1

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

established at selected universities, and procedures were

adapted from the EPA Waste Minimization Opportunity Assessment Manual (EPA/625/7-88/003, July 1988). That document has been superseded by the Facility Pollution Prevention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 polished, electropolished, passivated, inspected, and shipped. The

team’s report, detailing findings and recommendations, indicated 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 investigators and EPA’s Risk Reduction Engineering Laboratory, Cincinnati, 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, Philadelphia, PA.

Introduction

The amount of waste generated by industrial plants has become 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 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 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 experience 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 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 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 proceWaste Minimization Assessment for a Manufacturer

of Surgical Implants

United States

Environmental Protection

Agency

Risk Reduction

Engineering Laboratory

Cincinnati, OH 45268

ENVIRONMENTAL

RESEARCH BRIEF

Research and Development EPA/600/S-94/009 September 1994

Harry W. Edwards*, Michael F. Kostrzewa*,

and Gwen P. Looby**

E AP

* Colorado State University, Department of Mechanical Engineering, Fort Collins,

CO

** University City Science Center, Philadelphia, PA
2

dures outlined in the EPA Waste Minimization Opportunity

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 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

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 numerically-controlled (CNC) 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 further 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

deionized 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 solution, 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 products are inspected, packaged, and shipped.

An abbreviated process flow diagram for surgical implant manufacture 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

Stainless steel

titanium

Plate

fabrication

Machining

• Cutting

• Grinding

• Threading

Machining

• Sanding

• Milling

• Turning

• Drilling

• Broaching

• Grinding

• Milling

Vibratory

polishing

Electroplating

Passivation

Vibratory

polishing

Electropolishing

Etching

Inspection 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 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 minimization opportunity, in most cases, results from the need for less

raw material and from reduced present and future costs associated 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 independently 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. Environmental Protection Agency. The EPA Project Officer was Emma

Lou George.
3

Table 1. Summary of Current Waste Generation

Annual Quantity Annual Waste

Waste Generated Source of Waste Waste Management Method Generated (lb) Management Cost

*

Oil-based cutting fluid Machining of fasteners Shipped offsite for disposal 85,900 $88,100

 (recycled or incinerated)

Scrap metal Machining of fasteners Sold to recycler 80,600 (16,100)1

Water-based cutting fluid Machining of plates Shipped offsite for disposal 76,000 58,530

 (recycled or incinerated)

Scrap metal Machining of plates Sold to recycler 27,400 (5,500)1

Rinse water Electropolishing of fasteners and plates Treated onsite; sewered 995,000 1,920

Spent electropolishing solution Electropolishing of fasteners and plates Treated onsite; sewered 18,300 8,060

Spent passivating solution Electropolishing of fasteners and plates Treated onsite; sewered 3,720 140

Wastewater Vibratory polishing of fasteners and plates Treated onsite; sewered 6,350,000 12,250

Wastewater Sparge ring around clarifier in onsite Treated onsite; sewered 2,870,000 5,530

 wastewater treatment plant

Wastewater treatment sludge Onsite wastewater treatment plant Shipped to municipal landfill 16,900 02

* Includes waste treatment, disposal, and handling costs, and applicable raw material costs.1 Credit received.2 Plant pays a flat monthly rate for trash hauling.

Table 2. Summary of Recommended Waste Minimization Opportunities

Annual Waste Reduction

Net Annual Implementation Simple

Minimization Opportunity Waste Stream Reduced Quantity (lb) Per cent Savings Cost Payback (yr)

Institute a formal cutting fluid management Water-based cutting fluid 24,330 32 $19,9001 $6,400 0.3

 program for machines using water-based

 cutting fluids. To help maintain the quality

 of the fluid and extend its life, install

 coalescing oil skimmers on certain

 machines

Reuse treated wastewater in the vibratory Wastewater 6,350,000 100 3,250 900 0.3

 polishers instead of using tap water.

1 Total annual savings have been reduced by the annual operating cost required for implementation.
4

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

Penalty for Private Use

$300

EPA/600/S-94/009