By James Bruggers
LOUISVILLE, Ky. (AP) — First there’s a hissing sound as a gate opens to expose the glowing orange inferno burning within the maw of the Kosmos Cement kiln.
Two rollers grab a scrapped rubber tire before pitching it at 85 mph as far as 110 feet into the bowels of the kiln, where it vaporizes in an instant in 3,000-degree temperatures.
As frequently as eight times a minute, 24 hours a day, that scene repeats itself, with the energy from those incinerated tires powering the southwestern Jefferson County plant owned by Mexico-based CEMEX, which produces, distributes and sells cement and ready-mix concrete and related building materials in as many as 50 countries.
The kiln is so hot that the tires combust completely, meaning there is no significant increase in air pollution, the plant and the Louisville Metro Air Pollution Control District have found.
In fact, the plant’s hourly annual average rate for emissions of nitrogen oxides, a key contributor to smog, is 37 percent less this year than in 2009, when it was burning only coal, said Shannon Graves, the environmental manager at the plant.
“Our numbers match theirs,” confirmed Thomas Nord, spokesman for the local air district. “It’s (burning tires) an acceptable form of fuel.”
The plant started burning tires in place of coal in 2010, after testing in 2009.
The changeover has helped Kentucky waste managers keep an estimated 2 million tires out of landfills, while the plant has burned as much as 24,000 fewer tons of coal, Graves said.
Tires make up about 15 percent of the plant’s fuel, with coal and some pet coke, a residue from petroleum distillation, supplying the rest, she said. The tires are kept in semi-trailers, out of the rain, and are loaded and guided onto a conveyor track by three workers.
“It’s an amazing process,” said Pete Flood, a supervisor with the Louisville Metro Solid Waste Management Division. “It’s a win for everybody.”
In addition to air-quality benefits, he said Louisville metro government has saved thousands of dollars a year in used-tire disposal costs by turning them over to CEMEX, including many that are dumped in neighborhoods — where they collect water, breed mosquitoes and clutter the landscape.
The company gets most of its tires from a contractor, Graves said.
Environmental attorney Tom FitzGerald, director of the Kentucky Resources Council, said he closely reviewed the tire-burning proposal and the test burning.
“When they first came to us, I was skeptical about any combustion of tires,” he said, noting that tires burned at lower temperatures can produce high amounts of pollution.
“But this is a very sustained (high) temperature and combustion condition, and you are seeing a marked improvement over … burning coal.”
CEMEX began work on its patented tire injection machine in 2003 at its cement plant in New Braunfels, Texas, said Sara Engdahl, spokeswoman for the company.
In addition to the New Braunfels plant, the machine is used at CEMEX facilities at two Florida plants, a plant in Georgia, one in Tennessee and one in California, she said.
It’s different from other tire-burning methods because whole tires are fed into the kiln, without needing to be shredded, she said.
That ensures the tires get to the hottest part of the kiln, which allows for immediate combustion, and thus the fastest release of heat into the system, she said.
Tires actually contain more heat potential than coal, Graves said. The U.S. Environmental Protection Agency said the heat content of tires is 10 percent to 16 percent higher than coal.
The kiln is a 200-foot-long, 30-foot-diameter cylinder that slowly rotates. Inside, raw materials such as limestone, clay, sand and combustion wastes from the nearby Mill Creek power plant are mixed and heated in the critical part of the cement-making process.
Iron in the tires also becomes part of the cement, Graves said.
The machine weighs each tire and automatically adjusts the force needed to make sure the tire is propelled to where it needs go inside the kiln, Graves said.
On the monitor, some can be seen flying into the fire like an Aroldis Chapman fastball. Others look like a Barry Zito curveball.
The price of burning coal and tires is about the same, said Alex Guyse, plant operations manager.
While the tires are cheaper, burning them requires more labor, he said. The company needs a crew of three to load and guide the tires onto a conveyor track that feeds the throwing machine.
The company is looking to augment its tire burning with something called refuse-derived fuels, or the “fluff” of paper and plastic left behind at recycling plants. It is seeking approvals from regulators, including the air district, Kentucky Division of Waste Management and the Metro Planning Commission.
FitzGerald said he will continue to “rigorously scrutinize” any alternative fuel proposals from the company. But so far, he said, preliminary testing on the recycling waste shows comparable or improved air-quality benefits.
Nord said the air district has not completed its review of the testing on the recycling waste.
But Graves said burning tires and recycling waste for about half the plant’s fuel will shrink the Kosmos environmental footprint by relying even less on coal.
“For a number of reasons, sustainable fuels are the future of our industry,” Graves said. “Raw materials are becoming more scarce.”
And environmental improvements, she said, “are a big source of pride.”