Framework for Systematic Evaluation of Life Cycle Strategy by means of Life Cycle Simulation.pdf
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EcoDesign2003/1 B-8 Proceedngs 01 EurDeslgn2003 Third lnlernanonal Sympasun on Env ronmenlaiy Canwlods OeSlgn and Inverse Mandamunng Takyo. Japan. December 8.11.2003 Framework for Systematic Evaluation of Life Cycle Strategy by means of Life Cycle Simulation Shozo Takata Waseda University fakatawasedajp Tomoyuki Ogawa Waseda University ogawatof&.mgmt.waseda.acjp Abstract In this paper, afiamework of evaluation of theproducf life cycle in the closed loop manufacturing is discussed The fromework provides a proeedure IO orgonize a system of environmenfal indicators and to c a m out the evaluation in the process of designing product life cycler in fhe closed loop manufactwing. For consmrcting the system of indicators, a structured set of basic indicators is proposed If consists of “goal” indicators and “measwe” indicators. The m e m e indicators are related to fhe life cycle options, which should be selected according to the product life cycle snategy represented by the goal indicafors. The relafionship between huo sets of indicators can be analyzed by mea& of I cycle simulation combined with Ire cycle assessment. .The paper also presents an illusnorive eUrmpIe of consmrcting fhe system of indicators and the analysis of product life cycle of mobile phones by means of the l i f e cycle simulation. This ample indicates compler relations, between the goal indicators and the memure indicators and fherefore, implies thaf the. life cycle simulation is quite useful for supporting the life cycle design 1. Introduction . Since the Industial Revolution, we have been improving our quality of life by m& of mass production, which have induced mass consumption of natural resources and energy, and mass disposal. However, the scale of ow industrial activities has already become beyond the limit. We m o t continue to c o m e resources and energy, and to dispose of waste without consideringtheir exhaustion and overflow any m o r e . The closed loop manufacturing, therefore, has been proposed as one of the solutions to the problem. The concept bebind it is to change ow goal in manufacturing *om “bow efficiently we can produce products” into “how we can avoid to produce products while keeping customers satisfaction and corporate profits.” For realizing close loop manufacturing, we need to design and manage the Yasushi Umeda Tokyo Menopolifan University ume&-yasushic.mer-uacjp Tomoya Inamua Tokyo Metropolitan University inamuraecomp.metro-u.acjp product life cycle in a proper way. It is, however, not easy to design the product life cycle that is environmentally friendly as well as economically feasible. One of the reasom is that we still lack for a systematic daigo method of the d u c t life cycle so as to achieve these goals, although a number of technologies have been developed associated with 3”R”s (reduce, reuse. recycling) so far. For establishing the design method of the product life cycle, we need evaluation methods of product life cycle smtegy. In this research, we propose an evaluation h e w o r k in terms of a systm of indicators, which are organized to fit a specific product life cycle, as well as a life cycle simulation, wbicb simulate dynamic behavior of the closed loop mufacming system. In the following, an overview of envimnmentd indicators and their issues are given iirst. Then we present the b e w o r k for evaluation of Droduct life cvcle. . , Finally, the life cycle simulation system developed as a general tool for the product life cycle evaluation is described. 2. Environmental Indicators For the environmental evaluation of manufaauriog activities, many indicators have been pmposed so Eu. Among them, the indicator, which shows the final objective of the life cycle design, can be represented as Eauation (1) 141. . I . . Satisfaction of the whole society T o t a l environmental loads global pmductivity = (1) Various concepts of global indicators similar to t h i s equation have been proposed, including Factor IO, Factor 4 5, and Eco-efficiency 6. While these concepts directly represent Quation (l), it is not clear bow to measure and evaluate. We can point out two reasons for this problem. One is the difficulty to evaluate and to quane satisfaction of the society, represented as the numerator of Fquation (1). The other mmes from the diffculty in determining essential elements of envi”ental loads, the denominator of Equation (l), and their weighs in general form We the latter issue is 0769520460 0 Z O X IEEE - 198 - under discussion among specialists of impact analysis of LCA (Life Cycle Assessment), general conclusions have not been obtained. It is, therefore, difficult to use such global indicators for the evaluation of the product life cycles under present condition. With the progress in environmental studies, various more practical and quantitative indicators have been proposed. Among them, the most standardized and practical framework might be LCA (e.g. I). Besides, recycling indicators such as recycling rate and potential recycling rate are discussed in the context of recycling