The dry cleaning process offers several opportunities for pollution prevention (P2).
Three common P2 approaches are

• Process modification
• Material substitution (use less toxic materials)
• New technology (upgrade equipment).

Following is a short list of common pollution prevention opportunities common to the dry cleaning industry. Additional information on new technologies also follows.

Process Modification

• Monitor equipment efficiency (e.g., pounds of clothes cleaned per drum of solvent) on a regular basis to detect occurrence of leaks or other problems that may result in loss of solvent.
• Minimize the time machine doors and button traps are open to reduce solvent losses.
• Size garment loads correctly. Overloading may reduce the effectiveness of solvent recovery equipment; under loading makes less efficient use of solvent.
• Operate all machines per manufacturer’s specifications and recommendations.
• Utilize properly designed cleaning processes and recommended amounts of additives (i.e., detergents, sizing, etc.) to ensure good cleaning performance and minimize re-cleans.
• Check hoses, couplings, pumps, valves, and gaskets frequently in order to detect leaks. Make repairs promptly.
• Use spigots and pumps when dispensing new materials and funnels when transferring wastes to storage containers to reduce possibilities of spills.
• Keep all containers covered to prevent evaporation and spillage.
• Provide secondary containment in areas where solvents are stored.
• Look for and reject damaged containers when materials are delivered.
• Keep storage and work areas clean and well organized, and keep all containers properly labeled.
• Clean lint screens regularly to avoid clogging of fans and condensers.
• Extract solvents from filters as thoroughly as possible. Gravity drainage and “cooking” are commonly used techniques.
• If the solvents cannot be made reusable, try to find a way to recycle them. One possibility for accomplishing this is to purchase solvents from a company that will pick up and recycle the spent solvent.

Material Substitution

• Utilize water-based or less hazardous pre-spotters instead of those containing solvents.
• Use alternative petroleum solvents that have higher flash points (to reduce fire hazard) and lower VOC content.
• Use solvents and techniques that have been developed as alternatives to perc, including silicon-based product, glycol ether products, and liquid carbon dioxide.

New Technology (Equipment Upgrades)

• Replace current perc machine with a dry-to-dry closed-loop, non vented machine that contains an integral refrigerated condenser and an integral carbon adsorber.
• Buy energy efficient equipment and appliances when upgrading.
• Switch to an alternative fuel in delivery vehicles.
• Switch to carbon absorbers that use a polymer surface for adsorbing solvent vapor, which results in a minimization of hazardous solid waste.
• Consider adding a wet cleaning operation for a portion of the cleaning.
• Utilize new emerging technologies such as ultrasonic or carbon dioxide cleaning

Wet Cleaning

In 1998, the International Fabricare Institute (IFI) stated that most garment care establishments using their existing equipment and procedures-can wet clean from 30 to 40 percent of all customers' garments with minimal difficulty. IFI further stated that 60 to 80 percent of all customers' garments can be wet cleaned using specialized equipment, specialized detergents, and trained and skilled labor. However, wet cleaning is not a complete replacement technology.

In general, the process steps for wet cleaning are the same and are represented in the process map for dry cleaning (Figure A). Wet cleaning, like dry cleaning consists of four major steps including preparation, washing, drying, and finishing; however, a wet cleaning machine only washes the clothing. Clothing must then be transferred to a separate dryer (like older “transfer” dry cleaning machines). A detailed process map for wet cleaning was developed by Massachusetts Toxic Use Reduction and is available in their Training Curriculum for Alternative Clothes Cleaning. For further description and flow diagrams of the wet cleaning process see the U.S. EPA’s compliance resource entitled “ Profile of the Dry Cleaning Industry.”

Wet cleaning is desirable as an alternative because is uses only water, detergents, soap, sizing, and softeners, and does not produce hazardous waste (although some stain removal chemicals may be hazardous).

Ultrasonic Cleaning

Ultrasonic cleaning is being researched and developed as a possible alternative to traditional dry cleaning. Ultrasonic cleaning works by using the pressure of sound waves directed at a garment through a soap and water solution. The pressure removes the stains from the garments. Ultrasonic cleaning is also desirable because it produces no hazardous wastes or air emissions.

Carbon Dioxide Cleaning

Both supercritical and liquid carbon dioxide are being explored as methods for garment cleaning. Carbon dioxide technologies are desirable because they are non toxic, easily recycled, inexpensive, non-flammable, non-corrosive, and readily available. Liquid carbon dioxide is more favorable as it is safer than supercritical carbon dioxide.

Supercritical carbon dioxide works at high temperature and pressure. Grease and oils dissolve when exposed to supercritical carbon dioxide. Oil and grease can then be removed from the carbon dioxide and recycled by reducing the pressure. The carbon dioxide can then also be recycled.

Liquid carbon dioxide requires lower temperature and pressure than supercritical carbon dioxide. Liquid carbon dioxide can be combined with surfactants for more effective cleaning and can also be separated from dirt and greases and recycled.