By Shay Chandler
They say history repeats itself.
Approximately 4 billion years ago, during the Archean Eon, free
oxygen was poisonous to all living organisms. In fact, pretty much the only
living things were tiny bacteria called cyanobacteria that inhaled carbon
dioxide and exhaled oxygen. While this process, which we know of today as
photosynthesis, doesn’t seem outlandish, the fact that free oxygen was a bad
thing for the environment rather than a good one is (imagine switching the terms carbon
dioxide and oxygen whenever you have a debate with a
climate change denier). In fact, any free oxygen in the atmosphere would cause
massive die-offs within the cyanobacteria population (Stanley & Luczaj).
Luckily, the early Earth offered a solution to this problem.
A chemical sink is defined as a natural reservoir that is capable of absorbing
a chemical as rapidly as it is produced. Archean sinks included reduced sulfur
and iron in the form of the mineral pyrite as well as Banded Iron Formations,
which are certain formations that contain weakly oxidized iron in alternating
layers (Stanley & Luczaj). However, eventually these sinks filled up –similarly
to shoving an entire plate full of pasta down your kitchen sink, only you don’t
have a garbage disposal, and eventually the whole system becomes clogged up, and
then the real mess sets in.
Geologists call that mess the Oxygen Crisis. When the sinks
were filled to the brim, the excess oxygen began to saturate the atmosphere. This
occurred roughly 2 billion years ago. Luckily (for us), the age of free oxygen
eventually led to the evolution of oxygen breathing organisms.
It’s a story every geologist knows well.
According to Dr. Peter B. Kelemen, a geologist at Columbia
University’s Lamont-Doherty Earth Observatory, history is repeating itself
right now.
This time, sinks are filling up with carbon dioxide rather
than oxygen.
Dr. Kelemen has been studying the process of carbon
mineralization in Oman, a Middle Eastern country on the very tip of the Arabian
Peninsula (Fountain). There, you’ll find jagged outcrops of ancient rocks that
have white veins running through their surfaces, etched into every vacant space
like wrinkles webbed across a face.
The rock bodies are called peridotites, which are intrusive
igneous rocks that contain at least 10% of olivine and pyroxene. They typically
originate deep inside the earth’s mantle (Kelemen & Matter). The white traces running through the
peridotites are actually veins of carbon that has been transformed into its
mineral form, carbonate.
Carbon mineralization is the equivalent of geologic alchemy,
in which gas is turned into stone. This process occurs naturally as peridotite
weathers at the Earth’s surface, allowing it to react with water and carbon
dioxide to form several types of minerals, including carbonates in the form of
calcite, magnesite, and dolomite (Kelemen & Matter).
It was originally believed that carbon mineralization took up
to 100 million years to occur, but recent carbon dating has shown that the Oman
veins formed approximately 26,000 years ago. (Kelemen & Matter). If
cyanobacteria could have talked during the Archean Eon, I’m sure they would
have protested the filling of the old sinks. Today, it’s something we would
love to figure out how to do, and as fast as possible.
In fact, some earth scientists believe this could be a partial
solution to our looming carbon dioxide dilemma: While humans are continuously
producing greenhouse gasses, and it doesn’t seem like we’re going to stop
anytime soon, it would be very convenient to have a place to store the emissions.
This is a relatively new idea and much more research is
currently in the works. However, one Icelandic energy company has already seen
success by injecting carbon dioxide into volcanic basalts. Holland, researchers
have suggested spreading crushed rock along coastlines to increase surface area
for mineralization. In Canada and South Africa, they are trying to kill one
bird with two very literal stones: By using mine tailings, or waste products
from a mine, industries can put leftover byproduct to good use by capturing
carbon in the form of mineralization (Fountain).
Dr. Kelemen is currently working on his own plan. One option
is to drill two wells. Water mixed with dissolved carbon dioxide will be pumped
into the first one. As the water travels through the well, subjecting the
carbon dioxide to increased pressure and temperature, carbonate will mineralize
out of the water. The clean water is then pumped out the other well (Kelemen
& Matter).
No solution is perfect, and this one has its fair share of
holdups, including the fact that humans have emitted roughly 40 billion tons of
carbon dioxide each year. That would require a lot of rock to capture so much carbon dioxide. The outcrop in Oman,
which is about 200 miles long and up to 25 miles wide, can only store about one
billion ton annually (Fountain).
Dr. Kelemen believes that with the right scientific
advancements, it may be possible to store hundreds of years of carbon dioxide
emissions in places with peridotite formations such as Northern California,
Papua New Guinea, and Albania (Fountain).
Rarely does the phrase “history repeats itself” ever refer
to anything good. Luckily this time it refers to a solution that may have been
right under our feet the entire time.
Fountain, Henry. “How Oman’s Rocks Could Help Save the
Planet.” The New York Times. Apr 26,
2018. https://www.nytimes.com/interactive/2018/04/26/climate/oman-rocks.html?rref=collection%2Fsectioncollection%2Fclimate&action=click&contentCollection=climate®ion=rank&module=package&version=highlights&contentPlacement=1&pgtype=sectionfront
Kelemen, Peter B., and Matter,
Jurg. “In situ carbonation of peridotite for CO2 storage.” PNAS, Sep 22, 2008.
Stanley, Steven M., and John A.
Luczaj. Earth System History. 4th
ed., W. H. Freeman and Company, 2015.
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