Alternative Cleaning Solvents and Processes

In recent years, concerns over the ozone layer, photochemical smog and worker health have made traditional solvent cleaning products and processes increasingly regulated and expensive. Ozone-depleting chlorinated solvents, particularly, are now subject to strict environmental requirements. Under the Montreal Protocol, production of 1,1,1 TCA and CFC-113 have been prohibited since January 1, 1996, and other ozone-depleting substances are also scheduled for phase out. In addition, the 1994 National Emission Standards for Hazardous Air Pollutants (NESHAPs) place emission and operating standards on the use of carbon tetrachloride, chloroform, perchloroethylene, 1,1,1 trichloroethane, trichloroethylene, and methylene chloride.

Many users of solvents, whatever the application, are looking for safe and effective alternatives. Whatever the motivation -- cost, safety, regulatory -- companies may be able to achieve significant economic and environmental benefits by switching to alternative cleaning products or processes.

Changing from a proven process to a new technology is a challenging task. Some alternatives offered as the "perfect" solutions have been found to be ineffective cleaners, too expensive, or present safety hazards. Knowledge of cleaning needs and cleaning options will aid in selecting the most cost effective and technically feasible solution without compromising worker health and safety or environmental protection.

Safety and health concerns should be a primary con-sideration when selecting an alternative process or product. A safer, less toxic alternatives should be chosen, provided it can meet the cleaning criteria of the intended application. Consult your local health and safety specialists and the appropriate Material Safety and Data Sheets prior to implementing any alternative cleaning process or product.

Alternatives should be tested for compatibility before implementation, not only with the components to be cleaned, but also with the cleaning equipment. No single process or product will work in every case. Careful selection and deliberate implementation are the keys to success with any new process or product.

It is essential that all environmental impacts be evaluated before switching to a new cleaning process or product. The new process may reduce certain types of pollutants, but create new ones, especially if pollution is transferred from one media to another. Each alternative should be evaluated for its impact on total materials usage, air emissions, solid and hazardous waste generation, wastewater discharges, energy and water use, and the associated costs of managing these impacts. In addition, no matter what alternative you choose, all of these environmental impacts must be evaluated in terms of applicable regulations. DEQ and your local sewerage agency can help you define those requirements.

The first and most important part of the search for an alternative is to define cleaning needs by asking:

Once cleaning needs have been assessed, evaluation of the alternatives can begin. Following are brief descriptions of the most popular alternatives.

In some applications, hot water alone may be sufficient to clean parts. Others may require a wash, rinse, and dry cycle. Detergents and surfactants may be added, along with special additives such a builders, pH buffers, inhibitors, emulsifiers, deflocculants, complexing agents, and anti-foaming agents.

Immersion, pressure spray or ultrasonic process equipment are often used in aqueous cleaning, depending on the application. In immersion cleaning, the parts are immersed in a cleaning solution, and some form of agitation and/or heat is added to supply the energy needed to remove contaminants. In pressure spray washing, a high pressure spray delivers more mechanical action to help remove soils from surfaces. The ultrasonic method combines water, adetergent and high frequency sound waves to create bubbles which help to dissolve and displace particles from the surface.

Aqueous cleaning may create new waste streams and environmental requirements, such as sludge disposal or sewer permits. Check with DEQ and your local sewerage agency to determine those requirements.

Semi-aqueous cleaners are made of natural or synthetic organic solvents, surfactants, or corrosion inhibitors, and other additives. These cleaners are often used with immersion or ultrasonic systems.

Water insoluble semi-aqueous cleaners, such as high-molecular-weight esters, terpenes, glycol ethers, and petroleum hydrocarbons, are a mixture of a non-water-soluble solvent, and an emulsifying surfactant and water. Terpenes, often found in household cleaners, deodorizers, and pharmaceuticals, are extracted from plants such as tree bark or citrus fruits. Hydrocarbons, usually combined with a surfactant and rust inhibitor, are effective in removing cutting oils, coolants, greases and waxes, and can be effectively recycled.

Water-soluble semi-aqueous cleaners use water as a filler to reduce volatile organic compound (VOC) emissions. Common water-soluble, semi-aqueous cleaners include low-molecular weight alcohols, ketones, esters, and organic amines.

Semi-aqueous cleaners are non-ozone depleting but they may contain VOCs. Concerns with the use of semi-aqueous cleaners include aquatic toxicity, human health effects, and flammability, depending on the concentrations of water. Semi-aqueous cleaning may also entail new wastewater discharge requirements.

There are at least three carbon dioxide (CO₂) blasting technologies in use: CO₂ snow, CO₂ pellet, and fragmented CO₂. Solid CO₂ is blasted, at high pressure, against the surface to be cleaned. As the material impacts the surface, it sublimes, returning to the gaseous state. This alternative may be more expensive than other options.

Supercritical fluids (SCFs), which result from subjecting substances to temperatures and pressures above their critical points, possess properties intermediate between liquid and gases. Precision surface cleaning with supercritical CO₂ takes advantage of these unique properties. SCFs can rapidly penetrate substrates and small spaces, dissolve the contaminants, and then be easily and completely removed since the SCFs lack surface tension. This process is relatively new and expensive.

The media blasting process combines an abrasive media, a pressurized delivery system and one of a variety of cleaning chambers. This method leaves no residue on the cleaned surface, but it is not typically appropriate for grossly contaminated parts, since the contaminants can cause the media to stick together. However, media cleaning is appropriate for ordinary machining oils and contaminants. Media blasting is also used for removing paint and surface corrosion. Glass beads and sand have been used as media in this process for years. The more recent use of plastic, sodium bicarbonate and wheat starch as blasting media allow the technology to be used on a wider variety of surfaces and soils. Abrasive blast waste, however, may need to be tested for hazardous waste determination and may increase waste disposal responsibilities.

