The feasibility of in situ geological sequestration of supercritical carbon dioxide coupled to underground coal gasification

Based on the thermophysical properties of supercritical carbon dioxide and available power plant engineering information, it is shown that the maximum achievable efficiency of carbon dioxide sequestration in underground cavities left after in situ coal gasification is approximately only 14%. Available evidence indicates that the claim that the syngas thus produced can be employed to synthesise "green" liquid fuels is over-optimistic. In addition, a brief analysis is presented of environmental issues relating to the potential contamination by carcinogenic polycyclic aromatic compounds dissolved by supercritical carbon dioxide. An estimate of the solubility of the carcinogenic compound benzo[a] pyrene based on molecular polarizability is presented.