The author-list for this Science paper is dazzling [from 1 November 2002]. The abstract:
Stabilizing the carbon dioxide-induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energy demand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (~1013 watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission-free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non-primary power technologies that could contribute to climate stabilization include efficiency improvements, hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development.
Here are the co-authors and their affiliations:
Martin I. Hoffert,1* Ken Caldeira,3 Gregory Benford,4 David R. Criswell,5 Christopher Green,6 Howard Herzog,7 Atul K. Jain,8 Haroon S. Kheshgi,9 Klaus S. Lackner,10 John S. Lewis,12 H. Douglas Lightfoot,13 Wallace Manheimer,14 John C. Mankins,15 Michael E. Mauel,11 L. John Perkins,3 Michael E. Schlesinger,8 Tyler Volk,2 Tom M. L. Wigley16
1 Department of Physics,
2 Department of Biology, New York University, New York, NY 10003, USA.
3 Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
4 Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA.
5 Institute of Space Systems Operations, University of Houston, Houston, TX 77204, USA.
6 Department of Economics, McGill University, Montreal, Quebec H3A 2T7, Canada.
7 MIT Laboratory for Energy and the Environment, Cambridge, MA 02139, USA.
8 Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
9 ExxonMobil Research and Engineering Company, Annandale, NJ 08801, USA.
10 Department of Earth and Environmental Engineering,
11 Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA.
12 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA.
13 Centre for Climate and Global Change Research, McGill University, Montreal, Quebec H3A 2K6, Canada.
14 Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375, USA.
15 NASA Headquarters, Washington, DC 20546, USA.
16 National Center for Atmospheric Research, Boulder, CO 80307, USA.
That first sentence in my quote should read “Injecting CO2 directly into the deep ocean would engage the buffering process that ultimately must mediate the ocean’s uptake of most, if not all, of the accumulated and future anthropogenic CO2 emissions not directly absorbed by seawater.”
I was writing, and thinking, fast. Most of the CO2 will be absorbed by seawater on a time-scale of centuries, but there will be a long “tail” of ~ 20-30 % of the CO2 emissions that stays in the atmosphere for thousands, possibly tens of thousands, of years, because the sedimentary buffering mechanisms are slower than ocean mixing.
Caldeira (and other co-authors, I think), back in the early ’90s (I’ll try to find the exact citation), wrote a paper proposing that the process of carbonate could be artificially enhanced to buffer CO2 at (or near ) the source. This would enhance ocean uptake of CO2 and also minimise ocean acidification and resulting ecological impacts.
Thanks, Will — I just corrected that first sentence. Do you have a “bottom line” on the direct injection of CO2 as an oceanic sequestration strategy? Is it both effective and safe?
Relatively safe I would say. “Relative” in this case means relative to leaving the CO2 in the atmosphere and letting it dissolve in seawater via the surface ocean. The former poses risks via warming the atmosphere, the latter via changing the chemistry of the upper ocean. Direct injection has the advantage of bypassing the surface ocean and delivering the CO2 where a lot of it will end up eventually anyway.
The disadvantages are likely to be 1) cost (energy and money). Probably making some form of hydrate as in Brewer’s experiments and transporting the material to the deep ocean.
2) Environmental risk. There are likely to be ecological impacts, if the sequestration is carried out at a scale which will would make a serious difference to the atmospheric buildup of CO2.
I suppose the cost of any sequestration scheme would have to be weighed against other mitigation options, including not producing the emission in the first place.
The Caldeira et al. paper I referred to earlier is:
Caldeira, K., and Rau, G., 2000, Accelerating carbonate dissolution to sequester carbon dioxide in the ocean: Geochemical implications: Geophysical Research Letters, v. 27, p. 225-228.
Abstract:
Various methods have been proposed for mitigating release of anthropogenic CO2 to the atmosphere, including deep-sea injection of CO2 captured from fossil-fuel fired power plants. Here, we use a schematic model of ocean chemistry and transport to analyze the geochemical consequences of a new method for separating carbon dioxide from a waste gas stream and sequestering it in the ocean. This method involves reacting CO2-rich power-plant gases with seawater to produce a carbonic acid solution which in turn is reacted on site with carbonate mineral (e.g., limestone) to form Ca2+ and bicarbonate in solution, which can then be released and diluted in the ocean. Such a process is similar to carbonate weathering and dissolution which would have otherwise occurred naturally, but over many millennia. Relative to atmospheric release or direct ocean CO2 injection, this method would greatly expand the capacity of the ocean to store anthropogenic carbon while minimizing environmental impacts of this carbon on ocean biota. This carbonate-dissolution technique may be more cost-effective and less environmentally harmful, and than previously proposed CO2 capture and sequestration techniques.
If I understand your points I conclude that geologic sequestration is the safer option. And from what I know of the energy industry technology I would expect it to be cheaper.
I give practical sequestration a high priority on the assumption that it will prove to be cheap enough to offer a transition technology until we develop competitive alternatives to coal. Further, if it turns out either to not be “safe” or would make coal-fired electricity equivalent to 1$ per kWh or $500/ton coal prices, then we are going to see really big GHG concentrations. I say that anticipating that the developing economies are not going to cripple their growth.
Does that sound correct to you?