United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-92/032 Sept. 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer of
Injection-Molded Car and Truck Mirrors
Marvin Fleischman and Clay Hensen*
Gwen P. Looby and F. William Kirsch**
Abstract
The U.S. Environmental Protection Agency (EPA) has funded
a pilot project to assist small- and medium-size manufacturers
who want to minimize their generation of waste but who lack
the expertise to do so. Waste Minimization Assessment Cen-
ters (WMACs) were established at selected universities and
procedures were adapted from the EPA Waste Minimization
Opportunity Assessment Manual (EPA/625/7-88/003, July 1988).
The WMAC team at the University of Louisville performed an
assessment at a plant that manufactures injection-molded car
and truck mirrors — over 2.5 million/yr. Purchased parts and
injection-molded plastic parts manufactured onsite are painted
as needed and assembled. The team's report, detailing find-
ings and recommendations, indicated that a large quantity of
waste is generated by the painting process and that waste
plastic also is generated in significant amounts. The greatest
cost savings can be achieved in this plant by using an alternate
method of disposing of the waste paint sludge generated in the
paint booths.
This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cin-
cinnati, OH, to announce key findings of an ongoing research
project that is fully documented in a separate report of the
same title available from University City Science Center
Introduction
The amount of waste generated by industrial plants has become
an increasingly costly problem for manufacturers and an addi-
tional stress on the environment. One solution to the problem
of waste is to reduce or eliminate the waste at its source.
' University of Louisville, Department of Chemical Engineering
" University City Science Center, Philadelphia, PA
University City Science Center (Philadelphia, PA) has begun a
pilot project to assist small- and medium-size manufacturers
who want to minimize their formation of waste but who lack the
inhouse expertise to do so. Under agreement with EPA's Risk
Reduction Engineering Laboratory, the Science Center has
established three WMACs. This assessment was done by
engineering faculty and students at the University of Louisville's
WMAC. The assessment teams have considerable direct ex-
perience with process operations in manufacturing plants
and also have the knowledge and skills needed to minimize
waste generation.
The waste minimization assessments are done for small- and
medium-size manufacturers at no out-of-pocket cost to the
client. To qualify for the assessment, each client must fall
within Standard Industrial Classification Code 20-39, have gross
annual sales not exceeding $75 million, employ no more than
500 persons, and lack inhouse expertise in waste minimization.
The potential benefits of the pilot project include minimization
of the amount of waste generated by manufacturers, reduced
waste treatment and disposal costs for participating plants,
valuable experience for graduate and undergraduate students
who participate in the program, and a cleaner environment
without more regulations and higher costs for manufacturers.
Methodology of Assessments
The waste minimization assessments require several site visits
to each client served. In general, the WMACs follow the pro-
cedures outlined in the EPA Waste Minimization Opportunity
Assessment Manual (EPA/625/7-88/003, July 1988). The
WMAC staff locate the sources of hazardous waste in the plant
and identify the current disposal or treatment methods and
their associated costs. They then identify and analyze a variety
of ways to reduce or eliminate the waste. Specific measures to
Printed on Recycled Paper
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achieve that goal are recommended and the essential support-
ing technological and economic information is developed. Finally,
a confidential report that details the WMAC's findings and
recommendations (including cost savings, implementation costs,
and payback times) is prepared for each client.
Plant Background
The plant produces injection-molded car and truck mirrors.
Over 2.5 million mirrors are produced each year.
Manufacturing Processes
Raw materials used by the plant include resins, paint, finishing
material, mirror glass, and miscellaneous parts. The folbwing
processes are involved in making the product.
Injection Molding
The resins used to produce the plastic mirror parts by injection
molding are dried in a gas-fired dryer prior to processing.
Repelletized scrap is blended with some of the new resin
material.
Ten injection-molding presses are operated continuously. The
resin is melted by the machines' heaters and injected into the
mold. The set mold is released and scrap is removed from the
part; scrap plastic is discarded or repelletized for recycle.
The parts are then trimmed to remove excess plastic, inspected,
cleaned with alcohol and mineral spirits, and buffed. Finished
parts are sent to the painting department or directly to the
assembly area.
Waste Minimization Opportunities
The type of waste currently generated by the plant, the source
of the waste, the quantity of the waste, and the annual man-
agement costs are given in Table 1.
