Table 2. Summary of Recommended Waste Minimization Opportunities

Annual Waste Reduction
Net Annual Implementation Simple
Minimization Opportunity Waste Steam Reduced Quantity (Ib) Per cent Savings Cost Payback (yr)
Replace the presently used conventional paint Paint fitters/overspray 1,000 9 $33,920 $2,800 Or
spray guns with high-volume, low pressure Evaporated mixing materials 2,190 25
(HVLP) paint spray guns in order to increase Evaporated paint solvent 2,850 25
paint transfer efficiency and reduce consumption
of paint, catalyst, reducer, and thinner. Paint
overspray losses will be reduced considerably,
leading to significant cost savings.
Install a closed-loop paint spray gun washer to Evaporated solvent 16,300 90 §,120 1,500 03
reduce the quantity of solvent that evaporates (paint gun cleaning)
during paint gun cleaning. Recovered spent
solvent can be processed in the plant's solvent
fecovery unit; a small additional quantity of still
bottoms will be generated.
Replace the solvent-based wash currently used Cleaning 2,600 67 3,510 2,150 06
for silkscraens with a low-solvent wash, a Evaporated si 1,130 100
recirculating system, and a wash booth. (cleaning of silk screens)
Replace a portion of the solvent-based paints Solvent still bottoms 1,150 35 3,570 0 Immediate
used currently with water-based paint. Evaporated solvent 6,290 35
(paint gun cleaning)
mixing materials 2,980 35
Install an additional counter-flowing rinse at Rinse water 4,480,000 35 910 3,680 41
the end of the chromating line to reduce
water consumption.
Redesign plating baskets to reduce chromium Rinse water 1,380,000 W 250 500 20

dragout from the solution tanks to the rinse
tanks.



Table 1. Summary of Currant Waste Generation

Annual Quantity Annual Waste

Waste Generated Source of Waste Waste Management Method Generated (Ib) Management Cost
Metal dusvgrit Grinding of metal ‘Shipped offsite as municipal trash 440 go
Rinse water Cleaning and chromating Discharged to sewer 12,560,000 2,540
Evaporated solvent (lacquer thinner) Paint gun cleaning Evaporates to plant air 18,100 7,0702
Solvent still bottoms Onsite solvent recovery unit ‘Shipped offsite as hazardous waste 3,300 1,780
Paint filters/overspray Paint spray booths ‘Shipped offsite as municipal trash 11,19 47,7108
Evaporated mixing materials

(catalyst, reducer, thinner) __ Painting Evaporates to plant air 8,590 14,0004
Evaporated paint solvent Painting Evaporates to plant air 11,87 os
Cleaning rags Cleaning of silkscreens Shipped offsite as municipal trash 3,900 1,0708
Evaporated solvent (screen wash) Cleaning of silkscreens : Evaporates to plant air 1,130 1,670?

1 Plant pays a monthly fee for wash cispoesl

® Raw material cost of solvent evaporated.

’ Raw maternal cost of filters and paint captured in filters.
+ Raw material cost of material evaporated.
‘
‘


United States

Environmental Protection Agency

Center for Environmental Research Information
Cincinnati, OH 45268

Official Business
Penalty for Private Use
$300

EPA/600/S-94/010

BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35



United States
Environmental Protection
Agency

Aisk Reduction
Engineering Laboratory
Cincinnati, OH 45268

Research and Development

EPA/600/S-94/010 September 1994

EPA

ENVIRONMENTAL

RESEARCH BRIEF

Waste Minimization Assessment for a Manufacturer
of Aluminum and Steel Parts

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 manufactur-
ers, Waste Minimization Assessment Centers (WMACs) were
established at selected universities and procedures were
adapted from the EPA Waste Minimization Opportunity As-
sessment Manual (EPA/625/7-88/003, July 1988). That docu-
ment has been superseded by the Facility Pollution Prevention
Guide (EPA/600/R-92/088, May 1992). The WMAC team at
Colorado State University performed an assessment at a plant
that manufactures a variety of steel and aluminum parts. Raw
material is machined and the resulting parts are welded, ground,
and chromated. Parts are then painted and logos and other
lettering are screened onto the parts. The parts are shipped
following inspection, assembly, and packaging. The team’s
report, detailing findings and recommendations, indicated that
the waste streams generated in greatest quantity are rinse
water and paint wastes, and that the greatest cost savings
could be achieved by replacing the conventional paint guns
currently used with more efficient substitutes.

