Clean coal is a concept for processes or approaches that mitigate emissions of carbon dioxide (CO2) and other greenhouse gases, and radioactive materials, that arise from the use of coal, mainly for electrical power generation, using clean coal technology. Currently, the term clean coal is used in the coal industry primarily in reference to carbon capture and storage, which pumps and stores CO2 emissions underground. Plants using integrated gasification combined cycle (IGCC) involve coal gasification, which provides a basis for increased efficiency and lower cost in capturing CO2 emissions. Prior to the current focus on carbon capture and storage, the term clean coal had been used to refer to technologies for reducing emissions of NOx, sulfur, and heavy metals from coal.