Towards Inverse Production Life Cycle Design: a Simulation Tool Linking Mass Products Recycling to Environmental Legislation and Market Francesco Jovane1, Roberto Bosani1, Lorenzo Castelli2, Fabio Salsa 1
Institute of Industrial Technologies and Automation (ITIA) Italian National Research Council (CNR) V.le Lombardia 20/A, I-20131 Milano (Italy) e-mail:
[email protected] [email protected] 2
DEEI – University of Trieste Via A. Valerio 10, I-34127 Trieste (Italy) e-mail:
[email protected] Abstract Recycling costs of mass products depend on the technology adopted, size of plant, quantity being recycled, constraints imposed by environmental legislation on process and output (materials, components and energy recovered). The value of output depends instead on market factors. To obtain a profitable recycling process the relationship between: products to be recycled, technology, plant size, output, legislation and market must be known. Consequently, providing a tool embedding such a relationship would enable the various partners – from legislators to companies, to research people – to act in order to efficiently and effectively implement the cycle. The aim of this paper is to present the research work carried out by ITIA, in cooperation with DEEI, to develop a tool responding to the needs mentioned above. To this end an Inverse Production Design Tool (IPDTool) has been conceived and developed. It is based on: - the modelling of entities such as in/out product, market and regulations; - an IDEF0 model of the Inverse Production Plant; - a mathematical model to provide appropriate input for the simulation; - a simulation model based on the above. The IPDTool developed has been validated and used to assess the economic viability of an Inverse Production Plant in Italy. The results obtained show the usefulness of the IPDTool developed for Inverse Process designers and managers, product designers, legislators “designing” ecological laws and norms, scientists aiming at developing new Inverse Processes and related enabling technologies. The research work presented is a part of a research programme on Sustainable Production and Inverse Production Life Cycle Design in progress at ITIA-CNR. Paradigms developed for production will be studied in connection with Inverse Production to respond to changes in market, ecological constraints, technology.
1. The problem The continuous growth, in the last decades, of the standard of living of industrialized countries has lead to a large diffusion of durable goods, from new (i.e., cellular telephones, video recorders, cameras,...) to traditional ones (i.e., television sets, washers, refrigerators). The renewal of traditional durable goods leads, every year, to the disposal of domestic appliances whose number is in excess of 108. To comply with sustainability requirements [1], Inverse Production will have to be adopted more and more. It should avoid: • landfill conferment; • environment dispersion of the toxic substances contained into the appliances; • loss of reusable materials contained in the durable goods. Various Inverse Production Technologies have been developed. Numerous plants, based on them, are operating in various countries. For Inverse Production to be economically selfsustaining, it is necessary that the recycled material value on the market be higher than the Inverse Production costs while complying with ecological constraints. These costs depend on: • one side on technological aspects such as process technology adopted, plant size, etc.; • on the other side, on the existing environmental legislation, which may impose the characteristics of the final recycled material as well as constraints on the Inverse Process. Hence for Inverse Production to be economically selfsustaining, environmental laws, Inverse Process Technology and recycled material market value, must appropriately match. To design/assess such matching, a tool is required linking environmental laws, Inverse
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Processes Life Cycle
DESIGN PROCESS
DISPOSAL & INVERSE PRODUCTION
IMPLEMENTATION PROCESS
USE & MAINTENANCE
• • • •
market and ecological regulations have been modelled using numerical tables and mathematical constraints; in particular to avoid the problems related to the heterogeneity of the durable goods that have to be recycled, in this work we considered an average refrigerator [6] with an average weight estimated on the basis of historical treatments in the plant and the percentage composition in weight shown in the figure 2. An Inverse Production Plant has been modelled using IDEF0. A mathematical model has been developed to provide appropriate input for the simulation. A simulation model based on the above has been conceived and implemented. Validation of the specific IPDTool developed has been carried out using actual data from the Inverse Production Italian Plant. STEEL 59.65% ALUMINUM 3.9% COPPER/BRASS 3.19% PVC 1.99% PLASTICS 15.19% POLIURETHANE 6.87% GLASS 0.02% OIL 0.88% CFC 1.23% OTHERS 7.08%
Product Life Cycle
DISTRIBUTION
RECONFIGURATION PROCESS
R&D
PRODUCTION
USE PROCESS
DESIGN
DURABLE GOODS LIFE CYCLE
Process Technology, recycled material properties and market value. This paper presents the results of a research work carried out by ITIA, in cooperation with DEEI, aimed at the development of an IPDTool, linking mass products recycling, environmental legislation and market. Such a tool could be useful for Inverse Process designers and managers, product designers, legislators “designing” ecological laws and norms, scientists aiming at developing new Inverse Processes and related enabling technologies. The work is a part of the ITIA research programme on Sustainable Production which has covered from the emerging paradigm [2], to the role of research, to new production and design concepts [3] and their application to Inverse Production. The ITIA reference model for Sustainable Production is shown in figure 1.
