Procedia CIRP 29 ( 2015 ) 627 – 632
2212-8271 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the scientifi c committee of The 22nd CIRP conference on Life Cycle Engineering doi: 10.1016/j.procir.2015.02.032
ScienceDirect
The 22nd CIRP conference on Life Cycle Engineering
Defining Circulation Factories – A pathway towards Factories of the Future
Felipe Cerdas
a,d,*, Denis Kurle
a,d, Stefan Andrew
a,d, Sebastian Thiede
a,d, Christoph Herrmann
a,d,
Yeo Zhiquan
c, Low Sze Choong Jonathan
c, Song Bin
c, Sami Kara
b,daChair of Sustainable Manufacturing & Life Cycle Engineering, Institute of Machine Tools and Production Technology (IWF), Technische Universität
Braunschweig, Langer Kamp 19b, 38106 Braunschweig, Germany
bSustainable Manufacturing & Life Cycle Engineering Research Group, The University of New South Wales (UNSW), Australia c Singapore Institute Of Manufacturing Technology, Singapore
dJoint German-Australian Research Group in Sustainable Manufacturing and Life Cycle Management
* Corresponding author. Tel.: +49-531-391-7177; fax: +49-391-5842. E-mail address: f.cerdas@tu-braunschweig.de
Abstract
Manufacturing companies are increasingly perceived not only on the basis of their products but also of their factories and their embedding within the environment. For this reason, both existing and future factories face the challenges posed by a dynamic and changing market environment. Thus, a gradual change from a throughput to a circular economy leads to the emergence of two categories of factory systems. One category is producing goods, while the second one is recovering and treating waste, residues and the rest of the product at the end of its life. Against this background, this paper introduces the concept of Circulation Factories which combines manufacturing with remanufacturing and recycling into one integrated system. Circulation Factories will enable the realization of an industrial symbiosis transferring waste to value. Drivers and challenges are discussed.
© 2015 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the International Scientific Committee of the Conference “22nd CIRP conference on Life Cycle Engineering”.
Keywords: Circulation Factories; Factories of the Future; TBS; production; remanufacturing; recycling
1. Introduction
Manufacturing companies face a globally intense competition which drives them to be an essential source of innovation and development. Product related customer demands, legal and ecological challenges, technical trends and social pressure are imposed on the manufacturing industry, forcing factories to be flexible enough to meet all these product requirements in their production. Future factories also face several evolving trends: the necessity for an environmentally conscious production, technology push regarding information and communication technologies, an increasing importance of social aspects including the education of the workforce as well as the need for an improved integration of the factories to their local surroundings. In addition the topic of energy and resource efficient manufacturing systems has been put into the focus in the last decade. Research on manufacturing process and
system level has highlighted various starting points for the improvement of both today and future industries [1].
The vision of the Factory of the Future, described by Herrmann et al. [2] looks into various aspects that a factory will have to consider. One aspect is the symbiotic integration of factories into the surroundings, in particular to urban or domestic areas. Moreover, the envisioned factory has a positive impact on the ecology and is aiming at eco-effectiveness instead of eco-efficiency. Fulfilling the infrastructural requirements the Factory of the Future faces, elements such as the factory building shell or the technical building services (TBS) have to be designed with a higher adaptability [2]. Closing the loop of energy and material flows is one of the central challenges of the Factories of the Future. In order to achieve this goal, this paper presents a brief state of the research and introduces the concept of Circulation Factories as an important enabler for the factory of the future. © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
2. Theoretical background and State of the Research
2.1. Closing the loop: Closed Loop Production, Reverse Logistics and Remanufacturing
Closed Loop Production (CLP) systems are regarded as a cornerstone strategy towards sustainable manufacturing [3][4]. The World Economic Forum stated in 2009 that running a business in a closed loop context is considered to be ethical and environmentally responsible due to the potential reduction of carbon emissions, water consumption, waste avoidance and embodied energy throughout the life cycle. The reduction of energy and resources consumption within manufacturing processes (e.g. recycling 1kg of post-consumer aluminum scrap saves around 41 kWh) has been identified as another opportunity to increase the profitability of CLP [5]. In a cradle-to-cradle manufacturing system [6], the producer realizes the amount of material available to be recovered and thus preventing the consumer of disposing valuable resources to a landfill. A closed loop supply system includes forward production activities [7][8] and product back-flows to the manufacturer. Ferguson and Souza [9] present a classification of the nature of the aforementioned reverse flows. They divide into three different reverse flows. Consumer returns, this lightly used products that use state of the art technology and that come from retailers within the first month, mostly not because of defects. End of Use contains products that are intensively used with their technology outdated (i.e. from older product generation). End of Life returns comprise of products with no evident functionality and very old equipment which might require the use of high amounts of energy and material to recover the remaining value. In the field of closed loop supply chains Kaynak et al. [10] defined reverse logistics (RL) as the systematic planning, implementation and management of the flow of returned products and material for the purpose of recapturing value. Hanafi et al. present different strategies to couple RL with EoL products [11]. Kara et al. modeled a RL network for EoL appliance collection in Sydney in order to cost prediction [12]; and as concluded by Subramoniam et al. [13], a proper network for RL positively influences further steps for the implementation of a closed loop supply. Remanufacturing is a central activity within the field of CLP. Most research refers to a publication from 1983 [14] in which remanufacturing is defined as “the restoration of a used product to like-new condition with respect to quality by replacing components or reprocessing used parts”. Abdulrahman et al. [15] describe remanufacturing as different from repairing, reconditioning and recycling. Direct reuse and remanufacturing are seen as the best end-of-life alternative and the most reasonable practice to close the material loop due to both the economic and environmental benefits brought by the implicit saving of resources [1][16-18]. The stochastic nature of the recovered product regarding availability, timing and quality cause the main challenges for remanufacturing.
