An ash dump is a holding area for ash, a byproduct of combusting materials such as wood and coal. Ash dumps can become a serious environmental issue, especially when they are related to industrial processes. There are a number of ways to set up and maintain an ash dump, with the goal generally being to create a holding area which will allow hot ash to cool down so that it can be properly disposed of at another location.
In the sense of an ash dump in a residence, the dump is attached to a fireplace or firebox. A small toggle in the floor of the fireplace allows people to push ashes into the ash dump. Later, they can be accessed through an ash dump door for cleaning. This allows people to accrue a large pile of ashes to discard all at once. In some cases, the door is left off, and ashes are simply dumped into a large pit under the house with no means for collection, although this is not recommended. When it's time to clean out, the ashes can be buried or worked into the soil in small amounts as a soil conditioner.
Industrial ash dumps such as those attached to coal-fired power plants operate on similar principles, but a much larger scale. One issue with such ash dumps is that sometimes companies never make arrangements for offsite disposition, and the ashes accumulate on site. There have been cases in which the containment ruptured, allowing ashes to spill, often in wet conditions which turn the ash into a sludge which can be carried across the landscape.
A key problem with industrial ash dumps is that they can be hazardous. The ashes often contain dioxins and other toxic byproducts of combustion. If the contents of a coal ash dump are freely released, they can lead to environmental degradation including contamination of water supplies and ruining of land used for crops. This has led to several lawsuits in various regions of the world as citizens attempt to recover losses after ash dump contamination.
The issue of what to do with byproducts of combustion left over from the generation of heat or electricity is a pressing one in some areas. Materials in an ash dump take a long time to break down and the load of leftover ash and other materials is constantly increasing as the demands for heat and power rise. Some companies sell their ash to use as construction filler and in other applications.