Why
commercial use could be the future of carbon capture
Emerging
technologies point toward a variety of practical—and profitable—industrial
applications for carbon dioxide. That could also be good for the planet.
Nearly two years after the signing of the Paris Agreement to prevent
average global temperatures from rising by more than two degrees Celsius, the
world continues its urgent search for cost-effective methods of reducing
greenhouse-gas (GHG) emissions. Even the surprising growth of renewable energy
probably won’t make up for the expected increases in emissions from other
sources. In all likelihood, staying under the two-degree limit will require the
development and rapid adoption of advanced technologies.
Carbon capture and storage (CCS) has long
been seen as one technology with the potential to reduce GHG emissions
significantly. The basic idea is to collect carbon dioxide gas and confine it
underground. CCS hasn’t caught on, however, because it is expensive. But a new
twist on the concept might change its cost profile. If carbon dioxide could
be put to industrial use,
the resulting revenues could make carbon capture financially viable.
A few industrial applications for captured
carbon dioxide are already in play. One involves using the gas to make
chemicals and plastics, such as polyurethane foams for seat cushions. Covestro,
formerly Bayer MaterialScience, recently opened a plant that makes these foams
from carbon dioxide. Research also suggests that making carbon fiber out of
carbon dioxide gas would cost less than the typical production process, which
uses polymers. However, the quantity of carbon dioxide that might eventually go
into chemicals, plastics, and carbon fiber would be too small—between 40
million and 90 million metric tons per year—to make an appreciable dent in
global GHG emissions. Methods of carbon capture and use (CCU) that take up much
larger amounts of carbon dioxide gas will therefore be needed to help reduce
overall GHG emissions.
A look
at new uses for captured carbon
Creating large-scale CCU technologies
won’t be easy. One big challenge is that carbon dioxide is a highly inert
molecule. Because of this, transforming the captured gas into industrial
products typically requires a lot of energy. Another challenge is that oil
remains a highly cost-effective industrial feedstock, both as a fuel and as a
precursor in the synthesis of other substances, such as plastics.
These factors mean that clever solutions
to the energy-balance challenge are required, and it could be years before CCU
is a big business with major environmental benefits. Nonetheless, CCU should have a future in
an emissions-constrained world. That creates intriguing medium-term
prospects for investors, companies, and governments.
Some new applications for captured carbon
dioxide are being piloted; others are in the developmental stage. Three of
these applications stand out for their potential to reduce emissions and
generate revenue: fuel production, concrete enrichment, and power generation.
We estimate that carbon usage, driven largely by this trio of applications,
could reduce annual GHG emissions by as much as one billion metric tons in
2030, compared with a scenario in which these applications do not develop
quickly.
Fuel made from captured carbon
Captured carbon dioxide can technically be
converted into virtually any type of fuel or chemical that is otherwise derived
from petroleum. The question is how to do this economically enough so that the
resulting fuels and chemicals are cost-competitive with those derived from oil.
One method involves causing a chemical
reaction between hydrogen and carbon monoxide molecules to create the
hydrocarbon chains that make up liquid fuels. Getting the chemistry right is
difficult. Producing the chemical reaction is energy-intensive, roughly
equivalent to combustion in reverse. And if hydrogen fuel cells are ever
adopted more widely, demand for hydrogen could reach the point where it is more
economical to use as an energy source than to make liquid fuel. Recently,
however, several cheaper, more efficient catalysts to break down carbon dioxide
into carbon monoxide have been discovered, a critical first step.
If a goal of synthesizing fuels from
carbon dioxide is to reduce GHG emissions, then using energy to power the
synthesis makes sense only if the energy is both cheap and low or zero carbon.
A way to make this work would be to produce fuel from captured carbon dioxide
only when renewable power plants, such as solar or wind farms, are generating
excess electricity. This would also provide a means of storing energy from renewable sources in a
form that is portable and easy to use in existing industrial equipment.
Another method of turning captured carbon
dioxide into fuel depends on using microorganisms to power the necessary
chemical reactions. Microorganisms naturally consume carbon dioxide during
photosynthesis, which produces simple sugars such as glucose. Some of the
microorganisms can then ferment the resulting sugars into ethanol. Other
microorganisms produce lipids (along with proteins and starches), which contain
hydrocarbon components that can be refined into liquid fuel. Since microorganisms
are inefficient at converting solar energy into chemical energy, the trick is
to genetically modify them to make ethanol or lipids more efficiently and
quickly, or even to excrete liquid fuels directly. Once that is done, one more
issue remains: providing the microorganisms with enough space and the right
conditions to live. We estimate that microorganisms producing enough liquid
fuel to meet the annual needs of the United States would require a lake
one-third the size of California.
More research and investment will be
needed to scale these biological methods of making fuel from carbon dioxide up
to commercial size. Even so, the long-term potential of these techniques to
turn waste gases into valuable products has attracted interest from large
industrial firms.
Concrete enriched with captured carbon
The manufacture of cement, which serves as
the binding agent in concrete, accounts for roughly 8 percent of global carbon
dioxide emissions, a significant share of the total. This is because making
cement involves using immense amounts of mechanical and heat energy to quarry
rock for limestone and extract the lime by way of a high-temperature treatment
process. Cement is then combined with aggregates and water to make concrete.
