Evaluation of the potential impacts of an influx of CO2 on subsurface microbial populations using a thermodynamic approach

Palumbo-Roe, B.; West, J.M.. 2013 Evaluation of the potential impacts of an influx of CO2 on subsurface microbial populations using a thermodynamic approach. Nottingham, UK, British Geological Survey, 22pp. (OR/13/014) (Unpublished)

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The microbial community response to CO2 injection and the extent to which microbial communities play a role in the geologic sequestration of CO2 are not well known. In this study we use a thermodynamic approach to scope some potential microbial reactions induced by elevated CO2 concentrations in subsurface environments, characterised by limited availability and supply rates of energy sources. In these subsurface environments, the energy needed for microbial growth is supplied chemically through thermodynamically favourable electron transfer (redox) reactions. The thermodynamic approach consists of calculating the free energy of these redox reactions which can be used by microbes for their life processes – the energy yield. As many redox reactions involve protons, in a first approximation the available Gibbs free energies of possible microbially mediated redox reactions are shown as a function of pH and assuming unity activity of reactants and products of each reaction (standard state conditions). Both H2→H+ and SO2→SO4 electron donor reactions can have a favourable energy yield for the reduction of CO2→CH4 at standard conditions. We have also shown that the presence of impurities in the CO2 waste stream could provide useful energy sources for microbial activity, particularly for SO2 when coupled to CO2 reduction. We have also calculated the energy yields for a range of probable microbially mediated reactions using the fluid composition measured at the Ketzin CO2 injection site in Germany, where the microbial community response to CO2 injection has been monitored. Based upon in situ concentrations, the influence of thermodynamic constraints on the microbial community composition observed before and after CO2 injection at the Ketzin saline aquifer has been evaluated.

Item Type: Publication - Report (UNSPECIFIED)
Funders/Sponsors: NERC
Additional Information. Not used in RCUK Gateway to Research.: This item has been internally reviewed but not externally peer-reviewed
NORA Subject Terms: Earth Sciences
Biology and Microbiology
Date made live: 30 Jul 2013 15:19 +0 (UTC)

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