An Assessment and Prioritization of Design for Recycling Guidelines for Plastic Components

Transcription

1 An Assessment and Prioritization of Design for Recycling Guidelines for Plastic Components E. Masanet R. Auer, D. Tsuda T. Barillot, A. Baynes Dept. of Mechanical Engineering Apple Computer Inc. Apple Europe University of California, Berkeley 1 Infinite Loop 12 Avenue d Oceanie Berkeley, CA, USA Cupertino, CA, USA Les Ulis CEDEX-FRANCE Abstract The current paper summarizes the results of a study aimed at assessing the effectiveness of design for recycling strategies for plastic components. Interviews and site visits were conducted with computer disassemblers and plastics recyclers based in the United States and Europe to investigate the effectiveness of design for recycling guidelines. Both manual and automated recycling technologies for plastics were investigated. Based on this investigation, six key design for recycling guidelines are prioritized based on their potential for improving the recyclability of plastic components. The results of this study can be used to help prioritize design for recycling strategies so that both product recyclability and design productivity are maximized. 1. INTRODUCTION Design for recycling (DFR) has become an increasingly important dimension of environmental management for computer manufacturers in recent years. Proposed takeback policies in Europe, recycle-oriented eco-label requirements and increasing environmental awareness have all prompted the computer industry to continuously improve the recyclability of its product designs. Designing computers to be recyclable has therefore come to be viewed not only as environmentally beneficial but also as a strategic business requirement for computer OEM s. A host of DFR guidelines for computers have been offered in the published literature [l], in industry guidebooks [2] and by eco-label criteria. A number of these DFR guidelines are aimed at improving the recyclability of plastic components, for example, the use of plastic identification labels to allow for manual plastics sorting. However, it is not yet clear just how effective these DFR guidelines are at improving the recyclability of computer plastics in actual practice. Because DFR efforts can require a significant investment of both time and resources during the product design process and can sometimes compete with other design requirements, it is desirable to determine which DFR guidelines are truly most effective so that both recyclability and design productivity can be maximized. In order to assess the effectiveness of DFR guidelines for plastic components, Apple recently performed a detailed study of computer recycling practices in both the United States and Europe. Twenty-four site visits and telephone interviews were conducted with computer disassemblers and plastics recyclers to determine which DFR guidelines were most effective at improving the recyclability of computer plastics. Additionally, future trends in computer recycling were also investigated - using the interview process and a literature review - to estimate which DFR guidelines are likely to be most effective for future computer designs. This paper discusses the findings of this study and provides an assessment and prioritization of six key DFR guidelines for computer plastics. 11. DESIGN FOR RECYCLING GUIDELINES The DFR guidelines assessed in the current paper are listed in Table 1 and are elaborated in the bullet points that follow. Each of these guidelines is either suggested or required by a major eco-label, as indicated in Table 1 by an S or R, respectively. The specific eco-label sources for these guidelines are Sweden s TCO 99 (Report 5) [3] and Germany s Blue Angel RAZ-UL 78 [4]. Table 1. Summary of DFR guidelines with reference to eco-label source U it l W l 6 Design for Recycling Guideline F 99 Angel Plastic components > 25 g labeled R R per oer IS Large plastic parts limited to one R polymer type Large plastic parts must not be No molded-in or glued-on metal e shall be same color Use of snap fits wherever possible 1. Plastic components > 25 grams shall be labeled in accordance with IS Requires that plastic parts be labeled with a material identification marking to allow for visual identification of polymer type. S X/02/$ IEEE 5

2 All plastic components > 100 grams shall be made from the same type of plastic material. Aimed at increasing the volumes of similar plastics for recycling by limiting plastic parts to one polymer. No plastic component > 25 grams shall be painted so that the dry weight of the plastic component increases by more than one percent. Aimed at minimizing the adverse effects paints can have on the mechanical properties and aesthetics of recycled plastics. No metallization of plastic components, no molded-in or glued-on metal parts. Aimed at reducing metals that are permanently attached to plastic parts because this can impede the recycling process. All components made of one sort of plastic are dyed uniformly. Aimed at increasing the volume of single polymer, single color plastic parts for recycling. At least half the separable connections are snap-fits. Aimed at minimizing manual disassembly time by making components quickly and easily separable RECYCLING OPTIONS When considering the recyclability of computer plastics, it is important to note that several different recycling options exist for plastic components. The most common recycling options can be divided into four general categories [5]: Mixed polymer applications, such as pothole fillers. Applications of this type are generally low grade and are suitable for highly mixed batches of plastics. Limited mixed