Captured carbon dioxide can’t readily
lessen the amount of energy that goes into this process. But using captured
carbon dioxide during the making of concrete would sequester the gas in
buildings, walls, bridges, sidewalks, and other concrete structures, allowing
the material to serve as a major carbon sink.
Carbon dioxide can be added to concrete in
two ways. The first is to make the gas into a carbonate mineral aggregate that
goes into concrete and construction fill. This is not practical now, because
natural aggregate is inexpensive. A more promising approach is to infuse wet
concrete with carbon dioxide. This technique, known as “carbon curing,”
involves curing concrete in a carbon dioxide–rich environment, causing the
carbon dioxide to react with water to form carbonate ions, which then react
with calcium ions in the concrete to form solid calcium carbonates. This is an
exothermic and spontaneous chemical reaction that releases rather than consumes
energy.
Carbon curing can produce concrete that is
4 percent carbon dioxide, by mass. Carbon curing can also shorten curing times,
increase concrete’s water resistance, and strengthen it—improvements that
should make it more appealing to concrete makers and construction companies,
regardless of the environmental benefits.
Power generation using supercritical carbon dioxide
Repurposing captured carbon dioxide as an
ingredient in products such as fuel and concrete represents one means of
lowering emissions of the gas. A different approach is cutting GHG emissions
from power generation by using carbon dioxide to make turbines run more
efficiently. Although this would not repurpose carbon dioxide as a product, it
could prevent a significant amount of emissions.
Steam turbines powered by fossil fuels
have been used to generate electricity for more than a century. But carbon
dioxide, heated and pressurized into a supercritical fluid, transfers heat more
readily and takes less energy to compress than steam, which can make turbines
more efficient. A conventional steam turbine converts roughly 33 percent of the
energy in fuel to electricity. Using supercritical carbon dioxide instead can
boost the energy-conversion rate to 49 percent.
Increasing the efficiency of turbines is
important because fossil fuels are expected to be important sources of power
for decades to come. In principle, supercritical carbon dioxide can replace
steam in any power-generation process that relies on steam turbines. Whether it
will be economical to do so on a large scale is another matter. One question is
how much it will cost to retrofit or replace steam turbines. Another is whether
utilities will be rewarded for switching to turbines that are more energy
efficient and less emissions intensive.
These uncertainties make it difficult to
predict how supercritical carbon dioxide technology for turbines might affect
the power sector or overall GHG emissions trends. But the potential of the
technology, reinforced by research investments by industrial heavyweights,
means it is worth watching. Early indications of its viability should emerge
after Sandia National Laboratories launches its demonstration plant, which is
scheduled for 2019.
Scaling
up the use of captured carbon
At the moment, none of the three uses
listed above for captured carbon dioxide has been developed to the point where
it is commercially viable. But all three have the potential to become
profitable in the medium to long term as the technologies advance and countries
pursue their plans to reduce GHG emissions.
Two major sets of costs need to be
addressed. First, the technology used to collect carbon dioxide from the flue
gases of power plants and industrial facilities would have to become more
cost-effective. Capturing and transporting the gas can cost as much as $80 per
metric ton. Firms working in this area expect to halve that cost in the coming
years. Second, as noted earlier, the technologies for using captured carbon
dioxide need to become more efficient and cost-effective.
CCU technologies also have to win support
in industry, which has proven alternatives to fall back on: fossil fuels
instead of synthetic ones; ordinary concrete instead of carbon-cured concrete;
steam turbines instead of carbon dioxide turbines. Conventional practices can
be difficult to overcome, even when better ones come along. Policy makers can
play a role in accelerating the development and adoption of CCU technologies.
Just as regulatory support helped ensure steady demand for renewable energy in
some countries, the right policy environment will encourage companies and
investors to get behind CCU.
Reducing and eventually stopping increases
in the atmosphere’s GHG concentration will require multiple methods of cutting
emissions to be used widely. Since existing methods are being adopted slowly,
relative to the GHG challenge, new methods may be needed. This is one reason
why carbon capture features prominently in some emissions-reduction scenarios:
the International Energy Agency, for example, expects carbon storage to account
for 14 percent of GHG-emissions reductions from 2015 to 2050. While carbon
capture and storage has been slow to catch on, CCU seems to have more promise,
partly because of its revenue-generating potential. Making CCU work at scale in
the long-term will depend on technology investment decisions made today.
Companies and governments that provide the right support now may position
themselves to reap the benefits from CCU in the years to come.
By Krysta Biniek, Ryan Davies, and Kimberly Henderson January 2018
https://www.mckinsey.com/business-functions/sustainability-and-resource-productivity/our-insights/why-commercial-use-could-be-the-future-of-carbon-capture?cid=other-eml-alt-mip-mck-oth-1801&hlkid=2aebce9371fb4054b59537429d3bae38&hctky=1627601&hdpid=b7c42a50-151b-48ef-ab67-f3f597beac98
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