“Dry cleaning methods should generate fewer environmental problems and require less energy than wet washing methods.”
-- Dept of Energy Report from University of Arkansas
Many options are available to process coal without creating coal slurry including de-watering and cleaning coal without water. If coal is washed using a wet process, which creates the coal slurry, the slurry does not need to be disposed of immediately into impoundments or injected into abandoned mines. Dewatering processes press or filter the water from the waste. Several methods are available and fairly widely used. The most appropriate method depends on the slurry composition and planned disposal method.
Companies in West Virginia have already utilized dry press filters. This technology relies on a closed loop of water to wash the coal. Waste slurry is pressed and dry filter cakes are created. These dry filter cakes may then be stored appropriately and more safely in lined landfills. Marrowbone Development in Mingo County used a dry press filter well throughout most of the 1980s. Some plants, such as the Panther plant in Kanawha County, use dry press technology today. Existing coal processing plants can be paired with a filter or belt press that will dry the slurry into filter cakes that can be disposed of in a lined landfill. The cost is slightly higher (50 cents to one dollar per ton) for a conventional plant to operate with a filter press than without.
New technology is also available. Virginia Tech scientists have developed a technology that removes water from coal slurry, lowering the amount of toxic waste potentially seeping into the water table and poisoning wells. A Chinese company that builds zero-water discharge preparation plants set up shop in Lexington, Ky., in 2005. Guohoa Technology has already built over 430 preparation plants in Asia and advertises itself as cheaper than existing plants. In addition to eliminating liquid slurry and consuming 80% less water, these closed loop technologies recover more of the fine particles of coal. That means fewer toxic coal particles in the refuse and more efficient coal recovery for the operator.
Other methods of coal processing don’t involve water at all. Such methods are popular in the Western United States, Asia and Australia where water resources are scarce and, therefore, highly valued. Dry processes vary from using air and motion to electromagnetism to separate out the coal without water and many have been around for decades. The initial capital expenditure on a dry plant is less than a wet plant and since dry processes use less energy and do away with the need for chemical input and large waste disposal areas. The operating cost is also lower.
The Sludge Safety Project cannot verify the safety of any alternative technology and all disposal of coal refuse must be cafeful contained and monitored. It is clear that technological alternatives to the dangers of coal slurry exist and must be employed by the industry.