&EPA
United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S-94/009 September 1994
ENVIRONMENTAL
RESEARCH BRIEF
Waste Minimization Assessment for a Manufacturer
of Surgical Implants
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ment has been superseded by the Facility Pollution Prevention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 surgical implants from stainless steel and
titanium stock. The metal stock is machined, vibratory pol-
ished, electropolished, passivated, inspected, and shipped. The
team's report, detailing findings and recommendations, indi-
cated that wastewater and waste cutting fluid are the wastes
generated in the greatest quantities and that significant cost
savings would result from implementing a formal cutting fluid
management plan.
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, Phila-
delphia, PA.
Introduction
The amount of waste generated by industrial plants has be-
come an increasingly costly problem for manufacturers and an
* Colorado State University, Department of Mechanical Engineering, Fort Collins,
CO
" University City Science Center, Philadelphia, PA
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 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 Reduc-
tion Engineering Laboratory, the Science Center has estab-
lished three WMACs. This assessment was done by engineering
faculty and students at Colorado State University's (Fort Collins)
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 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 re-
duction of 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 proce-
&SS Printed on Recycled Paper
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dures outlined In the EPA Waste Minimization Opportunity
Assessment Manual (EPMG25/7-B8/Q03, 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 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 surgical implants. Nearly four million
parts are produced each year during 4,160 hr of operation.
Manufacturing Process
Fasteners and plates are manufactured from stainless steel
and titanium sheets, rectangles, and round stock.
The first step in the plate manufacturing process is the sanding
and cutting to size of stainless steel stock. Computer numeri-
cally-controlled (CMC) mills are used to mill the sides of the
plate, and another mill finishes the top and bottom of the plate.
Lathes, drills, broaches, and additional mills are used for fur-
ther machining operations. Then the parts are placed in one of
several vibratory polishers that utilize aluminum oxide chips
and water for additional finishing. Sand blasting may be used
in place of vibratory polishing for some parts. The final finishing
step is electropolishing, which uses an alkaline cleaner, a hot
water rinse, a cold water rinse, a phosphoric acid solution, a
hot water rinse and hold, an electropolishing solution, and a
datonlzed water rinse. After the part dries, a logo and serial
number are etched chemically onto its surface. Finally, the
parts are passivated (made less reactive) in a nitric acid solu-
tion, inspected, boxed, and shipped.
Fasteners are manufactured in a separate area of the plant.
Cylindrical metal blanks are cut and machined to form a screw
head on one end. Centerless grinders are used to shape the
head and reduce the outside diameter. Threads are cut into the
blanks using mills. The fasteners are polished in the vibratory
polishers, electropolished, and passivated. The finished prod-
ucts are inspected, packaged, and shipped.
An abbreviated process flow diagram for surgical implant manu-
facture is shown in Figure 1.
Existing Waste Management Practices
This plant already has implemented the following techniques to
manage and minimize its wastes:
* An aqueous, citric-based cleaner has replaced solvents used
for cleaning machined plates prior to polishing.
• Water meters have been installed on all aqueous waste
streams that are discharged to the treatment unit, to monitor
and control water usage.
• Scrap metal is shipped offsite for recycling.
• Centrifuges have been installed on many of the machines
used in fastener fabrication to separate metal chips from the
oil-based cutting fluid, extending the fluid's life and reducing
waste generation.
Fastener
fabrication
Plate
fabrication
Stainless steel
titanium
Passivation
1
Inspection
Etching
*
Passivation
Parts shipped
to customers
Figure 1.
Abbreviated process flow diagram for surgical implant
manufacture.
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 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-
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.
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.
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United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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EPA
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EPA/600/S-94/009
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