COAL IS ONE of a variety of energy sources that both developed and developing nations use. It is the fossil fuel that is relied upon most heavily for electricity generation in the United States. Organic matter from the Carboniferous period, which occurred approximately 360–286 million years ago, forms currently accessible coal deposits. There are several different types of coal, each with varying degrees of thermal value. In the process of electricity and heat generation, coal combustion releases many pollutants into the air, water, and land. These pollutants include mercury, sulfur oxides, nitrogen oxides, methane, and carbon oxides. The dispersal of such toxins into the environment has many ecological, human health, and economic effects. More specifically, coal combustion contributes to the climate-changing effect of increased atmospheric ...