Biochemical Cleaning Solvents

Cleaning is an essential part of manufacturing. Tools and equipment are cleaned to maintain their condition and keep them functioning properly. Manufactured goods must be cleaned to insure their proper operation, prior to painting and bonding, and to improve visual appearance. But there is an environmental price for cleaning practices. The petrochemical solvents used in many cleaning operations have a negative impact on the environment and worker health and safety. Petrochemical solvents are effective cleaners, and their use has become ingrained in industry practices. As a result, members of industry are often reluctant to make changes in cleaning practices. Consequently, the main driving forces behind transitions are environmental regulations.

Several regulations have motivated manufacturers to search for new cleaning methods. The Montreal Protocol has implemented a scheduled phase-out of chemicals that deplete the ozone layer (ozone depleting chemicals or ODCs). Two common cleaning solvents affected by this protocol are Freon 113, a solvent used extensively in cleaning electronics, and 1,1,1- Trichloroethane (or TCA) which is widely used in removing greases and oils. In the United States, all production and shipments of these solvents will be eliminated in 1996 [1]. The Clean Air Act has identified 189 chemicals as hazardous air pollutants (HAPs), which are now subject to National Emission Standards. Manufacturers who exceed emission standards may be subject to maximum available control technology, meaning the manufacturer must implement the most extensive emission control technology available [2]. The Clean Air Act also established local air quality standards which regulate the emissions of volatile organic compounds (VOCs), which include any organic (carbon-containing) chemical which evaporates and can undergo chemical reactions in the lower atmosphere. These chemical reactions cause the formation of ground-level ozone, which contributes to smog [3].

One of the chief difficulties of alternative cleaning solvents is that, in general, a petrochemical which has a wide variety of applications must be replaced with an alternative solvent which is more application specific. Petrochemical solvents have excellent cleaning properties: they are powerful solvents which can dissolve a wide variety of contaminants.

Inland Technology Inc., a research and development company based in Tacoma, WA, specializes in finding alternatives for clients faced with the need to replace highly regulated cleaning solvents. Inland focuses on nine particularly common and problematic cleaning solvents: methylene chloride, trichloroethylene, Freon 113, methyl ethyl ketone (MEK), 1,1,1 trichloroethane (TCA), stoddard solvent, acetone, perchloroethylene, and toluene. These are all ODCs, HAPs or VOCs. They represent a disposal problem and a safety and liability hazard. In replacing these problem solvents, Inland has found that biochemicals, chemicals which are derived from plant matter, often play an important role in the development of environmentally benign solvent alternatives. Inland has a number of successful solvent alternatives which are derived wholly or in part from biochemicals. These alternatives have proven effective in cleaning applications demanding stringent quality standards, and have received specification approval for cleaning applications from organizations such as Lockheed-Martin, NASA, and Rocketdyne.

Biochemicals can be effective replacements for petrochemicals, but their use tends to be more knowledge intensive than the use of petrochemical solvents. Manufacturers must learn how to apply a biochemical cleaning solvent in each individual cleaning situation. Implementation of alternative cleaning methods requires that workers be trained in new cleaning techniques and educated in the handling of unfamiliar solvents. Biochemicals can be effective replacements for petrochemicals, but their use tends to be more knowledge intensive than the use of petrochemical solvents. Manufacturers must learn how to apply a biochemical cleaning solvent in each individual cleaning situation. Implementation of alternative cleaning methods requires that workers be trained in new cleaning techniques and educated in the handling of unfamiliar solvents.

Case Study: The Boeing Aerospace Corporation used a significant amount of MEK as a surface preparation solvent for airplane parts, prior to painting and sealant application. They were seeking to eliminate this solvent, a source of VOC and HAP emissions. The application was very sensitive: cleaning requirements are stringent because of the need for very high quality binding of sealants on aircraft. The criteria this new cleaning technology had to meet included: compatibility with the sensitivity of metal substrates, sealants and paints used in aircraft; the ability to clean the same variety of contaminants as MEK; lower toxicity than MEK, so as to not trade a regulatory burden for health and safety hazards; reasonable economic competitiveness; and cleaning performance at least equal to MEK.