This Research Brief was developed by the principal investiga-
tors and EPA's Risk Reduction Engineering Laboratory, Cincin-
nati, 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.

“Colorado State University, Department of Mechanical Engineering
“University City Science Center, Philadelphia, PA

Introduction

The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
additional stress on the environment. One solution to the
problem of waste generation is to reduce or eliminate the
waste at its source.

University City Science Center (Philadelphia, PA) has begun a
pilot project to assist small and medium-size manufacturers
who want to minimize their generation of waste but who lack
the in-house expertise to do so. Under agreement with EPA's
Risk Reduction Engineering Laboratory, the Science Center
has established thrae WMACs. This assessment was done by
engineering faculty and students at Colorado State Univérsity'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 in-house expertise in waste minimiza-
tion.

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 experi-
ence for graduate and undergraduate students who participate
in the program, and a cleaner environment without more regu-
lations and higher costs for manufacturers.

&B Printed on Recycled Paper

> D»


Methodology of Assessments

The waste minimization assessments require several site visits
to each client served. In general, the WMACs follow the proce-
dures outlined in the EPA Waste Minimization Opportunity
Assessment Manual (EPA/625/7-88/003, July 1988). The WMAC
staff locates 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 ways to
reduce or eliminate the waste. Specific measures to achieve
that goal are recommended and the essential supporting tech-
nological and economic information is developed. Finally, a
confidential report that details the WMAC’s findings and recom-
mendations (including cost savings, implementation costs, and
payback times) is prepared for each client.

Plant Background

This plant manufactures a variety of aluminum and steel parts,
primarily for local medical and computer products manufactur-
ers. It operates 5,600 hr/yr to produce approximately 750,000
parts/yr.

Manufacturing Process

Steel and aluminum undergo shearing, punching, and bending
operations to form desired parts. Welding and grinding are
performed on the resulting parts as needed. Large parts are
hung on an overhead conveyor and small parts are placed in a
hanging basket prior to undergoing chromating. The process
baths used in the chromating line are dependent on the type of
part being coated.

After chromating, the parts are prepared for painting and hung
on an overhead conveyor. The conveyor runs to four spray
booths where the parts are painted with solvent-based paints,
water-based paints, or powder-based coatings. Parts are dried
in a natural gas-fired oven following painting.

Logos and other lettering are screened onto the parts, which
are then inspected, assembled, packaged, and shipped.

‘Shearing,
‘Steel and > punching,
aluminum blending

Inspection, assembly,
packaging, shipping

An abbreviated process flow diagram for Aluminum and Steel
Part Manufacturer is shown in figure 1.

Existing Waste Management Practices

This plant already has implemented the following techniques to
manage and minimize its wastes.

+ The use of “Just-in-Time” ordering reduces stock and
misordering that could lead to waste generation.

Scrap metal from machining processes is recycled.

Flat sanding using a water knife and a baghouse reduces
dust.

Reactive rinsing (using the same rinse tank after dipping in
the caustic soap and dipping in the acid tank) neutralizes the
water and reduces water usage.

Solvent recycling and reuse reduces the amount of solvent
wastes generated.

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 waste management cost for each waste
stream identified are given in Table 1.

Table 2 shows the opportunities for waste minimization that the
WMAC team recommended for the plant. The minimization
opportunity, the type of waste, the possible waste reduction
and associated savings, and the implementation cost along
with the simple payback time are given in the table. The
quantities of waste currently generated by the plant and pos-
sible 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-

Figure 1. Abbreviated Process Flow diagram for aluminum and steel part manufacture.


ciated with 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 also should be noted that the savings
given for each opportunity reflect the savings achievable when
implementing each waste minimization opportunity indepen-
dently and do not reflect duplication of savings that may result
when the opportunities are implemented in a package.

Additional Recommendations

In addition to the opportunities recommended and analyzed by
the WMAC team, one additional measure was considered. The
potential savings of this measure are somewhat hypothetical in
nature, but it was brought to the plant's attention for consider-
ation.

+ Replace the present deoxidizer used in the chromating line
with a nonchromated deoxidizer in orderto reduce chromium
concentrations in the waste rinse water. If chromium levels
continue to be problematic, the plant may need to install a
chromium reduction unit. This measure would make the
purchase of that unit unnecessary.

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. Environmen-
tal Protection Agency. The EPA Project Officer was Emma
Lou George.