Review on: Matter et. al., 'Rapid carbon mineralization for permanent disposal of
anthropogenic carbon dioxide emissions', Science, 2016, 352, 6291, 1312-1314. [1]
This
article [1], just published on the 9th June issue of Science Magazine,
has already received a lot of coverage on the web. Of course, having an intense passion in
Chemistry and Geology, I am totally excited by this wonderful work! It represents the two subjects holding hand-in-hand,
contributing towards a better future.
The
rising level of CO2 in the atmosphere has been a serious issue, and
many means have been devised to counteract this important factor that leads to
global warming. A strategy is known as carbon capture and storage (CCS). It is the process of capturing excess anthropogenic
CO2, and to store and then deposit it to a sink, so that the CO2
will not enter the atmosphere. The deposition site is usually a geological
formation under the ground. Of course, deep ocean storage is not yet a feasible
approach, because the introduction of CO2 into ocean will lead to
ocean acidification.
So what rock should we shoot the gas into? Most researchers tend to favor a sedimentary rock,
sandstone, as the sink, because of the well-established research experience
with this type of rock. Yet, a potential pitfall is that the fissures present
in the rock layers of sandstone can lead to the leaching of CO2 back to the atmosphere.
Thus,
the researcher direction in the field has changed. In this collaborative work, the researchers injected
CO2 into the igneous
rock – the extrusive volcanic rock known as basalt. This is a great strategy
because the minerals present in basalt can react with CO2, and through a carbonation reaction, that results
in the formation of the mineral calcite, a polymorph of CaCO3. In
this way, the excess CO2
can thus be mopped up. The reaction rate was much faster than the rates modeled
by computational methods. Also, the research represented a nice example of using
an isotopic labeling technique (14C in this case) to characterize
the formation of carbonate minerals from CO2.
This
is an impressive idea, yet the researchers also noted a possible obstacle to
the generalization of this process is cost. Also, when a scaling up of the
process is required, the reaction rate has to be acceptable to compromise the
long-term cost. It is quite obvious a better understanding of the mechanism is
required to fine-tune the carbonation reaction and to shut down other
unproductive pathways – like the sandstone scenarios. To me, it seems that
catalysis will be able to contribute to an improvement of the CCS process (Once
a chemist, always a chemist?!). Indeed, I have found a paper back in 2013 in
‘Catalysis Science & Technology’, where the authors demonstrated the use of
nickel nanoparticles as a catalyst for the mineralization reactions from carbon
dioxide. [2] So, it seems that the door has already been opened and there are
active research projects towards this direction. If the time course of the
carbonation / mineralization reaction can be significantly shortened through the application of a
low-cost catalyst, the process will become common place and then this can
alleviate the problem of excess CO2 in the long term.
One
final chemical point of view is that we should bear in mind that CO2
is a potential one-carbon building block. In photosynthesis, CO2 is
used to form the six-carbon sugar, catalyzed by the enzyme complex Rubisco. So,
similarly, if CO2 can be stored efficiently, this can be a great
starting substrate for the production of other compounds, often employing
organometallic catalysis.
All in
all, it is a truly brilliant contribution, and it is more so because it has a
great potential to lead to a better future.
by Ed Law
11/6/2016
Reference:
1. Rapid carbon mineralization for permanent disposal of
anthropogenic carbon dioxide emissions.
J. M. Matter et. al., Science, 2016, 352, 6291, 1312-1314.
Further
commentaries on:
http://www.sciencemag.org/news/2016/06/underground-injections-turn-carbon-dioxide-stone
http://science.sciencemag.org/content/352/6291/1262
2. Nickel
nanoparticles catalyse reversible hydration of carbon
dioxide for mineralization carbon capture and
storage.
G.
A. Bhaduri and L. Siller, Catal. Sci. Technol., 2013, 3, 1234.
