Biological sequestration of carbon dioxide in geological formations

This paper presents the results of experimental investigation and analysis of challenges for utilizing enzyme bovine carbonic anhydrase for sequestration of CO2 in saline formations. Several sets of controlled bench-top experiments were conducted, and results are presented in this paper, where effects of various parameters including pH, concentration of enzyme, and temperature on enhancing hydration and subsequent precipitation of CO2 in the form of calcium carbonate were tested. A mathematical model describing the extent and rate of precipitation was developed upon analyzing the results of these tests. Subsequently, core flood tests were conducted where effect of enzyme on precipitation of CO2 in Berea cores, and its impact on porosity and permeability of the porous media were investigated. These tests indicated that the pressure drop across cores was increased about 2-4 times, which is an indication of precipitation of CO2 in the form of calcium carbonate in porous media. In addition to above tests, effect of timing and scheme of the injection on extent of CO2 precipitation in porous media was tested. It was observed that co-injection of CO2 and enzyme solution leads to higher pressure drop across the cores in tests reported here. Finally, the learning of above tests has been used to outline a series of potential challenges and propose solutions for effective utilization of enzyme bovine carbonic anhydrase for safe sequestration of CO2 in saline formations. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.