from the production of shale oil and shale gas are higher than conventional oil production and a report for the European Union warns that increasing public concern about the adverse consequences of global warming may lead to opposition to oil shale development. Emissions arise from several sources. These include released by the decomposition of the kerogen and carbonate minerals in the extraction process, the generation of the energy needed to heat the shale and in the other oil and gas processing operations, and fuel used in the mining of the rock and the disposal of waste. As the varying mineral composition and calorific value of oil shale deposits varies widely, the actual values vary considerably. At best, the direct combustion of oil shales produces carbon emissions similar to those from the lowest form of coal, lignite, at 2.15 moles CO2/MJ, an energy source which is also politically contentious due to its high emission levels. For both power generation and oil extraction, the CO2 emissions can be reduced by better utilization of waste heat from the product streams. In-situ processing Currently, the in-situ process is the most attractive proposition due to the reduction in standard surface environmental problems. However, in-situ processes do involve possible significant environmental costs to aquifers, especially since in-situ methods may require ice-capping or some other form of barrier to restrict the flow of the newly gained oil into the groundwater aquifers. However, after the removal of the freeze wall these methods can still cause groundwater contamination as the hydraulic conductivity of the remaining shale increases allowing groundwater to flow through and leach salts from the newly toxic aquifer. See also Oil shale geology Oil shale industry Oil shale economics References External links and further reading Oil Shale and Tar Sands Draft Programmatic Environmental Impact Statement (EIS) Concerning potential leases of Federal oil sands lands in Utah and oil shale lands in Utah, Wyoming, and Colorado Oil shale Oil shale industry Oil shale industry