Let's face it, coal is nasty stuff. It contaminates everything it comes in contact with and creates problems at every step of its life cycle: from unhealthy and unsafe underground mines, to the environmental catastrophe of mountaintop removal, to the problems associated with handling the enormous piles of ash that are produced every day. But by far, the biggest problem is the enormous amount of carbon dioxide emitted. According to the EPA, coal contributes 31 percent of all CO2, the largest of any source.