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Climate engineering responses to climate emergencies

Author(s): Blackstock JJ, Battisti DS, Caldeira K, Eardley DM, Katz JI, Keith DW, Patrino AAN, Schrag DP, Socolow RH, Koonin SE

Published: July, 2009

Publisher: Novim Group

Tags: Stratospheric Aerosols, Cloud Brightening, Surface Albedo Modification, Environmental Side-Effects, Tropospheric Aerosols

URL: http://www.novim.org/projects/climate-engineering

Abstract: Despite efforts to stabilize CO2 concentrations, it is possible that the climate system could respond abruptly with catastrophic consequences. Intentional intervention in the climate system to avoid or ameliorate such consequences has been proposed as one possible response should such a scenario arise. In a one-week study, the authors of this report conducted a technical review and evaluation of proposed climate engineering concepts that might serve as a rapid palliative response to such climate emergency scenarios.


Electrochemical Acceleration of Chemical Weathering as an Energetically Feasible Approach to Mitigating Anthropogenic Climate Change

Author(s): House KZ, House CH, Schrag DP, Aziz MJ

Published: December, 2007

Publisher: Environmental Science & Technology

DOI: 10.1021/es0701816

Tags: Enhanced Weathering

URL: http://pubs.acs.org/doi/abs/10.1021/es0701816

Abstract: We describe an approach to CO2 capture and storage from the atmosphere that involves enhancing the solubility of CO2 in the ocean by a process equivalent to the natural silicate weathering reaction. HCl is electrochemically removed from the ocean and neutralized through reaction with silicate rocks. The increase in ocean alkalinity resulting from the removal of HCl causes atmospheric CO2 to dissolve into the ocean where it will be stored primarily as HCO3− without further acidifying the ocean. On timescales of hundreds of years or longer, some of the additional alkalinity will likely lead to precipitation or enhanced preservation of CaCO3, resulting in the permanent storage of the associated carbon, and the return of an equal amount of carbon to the atmosphere. Whereas the natural silicate weathering process is effected primarily by carbonic acid, the engineered process accelerates the weathering kinetics to industrial rates by replacing this weak acid with HCl. In the thermodynamic limit—and with the appropriate silicate rocks—the overall reaction is spontaneous. A range of efficiency scenarios indicates that the process should require 100–400 kJ of work per mol of CO2 captured and stored for relevant timescales. The process can be powered from stranded energy sources too remote to be useful for the direct needs of population centers. It may also be useful on a regional scale for protection of coral reefs from further ocean acidification. Application of this technology may involve neutralizing the alkaline solution that is coproduced with HCl with CO2 from a point source or from the atmosphere prior to being returned to the ocean.


Permanent carbon dioxide storage in deep-sea sediments

Author(s): House KZ, Schrag DP, Harvey CF, Lackner KS

Published: August, 2006

Publisher: Proceedings of the National Academy of Sciences

DOI: 10.1073/pnas.0605318103

Tags: Marine Carbon Storage

URL: http://www.pnas.org/content/103/33/12291.abstract

Abstract: Stabilizing the concentration of atmospheric CO2 may require storing enormous quantities of captured anthropogenic CO2 in near-permanent geologic reservoirs. Because of the subsurface temperature profile of terrestrial storage sites, CO2 stored in these reservoirs is buoyant. As a result, a portion of the injected CO2 can escape if the reservoir is not appropriately sealed. We show that injecting CO2 into deep-sea sediments <3,000-m water depth and a few hundred meters of sediment provides permanent geologic storage even with large geomechanical perturbations. At the high pressures and low temperatures common in deep-sea sediments, CO2 resides in its liquid phase and can be denser than the overlying pore fluid, causing the injected CO2 to be gravitationally stable. Additionally, CO2 hydrate formation will impede the flow of CO2(l) and serve as a second cap on the system. The evolution of the CO2 plume is described qualitatively from the injection to the formation of CO2 hydrates and finally to the dilution of the CO2(aq) solution by diffusion. If calcareous sediments are chosen, then the dissolution of carbonate host rock by the CO2(aq) solution will slightly increase porosity, which may cause large increases in permeability. Karst formation, however, is unlikely because total dissolution is limited to only a few percent of the rock volume. The total CO2 storage capacity within the 200-mile economic zone of the U.S. coastline is enormous, capable of storing thousands of years of current U.S. CO2 emissions.


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