The Lehigh Cement Co. will begin a series of tests next month using dried sewage pellets from two Baltimore treatment plants to replace some of the coal burned by Lehigh's state-of-the-art kiln near Union Bridge.
It will be the first such use in North America, said plant manager Peter Lukas. Lehigh's parent corporation, Heidelberger Zement, and other cement makers have been using sludge pellets for about 20 years in Europe, he said, where the cost of other fuels, such as coal, was high.
"Nothing should change by us using this secondary fuel," Lukas said of the pellets, which are sold commercially as fertilizer.
Although Lehigh has had its share of complaints from Union Bridge residents over the years about cement tanker trucks using Main Street, plant and government officials say they expect little fuss over the use of the pellets.
Lehigh has held meetings with its 170 employees, town officials and residents, as well as local Rotary clubs, to explain the tests. The company will install temporary equipment to dispense the pellets - at a cost of about $500,000 - before the tests begin next month.
"We do plan on being present when they have the test burn," said Richard J. McIntire, spokesman for the Maryland Department of the Environment, which on Monday issued an air-quality permit for the tests that is good for 180 days. "Sludge is pretty much inert. I can't think of any problems."
Emissions will be monitored independently at Lehigh's expense.
Union Bridge Mayor Bret D. Grossnickle said he has had only a few questions from the town's 1,000 residents.
"I don't anticipate any problem - but I'm not a chemist," Grossnickle said. "I don't think it's any worse than coal."
That's the idea, said Lukas, 44, a native of Germany who has seen all sorts of ersatz fuels vaporized in kilns overseas, including shredded woods and plastics, and animal meal in the wake of mad cow disease.
With the advent of the euro in 2002, Lukas said, the corporation's German kilns burned 168 billion obsolete deutsche marks - about $80 billion. The paper, burned with other fuel, was gone in four to five hours, he said, and would have lasted less than an hour if used as the sole fuel.
In Union Bridge, the plant burned up to 1 million old tires a year before November 2001, when its new kiln went into operation, said Wallace L. Brown Jr., the plant's environmental engineer and community liaison.
Lehigh says its $265 million modernization and expansion gave it the largest capacity single kiln on the continent. At 465 feet, its spaceship-like preheater tower is the tallest structure in Carroll County, besides some communications towers.
The tower and the 230-foot- long kiln heat pulverized limestone from an adjacent quarry, mixed with sand, clay and iron flakes, to produce a new entity: crumbly clumps of cement called clinker, which is produced at a top capacity of about 6,500 tons a day. The physical and chemical reactions that create the clinker require temperatures near 2,000 degrees in the tower and up to 3,000 degrees in the kiln.
And that means feeding them truckloads and railcars full of coal - 20 tons to 30 tons of coal an hour, Lukas said. The sewage pellets have "heat value, so we can use it to replace some coal."
In the testing, he said, the percentage of pellets probably will begin at 5 percent and increase to probably no more than 25 percent, because above that level the phosphates in the pellets could affect the qualities of concrete, such as strength and elasticity.
About 55 dry tons of pellets are produced each day at the Back River and the Patapsco waste-water treatment plants by Synagro-Baltimore LLC, a subsidiary of Synagro Technologies Inc. of Houston. Each plant could produce twice that, said Pam Racey, vice president of business development for Synagro.
Baltimore was prodded to build the plants to deal with its sewage disposal problems after a trainload of sludge from Back River traveled the East Coast in 1989 in search of a place to dump.
As a fuel, the material is fairly innocuous. "This is sold at Lowe's," Brown said, plopping down a plastic bag full of small dark pellets that smell faintly of fertilizer.
State environmental officials hope the material will prove as useful for fuel as for fertilizer.
Said McIntire: "That's why were looking at it. It's a possibility."