What are the pros and cons of using coal cinder to grow orchids?

Coal cinder is both permeable to water and air and able to retain water and nutrients. It is light in weight, does not compact, and is widely available. Because it has been subjected to high temperatures, orchid plants grown in coal cinder are less likely to suffer frompests and diseases. Because coal cinder contains certain minerals, it is beneficial to variation in orchid plants. These are its advantages. Its low organic matter content, however, is a shortcoming. Using coal cinder as a bottom layer can also create the drawback that the coal cinder at the bottom stays wet and is difficult to dry out. (Zhang Bingfu)