July 14, 2016

Carbon Capture Options

There have been recent articles about “CarbFix, a pilot program at Iceland’s Hellisheidi Geothermal Power Station utilizing carbon capture and storage (CCS). CO2 gas is pumped underground and leads to its transformation to minerals.  This process eliminates the concern for underground storage sites that will remain stable for a long period of time (i.e. no earthquakes or geological faults are going to occur:  any rupture of underground storage layers would lead to catastrophic release of CO2 that affects the biomass near surface layers.)
Along with this single advantage come a few issues to consider with this approach, including its broader applicability:
(i)                 The geology of the Icelandic underground reserve. The process is intrusive to the natural balance. Per literature estimates, 1 million ton of CO2 would require 1 km3 of basalt reserve.
(ii)               According to literature and assuming the underground storage facility is at the right temperature to ensure fast kinetics per the article claim, a pressure of 200 to 400 bar might be required to drive the storage process.  Formation of carbonates might even make seeping of carbonated water more difficult.  How many kgs of CO2 are released to atmosphere by large capacity pumps per ton of CO2 sequestered underground per cubic meter of Basalt? (This question is moot if the pumps operate using hydrothermal power).
(iii)             Water requirements. What volume of Icelandic water is required to dissolve 1 ton of CO2 gas where the pH of the water is a crucial factor in getting the maximum dissolution of CO2 gas?    If the process uses saline water or seawater, then implications to underground mineral water contamination have to be considered.
(iv)             The process is localized to the Icelandic territory. Most coal fired power plants or other CO2 emitting industrial facilities do not have the advantage of an underground basalt reserve, which became transformed to their present state from other minerals that already lost their CO2 content due to thermally elevated conditions above ground or underground.
Compared to other carbon capture and conversion processes (i.e. Carbon Capture and Mineralization (CCM) or Carbon Capture and Utilization (CCU)), the Icelandic project is expected to handle a much greater quantity of CO2 conversion at a minimum power loss. There are few industrial CCM and CCU processes that are either under pilot test or production stage that claim CO2 capture. If these facilities are powered by fossil fuel, then these cannot claim any carbon capture. Examples of these CCM/CCU processes are modified Solvay, Chlor-alkali, urea, polymerization, pilot electrochemical processes, and others.  The major advantage over the CCS basalt project is that the end products are usually commodity chemicals used for commercial purposes.  Finally, one process that uses membrane/ion exchange technology to process alkaline waste from industrial sites can compete with CCS basalt project in terms of energy and chemical byproducts.
Another trend that is getting serious consideration by scientists around the world is CO2 gas conversion to carbon monoxide (CO) gas and other basic precursors heavily used as start-up chemicals in chemical industry. That is, recycle CO2 gas instead of losing it to underground storage. A major hurdle in this regard is energy consumption, and scientists are searching for a breakthrough. A multibillion dollar CCU recycle process that is not CCM can have a major contribution to CCS technology at the global scale with world geopolitics. However, this topic will require a separate discussion.

The author of this blog post has a Ph.D. in Analytical Chemistry and is the inventor in 10 patents. His experience includes research in carbon capture, cartridge membrane mineral concentrators, semiconductor, metal, and ceramic surface cleaning and functionalization with surface coatings.   Click to read more about this technical expert. 

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