NORWALK, CALIF. — Advanced soil chemist Hinrich L. Bohn has a way for flexographic film printers to use solvent-based inks without damaging the environment.
The University of Arizona professor described his low-temperature catalytic oxidizer, or biofilter, during a panel discussion at the Jan. 12 meeting of the California Film Extruders & Converters Association in Norwalk.
California's limits on emitting volatile organic compounds have forced some film printers to use water-based ink, which dries slower and delivers less gloss and fewer details than solvent-based ink.
In eliminating VOCs, an engineered biofilter bed offers an alternative to more costly VOC incineration methods that generate atmosphere-damaging nitrogen oxide as a byproduct.
Biofiltration, originally a European concept, has applications in printing, chemicals, petroleum and food and waste processing, Bohn said.
So far, Sunshine Plastics Corp. in Montebello, Calif., is the only processor among more than 30 domestic locations using systems from Bohn Biofilter Corp. of Tucson, Ariz.
A Bohn business representative, Birmingham Equipment Co. of Whittier, Calif., installed the system, which has operated on a construction permit since September 1997, and, according to Bohn, has been achieving VOC destruction rates of 95 percent.
A South Coast Air Quality Management District regulation limits the Sunshine facility to the monthly emission of 900 pounds of noncontrolled solvents. Sunshine expects to receive its final permit soon, Steve Hoskins, vice president of sales and marketing, said in a telephone interview.
Meanwhile, Diamond Bar, Calif.-based SCAQMD may issue biofiltration research-and-development permits to Sierra Pacific Plastics Inc. of Pomona, Calif., and CMC Printed Bag Inc. of Whittier.
``The biofilter is probably the most economical method that I know of, and that includes water ink,'' said Michael Morsch. As Sunshine's general manager, he chose biofiltration instead of a form of incineration.
In October, Morsch formed the converter-printer Sierra Pacific, which operates a six-color Paper Converting Machine Corp. flexographic press with doctor blades and five bag machines in a 15,000-square-foot facility.
Nationwide, customers want the quality available only with solvent-based inks, providing another reason for California plants to abandon water-based inks. Typically, the printing units of big players Huntsman Corp. of Salt Lake City, Bemis Co. Inc. of Minneapolis and Printpack Inc. of Atlanta operate their presses outside California's regulatory climate.
With Bohn's method, an exhaust system feeds vapors from an airtight pressroom into a network of perforated pipes in a confined bed of natural media. Sunshine's 4-foot-deep square bed measures 80 feet by 80 feet.
As the contaminated air flows through the bed's fine pores, ``the microbes eat VOCs like propylene, ethanol and a whole host of other contaminants,'' Bohn said. ``The microbes have a chance to consume, and convert them, to carbon dioxide and water.'' Soil beds last indefinitely.
Bohn cited advantages: No fuel is necessary, no secondary pollutants are generated and the catalyst microbial bacteria ``is free and continues to self-regenerate.''
Space is critical. ``For those of you in a very closely confined urban location, the space that a biofilter needs may be more than you can afford,'' Bohn said.
