Title: Heat as a by-product or sub-product of CO₂ storage in mafic and ultramafic rocks

Authors: Diogo R.N. Rosa; Rui N. Rosa

Addresses: Department of Petrology and Economic Geology, Geological Survey of Denmark and Greenland, Øster Voldgade 10, Copenhagen K 1350, Denmark ' Department of Physics and Geophysics Centre of Evora, University of Evora, Rua Romao Ramalho 59, Evora 7000 671, Portugal

Abstract: Since carbonates are at a lower energy state than free CO₂, storage through carbonation of silicate rocks is thermodynamically favoured and proceeds spontaneously by releasing heat. In an in-situ CO₂ injection site, the heat released in these exothermic reactions can be exploited in a geothermal power-plant, effectively contributing toward the economic viability of the storage process. Our calculations suggest the possibility of generating up to about 25 TWh of electrical energy while capturing permanently about 240 Mton CO₂ per 1 km³ of peridotite or basalt rock. That broadly corresponds to exploring an electric power plant having up to 60 MW gross output during a period of 50 years. These results show that geothermal energy and CO₂ storage, often portrayed as conflicting uses of the subsurface, can actually work together, enhancing the economic feasibility of each other in case mafic and/or ultramafic rock formations are used as reservoirs.

Keywords: basalt rock; silicate minerals carbonation; CO2; carbon dioxide; carbon storage; geothermal energy; heat release; exothermic reactions; geothermal power plants; electricity generation; mafic rocks; ultramafic rocks.

DOI: 10.1504/IJGW.2012.049435

International Journal of Global Warming, 2012 Vol.4 No.3/4, pp.305 - 316

Received: 08 Nov 2011
Accepted: 25 Apr 2012
Published online: 13 Dec 2014 *

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