In sufficient quantity, these could pose environmental problems. Some of these by-products may contribute to acid rain, though the exact causes and possible solutions are still being studied by scientists within and outside of the industry. Mining companies plan the reclamation process before digging. In many cases, land is left in better condition than before mining started. This acid is now being chemically removed before the water is discharged into streams.
Slurry pipelines require large amounts of water.
But lakes created during land reclamation can help replace some of the water used. Fine ash particles fly up into the air when coal burns. Special devices placed in the smoke stack trap most of this ash. For example, one method uses electrically charged particles to trap ash. Sludge is a by-product of using scrubbers.