1 Effects of Vertical DIC Distribution on Storage Efficiencies of Direct Injection of CO2 into the Ocean Baixin Chen, M. Nishio, and M. Akai National Institute of Advanced Industrial Science and Technology (AIST), Namiki, Tsukuba East, Tsukuba , Japan

2 Why ocean sequestration? Large capacity (IPCC Srpt. on CCS 05) :  “Roughly 2,300 to 10,700 GtCO 2 would be added to the ocean (above the natural pre-industrial background) in equilibrium with atmospheric CO 2 stabilization concentrations ranging from 350 ppm to 1000 ppm, regardless of whether the CO 2 is initially released to the ocean or the atmosphere.” Actually, it is an artificially acceleration of natural oceanic uptaking of CO2 across air/sea interface.  Over the past 200 years the oceans have taken up 500 GtCO 2 from the atmosphere out of 1300 GtCO2 total anthropogenic emissions..

3 Questions: Assessments on CO 2 Ocean Sequestrations How long the CO2 injected could be kept in the ocean ? (efficiency) Is it safe for marine organisms and animals? (bio-impacts in near and far fields) The long-term impacts on global ecosystem ( ? )

4 How to perform (IPCC Srpt. on CCS, 2005)

5 Injection of CO 2 by moving-ships

6 CO2 Injection Nozzle & Droplet Size Distribution (Minamiura et al., GHGT-7, 2004) Nozzle and CO 2 drops from Lab. Exp. Drop deformation Hydrate layer formed at the interface

7 How long the CO2 injected could be kept in the ocean ? Efficiency or retention :  OGCMs (depth, locations) Caldeira et al. (GRL, JGR, 02) Orr et al. (Climate Change 02 and GHGT-5-00 ) …..  Box models ( depth, bio-chemical systems ) Herzog et al. (Climatic Change, 2003) Sohma et al, (JGR, 20050) …. In this study : If the injection parameters play the role on storage efficacy?

8 How to handle the injection parameters ? 1. Plume dynamics (coupling the injection parameters and currents) in short-term 2. For long-term efficiency, By OGCMs for long-term  Using fine resolution: 10 th meters vertically (Very difficult if not impossible currently)  Nesting grids systems Good and will be trying By Box models  OK (How about the horizontal transportation roles?) In this study : Implemented the initial vertical distribution of DIC from (1) to the existed data from (2).

9 : the storage efficiency with an initial vertical distribution (pdf) : the storage efficiency without initial vertical distributions (OGCM data). h : the depth of the ocean (m) t : time (year) P[ x (h)] : the mass pdf of DIC initial vertical distributionas a normalized depth (x (h) ). Effect of injection parameters on storage efficiency:

10 Long-term storage efficiency data interpolated from OGCMs

11 The data can be interpolated numerically (Caldeira et al. GRL 2002) Injection site: Tokyo T > 100 years T < 100 years T = yrs T = yrs Injection site: Tokyo

12 Initial Vertical Distributions of DIC produced by coupling injection parameters with ocean current from two-phase models

13 Near-field Two-phase Model CO2 droplet Dynamics and biological impacts X1 X2X2 X3 Ocean surface Can go to the bottom Turbulent diffusion Injection ports installed nozzles Towing pipe Initial DIC distribution

14 Evolution of DIC Plumes (Chen et al., JGR, 05) T=1.0 min T=23 min T=70 min X=180 mX=10 m Injection rate : 100 kg/sec Initial drop size: 15 mm Injection depth : 2000 m Injection port : Horizontal

15 Vertical distributions of DIC Injection site: Tokyo at Depth of 2000 m

16 Effect of initial DIC vertical distribution on efficiency

17 CO 2 Injection Parameters Injection type: Moving-ship Injection rate: 100kg/sec by moving-ship (0.1 Ggt C /year) Droplet sizes: 5, 10, 15, 20, 30, 40 mm Injection depth: 1000, 1500, 2000, 2500 m Injection site: Near Tokyo (T, S and current data )

18 Injection site: Tokyo Effects of initial droplet size on efficiency

19 Effects of injection parameters on efficiencies Injection site: Tokyo Time : 500 yrs

20 Efficiency and (Sensitivity) Injection depth H (m) By 8 OGCMs (Orr et al. GHGT-5) 15 – 37 (+0.42) 26 – 57 (+0.35) 50 – 82 (+0.25) By 8 sites (MOM) (Tokyo, New York, Bombay …, By Caldeira et al. GRL 2002) 15 – 30 (+0.33) 40 – 57 (+0.17) 70 – 89 (+0.10) By droplet sizes (D 0 = 5 – 40 mm) 20 – 25 (0.21)* 38 – 47 (0.20) 50 – 60 (0.11) 62 – 72 (0.10)** * : H = 1000 m and D 0 = 5 – 10 mm; ** : H = 2500 m

21 Conclusions & discussions Within 500 years after releasing CO 2 at rate of 0.1 Ggt C /year by moving-ship:  Efficiency is related with not only depths and sits but also drop size injected.  For droplets size D0 = 5 – 40 mm, the storage efficiencies could be reduced by range of 5% to 20% if release depth less than 2600m due to the rising plumes.  Implement of DIC vertical pdf into OGCM for further checking. (Nesting grids system ?)  The roles of injection parameters on biological impacts in near-field should is another challenge.

22 Thank you !

23 In this study: Assessments on CO 2 Ocean Sequestrations How long it could be kept in the ocean ? (efficiency)  OGCMs (depth, locations) ( Caldeira et al. in GRL, JGR 02; Orr et al. in Climate Change 02 and GHGT-5-00; ….. )  Box models (depth, bio-chemical systems) ( Sohma et al, JGR-05, …. ) How about the injection parameters? Is it safe for marine bio-masses? (bio-impacts)  Lab. Exps. (Acute injury of fishes, Mortality and Injury of zooplankton by Portner; Shirayama; Ishimatsu ; JO and IPCC SRPT. on CCS) for Near-field and short-terms.  Long-term impacts on bio-eco system ( ? ) Do the Injection parameters play the role ? The impacts on global ecosystem ( ? )

24 Methodologies: Implement the near-filed two-phase box model to the OGCM by:  Provide the initial vertical distributions of DIC from near-filed model  Use data of long-term storage efficiency from OGCMs and Box models to estimate the effects of initial-vertical DIC distribution. because the time scales : dt OGCM (2 ~ 3 hrs) > T diss (1~ 1.5 hrs)  We checked the injection depths and D0s for two injection types (horizontal and vertical injection ports) at a fixed injection rate (100kg/sec).

25 Model validation (vs field Exp data by P. Brewer et al. 2002)

26 Ascending /Descending of CO 2 droplet in the ocean

27 Model of an Individual CO 2 Droplet (dissolution and movement) Key Parameters: Sh : Sherwood number Cs: The solubility α : The effective area coefficient C d : Drag coefficient

28 Sub-models of drag coefficient (Lab. data from Dr. Ozaki) u r = | u d – u w | The relative velocity

29 Near-filed Bio-impacts for two CO 2 release types Vertical release type Horizontal release type Elapsed time: 180 min