&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 That docu- ment has been superseded by the Facility Pollution Prevention Guide (EPA/600/R-92/088, May 1992).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 ------- 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. ------- to Q) O II "Si fg g I I •5 b I W CD £ I I CO" co" O & .£ i s .E .e plate ing | c OJ c (0 1 1 I s 8 8 S f f £ 5 § 1 1 S II a a S ^ co- CO ci CM 8 I a I i I 1 TO ------- 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-94/009 ------- |