polymer applications, such as floor tiles. Applications of this type are suitable for mixed batches of plastics in limited combinations (such as combinations of PC, ABS and PC/ABS). Single polymer, multicolor applications, such as internal computer components. Applications of this type are limited to one polymer and thus approach the mechanical properties of virgin plastic, but are generally of lower aesthetic value due to mixed colors. Single polymer, single color applications, such as computer housings. Applications of this type are considered the highest level of recycling, because computer plastics are recycled back into products of similar mechanical and aesthetic quality. In the current paper, a plastic component is considered to be more recyclable if it allows for more potential recycling options. For example, a plastic part that can be recycled into any of the four recycling options above is considered to be more recyclable than a plastic part that is only suitable for mixed polymer applications. IV. INTERVIEW SCOPE Eighteen disassemblers and six plastics recyclers were interviewed as part of this study. Both manual and automated systems for disassembly and sorting were investigated. Of the disassemblers interviewed, sixteen were using both manual disassembly methods (Le., using handheld power tools) and manual sorting methods for plastic components. The remaining two disassemblers were employing automated disassembly systems. Both of these automated disassembly systems were destructive: computers were fed into a shredder and the resulting mixture of materials was sorted automatically through the use of magnets and eddy currents. One of these systems employed automated plastics sorting equipment and the other was smelting plastics along with the metals fractions. Of the six plastics recyclers interviewed, four were employing automated plastics sorting equipment. Three of these automated sorting systems were based on density separation techniques and one was based on froth flotation. Table 2 summarizes the number of interviews carried out for each disassembly and sorting method described above. Disassembly Method: Manual I Automated 16 2 V. GENERAL FINDINGS Plastics Sorting Method: Manual I Automated 16 4 It was found that most batches of computers received by the disassemblers in this study were highly heterogeneous. The typical batch of computers contained dozens of different computer models from several different OEM s ranging from years to decades old. The plastics in these batches were also highly varied, and thus many different combinations of polymers and colors were typically present. These findings agree with previous assertions in the published literature that it is rare to encounter large quantities of similar plastics when recycling computers [6]. Due to the heterogeneity of the typical batch, it was found that it was generally not economical to sort all plastics for recycling. This study found that most often only the highest volume polymers in any given batch of computer plastics were being sorted for recycling. Table 3 summarizes the market share of the various polymers used in computer products [7], and the volume of each polymer that was found in large batches of computer plastics for three recent recycling studies [8][5][9]. 6

3 Table 3. Common computer plastics and the percentage of each found in recent recycling studies I Polymer I Market Study I Study I Study I Type 1 Share I HIPS I 22.7% I 25% 1 10% I 5% ABS PC PCIABS 20.5% 39% 34% 57% 19.2% 4% 5% 11.7% 6% 29% 2% PPO I 6.5% 1 17% 1 12% 1 36% Other I 19.4% I 9% I 10% I >I% It can be seen that by market share, the dominant computer plastics are high-impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), PCIABS blends, and polyphenylene oxide (PPO). It can also be seen, however, that the relative volume of each polymer that is found in any given batch of computer plastics can vary significantly. Thus it was found that the specific polymers that were sorted for recycling typically varied from batch to batch. This study also found that plastics recycling is typically one of the lowest revenue activities for disassemblers. The highest revenues were seen to come from reselling computers and components (e.g. hard drives), and from recycling printed wiring boards for precious metals content. These high revenue items represented such a large portion of income for some disassemblers that they said their operations were not likely to be profitable without them. VI. ASSESSMENT OF DFR GUIDELINES This section provides an assessment of the six DFR guidelines outlined in Section I1 based on the results of the interview process. 1. Use of IS0 labels IS0 labels are designed to allow a human laborer to visually identify the type of polymer used in a plastic part during manual sorting operations. For the manual sorting operations in this study, IS0 labels were found to be used extensively by those who were sorting plastic parts by polymer type. It was also found that if the polymer type of a plastic part could not be visually identified, it was most often limited to mixed polymer recycling applications. It was therefore found that the use of IS0 labels is a highly effective strategy for improving the recyclability of plastic parts for manual sorting systems. Interestingly, several interviewees noted that up to 20% of the IS0 labels they encounter are incorrect. It was suggested that these errors are likely due to substitutions of different plastics at the factory or to the use of old molding dies to make new plastic parts. Thus it also may be important to periodically ensure that IS0 labels are still accurate. For the automated sorting systems in this study, however, it was found that IS0 labels have no effect on the recyclability of plastic parts. These systems are designed to separate plastics based on the mechanical, optical and electrostatic properties of the plastic and thus visual identification markings are not exploited. 