Fig. 2: weight composition of the average refrigerator •
Fig. 1: product and related process life cycle matrix [4] New research work is being carried out – within the above Program on Sustainable Production – on Process Life Cycle considering Production and Inverse Production. The Agile Paradigm, developed for Production is being studied in connection with Inverse Production. Flexibility and reconfigurability [5] are being studied as a response to, respectively, tactic and strategic changes in market, ecological constraints, technology.
2. Towards a life cycle process design
•
The IPDTool developed has been used to: - assess the economic viability of the actual plant versus changes in in/out product, market prices, ecological regulations; - give suggestions for redesigning the plant. The usefulness of the IPDTool developed for industry, legislator, research has been accomplished.
2.1 Modelling in/out product, market, ecological regulations and Inverse Production Plant The Inverse Production Plant for refrigerators and freezers used as a test bed has been modelled using the IDEF0 methodology (see Fig. 3). Norms
Law Re-usable parts
A fundamental step towards process life cycle design is the availability of an appropriate Inverse Production Design Tool. Hence, an IPDTool based on simulation and responding to the aforementioned requirements, has been conceived and developed considering, mainly refrigerators and, as a test bed, an Italian Inverse Production Plant for white goods along with the Italian related ecological regulations. As reported in the following paragraphs: • Entities such as in/out products (respectively durable goods to be disposed and recyclable materials),
Scraps Refrigerators
Recovery/ Recycling
Compressor Frame
A0
Toxic Emissions Recovered Materials Human Resources Energy
Machines
Fig. 3: the IDEF0 context diagram (A-0)
2
A
B
D
E2
E1
C
Fig. 4: Inverse Production Plant layout The plant is composed by six macro-sectors (and the IDEF0 model reflect this structure): • Storage of the appliances on a large open square adequately equipped to collect the fluid that could be dispersed because of the movements. • First treatment of the refrigerators (weighing of the goods, separation of mobile parts). All the components extracted during the first treatment phase are stocked in appropriate containers for their selling or bestowal to recyclers or external specialized disposers. • Reclamation of the refrigerators with the recover of technical liquids (cooling gases, CFC12 and lubricating oils). These liquids must be accurately stocked in watertight containers to be bestowed to specialized disposers. • Separation of the compressor. • Crushing of the treated refrigerators. A conveyor (Fig. 4, point A) carry the durable goods to the crushing room (B). A system of atmosphere neutralization (C) avoid the explosion in the camera. • Separation of the crushed materials. A system of transport (D) extracts the crushed material and convoys it towards the selection and final separation system (E1, E2). At the end of the process we therefore obtain homogenous material ready to be reused upon the quality, the homogeneity, the economic convenience and/or the existing legislative constraints. After the process modelling, we have developed the economic analysis of the activity considering: • Annual amortization of the machinery. • Rental for the area in which the plant is located. • Costs of the personnel. • Financial costs. • Operating costs (book keeping activity + unexpected events). • Costs of working (maintenance, energy, heating, materials of consumption). Three main steps of the Inverse Process have been considered: • Pre-treatment. • Crushing. • Selection phases.
