High-quality coal is very important - meaning in particular higher kilocalorific content, lower sulphur and lower ash. That translates into less coal being burned for same output, and less water being consumed too. Less of the pollutants are emitted, especially in the ultra-super-critical coal plants and those of similar ilk, and lower CO2 emissions per MW of electricity generated. We here in Australia have a good deal of the higher-quality coal (see for instance Whitehaven's mines). Now just think about the use of that relative to poorer-quality coals being burned in sub-critical plants, and it's clear that it's an absolute winner. The better plants are necessary for the higher-quality coals, as they burn at higher temps and the superior plants are designed for that. On the contrary, the high-quality product will damage lower-quality burners again because of the temperature. Too high sulphur content will damage equipment, so a lower sulphur content can and will attract a premium over the benchmark pricing.