2.2. Waste to value: Industrial Symbiosis
Industrial Symbiosis aims to create physical links between independent companies by exchanging materials, energy,
water and by-products [19]. It recognizes the challenges of unused material flows usually related to resources scarcity and waste issues [21]. Qualitative material, energy and waste (MEW) process flow maps and guidelines have been elucidated to foster the identification of improvements to reduce the environmental impact of a factory [21]. Recent activities increasingly focus on a new ‘resource-based paradigm’ questioning the meaning of what is perceived as wastes instead of potential resources until proved otherwise [22]. Chertow and Park [19] propose a reuse potential indicator expressing the usefulness of the material either as waste or potential resource, also including the reuse of secondary materials. Baumgärtner also supports the notion of time dependency of waste and its reuse potential as material, since it is not only waste due to its physical and/or chemical properties, but rather due to the discrepancy between its generation and consumption [23].
2.3. Hybrid Manufacturing / Remanufacturing Systems
A hybrid manufacturing/remanufacturing system is defined as a production model that is able to satisfy product demand through manufacturing of new products or remanufacturing of recovered products [24]. Hybrid manufacturing/ remanufacturing systems consist of both serviceable and returned product inventory as well as reverse and forward logistics [24]. Kim et al. [25], Vercraene et al. [26] and Cai et al. [27] present different models to optimize and coordinate integrated disposal and remanufacturing activities within production operations. As argued in their research, a main challenge of a hybrid production system is the inventory management due to the new sources of material flow implied [25]. Kenné et al. [28] also address production planning within hybrid manufacturing/remanufacturing systems, using a stochastic optimization model considering production rates of manufacturing and remanufacturing equipment and stock levels of manufactured and remanufactured product. Wang et al. [29] designed a logistic network for a hybrid system consisting of a factory, distribution center, consumption area, recycling center and solid waste disposal location using mixed-integer linear programming. Tang et al. [30] present an exemplary application in the automotive industry with manufacturing and remanufacturing operations on the same production line. In their study, used and new car parts are manufactured and remanufactured in the same factory and by the same workers. The remanufactured products share about 30% of the annual sales. Laan et al. [31], present the example of a Dutch manufacturer, who produces photocopiers composed of modules that are easy to disassemble. After the first use the modules are evaluated and then remanufactured and assembled in a new photocopier which is sold as a new product. Kondoh et al. [32] proposed a conceptual factory model of a closed loop manufacturing system considering material flow with quantity fluctuations, quality diversity and variations in timing of the recovered products. Another example is a German research projects that examines the recyclability of waste from the lithium-ion battery production and from spent batteries to close the loop and produce new battery cells from the waste [33]. Finally, a Swedish project
examined the possibilities of dismantling LCD screens and transform parts of it into new products. The light guides and optical films from the LCDs are recovered and assembled into lighting devices [34].
2.4. Research gap
Concluding from the aforementioned research state, there is a clear need for an extended research on a comprehensive description of a production model that merges the elements of a CLP system (reverse and forward logistics, remanufacturing and manufacturing, disassembly and assembly, etc.) into the operation elements of one generic company (i.e. facilities, TBS, equipment, human labor). This paper intends to contribute to the field by providing the definition of a new production concept called Circulation Factories. The concept is expected to broaden the research field by identifying potential mechanisms to reduce the gate-to-gate energy and resources consumption, to link material and energy flows with external symbiotic partners and to reduce the environmental impact of the product throughout the life cycle.