related legislations. The report of World Resource Institute Z collects a wide variety of envir6nmental performance indicators and classified them into four categories; viz, materials use, energy consumption, nonproduct output, and pollutant releases. While these indicators represent environuienral characteristics of the manufactruing system from various points of view, there is no h e w o r k to organize these indicators in such a way that they can be used effectively for the life cycle design. “Environmental accounting” (e.g., 3), which evaluates financially the balance between paid envimnmental costs and gained environmental performances, provides a certain type of the evaluation hework. However, in the narrow sense, it evaluates effects of environmental costs that are regarded as additional costs on those for essential business activities. Therefore, it is not an appropriate tool for the life cycle design, which should be the essential business activities in the closed loop manufacturing. The above-mentioned indicators can be classified into two categories; one is “goal” indicators that represent environmental goals to be achieved associated with enterprises or products, and the other is a ?masure” indicators that evaluate effectiveness of life cycle options (viz., reduce, remanufacturing, reuse, recycling, maintenance, final dumping, and so on) in circulations of products, parts and material. The global indicators and environmental performance indicators are categorized into the former. Examples of the latter include the recycling indicators. In addition to the lack of liamework for utilizing the indicators in the life cycle design, an issue addressed in this research is the fact that there is no systematic meens to relate these two categories of indicators. Another issue is the lack of indicators for evaluating circulation of produdpartslmaterial. For example, while LCA is quite effective and practical tool, it cannot directly represent and evaluate circulation. Environmental performance indicators also do not directly deal with the circulation. While the recycling indicators aim at representing and evaluating the circulation, current indicators are not sutfrcient for evaluating remanufachuing and component reuse, which are the key life cycle options. I 3. Framework for Systematic Evaluation of Life Cycle Strategy 3 . 1 . Indicator system For designing product life cycle in light of the corporate strategy, we have to evaluate it from various points of new, such as economic efficiency, environmental load and customer satisfaction. For tbis purpose, we need a proper set of indicators, which satisfies the following requirements. a) The set of indicators should be SinIctured in such a way that both goals to be achieved such as reduction of environmental load and methods to be adopted such as 3”R”s can be evaluated. In particular, indicators for evaluating circulation of products, parts and material are needed for designing the closed loop manufactur- b) The set of indicators should be effective to prioritize the technology, which should be developed for realizing closed loop manufacturing and consequently achieving environmental improvement c) The set of indicators should enable the evaluation of the product life cycle in line with the corporate strategy for ensuring profitability as well as environmental improvement Taking the above requirements into accounG ve propose to organize basic indicators as shown in Figure 1. The upper part of the figure shows “goal” indicators associated with overall strategies such as corporate strategies, product development strategies and environmental policies. For clarifying the purposes of the indicators, they are classified into several categories corresponding with the type of goals, such as resource, waste, energy, emission, value and economy. The lower part of the figure shows “measure” indicators, which are related with the life cycle options to be selected for realizing the life cycle strategy, such as reduce, rme, maintenance and recycling. These indicators are %sic” in the sense that they are essential regardless of product types; in other words, a system of indicators specialized for each product life cycle design is derived from tbis generic set of basic indicators. For making use of the indicators in designing the product life cycle, we need to stnrcture a system of indicators in line with the product life cycle strategy. Considering complexity of the problems in designing h e product life cycle, it is difficult to provide the system of indicators, which is generally effective for evaluating any types of products. The approach proposed in t h i s study, therefore, is to provide a general procedure for Constructing the system of indicators from the basic indicators shown in Figure 1 and for evaluating the partkxlar product life cycle. This approach is ing systems. - 199 - Figure 1. Goal and measure basic indicators disadvantageous in that it becomes diffcult to compare prcduct life cycles, which are quite different with each other. In our opinion, however, it is more important to provide a realistic evaluation system, which could facilitate the realization of the closed