After extensive testing the solvent chosen as the best alternative was a highly refined terpene, a biochemical derived from the peels of citrus fruits. Inland named this solvent CitraSafeŽ. This solvent was approved by Boeing. The comparative costs of the cleaning solvents are around $4 per gallon for MEK as compared to $20 per gallon for CitraSafeŽ. Nevertheless, Boeing deemed CitraSafeŽ to be cost-effective. Why? Its use allowed Boeing to avoid complex regulatory demands, representing savings in administrative time and in investments in control technology, as well as a decreased potential for future liability concerns. Because CitraSafeŽ evaporates more slowly than MEK, it is consumed at a much slower rate than MEK. Annual use for CitraSafeŽ is about one fourth of the use of MEK. Third, because of the low toxicity of the CitrasafeŽ product, Boeing found that it could launder and reuse the wipe rags used in cleaning. Boeing had been disposing of these rags as hazardous waste. The reuse of these rags resulted in annual savings of $750,000, itself more than enough to cover the cost of Boeing's annual use of CitraSafeŽ.

Case Study: Another solvent replacement project addressed the cleaning of paint application equipment. A manufacturer was searching for alternative cleaning technology for paint application equipment used with the Atlas satellite launching vehicle. It hoped to eliminate the use of ozone depleting chemicals and hazardous materials as cleaning solvents. Inland decided to develop a cleaning solvent which would satisfy the most stringent regulations which they could foresee. The result was EP 921, a hybrid cleaning solvent (one containing biochemicals and petrochemicals) which contains the citrus terpene d-limonene and closely mimics the cleaning capacity of MEK in paint applications. The difference in emissions for EP 921 was shown with a test of the most environmentally compliant paint gun washer available. Inland estimated the daily operation of this washer and found that 55 gallons of MEK would be emitted due to evaporation each year. Using the same washer with EP 921 would result in losses due to evaporation of less than one tenth gallon. This solvent has proven to be very effective and has received specifications from the Air Force for satellite maintenance, from General Dynamics and from Boeing. Killion Industries (Vista, CA), a manufacturer of store fixtures, was searching for a solvent to replace TCA in cleaning overspray from paints, adhesives and felt-tip markers. They found that EP 921 performed the cleaning functions of TCA, and was also a suitable replacement for MEK in cleaning paint equipment. Killion found that the use of EP 921 resulted in an 88 per cent reduction in solvent use, which resulted in a 77 per cent reduction in costs for cleaning chemical use.

The challenge of replacing a familiar petrochemical solvent with a more environmentally benign solvent requires that manufacturers be willing to carefully evaluate their current cleaning practices and determine their needs and goals for alternative practices. Alternative solvents may behave differently than the solvents they replace, and manufacturers must be prepared for a transitional period while they learn the proper application of an alternative cleaning method. But as the given examples demonstrate, the rewards for replacing environmentally harmful petrochemicals can be significant. Biochemical solvents can provide manufacturers with a cost effective method to achieve regulatory compliance.

1. Anderson, S.O., U.S. EPA, "Aqueous and Semiaqueous Alternatives for CFC 113 and Methyl Chloroform Cleaning of Printed Circuit Boards", Replacing Solvent Cleaning with Aqueous Cleaning, EPA600/SR-94/131, Washington, DC, 1994.
2. "Clean Air Act Glossary," Industrial Paint & Powder, Vol. 70; No. 8; August, 1994, Pg. 13.
3. Gardener, J., " Big City Smog Draws Scrutiny of Clean Air Act," Plastic News, August 15, 1994, P. 14.

Joseph Lucas, President of Inland Technology Inc. (800 552-3100), presented information on the uses of biochemical cleaning solvents at ILSR's conference, "Industrial Uses of Biochemicals: Strategies for a Cleaner Future," held on November 29, 1995. Factsheets 8 through 11 of the Pollution Solutions series focus on presentations from this conference.

POLLUTION SOLUTIONS is a series of fact sheets about pollution prevention strategies with biochemical substitutes prepared by the Institute for Local Self-Reliance (ILSR). If you would like more information, contact:

Michelle Carstensen Research Associate
Tel: (612) 379-3815 FAX: (612) 379-3920

FS 8 Š1996 The Institute for Local Self-Reliance. All Rights Reserved.

Used with permission of Michelle Carstensen.