UF researchers: technique cuts pollution from burning treated wood

August 16, 2000

A University of Florida research team has developed a new technique to reduce toxic pollution from incinerating pesticide-treated wood, a development that comes amid growing national debate over how to safely dispose of the wood.

The technique not only reduces toxins in air pollution generated by incinerating discarded treated wood, it also makes the toxins less likely to leach out of the ash and into the groundwater when it is placed in a landfill, said C.Y. Wu, a UF assistant professor of environmental engineering.

"Our technique solves two problems: It reduces emissions and leaching," said Wu, the lead investigator on the team, which will present its findings later this month at the American Chemical Society's annual meeting in Washington, D.C.

Wood treated with chromated copper arsenate, commonly known as CCA, contains arsenic and chromium, which are known carcinogens. Used in everything from decks to porches to playground equipment, it has come under increasing scrutiny in recent years as scientists have raised concerns about release of arsenic into the environment. One focus of the concern is disposal of the wood, which is often mixed with nontreated wood and incinerated. Concerns are particularly high in Florida, which has electricity-generating wood incinerators and is estimated to incinerate at least 70 percent of its waste treated wood, Wu said. The amount of discarded treated wood in Florida, meanwhile, is expected to grow from 5 million cubic feet per year today to 35 million cubic feet in 2015, according to research by UF and University of Miami scientists.

Wu said the team's research shows that when CCA-treated wood is burned, much of the arsenic may escape into the air. That's because the pollution control devices in the incinerators' smokestacks capture only relatively large particles. In the heat of the incinerator, however, the arsenic vaporizes and forms extremely tiny particles -- less than 1 micron in diameter, or more than 100 times smaller than the diameter of a human hair. These tiny particles cannot be perfectly captured in traditional pollution control devices.

The UF technique introduces limestone into the burning process, which reacts with the arsenic to form larger particles, in the range of 50 microns. Instead of escaping through the smokestack, those particles wind up in the waste ash. That may appear to merely transfer the problem from one place to another, but Wu said tests reveal that the arsenic-limestone particles also are much less likely to leach arsenic into the groundwater than the tiny arsenic particles.

So far, the incinerator technique has only been tested in laboratories, Wu said. But he noted that power plants already use a similar technique involving injecting limestone into air pollution devices to reduce sulfur dioxide emissions, which suggests adopting the process for wood incinerators is a distinct possibility.

John Schert, director of the Florida Center for Solid and Hazardous Waste Management at UF's College of Engineering, said the study shows considerable promise to address a major environmental problem.

"If somebody can figure out how to burn CCA-treated wood and not let the arsenic escape into the atmosphere, that's the Holy Grail for disposing of CCA wood," he said.
The other team members are Timothy Townsend, an assistant professor of environmental engineering; and Kenjiro Iida, John Pierman and Thabet Tolaymat, all students in the department of environmental engineering. The research was funded by UF's University Scholars Program.

Aug. 17, 2000
Writer: Aaron Hoover, ahoover@ufl.edu
Source: C.Y. Wu, 352-392-0845, cywu@ufl.edu

University of Florida

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