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CO

CO

22

storage in marine sediments storage in marine sediments

Matthias Haeckel Matthias Haeckel

Safety Cost

UBA Workshop on sub-seabed CO2 storage – 16-17 June 2008, Berlin

(2)

The oceanic CO

2

sink

WBGU (2006)

Inventories in Gt C Fluxes in Gt C / a

Fluxes in Gt C / a (1 Gt C = 3.67 Gt CO2)

IPCC (2007)

The ocean has taken up ~40%

of anthropogenic CO2 emissions

Global Carbon Budget

(3)

WBGU (2006)

The oceanic sink for anthropogenic CO2 is likely to further increase in the coming decades ...

Sarmiento et al. (1998)

acidic pH basic Today‘s

pH range

Relative concentrations

... and this will further increase ocean acidification

The oceanic CO

2

sink

(4)

pH

CO32-

CO2(aq)

Wolf-Gladrow et al. (1999)

The oceanic CO

2

sink

Pre-industrial present ∆pH = -0.12 (280 380 ppm CO2)

present 2100 ∆pH = -0.45 (380 800 ppm CO2)

... and the marine ecosystem is quite sensitive to changes in the pH

(5)

The oceanic CO

2

sink

Orr et al. (2005)

Year Year

Aragonite Saturation Calcite Saturation

Carbonate in upper ocean [µmol/kg]Atmospheric CO2[ppm]

Steffen et al. (2004)

Warm-water corals need a saturation index >3.5 to build reefs

(6)

CO 2 Phase Diagram

Critical point (74 bar, 31 °C)

Marine CO

2

storage options

(7)

Amount: 1 Mt/a CO2 since 1996 (total planned: 20 Mt)

water depth: 80 m; sediment depth: 800-1000 m; investment costs: 94 Mio€

CO

2

Storage in Shelf Sediments - Sleipner field

Marine CO

2

storage options

(8)

Seismic monitoring indicates rapid ascent of sCO2 through the Utsira sandstone formation (~200 m in less than a year)

• ~5 m thick clay layers were penetrated or bypassed by sCO2 within a few years

Top Utsira Sand

Base Utsira Sand Injection point

Marine CO

2

storage options

Some open questions: Where does the replaced saline water go?

What about small scale leakage?

How does a site behave when injecting in Gt-scale?

Torp, StatoilHydro (2007)

(9)

I. CO

2

Hydrates

Gas hydrates are stable at low temperatures and

high pressures

structure I CO

2

·5.75 H

2

O

Marine CO

2

storage options

(10)

CO

2

CH

4

Combination of CO

2

storage

and

methane hydrate exploitation

Marine CO

2

storage options

projects CLATHRAT and SUGAR

(11)

CO

2

hydrate is more stable than CH

4

hydrate

Duan & Sun (2006)

Marine CO

2

storage options

(12)

Methane gas recovery from hydrates exposed to CO

2

after 200 h in sandstone CO2(l)

Kvamme et al. (2007) CO2(l)

Hiromata et al. (1996) after 400 h CO2(g)/N2(g)

Park et al. (2006) CO2(g)

Lee et al. (2003) after 5 h

after 15 h

Marine CO

2

storage options

(13)

II. Liquid CO

2

In deep-sea sediments, pressure and temperature conditions form a zone where liquid CO2 is

gravitationally stable.

Marine CO

2

storage options

(14)

CO

2

storage in deep-sea sediments

(House et al., 2006)

CO2(l) will slowly dissolve into the porewater and react with the sediment

Marine CO

2

storage options

(15)

IPCC (2005)

IPCC (2005)

Marine CO

2

storage options

(16)

Marine CO

2

storage options

Potential capacities for CO

2

storage

Global estimates

(IPCC, 2005)

• Oil & gas fields: <1,000 Gt

• Deep saline formations: 1,000 – 10,000 Gt

Regional estimates

(Zweigel, 2004; Chadwick, 2004; House, 2006)

• Utsira formation - total pore volume: 600 km3 360 Gt structural traps: 50 km3 30 Gt

• UK offshore Bunter Sandstone: 110 km3 70 Gt

• US coast deep-sea sediments: >10,000 Gt

• less than 0.01 % of the deep-sea floor is needed to store the global anthropogenic CO2 production of the entire 21st century

(17)

Silicate weathering in anoxic marine sediments

Feldspars + CO

2

=> clays + HCO

3-

+ metal cations

Wallmann et al. (2008)

Natural analogues

(18)

Further evidence for silicate weathering

Feldspars + CO

2

=> clays + HCO

3-

+ metal cations

POC degr.

Wallmann et al. (2008)

Natural analogues

(19)

Pore water data from methanogenic sediments deposited at productive continental margins

Peru, Chile, California, Cascadia, Japan, Oman, Namibia, Angola, Australia, Bahamas, Blake Ridge, Carolina slope

Microbial CO

2

produced in anoxic sediments is almost completely neutralized through silicate weathering

Wallmann et al. (2008)

Natural analogues

(20)

Izena

NW Eifuku Hatoma

Yonaguni

China

Taiwan

Philippines

Natural analogues

(21)

Sensitive monitoring techniques are available for the marine realm:

e.g., hydro-acoustic bubble detection, water sampling, benthic flux measurements

Plume mapping of natural seepage

Natural analogues

Vertical pH profiles of the water column along a SE-NW transect across a natural CO2 seep at Yonaguni Knoll, Okinawa Trough

(22)

Environmental effects of natural CO

2

emissions

• high CO2 and low pH in the bottom water

• „normal“ benthic megafauna (e.g., echinoderms) is replaced by „dead zone“ area and specific fauna at vents (chemoautotrophs, opportunistic species, predators)

• reduced microbial activity

Natural analogues

Photos: SO196 - SUMSUN

Copyright: MARUM, University Bremen

(23)

SO196 - SUMSUN

Copyright: MARUM University Bremen

(24)

Lab experiments

Numerical Modelling

Field work

(D C uC) Ri

t

C = +

p u =

η κ

GH O

H CO

CaCO HCO

CO

+

2 2

3 3

2

75 . 5

Analysing lab results Upscaling from lab into field

In situ process study in natural laboratory

Kinetics of sediment weathering Hydrate formation in sediments

pressure reactors + Raman + NMR-MAS Conclusions

Projects SUGAR and CLATHRAT

(25)

1. CO2 storage below the seafloor is a realistic option and should be organized at the European level

2. Negative effects on ocean ecosystems can be avoided at small leakage rates ≤10 t CO2/km2/a

3. Appropriate monitoring strategies for leakage detection must be developed; sensitive techniques are available 4. On long time scales, CO2 leakage is mitigated through

silicate weathering processes

5. CO2 leakage can be further minimized via CO2 storage in solid gas hydrates at large water depths (>300 m)

6. Production of natural gas by hydrate conversion could provide incentives for off-shore CO2 storage

Conclusions

(26)

Pacala & Socolow (2004)

Stabilizing atmospheric CO

2

concentrations by reducing anthropogenic CO

2

emissions

Definition of 7 (8) wedges:

each wedge leads to a CO2

emission reduction of 1 Gt C / a in 50 years from now (equiv. to 25 Gt C)

in total CO2 emissions of 175 (200) Gt C have to be

avoided over the next 50 years

Conclusions

(27)

Pacala & Socolow (2004)

15 strategies to achieve a reduction of 1 Gt C / a in 50 years

Potential stabilization wedges

(= 25 Gt C)

Conclusions

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