2. Use of one polymer for all large parts Using only one type of polymer for all large plastic'parts on a computer is intended to increase the quantities of that polymer for recycling. When sufficient volumes of a given polymer are present in a batch of computer plastics, it is possible to target single polymer recycling applications. For both manual and automated plastics sorting systems in this study, it was found that only the high volume polymers in a given batch of computer plastics are being sorted economically for single polymer recycling applications. In general, the rest of the plastics in the batch were being targeted for mixed polymer recycling applications regardless of polymer type. Because the polymer composition of any given batch of computer plastics is typically random, this study found that choosing only one polymer for plastic parts does not necessarily increase their recyclability. For example, Table 4 shows that HIPS is a high market share plastic for computers, yet it only occurred in high volumes in one of three random batches of computer plastics. Conversely, PPO is a low market share plastic that can be seen to occur in high volumes in Study 3. Thus if an OEM chooses one polymer for all plastic parts, there is no guarantee that it will be found in high enough volumes in every batch to justify recycling into single polymer applications. This study also found that it was unlikely to encounter large quantities of any one model of computer in the highly heterogeneous batches that are typical of recycling. The polymer choice for any one OEM model can therefore have little influence on the overall polymer composition of the typical batch. Thus it appears that an OEM also has limited ability to improve the overall batch volumes of a given polymer (thereby increasing chances that it will be sorted for recycling) simply by using that polymer for all plastic parts on a given model. For the above reasons, it was found that using only one type of polymer for all large plastic parts does not guarantee improved recyclability. This DFR guideline was therefore not found to be a universally effective strategy for improving the recyclability of plastic components. 3. Limiting the use of paint When painted plastics are recycled, paints may remain as inclusions that can reduce the mechanical properties and aesthetic value of recycled plastics [lo]. Limiting the 7

4 amount of paint to 1% of the overall part mass is designed to minimize the potential for these deleterious effects. For the manual sorting systems in this study, it was found that nearly all painted plastics were not being sorted after disassembly but were instead commingled with mixed plastics for use in mixed polymer recycling applications. A common justification for this practice was that, given the potentially negative effects of paints, it was not prudent to invest manual labor in sorting painted plastics because of their uncertain recycle value. For the automated plastics sorting systems in this study, several recyclers said that painted plastics can be recycled into single polymer applications if paints are only present in small quantities. This is because batches of mixed plastic can be screened prior to automated sorting, and thus the recycling of painted plastics will only proceed if the amount of paint is within an acceptable range. These recyclers advised that to ensure maximum recyclability for painted plastics, it is crucial to keep the ratio of paint to plastic very low. Based on these findings, it appears that limiting paints to less than 1% of overall part mass is indeed an effective strategy for improving the recyclability of plastic parts. 4. Avoiding molded-in or glued-on metal parts Before a plastic component can be recycled, all attached metal parts must first be removed. If a metal part cannot be removed easily, it can require extra labor and can thus make plastics recycling less economically viable. For the manual disassembly systems in this study, it was found that molded-in metal parts were the most problematic for recycling. The majority of plastics with molded-in metal parts were being landfilled, incinerated or targeted for low grade, mixed polymer recycling applications like pothole filler. The common justification for this was that it is nearly impossible to remove molded-in metal parts by hand and thus no other recycling options exit. Glued-on metal parts, however, may not be a problem if they are designed for easy removal. It was found during the interviews that if glued-on metal parts can be quickly pried away or popped off, that they do not present a serious obstacle to plastics recycling. Thus these findings suggest that avoiding molded-in metal parts is indeed a highly effective DFR strategy, but that glued-on metal parts can be acceptable if they can be easily removed. This study also found that both molded-in and glued-on metal parts might not be a problem for automated plastics sorting systems. Automated sorting systems typically grind all plastic components into small flakes, which are then run through a series of magnets and eddy currents to remove any metal contaminants. In fact, in a recent recycling pilot study using automated plastics sorting equipment, plastic parts containing up to 25% metals by weight were accepted for recycling [9]. Thus for automated sorting systems, molded-in or glued-on metal parts appeared to offer no major problems for the plastics recycling process. 