David E. Riestenberg, Costas Tsouris, Peter G. Brewer,
Edward T. Peltzer, Peter Walz, Aaron C. Chow§ and E. Eric Adams§
: Oak Ridge National Laboratory, Post Office Box 2008, Oak Ridge, Tennessee 37831
: Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, California 95039-9644
§: Department of Civil and Environmental Engineering, Massachusetts Institute of Technology,
77 Massachusetts Avenue, Cambridge, Massachusetts 02139
Environmental Science and Technology (2005) 39: 7287-7293.
Received: 2005 January 19.
Revised: 2005 June 17.
Accepted: 2005 June 22.
We have carried out the second phase of field studies to determine the effectiveness of a coflow injector which mixes liquid CO2 and ambient seawater to produce a hydrate slurry as a possible CO2 delivery method for ocean carbon sequestration. The experiments were carried out at ocean depths of 1000-1300 m in Monterey Bay, CA, using a larger injector than that initially employed under remotely operated vehicle control and imaging of the product. Solid-like composite particles comprised of water, solid CO2 hydrate, and liquid CO2 were produced in both studies. In the recent injections, the particles consistently sank at rates of ~5 cm/sec. The density of the sinking particles suggested that ~40% of the injected CO2 was converted to hydrate, while image analysis of the particle shrinking rate indicated a CO2 dissolution rate of 0.76-1.29 µmol/cm²/sec. Plume modeling of the hydrate composite particles suggests that while discrete particles may sink 10-70 m, injections with CO2 mass fluxes of 1-1000 kg/sec would result in sinking plumes 120-1000 m below the injection point.
© 2005 American Chemical Society.
Gratefully acknowledged is support by the Ocean Carbon Sequestration Program, Office of Biological and Environmental Research, U.S. Department of Energy, Grant KP1202030, under Contract DE-AC05-00OR22725 with UTBattelle, LLC and Contract DE-FG02-01ER63078 with MIT. Support for MBARI was provided by the David and Lucile Packard Foundation and the U.S. Department of Energy under Contracts DE-FC26-00NT40929 and DE-FG03-01-ER63065. We thank the captain and crew of the RV Point Lobos and the pilots of the ROV Ventana for their excellent work in making the field experiments possible. We also thank Dr. Marsha Savage for editing the manuscript.