COLUMBIA, Mo. – Coal-burning power plants spend millions disposing of fly ash, a fine powder loaded with mercury, lead and other toxic chemicals.
An estimated 70 million tons of the byproduct is produced in the U.S. each year, and most of it is buried in specially designed ponds and landfills.
Henry Liu, a retired civil engineering professor at the University of Missouri-Columbia, has a solution to the quandary of fly ash disposal. He wants to bring it into your homes and offices — literally.
Liu, 69, recently received a $500,000 grant from the National Science Foundation, his second such award, to further study ways to make weather-resistant bricks out of fly ash. He hopes to bring the product to market within two years.
Before retiring from the university in 2001, Liu led a research team that developed a way to ship compact, highly pressurized cylinders of coal, propelled by water, through pipelines.
In the process, Liu realized that the techniques he used to compress coal could be adapted to other substances, including yard waste, trash and fly ash. Upon retirement, he created the Freight Pipeline Co.
The waste is converted into biomass, cylinders of garbage that can be burned for fuel. The fly ash, cured and watered like a salted ham or a hybrid plant, is converted into what Liu calls an eco-friendly construction material.
"Using that pressure, we thought we could compact a lot of things other than coal," he said.
He quickly found a willing partner in utility companies such as Associated Electric Cooperative Inc. in Clifton Hill, which provided fly ash for his first phase of research; and Ameren UE, which is doing likewise for Liu's latest round of tests.
"It's absolutely pure stewardship, the beneficial use of what otherwise might be considered waste," said Mark Bryant, an Ameren official who oversees its coal combustion byproducts.
Cement manufacturers and brick makers already use fly ash — which has strong adhesive properties — as an additive. But unlike those efforts, Liu's bricks are made almost entirely of the powder.
Clay-fired bricks are heated in kilns to temperatures of 2,000 degrees, burning fossil fuels that produce air pollution and green house gases.
The limestone used to make Portland cement found in concrete bricks also must be burned at high temperatures, emitting similar pollutants into the atmosphere.
No such emissions exist with fly ash bricks, said Liu, who in 1965 moved from Taiwan to the United States, where he earned graduate and doctorate degrees at Colorado State University before joining the Missouri faculty.
Liu, a native of China, added that fly ash bricks are cheaper and more uniform in size than conventional bricks, he said.
Pat Schaefer, sales manager for Midwest Block and Brick in Jefferson City, calls Liu's research intriguing — and savvy.
"The architectural world is pushing tremendously toward sustainable, green-type buildings," he said. "One hundred percent recycled would fit very well in that industry."
The pressurization process hardens and traps the trace elements of mercury and other toxins within the bricks, said Liu. He plans to further study that aspect by building an 11-square-foot cell entirely of fly ash bricks, including the floor and ceiling, to monitor air quality.
But even should those tests prove favorable, whether consumers can accept a home constructed of power plant remnants remains to be seen, suggested Bryant.
"He's using a good concept," said Bryant. "The question becomes: Can you develop a market and will the public ultimately accept the use of this product in their homes and in their workplaces? It's still too early to tell."