International Conference on Earth Science and Climate Change
Earth Science 2022

Estimation of atmospheric CO2 amount reduction through adecarbonation method based on seawater electrolysis,
aimed to create a global-scale CO2 capture strategy.
Dr. Katsuyoshi Tatenuma 1, Dr. Fabio Spaziani 1,2
1 Kaken Inc., 1044 Hori, Mito 310-0903, Ibaraki, Japan

2 ENEA (C.R. Casaccia), Via Anguillarese 301, 00123 Rome, Italy

Dr. Tatenuma's favorite R&D fields are chemical analysis, nuclear medicine, and related materials. Recently he isfocusing on the development of innovative disinfectant and material for environmental purification based on iodine.

Dr. Spaziani's activity is focused on environmental chemistry research at ENEA (Italian National Agency for New
Technologies, Energy and Sustainable Economic Development) in Roma (Italy), and on the development ofinnovative materials for environmental and nuclear-fusion energy applications by joining the research group ofKaken Inc. in Japan.

9:35-10:00(GMT), 18:35-19:00(JST)
April 27, 2022
1/20

Overview
Atmospheric CO2 has increased by 50% compared to before the Industrial
Revolution happened 250 years ago.
As a strategy to globally reduce the atmospheric CO2 surplus, which causes
the global warming phenomenon, we propose a method to improve the natural
CO2 absorption capacity on the ocean surface layer by forming CaCO3 throughseawater electrolysis .
According to this approach, it is conceivable to remove up to 12 GtonCO2
accumulated in the atmosphere every year, and it may be possible to prevent theoutcomes of global warming.

Contents➢ Status of CO2 accumulation in the atmosphere.
➢ Why does CO2 accumulate in the atmosphere ?
➢ How to remove CO2 in the atmosphere ?
➢ What amount of atmospheric CO2 should be removed toprevent global warming ?
2/20

Status of CO2 accumulationin the atmosphere

3/20

Population growth vs. atmospheric CO2 concentration
Population 7.88G
CO2 413ppm

CO2(ppm)

Population(2021)

420
400

87

Concerns about global
warming caused by CO2 !!

380
360

65World Population

340

4320

atmospheric CO2
concentration

300

3278ppm

280
260
600

G

2
Industrial
revolution

800

1000

1200

1400
Year

1600

1800

2000

12200

0

4/20

Huge amount of CO2 emissions
CO2 + Ca(OH)2→CaCO3 + H2Ono-CO2Stack

In order to dispose of all the CO2 emitted from a coal-fired
power plant (1million kW) through the reaction withCa(OH)2, 3000 trucks with a load capacity of 10 tons would
be required every day to haul the CaCO3 produced.

Recovery System of CO2
CaCO3

Boiler
CO2
CO2

CO2

CO2

3000 trucks/day
5/20

Strange role of CO2 !?
Greenhouse effect Greenhouse gases in the atmosphere

Greenhouse gas layer

EarthH2O
CO2
CH4N 2OO3Freons
SF6in airglobal warming potential
0~7 %10.04121
1,8x10-4310
0. 4x10-44x10-4~10,000
3~5x10-8
23,900without atmosphere -18 °C
actual average temp +15 °C

Light = Heat Temp. constantLight < Heat Temp. decrease
Light > Heat Temp. Increase

Effect ofgreenhousegases

 CO2 therapy
Self-breathing controlled by CO2 in blood→used as therapy for Syowa Emperor !
LightHeat

It is important to keep the CO2 balance
for Organism and the Earth !
6/20

Carbon circulation
Carbonas C (Gton)
1.1~1.6 GtonC/y
0.16 GtonC/y➢ Carbonate produced in the oceans➢ Carbonate accumulated in the oceans➢ CO2 emission by human breath (5.7 bln)

➢ CO2 emission by fossil fuel consumption➢ Atmospheric CO2➢ Inorganic Carbonate dissolved
in sea water

0.49 GtonC/y (8 % of total emitted CO2)
9.3 GtonC/y (50% CO2 remained in Air)709.0 GtonC
38,000 GtonC
Radius~6,400km
Atmosphere ~10km
av. Sea depth ~3.8km

Superficial
1,100 GtonC
Intermediate~Deep 38,000 GtonC➢ Carbonate exist on earth➢ Total reserve of oil and coal
➢ Total reserve Ca resource（in sea water）

49,100,000 GtonC
5,450 GtonC
600,000 GtonCa（Carbon 1: Ca 30 in sea water）

CO2 emission by human breathing

in atmosphere
4.5 GtonC/yBiosphere is a thin film on the Earth’s surface!
Oceans are the ideal CO2 absorbent!

approximately 1 kg(CO2)/day
20~30 ton(CO2)/life

7/20

Why does CO2 accumulate
in the atmosphere ?