3. Circulation Factories: Concept and Elements
A Circulation Factory is a conceptual model designed to integrate the main elements of a CLP system (i.e. forward and reverse material flows) under the same roof. To enable the required flexibility of a Circulation Factory in many regards (product, process, volume etc.), the conceptual model is expected to be understood as a cyber-physical system, where smart sensors embedded in interconnected physical objects (processes, products etc.) monitor and control them, usually including feedback loops between physical actions and cyber computations and vice versa. Due to the increased degree of connectivity and the ubiquitous availability of different data such as process and production status, design parameters as well as product and material quality aspects being stored in a cloud, future engineering quality will be marked by better consistency and options for optimizations [35-37].
Although cyber-physical systems tend to be self-organizing and adaptive on the shop floor level, there still exists a strong need for a superordinate unit in a whole factory context. This unit can be governed by a Life Cycle Planning department as the element that evaluates and controls the performance of the products and materials around its circular life from a holistic perspective. It coordinates in particular the performance of both manufacturing and remanufacturing, as well as assembly and disassembly activities and also aligns these activities to the material recycling. Figure 1, gives an overview of the proposed system.
3.1. Cyber world
The information flow from the physical level is taken by the Life Cycle Planning department. It manages iteratively the internal and external material and energy flows and is responsible for the economic, ecological and social evaluation of the whole system and its sub-systems. Life Cycle Planning [37] is engaged on finding alternatives to reduce the
consumption of energy and raw materials, by increasing the energy cost efficiency through energy-aware production planning and control [38] within the integrated forward/reverse production activities. The solutions provided by this department range from improvements on the product concept and design (including the development of new products as reviewed in [34]), design and improvement of take-back platforms regarding the business model employed, insights to develop a proper marketing strategy, establishment of symbiotic exchanges and control of the flow of the product all along its life cycle.
Fig. 1. Concept picture of Circulation Factories 3.2. Physical World
The function of the Circulation Factories is value creation, transferring product and material flows into new goods. Therefore, Circulation Factories consist of a production/re-production system able to perform manufacturing and assembly as well as disassembly and remanufacturing. The production/re-production system is organized in a matrix production system [39]. All these steps are carried out in parallel to the classical manufacturing and assembly steps, so that the remanufactured parts, components and materials can be directly supplied to the manufacturing lines. The products that cannot be remanufactured will either be fed into the in-house recycling or given to external partners for a symbiotic re-use, remanufacturing or material recycling. Faulty parts, components and materials created during the production matrix will either be re-evaluated and re-fed into the in-house re-use and recycling cycle or again given to external partners.
The production is not necessarily limited to one main product line, but can also comprise of various by-products from the recovered and remanufactured components produced in the Circulation Factory.
To enable the concept of a circulation factory and ensure smooth production conditions, the physical linkage between all systems (manufacturing/assembly, in-house recycling, TBS, symbiotic partners as well as further product-related systems) also requires well-controlled buffers to balance mismatches between demand and supply from the multiple sources. From a material and resource flow point of view, future production systems will be linked physically as well as virtually to the TBS. The virtual linkage will automatically monitor and control optimal production conditions not only with respect to temperature, lighting and humidity, but also in accordance to internal reuse, recycled and externally acquired material and resource flows. This may include direct reuse and/or in-house recycling of production waste and also external flows (e.g. intake water or residual steam), coming from other symbiotic partners such as further circulation factories or the direct environment. The latter idea has been often discussed when it comes to incorporating factories as part of a smart grid and the related balancing of electricity flows [2], but has not been particularized in terms of materials and resource flows. The energy flows of the three different productive units (i.e. Matrix Production, Disassembly and Evaluation and In-house recycling) are aimed to be continuously monitored and simulated [40] balanced and optimized, whereas the energy flows from the building shell (HVAC, refrigeration, compressed air and steam provision among others) to the productive entities are also expected to be optimized through load balancing and consumption monitoring, avoiding of unnecessary demand, avoiding system losses and increasing resource productivity [40] through finding opportunities to exchange the energy that is usually lost when the systems operate independently.
