che_october-2023 - 6

Seawater electrolysis stabilizes and immobilizes
atmospheric carbon dioxide
S
eawater is being used in a new electrolysis
scheme for carbon dioxide removal (CDR), while
also producing hydrogen as a byproduct. Developed
by Equatic (Los Angeles, Calif.; www.
equatic.tech), the platform draws seawater into a closed
electrolysis system, taking advantage of the pH difference
between the produced streams for efficient capture
and storage of atmospheric CO2 (diagram). " Splitting
the seawater into hydrogen and oxygen also creates
two streams - one alkaline from the cathode side of the
cell, and the other acidic from the anode side. The acidic
seawater is neutralized with crushed minerals to restore
its natural pH, and is returned to the ocean. The alkaline
seawater stores carbon as a solid mineral before atmospheric
air is passed through to immobilize additional
CO2 as dissolved bicarbonate ions. Finally,
the sequestered CO2 is returned to the ocean
as CaCO3, " explains Edward Sanders, chief
operating officer of Equatic. Proprietary electrodes
have been developed to prevent the
production of chlorine gas species in the cell.
This is a major breakthrough, says Sanders,
since the presence of Cl2 gas creates safety
issues and requires treatment with granular
activated carbon.
Using the ocean for CO2 storage holds
several benefits over other CDR methods,
explains Sanders, including the elimination of
costs associated with transport, pipeline concarbon
capture rate of 96%.
CLC technology features a metal
oxide that loops between an air
reactor and a fuel reactor. In the
air reactor, the metal oxide absorbs
oxygen from the air. It then
goes into the fuel reactor, where
this oxygen is used as an oxidizer
for the combustion process. The
oxygen-depleted
(or
reduced)
metal then returns to the air reactor
to absorb more oxygen, and
the process repeats. Using oxygen
instead of air in the combustion
process makes capturing
and removing harmful particles
from the resulting smoke much
easier.
This
is because when
pure O2 is burned, the only major
end products are CO2 and water,
which are then easy to separate
through
steam
condensation.
However, producing pure O2 is
often expensive. CLC technology
avoids this cost, as extracting the
oxygen already present in the air
is an inherent part of the process.
CHEERS is an international
project with nine partners from
Europe and China: Sintef Energy
Research (coordinator; Trond(Continues
on p. 8)
6
G
struction and subsurface exploration. " Unlike other landbased
direct-air capture technologies, this is functionally
permanent CO2 removal. There is no ocean degassing
caused by atmospheric CO2 removal. And unlike other
ocean-based technologies, Equatic is able to measure,
report and verify the CO2 drawdown within the boundaries
of the plant, without requiring open-ocean measurements, "
adds Sanders.
The company recently published details of its comprehensive
methodology for verifying its CDR performance,
using an array of sensors to provide continuous process
readings. Equatic currently operates two CDR plants in
in Los Angeles and Singapore, each with 100 kg/d of
CDR capacity. " Our next plant will be commissioned in
mid-2024 with a capacity of 10 tons/d, " says Sanders.
Equatic
Taking graphene into the next dimension
raphene has been touted as
a " super " material, boasting
ultra-high strength, superconductivity
and many more
superlative properties, but, as a planar
two-dimensional material, its commercial
use has been limited in terms of reactivity,
since reactions can only occur at the
material's edges. " With graphene, it's not
highly tunable to the exact application that
you want, so you're often designing your
application around what graphene could
do for it, versus designing the graphene
around what's needed for the application, "
explains Keith Norman, chief sustainability
officer of Lyten, Inc. (San Jose, Calif.;
www.lyten.com). Lyten has developed a
proprietary reactor technology to produce
three-dimensional graphene (photo) at
scale from a methane feedstock, creating
a new class of material that is more reactive
and tunable for a wider variety of applications.
Norman likens the production
of three-dimensional graphene to crumpling
and twisting a sheet of paper. " In our
reactor, bending and folding the material
increases the number of reactive sites by
orders of magnitude. Equally important is
that we can tune the material based on
how we operate the reactor. From what
we've seen, there are no other technologies
able to deliver a three-dimensional
graphene material to the market. The real
differentiation lies in the ability to consistently
tune three-dimensional materials to
exact specifications, " explains Norman.
With the unique graphene structures
the technology can yield, Lyten is currently
pursuing three distinct application
areas: cathodes for lithium-sulfur batteries;
light-weighting and reinforcement for
thermoplastic composites; and advanced
sensors and biosensors.
Lyten is in the process of closing its Series
B fundraising round, which includes
investment from leading automotive manufacturer
Stellantis. Lyten currently operates
an automated pilot-scale manufacturing
line
for graphene-enhanced Li-S
battery cells in San Jose, and has commercial
partnerships in place to utilize its
graphene in engineered composite-based
consumer products. Discussions are also
underway with a major tire manufacturer
to employ flexible graphene-based sensors
on the interior of tires.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
OCTOBER 2023
https://www.equatic.tech/ https://www.equatic.tech/ http://www.lyten.com http://WWW.CHEMENGONLINE.COM
che_october-2023

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