8/20

Mechanism of CO2 accumulation in the atmosphere!!
 Easily soluble in water Weak acidic substance

Property of CO2

Carbon balance
229350%45

Elements in seawater

CO2 is concentrated
in seawater

10.8 g/kg
19.40.41
0.14

CO2 0.4cc/L in airNa+ClCa2+Carbonate(HCO3-, CO32-)

26

50cc/L in seawater
Distribution of C and CaOcean cross section

LandlowCoastal area Open ocean

highDensity

9RiverSalt
1.90.5

Temp.

010122334(108 tonC/y)2C54510Ca
10mmol/kg

C
HCO3CO32-

2~2.5mmol/kg

5Depth (km)9/20

Earth is a chemical equilibrium planet !!
Atmosphere
CO2
CO2
CO2

Oceans cover around 70% of the Earth's surface

700GtonC(1)
Atmosphere

CO2
Absorption

Saturated CO2CO2CO2

CO2 equilibriumOcean

Superficialseawater~100m

Slow transfer
38,000GtonC(50~60)Ocean absorbs
CO2, which is
however slowly
transferred tothe deep sea.

Deep sea

EarthRadius~6,400km
Atmosphere ~10km
av. Sea depth ~3.8km

The ground, the oceans, and the atmosphere
maintain a chemical equilibrium of CO2.
10/20

How to remove CO2 in the atmosphere ?

11/20

Principle of Global Reduction of Atmospheric CO2
The ocean's natural CO2 absorption ability
can be increased through seawaterelectrolysis, since the process causes thedecrease of carbonate concentration on thesurface.
High CO2 reduction ability
Huge amount of H2 can berecovered simultaneously

AtmosphereCO2CO2Absorption
Decarbonation systemcurrent
Ca2+
HCO3-CaCO3
generation

Selfprecipitation

Surface

DecarbonatedseawaterConcentrated CO2
saturated CaCO3

Guide pipe

Energy for CO2
separation & Fixation:
not needed Permanent Isolation of CO2 from biosphere !

Controllable & Low-cost !
 Small CO2 emission !
 Non-need Chemical & Biological Additives !
 Ecological & Natural method !

 Simple,

Elucidate the following mechanism;➢ Ocean circulation➢ Biological pump
➢ Alkaline pumpelectrolysis
Solid CaCO3

SeabedCaCO3
sediment
deep sea
Mineralization
Permanent fixation

CO2 is concentrated 2 million folds from
Air → Sea → Seabed(mineralization)
12/20

CaCO3 production by electrolysis of seawaterLab.
test

Scale-up test

SEM x2000

SEM x2000

SEM x2000

The precipitate easily produced by electrolysis is composed of
Aragonite (CaCO3) and Brucite (Mg(OH)2).
The amount, chemical composition and crystals shapedepend on the electrolysis conditions.

SEM x1000

SEM x1000

at 300 kg/cm2 (3,000m depth)

at 500 kg/cm2 (5,000m depth)

Carbonate precipitate is stable at high pressure in deep sea.
13/20

Electrolysis Reaction of SeawaterElectrolytic flow cell
Seawater

Accumulation on seabed

Absorption

H2O → H2, OH-CaCO3
ClO- Activatedcarbon

2Cl → Cl2+2e- → HClO+HCl

pH8.1〜8.3

Porous membrane

CO2 in air

cathodeanode

Decarbonatedseawater
pH8.6〜8.7

mix

Lower TCO2,ACO2

Electrolyticzone

Main reaction at cathode : 2H2O+2e-→H2+2OH10
9pH

87

CaCO3
HCO 3-+OH- → CO3 2-+H2O
Mg2++2OH- → Mg(OH)2 Ca 2+

cathode pH10
pH8.1-8.3

Rawseawater

OH- generation

5generation

Totalelectrolytic
rectionMixed seawater
after electrolysis

Alkaline

H+anode pH 4

pH8.6-8.7

Electrolysis

64mix

CO2 no-emission

Main reaction at anode: 2H2O → O2+4H+ + 4e2Cl- → Cl2 + 2e-

2H2O+2Na++4Cl-+Ca2++2HCO3- → 2H2+CaCO3+CO32-+2HClO+2NaCl

CO2 is not emitted by this electrolysis treatment. It differs from the coral reef carbonate
chemistry, characterized by CO2 emission [Ca2+ + 2HCO3- → CaCO3 + CO2 + H2O]
14/20

