Using sludge to clean the air.

• Position: Emission Control - Brief Article

Paper mills produce sludge. They also give off toxic emissions containing oxides of nitrogen, including N[O.sub.x], a by-product of combustion. Researchers at the Illinois Institute of Technology, Chicago, have developed and patented a process by which sludge from municipal waste water or paper mills can be turned into activated carbon, an ingredient utilized by manufacturing plants to remove toxic chemicals like N[O.sub.x] from their emissions.

"Activated carbon is used by virtually every manufacturing plant to remove N[O.sub.x] in order to comply with the 1990 Clean Air Act Amendment," notes Nasrin Khalili, assistant professor of chemical and environmental engineering. "We have come up with a way to turn toxic paper mill sludge into something manufacturers (including paper mills) need."

Sludge from manufacturing plants must be specially treated and dried before it can be deposited into landfills--an expensive process. "Paper mills are happy to give me their sludge; otherwise it costs them money to get rid of,"...