5. Use of one color per polymer Using only one color for all plastic parts of the same polymer type on a computer is intended to increase the volume of single polymer, single color plastics for recycling (which is the highest revenue recycling option). For both manual and automated plastics sorting systems in this study, however, it was found that it was rare to encounter a high volume of single polymer, single color parts in any batch of computer plastics. This was due to the high heterogeneity of the typical batch of computers for recycling. Only two interviewees were sorting plastics by both polymer type and color in this study, and it was found that this practice was limited only to the high volume plastics in a given batch that fell into one of two common computer colors: black or computer beige. The rest of the polymers in a typical batch were not being recycled into single polymer, single color applications due to lack of sufficient volumes, and thus the color of those remaining polymers did not make a difference. An OEM s choice of both polymer type and color must therefore be present in high quantities in a heterogeneous batch of computer plastics to be recycled into single polymer, single color applications. As described in Item 2 of this section, the random nature of the polymer composition in a typical batch makes it difficult to ensure that any one polymer type will be consistently recycled. Because color adds an extra degree of variation, it is even more difficult to ensure that any one color of a given polymer type will be recycled in most batches. Given the wide range of color/polymer combinations that are used throughout the computer industry, a common view expressed during the interview process was that colors for each polymer type would have to be standardized at the industry level in order for this DFR strategy to be truly effectual. Because this level of control is unlikely in a market economy, several interviewees advised that color should not be a priority for computer plastics. This study therefore found that using only one color per polymer type on a computer does not guarantee improved recyclability. This DFR guideline was thus not found to be a universally effective strategy for improving the recyclability of plastic components. 6. Use of snap-fits Although snap-fits are generally perceived to promote faster disassembly for computer components, this study 8

5 found that snap-fits are not always preferable to threaded fasteners for ease of disassembly. For the manual disassembly operations in this study, six of fourteen disassemblers preferred threaded fasteners over snap-fit connections. Those who preferred fasteners found that it was generally faster to use a power tool throughout the entire disassembly process and disliked having to set the tool down to disconnect snap-fits by hand. Thus because snap-fits do not always speed up the manual disassembly process, it was found that snap-fit connections for plastic parts are not always effective for improving their recyclability. For the automated disassembly systems in this study, it was found to make no difference if plastic components were connected via snap-fits or threaded fasteners because the plastics were separated using destructive techniques. However, the use of threaded fasteners can sometimes produce small pieces of plastic with metal fasteners still attached after the shredding process. For automated plastics sorting systems, it was found that this sort of metal contamination posed no problems for plastics recycling because fasteners can be removed during the grinding and metals removal processes. Thus, the use of snap-fits was not found to be an effective strategy for improving the recyclability of plastic components for either automated disassembly systems or automated plastics sorting systems. VII. FUTURE TRENDS Because the delay between when a computer is purchased and when it is recycled can often be as much as a decade 1111, it is important that DFR strategies consider not only current recycling practices but future recycling practices as well. An additional goal of this study was therefore to determine how the recycling process for plastics is likely to change in the next ten to fifteen years. For disassembly operations, a frequent prediction made during the interview process was that automated disassembly systems were likely to replace manual disassembly systems in the future. It was found that this change will likely be driven by two important economic trends. First, it was found that due to the rapid pace of technology, disassemblers are becoming less able to resell computers and components over time because these items are becoming increasingly less valuable. And second, it was also found that the precious metals content in circuit boards is declining steadily [6] and thus disassemblers are also experiencing declining profits from circuit board recycling. Because component resale and circuit board recycling were found to be the highest revenue items for disassemblers, their operations are likely to become increasingly dependent on low revenue items like plastics recycling in the future. Due to steadily rising labor costs, many disassemblers predicted that automated disassembly systems would be the only viable way to process these low revenue items profitably in the future. An important implication of this prediction is that a shift to automated disassembly systems would necessitate the use of automated plastics sorting systems for recycling the shredded plastics. It was also predicted during the interview process that automated plastics sorting systems were more likely to be employed in the future than manual plastics sorting systems. A common justification for this prediction was that it is often difficult for manual plastics sorting systems to be profitable given high labor rates and the high heterogeneity of computer plastics. Initial support for this prediction was also found in the published literature. In a 1997 study, a panel of 67 recycling experts were asked to forecast the most likely recycling technologies for the future [12]. 