February’s issue of Power Engineering featured a story on efforts to increase the re-use of coal combustion products (CCPs). Traditionally, ash, slag and scrubber sludge have been re-used for about a dozen applications, the largest of which are for the manufacture of cement and aggregate, and for road construction. Now, there may be a brand new use for CCPs, one that could not only become one of the biggest single uses of coal byproducts, but one which would save trees as well.
Dr. Paul Chugh and his colleagues at The University of Southern Illinois at Carbondale are working on the design of utility poles made of CCPs. More than 100 million tons of CCPs are generated annually in the U.S., with only about 30 percent recycled for beneficial purposes. Meanwhile, the researchers’ report estimates 250,000 poles averaging 30 to 40 feet long and another million poles of 15 to 30 feet long are used annually in the Midwestern U.S. alone. That translates into the potential to use an immense amount of CCPs while sparing an enormous number of trees.
Two types of CCPs are being used for the study – Grand Tower F-type ash and SIU fluidized-bed combustion (FBV) spent bed ash. Each pole would use from 400 to 600 pounds of CCPs. In the experimental utility pole project, funded by the Combustion Byproducts Recycling Consortium, the CCPs are mixed into a grout and combined with polymers (PVCs) that act as a binding agent. Glass or other material fiber may be added to improve structural strength.
The researchers expect that the final product will be comparable or superior to the traditional creosote-coated wooden pole. In addition to eliminating the need for weatherproofing with creosote, which can cause pollution from rainwater runoff, the CCP poles would be fireproof and termite proof, would be cheaper to install than wooden poles and could not be as easily damaged by animals and humans.
The team projects that using CCP poles for the 250,000 utility poles needed in the Midwest each year would save that many trees and use from 87,500 to 100,000 tons of CCPs. They identify four challenges remaining for commercial development: perfecting a pole that tapers toward the top, developing a pole that can be made for less than $200 to compete with a 35-foot wooden pole, determining the effects of ultraviolet rays on long-term pole life, and developing a grout to mix with PCVs that will use the maximum amount of CCPs while creating the desired utility pole characteristics.