Adsorption - Introduction to Carbon Capture and Sequestration - page 270

We assume that 90% of the fl ue gas is captured and we use
monoethanolamine (MEA) and Mg-MOF-74 as reference materials. The
molecular structure of Mg-MOF-74 is shown in Figure 6.5.3 . For
Mg-MOF-74 we know the adsorption isotherms and the working capac-
ity. This allows us to estimate the total amount of material that one needs
for the CCS scenario shown in Figure 6.6.1 . For the total amount two
numbers are important: the primary material, which is the amount needed
to operate a power plant, and the recycle losses, which are typically
assumed to be 5% of the recycling stream.
By 2050, our scenario implies an extraction of 120,000 tonnes per
year, 50% for the primary use and 50% to supply the 5% recycling loss.
After 2050, we assume there will be no new coal-fi red power plants and
this number stabilizes to 60,000 tonnes per year. Our scenario, however,
is for the USA only.
Extrapolation to a global scale gives 900,000 tonnes per year, which
stabilizes to 450,000 tonnes per year.
One of the exciting properties of Mg-MOF-74 compounds is that we
can replace the metal (Mg) with a different metal. MOF-74 has been syn-
thesized with many different metals (e.g., Ni, Fe, Co, etc). Let us assume
that the compounds with these metals exhibit the same properties as
those with Mg. We can now simply compute the amounts we need of
each metal. In Table 6.6.1 , Sathre and Masanet compare these numbers
with the current world production of the metals and the proven reserves.
We see that for some metals (Co, V) we would need more than the global
reserves. If we were to base our MOF on Fe or Al, one would expect the
economy of scale to reduce the cost signifi cantly. However, if we were to
base our process on Co or V, we would see an explosion of the cost once
we start to scale up this process. This type of information is extremely
useful to guide our research. A vanadium-MOF-74-based process would
need to use 20 times less material to prevent resource limitations from
creating a bottleneck for this process. If we develop the most beautiful
carbon capture chemistry for Co-MOF-74, we also may want to think
whether these ideas can be transferred to more abundant metals.
Despite the beauty of the chemistry, if we cannot scale our materials to
process gigatonnes of CO 2 it will contribute little to carbon capture.
In Table 6.6.2 , the GHG emissions that would result from different
scenarios are summarized. We see that by 2050 the net emissions will
have reduced by almost 2 Gt CO 2 per year if we employ CCS. In