Through a process costing analysis, the extraction costs for a kg of every material have been defined. They depend on: • Amount of appliances dealt in one year. • Apparatus typology (i.e., domestic, commercial refrigerators and pre-treated frames already set in security) and corresponding weight. • The necessary operations for the extraction process. Since the same budget of expenses is allocated to a more or less wide volume of apparatuses, these costs may considerably vary. The economic budget of the activity is conceptually expressed by the equation (here simplified): Budget = Revenue from refrigerator withdrawal + Revenue from material sales – Disposal Costs – Extraction Costs
2.2 Non-linear programming model A mathematical model has been developed to determine the Inverse Production Mix which maximize the economic balance. Let x1, x2, x3 be respectively the number of domestic, commercial and pre-treated refrigerators (frames) recycled in one year. Weight composition of every appliance is divided in 20 different parts. We associate an economic value to every weight unit ci, i=1,...,20 where ci≥0 if it is possible to recover and re-sell that part. If, on the contrary, the part have to be disposed, it will be ci≤0. We define pij the weight of every part which compose the refrigerator, rj the price imposed by the enterprise for the appliance collection and ei the extraction cost for every Kg of the i-th part. Note that ei depends on the number of refrigerators treated in one year, more precisely: ei =
ki 20
3
∑∑p
ij
x
j
i =1 j =1
where ki is the extraction cost determined from the recycling process. It can assume only three different values: a0, a0 + a1, a0 + a1 + a2. We denote the deproductive volume with V: it is the minimum between real de-productive plant capacity and disposal demand, calculated annually. Hence economical balance maximization can be formalized in the following way:
3
20 3
3
max z = x1, x2 , x3
∑∑k p x
i ij j
20 3
∑r x + ∑∑c p x j j
i ij j
j =1
−
i=1 j =1
i=1 j =1 20 3
∑∑ p x
ij j
i=1 j =1
The decision variables are also subject to some constraints. First of all there is a constraint about the number of treated appliances: 3
∑x
=V
j
(1)
j =1
Then we have to introduce a minimum (lj) and a maximum (Lj) percentage about appliances to be recycled: lj ≤
xj
≤ Lj
V
∀ j.
(2)
We should also respect environmental legislative rules: 3
∑∑ p
3
≥ fm
ij x j
i∈I m j =1
∑∑ p i =1
ij x j
∀m
(3)
j =1
where Im is the set of those parts, materials and energy we must recover at least for the weight percentage fm (imposed by law). According to this percentage, we can determine the maximum waste quantity of the recycling process; it is fixed by Legislator and depends on product to be recycled and on process itself. At last, we have to consider non-negativity variables constraints. Note that the developed model is a non-linear programming model; its non-linearity depends on the extraction cost in the objective function. To solve this problem we use a classical technique introducing a parameter α defined as below: 20
3
∑∑ k p i
α=
ij x j
i =1 j =1 20 3
∑∑ p
(4) ij x j
i =1 j =1
Thus we have a new model in which the objective function is expressed as : 3
max z =
x1 , x2 , x3 ,α
∑
20
rj x j +
j =1
3
∑∑ c p i
ij x j
−α
i =1 j =1
Constraints (4) are added to the previous set of constraints, i.e., inequalities (1), (2), (3) and the nonnegative condition. The optimum value can be determined by a search in which iteratively we assign a value to α; in this way we have to solve step by step a linear programming model. The model was implemented in GAMS and solved using CONOPT [7] to determine an optimal solution.
2.3 Simulation The simulation model was developed using Simple++ (ver. 7.0) by Tecnomatix Technologies, a very suitable
tool to represent a productive (or de-productive) process, thanks to its peculiar object oriented structure. The model structure reflects the modularity and the hierarchical organization of IDEF0 representation, [8]. We use this technique to formalize all physical and informative fluxes involved in the recycling process and every model part (or function) can be exploded in one or more sub-functions. The simulation model consists of 13 modules (frames) in different levels [9]. As in the IDEF0 diagrams, the highest level frame (the context frame, A-0, fig. 3) contains all the others and transmits them inputs, controls and mechanisms that are necessary to the model to correctly working; it also gets the outputs generated by the subframes. The main frame into the Simple++ model represents the whole recycling activity; the Source generates the Entities, the Exits dispose them at the end of the process and some specific Tables collect the relevant reports of all the physical and economic flows. In particular, the legislative constraint satisfaction, estimated as the percentage of materials and energy that are effectively recycled, is monitored in the ‘LexCompliance’ Table. At the end of each simulation run, the simulator updates the information about all the process fluxes by means of the tables in the main frame. With simple arithmetic operations, the tables calculate economic value and assign extraction costs to every entity, thanks to SimTalk, the particular programming language included in Simple++, which increases stations control possibilities and permits to insert in the model all economic data. Along with the process profitability analysis, the simulation model has the aim to study the workload of every work station (and then of every area) facing many perturbations in the external conditions, to identify possible bottlenecks and to regularize refrigerator flux towards the crushing section. We collect statistics on three units: • Initial logistics (which comprehend refrigerators unload from suppliers, storage and drawing in/from the external large square). • Pre-treatment (security setting and components separation). • Crushing. The final phase (shattered materials selection and separation) is completely automated and historically free from break-downs. Since it doesn’t need particular analysis, we consider it always active and able to face every material flux coming from the shattering section. Statistics are collected in tables contained in the workstation blocks. At the end of each simulation run, the user can inquire into every station workload and decide whether it’s sustainable or not. In case of lack of balance, he can finally intervene on physical process. Generally, we consider a workload percentage of about 70% as an optimal result in case of manual operations, while in case of machinery (transporters, shatter and selection unit) it is
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important to saturate the resource with the highest possible percentage, until the (theoretical) maximum of 100%.
