How do regular coal and clean coal compare?

The composition of coal varies widely depending on its rank, original setting, and other geological parameters. For instance, coal with a lot of ash (which is simply the original clays or silts that were trapped in the plant before they became coal) has a lower heating value and is of lower quality. Similarly, coal with a lot of pyrite (sulfur) is highly polluting when burned because it releases chemicals that cause acid rain. On the other hand, high-quality clean coal has low ash, high BTU energy content, and low sulfur content, and is therefore most expensive.

The term "clean coal" refers to two different things: 1) a coal that has few impurities, as described above; and 2) clean coal technologies, which attempt to make coal "cleaner" by scrubbing the gases as it burns. However, these technologies have not lived up to the hype or promise because they are expensive to install and industry is hesitant to do so unless mandated by law.

The majority of utilities in North America are moving away from coal and toward natural gas because it is currently far less expensive and cleaner than coal, even clean coal or clean coal technology.

Regular coal, also known as traditional or conventional coal, refers to coal that is burned for electricity generation without advanced technologies to reduce emissions. Clean coal refers to technologies aimed at minimizing environmental impacts, including carbon capture and storage (CCS) to reduce greenhouse gas emissions. Clean coal technologies aim to mitigate the environmental effects associated with traditional coal combustion.