loop manufacturing, rather than to pursue generality at present. For evaluating the product life cycle based on the system of indicators, it is necessary to provide means to relate measure indicators to goal indicators. If you adopt a reuse option to reduce CO2 emission by 20%, for example, you may need to know how much should he a iate of reusable parts in order to achieve the goal in designing the product LCA is a well-known method for evaluating the amount of emission However, LCA itself could not provide the rate of mated circulation by meam of, for example, part reuse. It depends on various factors such as failure rate of the parts, the market life of the product, and the efficiency of the collection system. The relatioukhi between these factors is complicated and cannot be represented by a simple mathematical model. To cope with this difficulty, we propose to use socalled life cycle simulation (e.g., 7 - 9 ) , by which various types of circulation of products, parts, and material are evaluated. 3 . 2 . Evaluation procedure of l i r e cycle strategy The following is a proposed procedure to colstruct the system of indicators and to evaluate the product life cycle based on it in the process of the product life cycle design. Refer to Figure 2 BS an example of the system of indicators, which is derived from the basic set of indicators shown in Figure 1, in the case of a hypothetical personal computer. a) The corporate environmental sbategy and the environmental goal of ea& product life cycle should be represented by a set of goal indicators as shown in the upper part of Figure 2. These goal indicators can be organized by selecting the basic indicators l i s t e d in the upper part of Figure 1. They may include compound indicators derived f r o m multiple basic indicators. b) With the assistance of the life cycle simulation and the life cycle assessment, the life cycle scenario of the product should be generated by selecbing proper life cycle options so as to achieve the goal as shown in the middle part of Figure 2. At the same time, the set of measure indicators are organized using the basic indicators as shown in the lower part of Figure 2 so as to represent the behavior of the product life cycle and to evaluate the level of realization of the life cycle scenario. c) Foduct and process design are executed according to the life cycle scenario. The results are checked whether the desiaed Life cycle meets the oxprate -m- . Envhonmenul svltegy of company A r50% ofmetlma ( l e n c y IHefima efficiency = vdua llfedms / phyrlsal Inelme Figure 2. An example of the system of indicators applied to PC sintegy and enables the attainment of the goal of the product life cycle. If necessary, technological development is carried out in order to realize the designed life cycle. d) The designed life cycle is realized. e) The data is collected from the actual life cycle. Whether the goal could be achieved is checked with the established systems of indicators. If there are some problems, corrective actions are taken 4. Life Cycle Simulation 4.1. Requirements for life cycle simulation system To evaluate the environmental load during the closed- loop product life cycle as a whole in terms of material consumption, waste disposal, CO2 emission, etc., we need to h o w productlpdmaterial circulation taking reuse and recycling into account LCA alone does not deal with the effect of such circulation. We have, therefore, developed the life cycle simulation system, which can simulate produdparthaterial circulation in the closed loop mufacfiuing according to the designed product life cycle scenario. The results of the life cycle simulation can be used for LCA to obtain the total environmental load during the product life cycle. Recently, several life cycle simulation systems have been developed (e.g., 7-9U. However, they are specific to particular research purposes and had limited functions. It is necessary, therefore, to develop a life cycle simulation system, which is more powerful and can be used as a general tool for life cycle design. In order to be an effective tool for life cycle design, which can be adapted to various life cycle scenarios, the life cycle simulation system should have a capability of modeling both products and processes i n a flexible manner. The following are important requirements for the life cycle simulation system. a) The system should be able to represent various circulation paths such as repair, product reuse, part reuse and material recycling, and it should have a means to conml the material flow in these paths. b) Products and parts should be modeled independently and their relationships should be defmed so as to enable various reuse policies. c) Usage histories of parts should be maintained independently of products so as to deal with degradation of reused parts. d) Since different bodies could operate the processes such as production and disassembly, each process should be modeled =.an independent module with its own conwol system. e) The system should be able to deal with a sufficiently large number of products and par& for the staristical analysis. 