Waste coal is a byproduct of coal processing, containing coal, along with trace minerals, dirt, and other materials. It is potentially usable for a variety of applications, although there are environmental concerns associated with the recovery and use of waste coal. Depending on regional slang, a variety of colorful terms are used to refer to this coal product, including gob and culm. It is typically gathered in large piles in close proximity to a coal processing facility.
One potential use of waste coal is a fuel. It can be burned straight or cleaned and burned to generate electricity and many power plants are equipped to handle waste coal, although it is less efficient than conventional coal. Processing can also be used to extract usable metals in the coal for industrial uses. In some regions, waste coal piles have become recreational sites and have been reclaimed with the use of vegetation.
One of the key environmental concerns is the presence of a number of contaminants in the coal. These can include heavy metals. A poorly controlled waste pile may leach into the surrounding environment, introducing mercury and other materials into soil, air, and water. When waste coal is burned, these products can be released into the environment through the ventilation stacks and a large amount of potentially toxic coal ash is generated. This coal ash must be disposed of in some way and is difficult to get rid of because of the contaminants it contains.
In regions of the world where coal mining has been practiced for generations, abandoned waste coal piles can be seen. Many nations now forbid the practice of abandoning mining waste and companies must take measures to dispose of or control waste coal if they plan on closing a mine. Companies are also held responsible for pollution related to the coal. Environmental remediation plans may be presented to the community with the goal of getting approval for a particular method of dealing with the coal.
There is some controversy over how to handle mining waste like coal in some communities. The sheer volume of many waste piles is a significant issue, as plans for handling the material must consider the large amount of coal involved. Some communities support leaving piles in place despite the leaching issues, while others want it hauled somewhere else, and this raises concerns about passing pollution on to other regions. In addition to the waste, many companies must also deal with tailings, materials leached from coal while it is processed. Tailings do not have a use and are often very toxic.