Case Study, Minnesota Technical Assistance Program, University of Minnesota
Company: Lantz Lenses, St. Cloud, Minnesota
Product: Eyeglass Lens Manufacturer
Waste: Methylene Chloride and Acetone
Change: Replaced methylene chloride with a nonhazardous substitute, Oakite TRS60. Replaced acetone with manual grinding.
Savings: Eliminated the use of acetone in 1994 and methylene chloride in 1995. This eliminated approximately $3,200 in regulatory compliance costs; $2,500 in chemical costs, and $2,700 in disposal costs for both chemicals.
Benefits: Changed from large quantity generator (LQG) to very small quantity generator (VSQG) reporting status. No longer under regulatory compliance requirements associated with use of hazardous chemicals and halogenated solvents.
Lantz Lenses, located in St. Cloud, Minnesota, manufactured eyeglass lenses. It employed 90 people and had been in the lens manufacturing business for over 45 years. It produced over 600,000 lenses annually. (Editor’s note: In November 1995, Lantz Lenses was purchased by Vision Ease. The activities documented in this case study occurred prior to this purchase.)
Two hazardous chemicals, methylene chloride and acetone, were used during the lens-manufacturing process. Methylene chloride removed pitch (a material used to secure lenses during the grinding process) and other contaminants after the lenses were ground. Acetone removed abrasive pads from the lens grinding tools. In 1993, Lantz Lenses generated approximately 14,000 pounds of hazardous waste from these two chemicals.
Lantz Lenses wanted to eliminate its use of hazardous chemicals in order to reduce regulatory compliance costs and be exempt from a number of state and federal regulatory reporting and employee training requirements. It also wanted to reduce its production costs by implementing pollution prevention alternatives to hazardous chemicals.
Methylene Chloride
Methylene chloride was used by Lantz Lenses in its ultrasonic vapor degreaser to remove pitch and other contaminants from lenses. In 1994, Lantz Lenses: 1) purchased 14,400 pounds of methylene chloride; 2) lost 10,000 pounds to the air due to evaporation or volatilization; and 3) generated approximately 12,000 pounds of waste methylene chloride and pitch.
After testing alternatives to methylene chloride, Lantz Lenses identified Oakite TRS60, a water-dilutable terpene solvent, as an acceptable substitute for removing pitch from lenses. To use the TRS60, Lantz Lenses retrofitted its existing vapor degreaser as a two-stage immersion cleaning tank. This included disconnecting the condenser coil, and adding heating elements and air agitation to the two water and solvent baths. The heating elements raised the TRS60 temperature to 170°F, which is above the melting point of pitch, to maintain the same cleaning speed and effectiveness as methylene chloride. The existing degreaser lip vent was used to control the strong pine odor of TRS60, which some employees found objectionable. Total cost to retrofit the vapor degreaser was less than $300 for materials and labor.
The new cleaning system did not change labor requirements. It also did not change overall utility costs, even though the new cleaning tank required more electricity. This was because a room exhaust system required for the methylene chloride was shut down. In addition, the new cleaning system’s water requirements for dilution, makeup and a short spray rinse are approximately the same as that required for the condenser waterflow used in the old cleaning system.
Acetone
Acetone had been used as a solvent to remove abrasive pads from lens-grinding tools. In 1993, Lantz Lenses purchased 1,050 pounds (160 gallons) of acetone and generated approximately 2,300 pounds of acetone waste and approximately 920 pounds of acetone emissions.
After researching and testing alternatives, Lantz Lenses determined that the pads could be removed with manual scraping alone (at no additional labor cost), thereby eliminating the need for acetone.
Regulatory Issues
As a result of eliminating its use of methylene chloride and acetone, Lantz Lenses’ RCRA (Resource Conservation and Recovery Act) reporting status changed from a LQG to a VSQG. Eliminating the use of these solvents exempted the company from a number of regulatory reporting and employee training requirements, and reduced compliance activities for others. These included: Toxic Release Inventory (TRI) under SARA Title III Emergency Planning and Community Right-to-Know Act; Minnesota Pollution Control Agency's (MPCA) hazardous waste rules; Resource Conservation and Recovery Act (RCRA); Occupational Safety and Health Administration (OSHA) Hazard Communication Standard (Employee Right-to-Know Act); and federal Clean Air Act Amendment Requirements for National Emission Standards for Hazardous Air Pollutants (NESHAP).
Lantz Lenses became exempt from air permitting and most hazardous waste requirements. Although it generated oil waste and glass-grinding fines, which are considered hazardous. These materials were recycled as feed stock.
MnTAP provides free, nonregulatory technical assistance to Minnesota companies to help them reduce their use of hazardous chemicals. For more information about MnTAP or to request assistance, call 612/624-1300 or 800/247-0015.
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