xvEPA
United States
Environmental Protection
Agency
Research and Development
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
EPA/600/S-92/035 Sept. 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a
Manufacturer of Sheet Metal Components
Harry W. Edwards", Michael F. Kostrzewa", and Gwen P. Looby"
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. In an effort to assist these manufacturers
Waste Minimization Assessment Centers (WMACs) were es-
tablished 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
Colorado State University performed an assessment at a plant
that manufactures precision sheet-metal components, primarily
for electronics and medical equipment. Sheet metal is machined
into desired components that are anodized or chromated if
aluminum; degreased and painted if required; and assembled,
inspected, packaged, and shipped. The team's report, detailing
findings and recommendations, indicated that the plant could
achieve significant cost savings and waste reduction by replacing
its standard paint spray guns with high-volume low-pressure
paint guns, thereby reducing paint overspray.
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.
' Colorado State University, Department of Mechanical 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 Colorado State University's
(Fort Collins) WMAC. The assessment teams have consider-
able direct experience with process operations in manufactur-
ing 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, and
reduction of waste treatment and disposal costs for participat-
ing plants. In addition, the project provides valuable experience
for graduate and undergraduate students who participate in
the program, and a cleaner environment without more regula-
tions 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
procedures outlined in the EPA Waste Minimization Opportu-
nity Assessment Manual (EPA/625/7-88/003, July 1988). The
WMAC staff locate the sources of waste in the plant and
identify the current disposal or treatment methods and their
associated costs. They then identify and analyze a variety of
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ways to reduce or eliminate the waste. Specific measures to
achieve that goal are recommended and the essential supporting
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 manufactures precision sheet-metal components,
primarily for electronics and medical equipment. It operates
approximately 2,100 hr/yr to process about 300,000 square
feet of sheet metal annually.
Manufacturing Process
The major raw materials used by the plant are aluminum and
steel, but iron phosphate-coated sheet steel, tin-plated sheet
steel, and vinyl-coated sheet steel are also used.
The sheet metal is cut to size with hydraulic shears, and
patterns are cut with computer numerically-controlled (CNC)
turret punch presses. Some counterboring and tapping follows.
Burrs are removed using wet and dry deburrers, sanders,
grinders, and buffers. The deburred parts are formed and bent
to the desired shape.
All aluminum parts are then anodized (1%) or chromated (99%).
The anodizing/chromating line consists of a series of tanks
containing cleaning solutions, rinses, anodizing solutions, dye,
nickel acetate sealing solution, hot deionized water, and
chromating solutions. Instructions specified by the customer
are silk-screened onto the parts after anodizing or chromating.
About 25% of the fabricated steel parts are painted, usually
with solvent-based paints after degreasing with 1,1,1-
trichloroethane (TCA).
The components are then assembled as needed, inspected,
packed, and shipped.
An abbreviated process flow diagram is shown in Figure 1.
Existing Waste Management Practices
This plant has already implemented the following techniques to
manage and minimize its wastes.
• Reactive rinsing for cleaning prior to anodizing is used in
order to reduce the amount of fresh make-up water re-
quired and to help neutralize the rinse following the alkaline
cleaning solution.
• Air agitation of some of the tanks in the anodizing/
chromating line improves the effectiveness of the solutions
and extends their life.
• Water consumption is controlled through a flow meter on
the anodizing/chromating line. In addition, water con-
sumption is monitored daily in an effort to encourage
conservation.
• Chromating solutions are very effectively maintained so
that the frequency of dumping and replenishment is mini-
mized.
• Clean-up solvent is reused before offsite disposal.
• Scrap metal is segregated by type and sold to a scrap
dealer for recycling.
• A replacement aqueous cleaner is being phased-in to
replace TCA degreasing.
Waste Minimization Opportunities
The type of waste currently generated by the plant, the source
of the waste, the waste management method, the quantity of
the waste, and the annual waste management cost are given
in Table 1.
Table 2 shows the opportunities for waste minimization that the
WMAC team recommended for the plant. The type of waste,
the minimization opportunity, the possible waste reduction and
associated savings, and the implementation cost along with the
payback times are given in the table. The quantities of 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, in most cases, the economic savings of
the minimization opportunities result from the need for less raw
material and from reduced present and future costs associated
with waste treatment and disposal. Other savings not quantifi-
able 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 independently
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, additional measures were considered. These
measures were not completely analyzed because of insufficient
data or minimal savings and a projected lengthy payback.
Since these approaches to waste reduction may, however,
increase in attractiveness with changing conditions in the plant,'
they were brought to the plant's attention for future consideration!
• Install a solvent recovery unit to distill the waste cleaning
solvent for reuse.
• Encourage customers to consider specifying water-borne
instead of solvent-based paints for their products.
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.
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Aluminum Sheet Stock
Steel Sheet Stock
Scrap Metal
Recycled
Offsite
Chromate Conversion
Coating
- Cleaning
- Chromating
Painting
- Degreasing
- Painting
Anodizing
- Cleaning
-H2S04
- Dyeing
- Sealing
Rinse Water
and Spent
Sotutions
Neutralized
nd Sewere
Lacqu&rJh
MBC Catalyst
fteduc&r, TCA
Recycled and/or
Incinerated
ite
Final Assembly
Sheet Metal Components
Figun 1. Abbreviated process flow diagram.
•ArU.S. GOVERNMENT PRINTING OFFICE: 19*4 - 550-067/80173
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Table 1. Summary of Current Waste Generation
Waste Stream Generated
Source of Waste
Spent anodizing reagents
Spent anodizing rinse water
Spent chromate conversion
reagents
Spent chromate conversion
rinse water
Spent 1,1,1-trichloroethane
1,1,1-trichloroethane evaporation
Clean-up solvent and
other paint wastes
Clean-up solvent evaporation
Paint over spray
Scrap metal
Anodizing line
Anodizing line
Chromate conversion line
Chromate conversion line
Cleaning of parts in paint line
Cleaning of parts in paint line
Paint line
Paint line
Paint line
Machining
Waste Management Method
Neutralized and sewered
Neutralized and sewered
Neutralized and sewered
Neutralized and sewered
3 Shipped off site for recycling
and/or incineration
3 Evaporates to plant air
Shipped off site for incineration
Evaporates to plant air
Conventional disposal off site
Sold to a recycler
Annual Quantity Annual Waste
Generated Management Cost
2,460 gal
339,840 gal
25,870 gal
997,380 gal
190 gal
470 gal
200 gal
130 gal
5,570 Ib
N/A
$260
1,810
530
4,260
2,310
2,260
2,270
280
19,525
N/A
'Includes raw material costs.
Table 2. Summary of Recommended Waste Minimization Opportunities
Waste Generated
Minimization Opportunity
Annual Waste Reduction Net Implementation Payback
Quantity Percent Annual Savings Costs Years
Paint over spray
Chromate conversion
rinse water
Replace the conventional paint
spray guns with High Volume
Low Pressure (HVLP) spray guns.
The use of the proposed guns will
lead to improved paint application
efficiency.
Install an additional counter-
flowing rinse at the end of the
chromating line to reduce the
total amount of rinse water
consumed.
1,750 Ib
31
$6,060
$800
0.1
312,400 gal
31
1,080
2,160
2.0
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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$300
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EPA/600/S-92/035
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