Soiled Shop towels
Printers use either reusable fabric shop towels or disposable wipes for cleaning presses and related equipment. Reusable shop towels are typically sent to an industrial laundry for cleaning and return. Disposable wipes are often used when it is critical that no stray fibers are left behind and are discarded after use.
Depending on what the towels/wipes become saturated with, either type of towel can be considered a hazardous waste and if not managed properly can expose printers to enforcement actions or expensive environmental cleanup costs.
Best Management Practices & Pollution Prevention
Reusable Shop Towels
Reusable towels contaminated with a hazardous waste such as ink, solvent, or oil are not considered hazardous waste under federal and most state regulations, as long as they are not saturated, and are laundered and reused. Each state regulates towels differently and the printer must first comply with state regulations. The effluent released from the spent towels at the laundry can become a concern to the sanitary system (i.e., sewer treatment) as the contaminants are washed out. Most industrial launderers have set up treatment systems to minimize the impact of these contaminants.
It is important to remove excess solvent from shop towels prior to laundering. Gravity separation and hand wringing are common practices employed to remove excess solvent. Centrifuges may also be used.
Solvent collection through gravity separation
Gravity separation involves placing the shop towels inside a closed container with a false bottom. With gravity, the solvents move down and out of the towels into the false bottom. A false bottom typically consists of a metal grate and/or drain at the bottom of the container. It is important that waste solvent that collects in the bottom of the container is emptied regularly and disposed of properly, as it may be a hazardous waste. If the bottom fills up past the grate and the rags are laying in the solvent, they will become saturated and defeat the purpose of gravity separation. In order to extract the maximum amount of solvent for recovery this method should be combined with hand and or mechanical wringing, or centrifuging.
Hand wringing consists of hand squeezing the towels to extract the solvent. The amount of solvent extracted depends on the operator. Mechanical wringing consists of feeding the towels through a hand crank or electric powered wringer. These systems typically mount on the top of a 55-gallon drum. As the towel is wrung the solvent drips into the drum. The electric powered wringers must be equipped with explosion proof wiring.
A centrifuge is a mechanical device that spins an object to separate materials with different specific gravity. Centrifuging involves placing the shop towels in an industrial centrifuge where the towels are spun and the solvent is drawn out of the towels and collected. A centrifuge can extract 2 to 3 gallons of solvent from approximately 220 towels that have no free flowing liquids when placed in the centrifuge. When installing a centrifuge, be sure to check local fire codes that may affect ventilation and electrical requirements. The centrifuge must be constructed using explosion proof wiring systems if used with flammable or combustible materials.
Disposal wipes must be disposed of in a manner that maintains regulatory compliance and also minimizes corporate environmental liabilities.
Used wipes may be subject to hazardous waste regulations if the wipes contain inks, solvents, oil, or residues that are classified as hazardous. Towels that are contaminated with materials that are “listed” hazardous wastes must be considered as hazardous and must be disposed of as such. Towels that are contaminated with materials that are classified as “characteristic” must either be handled as a hazardous waste or the printer can evaluate the towel and if it does not exhibit any of the characteristics of a hazardous waste, it can be classified as nonhazardous.
However, even if the wipes do not contain hazardous solvents or residues, it may not be in the printer’s best interest to dispose of their wipes with the rest of the trash. If contaminants leach from the wipes at the landfill where they are disposed and the landfill becomes a Superfund site, the printer can be liable for costly site remediation. There is no statute of limitations for Superfund liability. If disposable wipes are used, it is important that the printer has a documented, accurate, and comprehensive picture of all the solvents and residual contaminants that could remain on the used wipes.
Best Management Practices for Shop Towels: (Some practices may be required based on state/federal regulations):
- Improve production methods by coordinating runs according to color, type or quantity, thereby reducing the number of cleanups.
- Soiled shop towels may contain hazardous or volatile solvents and residues. To reduce the risk of fire and control fugitive VOC emissions, soiled shop towel storage containers must be kept closed at all times.
- Observe good cleaning practices by using the least amount of solvent necessary to be effective.
- Closely manage the dispensing and storage of solvents and towels/wipes.
- Separate excess solvent from towels/wipes using techniques such as gravity draining, hand wringing, mechanical wringing, and centrifuging. Recovered solvent can be reused and recycled.
- Use alternative solvents that minimize hazardous waste and air pollution. For example, cleaning solvents that do not contain any listed chemicals or those with flashpoints below 140°F and a vapor pressure less than 10 mm Hg at 68°F are ideal.
- Never dispose of waste ink or solvent by pouring it into shop towel containers.
- Clearly mark used shop towel containers with the words “Used Shop Towels”
- Contact your shop towel launderer to ensure that they are meeting water discharge limits.
- Collect solvent waste for recycling.
- Establish accountability for solvent use and waste generation.
- Use water based inks, where applicable.
For access to vendors who may supply alternative materials and equipment, see the PNEAC Vendor Directory.
- Summary of EPA Regional Office and State Positions Concerning the Regulatory Status of Contaminated Shop Towels, PNEAC
- Proposed Federal Rule Regulating Solvent-Contaminated Towels and Wipes
- Any disposable shop towels that meet the definition of hazardous waste must be disposed of according to the Resource Conservation and Recovery Act and any applicable DOT regulations. For more information, see the “Hazardous Waste” section of the Virtual Litho Plant.
Health & Safety
Self-closing shop towel can
Proper use of shop towel
Soiled shop towels may contain hazardous or volatile solvents and residues. To reduce the risk of fire and control fugitive VOC emissions, soiled shop towel storage containers must be kept closed at all times.
Shop towels that contain oil or flammable liquids can present a fire hazard. Flow through bases on shop towel containers can help disperse heat. Always store used shop towels away from sources of heat.
Shop towels should be folded neatly when used for cleaning. Folding the towel helps prevent loose ends from being entangled when wiping a moving part.