s°/EPA
United States
Environmental Protection
Agency
Research and Development
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
EPA/600/S-92/031 Sept. 1992
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a
Manufacturer of Machined Parts
Harry W. Edwards and Michael F. Kostrzewa'
Phylissa S. Miller 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. 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 Colorado State University performed an
assessment at a plant manufacturing machined parts — ap-
proximately 500,000 units/yr. This facility performs precision
machine-shop work on a job shop basis. The process begins
with cutting the stock to size, machining, and hand deburring
the parts. Next, the parts are machine deburred in a large
tumbler, washed, degreased, shipped offsite for chromating,
and returned, assembled, inspected, packaged, and shipped.
The team's report, detailing findings and recommendations,
indicated that the majority of waste was generated by the
deburrer rinse but that the greatest savings could be obtained
by replacing the cutting fluid concentrate, thereby eliminating
the need for degreasing with 1,1,1-trichloroethane.
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-
' Colorado State University, Department of Mechanical Engineering
" University City Science Center, Philadelphia, PA
tional stress on the environment. One solution to the problem
of waste 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 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
reduced waste treatment and disposal costs for participating
plants. In addition, the project provides 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
x Printed on Recycled Paper
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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
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 produces machined parts on a job shop basis. The
plant operates 2,210 hr/yr to manufacture approximately 500,000
units.
Manufacturing Process
This plant manufactures precision machined parts on a job
shop basis. Raw materials include aluminum castings, alumi-
num sheet stock, and aluminum bar stock.
The following steps are involved in making the parts:
• Aluminum stock is cut to size then machined on computer
numerically-controlled (CMC) machines. Periodically the
cutting fluid is drained to a settling tank fitted with a belt oil
skimmer. The tank allows solid contaminants to settle
without filtration and the skimmer removes hydraulic oil
and other tramp oils. "Treated" fluid is then reused in the
machining equipment. Twice a year the "old" cutting fluid
is drained from a machine and replaced with a cleaning
solution to thoroughly clean the sump and fluid passages.
The cleaner is then drained, the machine is rinsed with
water, and the sumps are refilled with fresh, not recycled,
cutting fluid.
• These wastes along with spilled cutting fluid, cutting fluid
lost to machine failure, unrecyclable cutting fluid, and tramp
oil are collected in a drainage tank. This tank is periodi-
cally drained and the contents are shipped offsite to a
nonhazardous waste disposal facility. Metal chips from
machining are shipped offsite to a metal dealer for recy-
cling.
• After machining, parts are manually deburred then placed
in a large tumbler deburrer. Water from this operation
overflows to one of three settling tanks where a nonhaz-
ardous, clay-like sludge builds up. The sludge, containing
polyester fibers, water, pumice, and metal bits, is shipped
offsite to a municipal landfill while the wastewater requires
no treatment and is discharged to the sanitary sewer
system.
• From the deburrer, parts are processed through a large
continuous line washer or a small batch-type washer.
Wash water is replaced frequently to remove build up of
oils, dirt, and other nonhazardous contaminants. This wa-
ter is discharged to the sewer.
• Warm dip degreasing with 1,1,1-trichloroethane (TCA) is
used to remove stubborn oils from machined parts. Spent
solvent is distilled by an onsite solvent recovery unit. After
degreasing, parts are sent offsite for chromating then re-
turned for assembly, inspection, packaging, and shipping.
An abbreviated process flow diagram is shown in Figure 1.
Existing Waste Management Practices
This plant has already implemented the following practices to
manage and minimize its wastes.
• At the time of the initial visit, plant personnel were testing
a cutting fluid which would not leave a tramp oil residue on
machined parts. If the cutting fluid proved to be satisfac-
tory, then subsequent solvent degreasing operations would
be eliminated.
• A cutting fluid maintenance program is in place that in-
cludes periodic fluid maintenance and re-use. The equip-
ment used in the program includes a sump sucker, a belt
skimmer, and a settling tank.
• A solvent recovery unit is used to recycle TCA.
• Metal chips are shipped offsite to a scrap metal dealer for
recycling.
