Waste fuels debate on power

As deadline nears for Lehigh Cement Co., commissioners recommend more time to store and test alternative fuels

September 24, 2006|By Laura McCandlish | Laura McCandlish,Sun Reporter

Carroll County commissioners have recommended giving the Lehigh Cement Co. another a year to store dried, pelletized sewage sludge, known as biosolids, at its Union Bridge plant as the company continues to test the alternative fuel in its kiln.

The six-month testing period was to conclude in November, with a county amendment allowing the temporary storage of biosolids to expire at that time. But the supply of biosolids - trucked in from Synagro-Baltimore LLC - has been inconsistent, Lehigh officials said. The supply should pick up this winter, when farmers' demands for the processed sewage, used as a fertilizer source, lightens.

"We are moving in a very good direction, but still need more time to get all the adjustments worked out with the system," Kent D. Martin, the new Union Bridge plant manager, told the county's Environmental Advisory Council last week.

The council also unanimously recommended extending the test-period agreement by one year.

While the German-owned Lehigh company has successfully burned biosolids and other alternative fuels at its European plants for five to 10 years, the trend is just catching on here.

The Union Bridge plant is the first cement factory in North America to use this fuel source, Martin said.

"It's a win-win situation," he said. "It can help plant operating costs, and it's better for the environment. Land-filling is not a sustainable solution to getting rid of different wastes."

After the test-run concludes, Martin hopes the plant will gain approval to fire its rotating cement kiln with a heat source that is 20 percent biosolids, and 80 percent coal. It burns at temperatures that could reach as high as 3,000 degrees.

Although a pound of coal yields twice as much heat as the same amount of biosolids, the latter burns cleaner than the thousands of tons of coal Lehigh has burned hourly in the past, company officials said.

"We are very close to being able to demonstrate a successful technology," Ed Morton, the alternative fuels manager for Lehigh's parent company, told the environmental council.

There's no solid waste from the biosolids because the burnt ash is incorporated directly into the clinker, the powdered cement product. In the three months of test-burning, the Union Bridge plant consumed 5,000 tons of biosolids at a rate of up to 15 tons per hour, Martin said.

Still, officials said kinks need to be worked out.

The biosolids are particularly abrasive and have worn away the lining of the steel pipes that feed the kiln, causing holes. Replacing the lining with ceramic may curb the problem, Martin said.

The county's temporary zoning amendment allows Lehigh to store the biosolids in the plant's newer 130-foot silo. But the material doesn't pump as easily into the kiln, often clogging the pipes. Extended storage times compound the problem, Lehigh officials said.

But other benefits are already detectable, they said. Nitrogen oxide emissions, both with and without burning biosolids, decreased once the plant replaced the kiln's old burner in August.

Though processed from sewage, the tiny biosolid pellets have little odor. When they burn, the gas released is odorless, Martin said.

As the county voted to extend Lehigh's one-year permit, Commissioner Julia Walsh Gouge wondered if the Maryland Department of the Environment would object.

Since the amendment's text is identical to the one approved last November, County Attorney Kimberly A. Millender said that shouldn't be an issue.

"Everything has been in compliance with MDE," she said.

Before gaining final approval, a public hearing on the one-year zoning extension will be held, Millender said.

laura.mccandlish@baltsun.com

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