Coal and coalbed gas : fueling the future Coalbed gas has emerged as an important energy source and understanding this resource requires knowledge of elements of coal geology. The diverse heritage of coal and the maturing field of coalbed gas have given rise to definitions and terminologies that are used throughout this book. The ability to comprehend basic principles is the key to extrapolate from coal science to engineering applied coalbed gas. Understanding the global coal endowment occurrence and distribution related to the dynamic structural changes in the Earths outer shell through geologic time is essential to the exploitation of coalbed gas. Vast global coal resources of 9 27 trillion metric tons potentially hold coalbed gas in place of 67 252 trillion m3 based on comparisons with producing American fields