust. These plants exposed a greater surface area of crustal material, which allowed formation of carbonates from the atmospheric CO2.[1-3]

Figure caption

This outcrop of weathered bedrock is located at 57° 14' 37.88" N, 5° 56' 38.97" W, near Beinn na Caillich on the Isle of Skye.

(Photo by Richard Dorrell of geograph.org.uk, via Wikimedia Commons.)

The plants also removed calcium, magnesium, phosphorus and iron from rocks, which made the rocks more chemically active.[1-3] Labile nutrients from either the vegetation or the weathered rock washed into the oceans and promoted the growth of marine vegetation.[1-3]

A recent study in an open access article in Environmental Research Letters[4] examines whether mankind could perform the same process on an industrial scale as a means to combat global warming. The study was conducted by scientists at the Alfred Wegener Institute for Polar and Marine Research (Bremerhaven, Germany).[4-5]

The study focused on olivine, an abundant magnesium-silicate mineral that weathers quickly. On land, it's dissolved by the carbonic acid created by the combination of rainwater and atmospheric CO2. Olivine dissolved in surface ocean water sequesters 0.28 grams of carbon per gram of olivine.[4] Other chemicals in olivine, such as iron, will have a further affect on carbon sequestration by fertilization of marine plants, such a phytoplankton, which would sequester carbon when it dies and sinks to the ocean floor.[5] Olivine

So, that's why it's called olivine!

A mineral specimen of olivine in the Natural History Museum, London.

(Photo by Aram Dulyan, via Wikimedia Commons.)

Upon crunching the numbers, this doesn't look like the quick fix once imagined. Three gigatons of olivine would be required annually just to offset nine per cent of current anthropogenic CO2 emissions.[5] The olivine would need to be ground to micrometer-sized particles, a process which will consume energy. Using the present mix of energy sources would result in the emission of CO2 which is 30% of what the olivine would remove.[4-5]

Says Peter Köhler, the lead author of the study,
"If this method of geoengineering was deployed, we would need an industry the size of the present day coal industry to obtain the necessary amounts of olivine. To distribute this, we estimate that 100 dedicated large ships with a commitment to distribute one gigaton of olivine per year would be needed... We assess this approach as rather inefficient.[5]
One distribution option is to put the olivine in the ballast tanks of commercial vessels. As shown in the figure, most shipping lanes lie in regions favorable for olivine dissolution.[4]

Relative dissolution of olivine in ocean water

Relative dissolution, on a percentage basis, of 1 μm olivine grains in ocean water. (Fig. 3d of ref. 4, licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 licence.)[4)]

If we save the world from carbon, what sort of world will it be? Getting back to the economics topic of the first few paragraphs, Walter Reuther, president of the United Auto Workers, was given a tour of an automated automobile assembly plant in 1958. When asked whether he was concerned that such automation would put all his union members out of work, Reuther replied that machines don't buy cars.[6]


  1. Sid Perkins, "Did Plants Freeze the Planet?" Science Now, February 1, 2012.
  2. Timothy M. Lenton, Michael Crouch, Martin Johnson, Nuno Pires and Liam Dolan, "First plants cooled the Ordovician," Nature Geoscience, vol. 5, no. 2 (February 1, 2012), pp. 86-89.
  3. First plants caused ice ages, University of Exeter Press Release, February 1, 2012.
  4. Peter Köhler, Jesse F Abrams, Christoph Völker, Judith Hauck and Dieter A Wolf-Gladrow, "Geoengineering impact of open ocean dissolution of olivine on atmospheric CO2, surface ocean pH and marine biology," Environmental Research Letters, vol. 8, no. 1 (January-March, 2013). Open access article, with PDF file, here.
  5. Michael Bishop, "Researchers analyse 'rock dissolving' method of geoengineering," Institute of Physics Press Release, January 21, 2013.
  6. How Will You Get Robots to Pay Union Dues? How Will You Get Robots to Buy Cars?, Quote Investigator.

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