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 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 indepen-
dently 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, one additional measure was considered. This
measure was not completely analyzed because of insufficient
data. Since this approach to waste reduction may, however,
increase in attractiveness with changing conditions in the plant,
it was brought to the plant's attention for future consideration.
• Reduce inventory and evaporative loss of TCA. During the
period considered, approximately 10 55-gal drums of TCA
were purchased even though waste TCA is distilled onsite
and reused. Because the degreasing unit has been rede-
signed to accommodate larger pieces, the cooling coils
above the vapor zone are no longer used since the refrig-
eration unit is now undersized for the current tank volume.
One way to reduce evaporative losses is to improve
housekeeping and a list of housekeeping measures ap-
propriate to the plant were provided in the assessment
report.
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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Figure 1. Abbreviated process flow diagram.
Table 1. Summary of Current Waste Generation
Waste Generated
Cutting fluid wastes
Deburrer rinse water
Clay-like sludge
Large washer rinse water
Small washer rinse water
Spent 1, 1, 1-Trichloroethane
(TCA)
TCA still bottoms
Aluminum chips
Source of Waste
Machining.
Cutting fluid that can no longer be recycled, tramp
oil, spilled cutting fluid, and waste cleaning solution
are shipped off site to a disposal facility where the
waste is blended into cement.
Large tumbling deburrer.
Wastewater from the deburrer goes through a
settling tank and is sewered.
Settling tank.
Sludge from the settling tank associated with the
deburrer rinse water is sent to the municipal landfill.
Large, continuous line parts washer.
Wastewater from the continuous line parts washer
is sewered.
Small, batch-type parts washer.
Wastewater from the batch-type parts washer
is sewered.
Parts degreasing.
Spent TCA is distilled onsite and reused.
Onsite solvent recovery unit.
Still bottoms are accumulating onsite.
Machining.
Scrao aluminum is sold to a recvcler
Annual Quantity
Generated
7,300 gal
41 3,556 gal
Not available
33,800 gal
9,1 00 gal
15,600 gal
O2
Not available
Annual Waste
Manaojement Cost '
$13 ion
*fr 1 1?; I 9l/
63O
L/tXW
*>O
v/w
m
lU
2,800
No t a vailable
'Includes applicable raw material costs. ~~ " —
2Over a 3-yr period, less than a 55-gal drum of still bottoms has accumulated.
•ttV.a. GOVERNMENT PRINTING OFFICE: I9M • S30-4M7/MI*
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Table 2. Summary of Recommended Waste Minimization Opportunities
Waste Generated
1,1,1-Trichloroethane
Cutting fluid wastes
Cutting fluid wastes
1,1,1-Trichloroethane
Minimization Opportunity
Annual Waste Reduction
Quantity
Percent
Net
Annual Savings
Implementation
Costs
Payback
Years
Replace current cutting 15,600 gal'
fluid concentrate with a
cutting fluid that does not
leave an oily film on
machined parts. This will
result in elimination of
warm dip solvent degreas-
ing after machining.
Acid treat cutting fluid wastes 0 3
to induce the physical sepa-
ration of organic and aqueous
phases. The organic phase
would be disposed of as before
and the aqueous waste fraction
would be sewered.
Evaporate cutting fluid wastes 0 3
to effect a volumetric reduction
in disposal quantity.4
Replace 1,1,1-trichloroethane 15,600 gal'
with an aqueous cleaner.
100
$4,820 •
immediate
3,470
1,000
0.3
100
2,440
1,340
2,800
3,520
1.2
2.6
1 Figure given reflects total volume processed through the solvent distillation unit per year. The generation of still bottoms will be eliminated also.
Implementation of either the first or the last Waste Minimization Opportunity will result in the elimination of solvent use and the solvent recovery process.
*Net annual savings include annual purchase cost of 1,1,1-trichloroethane and the cost difference between the existing and proposed cutting fluid
concentrates.
3This WMO results in cost savings only.
4An air discharge permit may be required for the emissions that may result.
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/S-92/031
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