Estimation
Duty of CO2 reduction in Japan： -6% of 1990 (actual -14%: 0.047GtonC/y) Electric Power

CO2

Fixation Efficiency : 0.15~0.44 kg(CO2)/kWh
The use of clean energy is desirable

CO2

 Life Cycle Assessment (compared with nuclear power)
CO2 Emission : Fixation Ratio < 1/20

 Size of Decarbonation System<conditions> Sea Current Velocity of 1 m/s,
Decarbonation of 50%
Actual size of Seawater Intake
1.1x105 m2（100m-depth, 1,100m-width）
2.28x106 m2 /GtonC・y-1 （100mx22,800m）

Decarbonation
SystemCaCO3 sediment Cost and Economy effects in the case of Japanese total duty of CO2 reduction
CostSystem 2,000~4,000million(M) US$

IncomeCO2 removal cost of every coal fired power plants
with 100 million kWFabrication : 700~1,200 MUS$
Running : 300~700 MUS$ /y + Waste in Sea 30MC$/y

CO2 Reduction fee : 500 Million-US$/y (10 US$/tonC)
H2 Resource : 6,000~12,000 Million-US$/y Resource of Ca in sea
The Ca reserve in seawater is greater than the oilstock (5,500GtonC)

15/20

What amount of atmospheric CO2 should beremoved to prevent global warming ?

16/20

Huge amount of CO2 to be reduced
Giza pyramidCO2 veil
>400ppm

Bottom length 230m
Height 146m
(138m at present)
Slope 51.51°
Volume 2.59x106 m3
for comparison

excess CO2 in atmosphere
Extra accumulated CO2 : 260GtonC
CaCO3 2.2x1012 ton ≈ 6,700/vol.(Giza-pyramid)
CO2 accumulated every year : 4.5GtonC/y
CaCO3 3.8x1010 ton ≈ 110/vol.(Giza-pyramid)

refreshto remove extra
accumulated CO2

to remove CO2
accumulated
every year

6,700 times volume

110 times volumeof Giza-pyramidof Giza-pyramid

CO2 ~280ppm

Return to the atmosphere in the 1700s
17/20

900

“ CO2 reduction measures cannot be postponed.!! ”

Atmospheric CO2 / ppm

800

without any action
CO2 reduction by
Fossil fuel depletion

700

Catastrophic line

600
500

400
300
200
1700

Action forkeeping 550 ppm

413 ppm (2020)

800
700

+49%
Which way?

278ppmbefore industrialization

Back to 280ppm(1750)

1800

1900

600

2000

2100
Year

2200

2300

500

Accumulated CO2 in atmosphere / GtonC

Possible to solve the Global Warming and our ・？

2400
18/20

Concept & benefits of our technology developed
to reduce the atmospheric CO2 surplus
 Promoting the natural CO2 flux
 Global Reduction of emitted CO2
 Contrasting the atmospheric CO2 increase Simple, high performance and controllable method
 Isolation from biosphere No-emission of CO2 and wastes / no additives needed Environmentally friendly / does not disturb the ecological balance Does not disturb the economy growth Small economic stress➢ Stopping the runaway of global warming.
➢ Possibility to restore the old atmospheric environment !?
19/20

If you have any question, please send me by email.
For more information
Our homepage
http://www.kakenlabo.co.jp/
Speaker’s e-mailtatenuma@kakenlabo.co.jp
Our recent paper on this theme
Tatenuma K and Spaziani F (2022)
Adv Environ Stud 6(1):452-454
CO2CO2
Solar panels

CO2 PROCESSING
PLANT

CO2
pH control

ELECTROLYSIS SYSTEM

Clean energy

Products

Atmosphere
Absorption
Treatedseawater

Ocean surface

Ca2+
Mg2+

HCO3-

CaMg-CO3

H2

CaMg-CO3

Sedimentation
Carbonatesediments

SeabedHydro

Supplements
Fertilizer

Mineralization

20/20