Table 2 shows the opportunities for waste minimization that the
WMAC team recommended for the plant. The current plant
practice, the proposed action, the possible waste reduction and
associated savings, and the implementation cost along with the
payback times are given in the table. The quantities of hazard-
ous waste currently generated by the plant and possible waste
reduction depend on the production level of the plant. All
values should be considered in that context.
It should be noted that the economic savings of the minimiza-
tion opportunity, in most cases, results from the need for less
raw material and from reduced present and future costs asso-
ciated with hazardous waste treatment and disposal. Other
savings not quantifiable by this study include a wide variety of
possible future costs related to changing emissions standards,
liability, and employee health. It should also be noted that the
savings given for each opportunity reflect the savings achievable
when implementing each waste minimization opportunity inde-
pendently and do not reflect duplication of savings that would
result when the opportunities are implemented in a package.
Additional Recommendations
In addition to the opportunities recommended and analyzed by
the WMAC team, several additional measures were consid-
ered. These measures were not completely analyzed because
Painting
Parts are painted in one of three water-curtain paint booths.
The required paint is diluted with thinner as needed and mixed
with the appropriate catalyst.
Automatic spray guns and manual spray guns for touch-up
apply the paint. Parts are dried in a natural gas-fired oven and
inspected for defects. The last step of the paint process is the
cleaning of parts with solvent (acetone/xylene) after which the
parts are sent to the assembly area.
Assembly
The various types of mirrors are assembled from the manufac-
tured and purchased parts. The products are tested, inspected,
and packaged for shipping. An abbreviated process flow dia-
gram is shown in Figure 1.
Existing Waste Management Practices
The plant already had made the following efforts to manage
and minimize its wastes.
• Plastic pallets, foam padding, cardboard strips, and plastic
bags received as packing materials are reused by the
shipping department.
• A portion of the unfinished waste plastic is repelletized and
reused in the injection molding machines.
• Paint is purchased on an as-needed basis to avoid the
problems associated with disposal of paint held past its
shelf-life.
• Defective zinc mirror-housings are recycled.
Plastic Pellets
Injection Molding
V
Trimming, Inspection,
Cleaning, Buffing
Purchased
Pans
Finished Mirrors
Shipped to Customers
Figure 1. Abbreviated Process Flow Diagram.
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of insufficient data or minimal savings as indicated below. They
were brought to the plant's attention for future reference, how-
ever, since these approaches to waste reduction may increase
in attractiveness with changing plant conditions.
• Use hair nets, lint-free clothing, and other related items for
dust control in the paint spray areas in order to reduce the
number of parts rejected after the painting process. This
opportunity was not analyzed completely because of the
difficulty in quantifying the potential savings.
• Transfer paint from one container to another using a hand
pump in order to reduce spillage. The WMAC recom-
mends testing of this suggestion to determine if the pump
would transfer the paint satisfactorily.
• Install an onsite wastewater treatment plant to process
and recycle wastewater from the paint spray booths. This
opportunity may not be cost-effective for a plant of this
size.
• Investigate the possibility of replacing the solvent-based
paints with powder coatings. The WMAC could not deter-
mine if changes in the coating would meet customer
specifications and therefore could not develop a recom-
mendation in this area.
• Reduce evaporative bsses of solvents by covering open
containers.
This opportunity would yield minimal savings.
This research brief summarizes a part of the work done under
Cooperative Agreement No. CR-814903 by the University City
Science Center under the sponsorship of the U.S. Environmental
Protection Agency. The EPA Project Officer was Emma Lou
George.
Table 1. Summary of Current Waste Generation
Waste Generated
Source of Waste
Unusable paint
Paint sludge
Wastewater/solvent
Waste solvent
Plastic waste
Empty paint cans
Miscellaneous trash
Wooden pallets
Raw materials handling. Paint that has been held beyond
its shelf-life is disposed of off site as a hazardous waste.
Spray paint booths. Paint sludge removed from the water
pumps of the spray paint booths and other paint wastes are
combined and disposed of off site as a hazardous waste.
Spray paint booths. Solvent used to clean the paint spray
guns is sprayed into the water curtains of the spray paint
booths; tf>e aqueous emulsion that forms in the pumps is
removed and disposed of off site as a hazardous waste.
