What is the cleanest burning coal 90 percent carbon

This cycle is known to engineers as the Rankine Cycle, and is used in nuclear power plants as well. When the coal burns, it gives off sulfur dioxide, nitrogen oxide and carbon dioxide, among other gases. ... Scrubbers are more common, and can reduce sulfur emissions by up to 90 percent, when working properly.

Iwould go with i'm not positive because i'm dumb that