Case Study, Minnesota Technical Assistance Program, University of Minnesota
Company: Cottage Cleaners; Forest Lake, Minnesota
Process: Dry cleaning
Waste stream: Perchloroethylene (PCE or perc) (tetrachloroethylene)
Change: Replaced an old transfer dry-cleaning machine with a new and more efficient dry-to-dry machine.
Cost: $49,000 purchase cost for a new dry-to-dry machine.
Savings:
Reduced the amout of perc used from 455 gallons per year in 1990, to 38 gallons per year in 1992, saving $2,246 in 1992 in perc purchase costs.
Reduced the amount of hazardous waste generated from 375 gallons per year in 1990 to 240 gallons per year in 1992, saving $593 in 1992 in hazardous waste disposal costs.
Achieved compliance with Office of Safety and Health Administration (OSHA) and 1990 Clean Air Act Amendment (CAAA) requirements for perc emissions.
Achieved high employee satisfaction with the new equipment, because of reduced perc exposure.
Maintained high-quality cleaning results and customer satisfaction.
Cottage Cleaners, located in Forest Lake, Minnesota, is a 10-person shop that provides dry cleaning services to commercial and industrial customers. The dry cleaning process uses perchloroethylene (perc), an industrial degreasing solvent, to clean clothes. In 1990, Cottage Cleaners used approximately 455 gallons of perc at a cost of $2,484.
Perc is used by dry cleaners because it is an excellent cleaning solvent and its nonflammable properties make it safe for use. However, Cottage Cleaners was losing a large amount of perc from the older transfer machine when transferring clothes in and out of the machine, and from leaking gaskets and seals.
The old transfer dry cleaning machine used by Cottage Cleaners required that clothing be manually transferred from a washing unit to a drying unit. First, clothing is placed and agitated in a perforated, rotating drum containing perc and a small amount of water, soap and sizing. Once the wash cycle is complete, the perc solution is drained from the rotating drum through centrifugal force, which removes most of the perc from the clothes. Perc removed in the rotating drum is continuously filtered through a diatomaceous earth filter (many machines use carbon filters) to remove insoluble impurities. The filtered perc is then stored in a reservoir until it is used again in the dry cleaning machine. The diatomaceous earth filter is replaced weekly, and the filter material (muck) is disposed of as a hazardous waste because it contains small amounts of perc.
After the perc is filtered, it is distilled to remove soluble impurities such as oils, fats and greases that were on the dirty clothes. During distillation, the contaminated perc is heated, permitting the perc and water to vaporize. These vapors leave the still and enter a condenser where they pass over water-cooled coil surfaces and condense. Using a separator, water is removed from the perc-water mixture and discharged to the sewer system. The perc is then returned to the storage reservoir and the still bottoms are disposed of as hazardous waste.
After the clothes are washed, they are transferred to a drying unit where most of the remaining perc is evaporated, recovered in a condenser and reused. However, significant perc loss occurs when clothes are transferred from the washing unit to the drying unit.
In September 1991, Cottage Cleaners installed a new dry-to-dry machine. The difference between this new dry-to-dry machine and the old transfer machine is that washing and drying are done in the same unit, so there is no perc lost from opening doors and moving clothes. The new machine also is entirely enclosed and programmable for a variety of cleaning needs. It is "tighter" than the old machine, and no perc is lost through seals and gaskets.
The only perc releases from the new machine occur when the lint screen is cleaned and the diatomaceous earth filter is replaced. The lint and filter wastes are stored in closed hazardous waste containers until disposed of as hazardous waste. The new machine's reclaiming unit also recovers more perc for reuse than the old machine.
The incentives for Cottage Cleaners to purchase new equipment and reduce perc use included:
Achieve regulatory compliance. Cottage Cleaners needed to reduce its perc use and emissions in order to comply with a new federal regulatory requirement from the Office of Safety and Health Administration (OSHA). This requirement, which went into effect December 31, 1991, limits perc releases into the air to a maximum of 25 parts per million (ppm) during an eight-hour period.
Protect employee health. The new dry-to-dry machine greatly reduces employee exposure to perc.
Reduce costs. The price of perc has increased steadily each year, and is expected to substantially increase in cost in upcoming years. Less perc will be used in the new machine, which will reduce perc purchases.
Perc Purchase Cost Savings
During 1992, the first full year of using the new equipment, only 38 gallons of perc were used, as compared to 217 gallons in 1991 (the equipment transition year), and 455 gallons in 1990. This saved approximately $2,246 in reduced perc purchase costs in 1992. In 1993, the shop expects to purchase approximately the same amount of perc as it did in 1992, but at an increased price of $2.04 per gallon more.
Disposal Cost Savings
By using less perc in the new and more efficient machine, the shop generates less hazardous waste. As a result, the amount of hazardous waste has decreased from 375 gallons in both 1990 and 1991 to 240 gallons in 1992, with savings of $593 from reduced disposal costs in 1992.
Payback Period
The initial purchase cost of the new cleaning machine was $49,000. The payback period is calculated at 17 years; therefore, a quick pay-back is obviously not the reason the investment was made. However, as perc costs continue to rise, the payback on the new equipment will be realized more quickly.
Employee and Customer Satisfaction
Employee satisfaction with the new equipment is very high. The equipment is easy to operate, and the reduced perc emissions have eased employee health and safety concerns. In addition, the new equipment has improved the cleaning efficiency, resulting in a higher level of customer satisfaction and fewer complaints.
Because Cottage Cleaners uses only 38 gallons of perc per year in its new dry-to-dry machine, it receives some regulatory relief from the 1990 Clean Air Act Amendment (CAAA) standards for perc. Under the CAAA, Cottage Cleaners is defined as a "small area source" because it uses less than 140 gallons of perc per year. As a result, Cottage Cleaners has to comply with fewer regulatory requirements than dry cleaners using more than 140 gallons of perc annually. Cottage Cleaners will not need an operating air permit and will not be required to conduct self-monitoring. However, it is required to meet certain self-inspection, storage, reporting, recordkeeping, procedural, and leak detection and repair requirements.
In addition to being well under the permit compliance limits set by the CAAA, the shop's perc emissions of 8-11 ppm are well below the OSHA standard of 25 ppm.
Cottage Cleaners' investment in a new dry-to-dry machine has resulted in reduced regulatory burdens, allowing it to easily meet the new OSHA and CAAA regulatory requirements; improved employee and community health through reduced exposure to perc; and reduced perc purchasing costs.
For more information about this case study, or if you would like assistance with your pollution prevention efforts, call MnTAP at 612/624-1300 or 800/247-0015.
(12/93-92)