Parts cleaning. Waste solvent from parts cleaning is sent
to a secondary fuels program for disposal.
Materials handling, injection molding, and painting. Waste
plastic is sent to an offsite nonhazardous landfill.
Painting operation. Empty 5-gal and 1-gal metal cans are
sent to an offsite nonhazardous landfill.
Various processes. Waste cardboard, small plastic pieces,
and broken mirror glass are sent to an offsite nonhazardous
landfill.
Receiving department. Used wooden pallets are sent to an
offsite nonhazardous landfill.
Annual Quantity
Generated
Annual Waste
Management Cost
50 gal
21,040 gal
72,000 gal
14,020 gal
637,500 Ib
720cuyd
4,080 cu yd
1,180cuyd
$5,275'
1,182,6201
105.6401
101,940'
32,510
7,200
24,480
7,000
11ncludes raw material costs
•frv.8. GOVERNMENT PUNTING OFFICE: 1*94 - 530-M7/HOISO
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Table 2. Summary of Recommended Waste Minimization Opportunities
Current Practice Proposed Action
Waste Reduction and Associated Savings
Plastic waste generated by the plant is
discarded in dumpsters and disposed of
in an offsite nonhazardous landfill.
Empty steel paint-cans are discarded in
a dumpster and disposed of in an offsite
nonhazardous landfill.
Wooden pallets are discarded and
disposed of in an offsite nonhazardous
landfill.
Paint sludge from the spray paint booths
is sent offsite to a hazardous waste
disposal facility.
Waste solvent from the cleaning
operation is sent to a secondary
fuels program.
A mixture of acetone andxylene is used
for parts cleaning.
Waste paint sludge from the paint booth
pumps is manually scooped out each shift
and disposed of as hazardous waste.
Spray-gun cleaning solvent is sprayed
directly into the water curtains of the
paint spray booths.
Segregate the different types of
plastic waste and sell the waste
to a waste plastic dealer.
Sell the cans to a steel can
recycler. (The amount of dried
paint in the cans must be
minimized.)
Give the pallets to a pallet
rebuilder to eliminate disposal costs.
Send the paint sludge to a
facility that dries the wet sludge
thereby yielding a dry powder of
lesser volume for disposal.
Install a small batch distillation
system to reclaim used solvent.
Ship still bottoms offsite.
Replace the currently used solvent
with a di-basic ester in order to
reduce volatile organic compound
emissions and disposal costs.
Install hydroclones to remove
paint solids from the paint booth
water. The hydroclones will use
centrifugal force to coagulate the
paint solids and remove them from
the sump. The water will be
recirculated to the paint booths.
The new system should also reduce
the amount of water from the
system that must be disposed of.
Spray the solvent into a
collection container for disposal.
Waste reduction = 573,750 Ib/yr
Waste disposal savings = $29,270/yr
Additional labor cost * $18,360/yr
Revenue received - $2,870/yr
Net cost savings = $13,780/yr
Implementation cost = $0
Simple payback is immediate.
Waste reduction = 720 cu yd/yr
Waste disposal savings = $7,200/yr
(Revenue received is offset by hauling
cost.)
Implementation cost = $0
Simple payback is immediate.
Waste reduction = 1,185 cu yd/yr
Waste disposal savings = $7,000/yr
Implementation cost = $0
Simple payback is immediate.
Waste disposal savings = $24,300/yr
Implementation cost = $0
Simple payback is immediate.
Waste reduction = 9,820 gal/yr
Waste disposal savings = $17,850/yr
Raw material savings = $53,550/yr
Operating cost of system = $780/yr
Net cost savings = $70,620/yr
Implementation cost = $33,000
Simple payback = 0.5/yr
Increased raw material cost = $12,750/yr
Waste disposal savings - $20,150/yr
Net cost savings = $7,400/yr
Implementation cost = $0
Simple payback is immediate.
Waste reduction = 76,500 gal/yr
Waste disposal savings = $189,200/yr
Operating cost of system = $9,300/yr
Net cost savings =• $179,900/yr
Implementation cost = $26,000
Simple payback = 0.1 yr
Waste reduction = 33,130 gal/yr
Waste disposal savings = $39,800/yr
Implementation cost = $0
Simple payback is immediate
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
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EPA
PERMIT No. G-35
EPA/600/S-92/032
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