80% of these experts predicted that automated plastics sorting systems would be both technologically and economically attractive by the year And, in a 1999 study of manual versus automated plastic sorting systems, results suggested that the most economical approach to plastics recycling was to shred all computer plastics together and to sort them using automated techniques [7]. Although it is impossible to predict the future, these findings suggest that it is likely for both automated disassembly systems and automated plastics sorting systems to be in more widespread use in the next ten to fifteen years. The implication of this trend for computer manufacturers is that DFR efforts aimed at improving the recyclability of plastics for manual systems may be increasingly less effective as time goes on. VIII. PRIORITIZATION OF DFR GUIDELINES Based on the findings of this study, a suggested prioritization of DFR guidelines for plastic components is offered in Table 4. Each of the six DFR guidelines considered in this study has been assigned an effectiveness rating for both manual and automated systems, based on the assessments which have been provided in Section VI. Those DFR guidelines that were found to be highly effective for either manual or automated systems have been assigned a high design priority because of their observed ability to promote increased recyclability for plastic components. Conversely, those DFR guidelines that were found have questionable effectiveness for either manual or automated systems have been assigned a low design priority, as return on design effort is not guaranteed. 9

6 Table 4. Prioritization of DFR guidelines for plastic components DFR ## Guideline 1 Use of IS0 labels Use of snap fits Medium where possible *for molded-in metal parts only Effectiveness for: Manual Automated Design Systems Systems Priority High None High None Medium Although this study found that automated systems are most likely to be predominant in the future, a conservative approach was taken to assigning the design priorities in Table 4. Because of the inherent uncertainty in forecasting the future, a prudent approach is to continue those DFR efforts that are effective for manual systems until the transition to automated systems is more certain. An interesting observation, however, is that Table 4 shows that only one DFR guideline is likely to be highly effective in the future when the transition to automated systems occurs. IX. CONCLUSION Design for recycling is an important environmental management strategy for computer manufacturers. However, DFR efforts can require a significant investment of time and resources and can also compete with other important design requirements during the product design phase. It is therefore advantageous to focus DFR efforts on those strategies which are most effective for improving product recyclability. The current paper has shown that several DFR guidelines for computer plastics are not always effective for improving the recyclability of plastic components. The assessment and prioritization of DFR guidelines provided here can be used to help prioritize design for recycling strategies so that both product recyclability and design productivity are maximized. REFERENCES [ 11 Bosweil C, Defining Electronics Recycling in Goldberg LH (Ed.), Green Electronics, Green Bottom Line: Environmentally Responsible Engineering, Newnes Publishing, Boston, [2] American Plastics Council, A Design Guide for Information and Technology Equipment, Arlington, VA, [3] The Swedish Confederation of Professional Employees, TCO 99 Certification: Ecology for Displays, Portable Computers, System Units and Keyboards, Report No. 5, Edition 2,2000. [4] Basic Criteria for the Award of the Environmental Label: Environmentally Acceptable Workstation Computers RAL-UZ 78, RAL Regulatory Association, Germany, January [5] Dillon PS, Aqua EN, Recycling Market Development for Engineering Thermoplastics from Used Electronic Equipment, Chelsea Center for Recycling and Economic Development, University of Massachusetts, Technical Report #20, March [6] Biddle MB, Mann R, Recipe for Recycling, IEEE Spectrum, August [7] Arola DF, Allen LE, Biddle MB, Evaluation of Mechanical Recycling Options for Electronic Equipment, Proceedings of the IEEE Symposium on Electronics and the Environment, May [8] Hainault T, et a1, Recycling Used Electronics: Report on Minnesota s Demonstration Project, Minnesota Office of Environmental Assistance, Saint Paul, MN, [9] American Plastics Council, Plastics from Residential Electronics Recycling Report 2000, Arlington, VA, April [10]Biddle MB, Christy RM, Here Today, Here Tomorrow: Challenges of Recycling Engineering Thermoplastics, Proceedings of the IEEE Symposium on Electronics and the Environment, May [ 111 Matthews HS, Disposition and End-of-life Options for Personal Computers, Green Design Initiative Technical Report #97-10, Camegie Mellon University, Pittsburgh, PA, [ 121 Boks CB, Tempelman E, Final Report of the Delphi Study on Future Disassembly and Recycling Technology for the Electronics and Automotive Industry, Technical Report, Delft University of Technology, April \ 10