4.2. Configuration of the life cycle simulation system The life cycle simulation system has been developed in accordance with the requirements mentioned in the previous section. The system simulates the circulation of products and parts as shown in Figure 3 based on discrete simulation techniques. Production, sales, and usage are defined as arterial processes. Repair, reconditioning for product reuse, and disassembly and reconditioning for part reuse are defined as venous processes. The simulation system consists of 3 subsystems: a parameter setting subsystem, an execution subsystem, and an output subsystem. In the parameter setting subsystem, product configurations are specified. This includes sucb factors as periods of sales of each product, product-part relations, and part reuse policies. Parts may be reused in a product family within the same generation or across several generations. For each type of parts, a failure rate function is defined in terms of a Weibdl distribution for simulahg occurrences of failm. Obsolescence rate functions are defined for the product to represent the extent of discard because of users dissatisfaction with functions of the products. The obsolescence rate function is also represented in terms of a Weibdl distribution In addition, the obsolescence rate can be changed stepwise when a period of sales terminates or a new model 3 put on the market. The execution subsystem consists of two modules: a simulation engine module and a procks control module. The simulation engine module realizes the flow of products and parts through the life cycle processes, while the process contml module controls the flow of each process. Users of the system can implement various control algorithms in the process conml module. Figure 3. Life cycle processes deflned in the life cycle simulation system 5. An Example of the life cycle simulation applied to the life cycle design To demonstrate the effectiveness of the life cycle simulation for the life cycle design, we have conducted the life cycle simulation of mobile phones to evaluate tha potential effects of part reuse and recycling on decreasing the environmental load. Since the objective of thi!, example is to show the capability of the life cycle simulation for compariag various life cycle scenarios, we do not take the possibility of realization of the scenario; into account seriously in this example. In this example, we have selected total CO2 emission and resourcc consumption as the global indicators, and the following measure indicators. By executing the simulation, we discuss complex relations among them unctional lifeof the product, . - Physical life of parts, - Rate of reused parts dispatched to production RP), and Life utilization rate of parts CUR). H e r e , RRP indicates the rate of reused parts dispatched to production, to total amount of parts required to production. LUR indicates the extent to wbicb the total life of the part has been utilized (see Equation (2). LUR= average usage time p part / MTTF (2) 5.1. Simulation conditions We assume four kinds of life cycle scenarios for major parts of mobile phones, wbicb are PCBs rioted circuit board), LCDs (liquid crystal display), batteries and cases as shown in Table 1. We suppose that there are two product models in each product generation: one is an upper grade model and the other is a IOWR grade model. In this example, we consider three product generations as shown in Figure 4. Scenario .#l is a conventional one, which is regarded as a baseline. In scenario #2, closed loop recycling i s adopted for all parts. In scenario #3 and #4, part reuse is applied to PCBs and LCDS, while recycling is applied to batteries and cases, which may rapidly deteriorate during usage and not fit with reuse. Parts can be reused in the products of the same generation in scenario #3. In scenario #4, the parts of the upper e model can be reuse in the lower grade model of the next generation as well. For each product generation, the term of the production is set to one year. The production is executed to meet the demand of 2600 products of each model par day. This means that the total number of sold products is about 26003656a5,700,000. -mz- Table 1. Life cycle scenarlos 0 I 2 3 (Yean) Figure 4. Product generations and part reuse strategy A product is thrown away when the product is obsolete in terms of its fimctionality or one of parts is broken. Both of them are modeled by using the Weibull diwiiution curves. Functional life of a product is represented as a Weibull curve with m = 8 and r) = 1 4 5 W ours), of which B50 life is about 1.6 year. Therefore, we set the warranty period of each product as 1.6 years, which means that we do not reuse parts of which remaining lifetime is less than 1.6 year. Physical life of LCD is represented as Weibull curves with m = 4 and r) = 75825 ours). of which B10 life is about 5 years, and physical life of PCB has 4.5 years of B10 life with m = 4 and r) = 68243 ours). Environmental load is evaluated in terms of the amount of CO2 emission and resource consumption. CO2 emission rates and resome consumption rates at each life cycle processes are estimated based on E M - L C A lo (see Table 2). H e r e , we assume that reuse of PCB and Table 2. Data of CO2 and resource consumption LCD can reduce CO2 emissions i n t o 35% of their parts production as shown in this table. 