Carbon Dioxide Emissions from Oil Shale Derived Liquid Fuels

Abstract

Without mitigation or technology improvements, full-fuel-cycle carbon dioxide (CO₂) emissions from oil shale derived liquid fuels are likely to be 25 to 75% higher than those from conventional liquid fuels, depending on the details of the process used. The emissions of CO₂ from oil shale derived fuels come from three stages: retorting of shale, upgrading and refining of raw shale oil, and combustion of the finished transportation fuels. Emissions from these stages represent approximately 25-40%, 5-15%, and 50-65% of total fuel-cycle emissions, respectively. The most uncertain source of emissions is the retorting stage, due to variation in emissions with shale quality and retorting technology used. Mitigation options include higher thermal efficiency, minimizing carbonate decomposition, CO₂ sequestration by geologic injection, enhanced oil recovery, mineralization in spent retorts, or the use of non-fossil sources for process heat.