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Validation and preliminary analysis using IPDTool
Validation of the specific IPDTool developed has been performed using actual data from the Inverse Production Italian Plant. Several test runs have been performed covering up to one year of plant activities. Some inefficiency of the mathematical model have been ascertained. New mathematical constraints have been introduced thus obtaining good results. Inverse Production Volume and input refrigerators volume were identified as decisional variables and external factors which could sensibly influence the economic performance of the plant. Market prices and costs, considering that their oscillation in the shortmedium period are contained within +/- 10%, do not contribute to a sensible alteration in the economic balance.
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Assessment of the Inverse Production Plant using the IPDTool
Using the IPDTool developed an analysis of the economic viability of the plant – while complying with the ecological regulation – has been carried out considering the following variables: • Constraints on the input side. • Types of possible mix. • Inverse Production Volume. • Prices and costs. • Ecological legislation constraints. The main results from the analysis carried out, for different sets of variables and parameters following a predefined plan, may be summarized as follow: • Economical viability depends on the level of ecological constraints (i.e. values of total recovery in terms of materials and energy). It diminishes quite rapidly when constraints are being tightened. • Mix (combination of different white goods) and Inverse Production Volume can help to offset the above problem. • New clean and efficient Inverse Production Technologies have to be developed. • External logistics plays a fundamental role.
5. Conclusion For Inverse Production to be economically selfsustaining, environmental laws, Inverse Process Technology, contribution for goods to be disposed and recycled material market value, must appropriately match.
To design/assess such matching, an IPDTool has been conceived and developed. Hence: • Entities such as in/out products (respectively durable goods to be disposed and recyclable materials), market and regulations have been modelled using numerical tables and mathematical constraints. • An Inverse Production Plant has been modelled using IDEF0. • A mathematical model has been developed to provide appropriate input for the simulation. • A simulation model, based on the above, has been conceived and implemented. • Validation of the specific IPDTool developed has been carried out using actual data from an Inverse Production Italian Plant. • The IPDTool developed has been used to assess the economic viability of the plant considered versus changes in in/out product, market prices, ecological regulations. Relevant correlations between entities involved have been obtained. • The usefulness of the IPDTool developed for Inverse Process designers and managers, product designers, legislators “designing” ecological laws and norms, scientists aiming at developing new Inverse Processes and related enabling technologies [10].
References [1] J. R. Ehrenfeld: "Industrial Ecology: a framework for product and process design", Journal of cleaner production, Vol. 5, No. 1-2, pp. 87-95, 1997. [2] F. Jovane (editor), “Proceedings of the First International Forum on Sustainable Production: a New Industrial Growth”, ITIA Series, 1996. [3] C.R. Boër, F. Jovane, “Towards a new model of sustainable production: ManuFuturing”, Annals of the CIRP – Vol. 45/1/96, Ed. Hallwag, pp. 415-420. [4] F. Jovane, “Manufacturing between past and future: a challenge for technology”, International Conference on Manufacturing Science Technology and Human Factors, Athens, 12 October 1995. [5] A. Urbani, P. Pedrazzoli., L. Molinari Tosatti, I. Fassi, C. R. Boër, "Flexibility and Reconfigurability: an Analytical Approach and Some Examples", Proceedings of the CIRP First International Conference on Agile, Reconfigurable Manufacturing, Ann Arbor, MI, USA, 2001. [6] H. Wenzel, M. Hauschild, L. Alting: “Environmental Assessment of Products – Vol. 1 – Methodology, tools and case studied in product development”, 1999. [7] A.S. Drud, CONOPT – “A large scale GRG code”, ORSA Journal of Computing 6, 207-216, 1994. [8] R. Bosani, “Il paradigma della sostenibilità e la produzione di ritorno”, Master Thesis, Politecnico di Milano, 2000. [9] F. Salsa, “Recupero e Riciclaggio dei beni durevoli in ottica di sviluppo sostenibile”, Master Thesis, Politecnico di Milano 2001. [10] B. R. Allenby: “Industrial Ecology: Policy Framework and Implementation”, Prentice Hall, 1999.
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