Oil Shale as an Energy Resource in a CO2 Constrained World: The Concept of Electricity Production with in Situ Carbon Capture

Abstract

Oil shale contains large amounts of stored chemical energy: over 1 trillion barrels of oil equivalent is present in the Green River formation of the United States alone. Unfortunately, extraction of energy from oil shale generally releases significant quantities of greenhouse gases (GHGs). Liquid hydrocarbon (HC) fuels derived from oil shale have 1.2−1.75 times the fuel cycle GHG emissions of HC fuels produced from conventional oil. This paper proposes a concept that could provide transportation services from oil shale with significantly reduced carbon emissions, called electricity production with in situ carbon capture (EPICC). EPICC reduces CO₂ emissions by (1) utilizing waste heat to retort shale; (2) retorting shale beyond the point of liquid hydrocarbon production, converting much of the organic carbon in oil shale to char which is left in the subsurface; and (3) using the produced HC gas to generate electricity, which provides transportation services with no tailpipe emissions. The resulting life cycle GHG emissions from EPICC amount to ≈110 g of CO₂ per km, ≈0.5 times those of conventional fuel cycles or ≈0.33 times those from other proposed in situ oil shale conversion processes. Potential drawbacks of EPICC include uncertain operation of subsurface fuel cells, potential geophysical impacts without pressure management, and economic concerns associated with the value of stranded energy left in the formation and the long time period of retorting.