5.2. Simulation results Figure 5 shows the total material consumption in each scenario under the conditions described in Section 5.1. Recycling is effective to reduce the material consumption, because about 40% of material necessary for production can be supplied by recycling when closed loop recycling is adopted as in scenario #2, #3 and #4. In scenario #3 and #4, 0.5% and 14% of the parts dispatched to the production are reused parts respectively as shown in Figure 6. Let us d l these rates rota of reured parts dispatched to production (RRP). However, PCBs and LCDs, which are reused in these scenarios, account for only 11% of total material of a product Therefore reuse does not cont-ibute to the reduction of material consumption significantly as shown in Figure 5. Figure 6 suggests that part reuse among multiple generations is indispensable in this type of products, becausepart reuse in one generation (scenario #3) i s almost meaningless in this setting v.5 %). With regard to CO2 emission, recycling is not effective to reduce the emission as shown m Figure 7. because CO2 emission rates of recycling processes are not significantly smaller than production processes. Therefore, we can say that, as far as this case study is concerned, reuse among multiple generations is more effective for CO2 reduction than recycling, while recycling is more effective for reduction of material consumption The time until 50% of prod& are h w n away -203 - 450 : - E 4w 6 350 /I E zw 2 IS0 5 I w 5 50 O1234 Scenario No. Figure 5. Total material consumption Figure 6. Rates of reused parts dispatched to production (RRP) 8O.W ! 12.3 4 Scm-No. Figure 7. CO2 emission 40 35 30 2 5 8 B I5 IO 5 0 1 . 6 1.4 12 1 . 0 h”al life of pmmw (yun) Figure 8. RRP and CO2 M. functional life In order to understand complexity of the relatiom; between the goal indicators and the measure indicators, let us consider the effect of RRP on CO2 emission in scenario #4. When the average functiol life of the product is reduced fiom 1.6 years, which is the original setting, to 1.4; 1.2, and 1.0 year, products are taken back rapidly and RRF apparently increases as shown in Figure 8. T o t a l CO2 emission, however, also increases. (This amount of CO2 emission in each case is normalized to t h i : value per one hour usage of the product.) The reason of this result can be understood by evaluating the life utilization rate of parts (LUR), which is defined at the beginning of Section 5. Figure 9 shows the change of LURs with the change of the functional life. The LURs decrease w i t h the reduction of functional lives. This means that more parts are needed for the same period of usage time. In these cases, however, we assume that parts have enough physical lives compared with functional life of the products. If the physical lives of PCBs and LCDs are reduced to 2.8 years compared with 4.5 and 5 years, which are the original setting. Figure IO shows the change of LUR against the functional life. LUR increases because of shorter physical lives and has a large value at 1 . 2 years of the functional life, because most parts can be reused On the other hand, 1.4 y$ar of the functional life is too long for using the pam twice because the warranty period of the product is 1.6 year. In this case, as shown in Figure 11, RRPs are smaller t h a n those in the original setting (Figure 8) and CO2 emissions are larger when functional lives are 1.6 and 1.4 years. However, CO2 emissions in 1.2 and 1.0 years are almost the same as those in the original setting. As shown in this m e study, there are non-linear and complex relationships between measure indicators and goal indicators. Therefore, the life cycle simulation, ,which clarifies quantitatively these relationships, is i i effective tool for designing product lie cycles. 6. Conclusion In this research, the h e w o r k for the evaluation of product life cycles in tams of environmental indicators is discussed. The framework provides a procedure to organize a system of environmental indicators and to carry out the.evaluation in the process of designing a product life cycle in the closed loop manufacturing. For constructing the system of indicaton, a shucfllnd set of basic indicators is proposed It consists of “goal” indicators and “measure” indicators. The measure indicators are related to the life cycle options, which should be selected according to the product life cycle mtegy represented by the goal indicators. Although it is nffiessq to clarify the relations between the goal and measure indicators in designing the product life cycle, they cannot be modeled in a simple mathematical form 1.6 1.4 1 . 2 , 1.0 haional lire of pmducu (yean) Figure 9. LUR vs. functional life 58 , 1.6 1.4 1.2 1.0 flmaional life Of prcducu (yean) Figure 10. LUR vs. functional life (shorter parts lives) 1.6 1.4 1.2 1.0 flmctiansllifc Ofprodwcl (Yeala) Flgure 11. RRP and CO2 vs. functional life (shorter parts lives) because of an enormous number of facton involved in the relations. We, therefore, pro
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