Solvents in 100% concentration are used in a variety of cleaning applications. Some have been used for many years, such as the non-chlorinated solvents (e.g., acetone, alcohols, ketones) and petroleum distillates (e.g., mineral spirits, Stoddard solvents and naphtha solvents). Low vapor pressure solvents such as esters, terpenes, glycols, ethers and N-methyl pyrollidone are used in some applications. Hydrochlorofluorocarbons (HCFCs) were developed as temporary replacements for chlorofluorocarbons (CFCs); however, HCFCs deplete the ozone layer, and their production is scheduled for phase-out. For non-flammable solvents, a common method of cleaning is vapor degreasing. In this process, solvent losses occur mainly when the vapor zone is disturbed by air drafts, when the parts are lowered into or raised out of the machine, or when condensed solvent is removed with the parts. Recent developments in cleaning equipment now offer "closed" systems for solvent cleaning to minimize releases.

No single solvent provides the perfect cleaning solution for all applications. Among the many things to consider when choosing a solvent are the potential environmental, health and safety impacts, solvency, flammability, stability, cost, whether it is a regulated VOC, and whether it is approved as a Significant New Alternative Policy (SNAP) cleaning alternative.

This factsheet gives an introduction to alternative cleaning options, but additional information and opportunities, more specific to your business or industry, may be available. For information or resources, or a copy of this factsheet's companion, the Alternative Cleaning Process/Product Vendor List, please call the nearest DEQ regional office, or call the main receptionist at (503) 229-5630 or 1-800-452-4011.

Regional Office	Phone Number
Bend	(541) 388-6146
Coos Bay	(541) 269-2721
The Dalles	(541) 298-7255
Eugene	(503) 686-7838
Medford	(541) 776-6010
Portland	(503) 229-5263
Pendleton	(541) 276-4063
Roseburg	(541) 440-3338
Salem	(503) 378-8240

The Oregon Pollution Prevention Tax Credit program can provide significant savings to companies which eliminate the use of certain halogenated solvents. For more information, ask for the DEQ factsheet "Pollution Prevention Tax Credits" when you call your regional DEQ office.

This publication is available in alternative format (e.g. large type, braille) upon request by contacting DEQ at (503) 229-5317, or TTY (503) 229-6993.

Available for review through the DEQ Pollution Prevention Information Clearinghouse:

"Understanding Regulations on Solvent Cleaning Equipment," factsheet, DEQ Small Business Assistance Program, November 1996.

"HCFCs and Cleaning," factsheet, The Massachusetts Toxics Use Reduction Institute, October 1996.

"Alternatives to Solvent Degreasers for Parts Cleaning," factsheet, Maryland Department of the Environment, April 1996.

Closed Loop Aqueous Cleaning, report, The Massachusetts Toxics Use Reduction Institute, September 1995.

"Demonstration of Alternative Cleaning Systems," summary, EPA National Risk Management Research Laboratory, August 1995.

Clean Air Act Compliance for Solvent Degreasers: Regulatory Strategies for Manufacturers Affected by the Clean Air Act Amendments NESHAP for Halogenated Solvent Cleaners, guidance document, The University of Tennessee Center for Industrial Services and Tennessee Department of Environment and Conservation, April 1995.

Guidance Document for the Halogenated Solvent Cleaner NESHAP, guidance document, EPA Office of Air Quality Planning and Standards, April 1995.

"The Cost of Changing": Total Cost Assessment of Solvent Alternatives, guidance document, The Massachusetts Toxics Use Reduction Institute, June 1994.

Pollution Prevention for Degreasing Operations, guidance document, Indiana Department of Environmental Management, Dec. 1993.

Water-Based Alternatives to Solvent Cleaning, conference manual, The Cleveland Advanced Manufacturing Program, February 1993.

Solvents: The Alternatives, guidance document, Waste Reduction Resource Center for the Southeast, April 1992.

SAGE: Process and Solvent Alternatives, internet document, Research Triangle Institute, 1992.

Guidelines for Waste Reduction and Recycling: Solvents, guidance document Oregon DEQ Hazardous Waste Reduction Program, August 1989.

"A Practical Approach to Solvent Substitution," factsheet, Office of Technical Assistance for Toxics Use Reduction, Executive Office of Environmental Affairs, Commonwealth of Massachusetts.

"Overview of Machining Fluids and Aqueous Cleaning with Pollution Prevention Opportunities," factsheet, The Massachusetts Toxics Use Reduction Institute.

"Reducing Solvent Use in Vapor Degreasers and Dryers," factsheet, Office of Technical Assistance for Toxics Use Reduction, Executive Office of Environmental Affairs, Commonwealth of Massachusetts.

"Surface Cleaning," factsheet, The Massachusetts Toxics Use Reduction Institute.

"Surface Cleaning Technology Program," factsheet, Research Triange Institute, Center for Engineering and Environmental Technology.

Contact the Pollution Prevention Office at (503)229-5672 for access to the Information Clearinghouse.

Information on solvent and process alternatives for parts cleaning and degreasing.

Includes an electronic database of pollution prevention research and a pollution prevention library.

A free service for businesses looking to find markets for industrial by-products, surplus materials, and wastes.

A special thanks to The Massachusetts Toxics Use Reduction Institute Surface Cleaning Laboratory. Much of the body of this factsheet is an authorized reprint of their "Surface Cleaning" factsheet. Excerpts are also derived from "Alternative Cleaning Process/Product Vendor List," Department of Defense Pollution Prevention Technical Library, May 1995, available online at http://clean.rti.org/larry/vdr.htm, and "Solvents - The Alternatives," by Bob Carter, Waste Reduction Center of the Southeast, available online.