3.3. Cyber-Physical Integration
One main element in the Circulation Factory is the evaluation of products and parts for remanufacturing and re-use. The Return Resource Management (RRM) is the interface between the Life Cycle Planning and the reproduction part of the Production-Reproduction System. It provides guidelines for dismantling the recovered products and sorting their parts, but also on the following path of a specific part or amount of material (e.g. in form of the Recyclingpass [36]). Prior to physically remanufacturing or reusing different internal and/or external materials and resources, there needs to be an evaluation of the respective conditions of the item first. By determining the remaining useful lifetime and the condition of the recovered part once it arrives to the factory, it can be subsequently diverted to the matrix production system (remanufacturing) [41], sent to a recycling facility or exchanged with a symbiotic partner. The same evaluation is applied for faulty parts from the production and possible recyclable products and by-products from symbiotic partners. Depending on the manufactured goods the evaluation focuses on the respective parts to be recovered.
Beside the classification of materials and resources, there is also a need for recorded requirements of manufacturing and assembly processes to identify potential material and resource matching and establish circular flows [42].
Thus, each entity in a circulation factory requires two sets of information regarding providing and demanding materials and resources. Since there is extensive resource data regarding potential sources, sinks, material compositions, quantities, physical properties, timely availability, patterns of supply etc. involved, the evaluation of material and resource matching likewise the product matching is a key enabler towards circulation factories. This will further facilitate assessments of potential material and resource substitutes for instance based on its similarity fostering eco-effectiveness leading to decreased carbon emissions since by-products and reused materials exhibit lower embodied carbon [43].
4. Opportunities and Challenges
To better define the opportunities and challenges that Circulation Factories entail, a SWOT analysis on this concept has been carried out (Tab. 1). The increasing production throughput leads to a decrease in the availability of primary raw materials, followed by a rise of the prices for these materials as well as high pressure from legislations on producer responsibilities worldwide. Thus, reducing the primary raw material intensity by increasing the use of secondary materials e.g. through improved recycling processes seem to be promising.
Table. 1. SWOT analysis of Circulation Factories
S W
O
x Lower material demand x Reduced embodied energy x Flexible systems with regard to
number of units and different variants.
x Meet future global environmental legislation, overcome material scarcity.
x Flexible production -/ reproduction equipment is not available.
x Lack of matrix transport systems to realize matrix organization.
x Immature markets
T
x CF is also raw material supplier x Cannibalization of new products,
reduced motivation to design products with long lifetime x Unsecured integration into the
industrial symbiosis
x Uncontrolled fluctuation of materials
x Rebound Effects due to additional required sensors
and information infrastructure,
Another important factor is the quantity and steadily increasing rate of waste generation, particularly in high income countries with a high urbanization rate. Excessive quantities of waste resulting from unsustainable consumption patterns, durability of products and materials and inefficient production processes lead to losses in form of materials and energy, which directly links to an increased use of primary materials for energy generation. Above that, all these aspects are likely to intensify considering the rise of standard of living in high income countries and in particular the fast emerging national economies of the BRICS countries. Moreover, future
trends indicate that cross-sectional applications of technologies and resources are likely to expand by forming collaborative value chains and/or industrial parks facilitating future industrial symbiosis.
A scheme for the productivity of a linear system as well as a closed loop system has been described in Figure 2.
Fig. 2. Material Flow and Embodied Energy in Forward Production Systems (i) and in Closed Loop Production Systems (ii)
Productivity can be used as a function of the energy embodied in its product. By applying this idea a broader understanding of the advantages of a closed loop model can be shown. Productivity can be defined in general terms as the ratio of outputs to inputs. Assuming that the yield
y
is identical in both cases, (i) and (ii) (disregarding effects on product demand, price and possible subsidies), the Linear System’s productivity can be expressed as:TBS MAN MAN RM i i E e e e m y P ) ( 1 2 , (1)
where eRM is the specific embodied energy from the raw
material phase, eMAN1 and eMAN2 is the specific energy from the
manufacturing phase. In this case ۦi is the material flow
through the whole production process. The productivity for the case of Closed Loop Production systems can be expressed as a function of the embodied energy as follows:
TBS MAN i REM ii MAN RM ii i ii m e e m e me E y P ( 1) 2 ,(2)
where eRM, eMAN1 and eMAN2 are the same specific energies as in
case (i). In this case (ii) eREM is the specific embodied energy
in the remanufacturing phase, keeping in mind that it is a hybrid manufacturing/remanufacturing system. Furthermore, the energy for the TBS is not specific for a product and has to be added as an absolute value ETBS. In both cases the energy
demand for the TBS is comparable, as the reduced material flow ۦi-ii together with the newly added material flow ۦii have
a comparable need for the TBS. Moreover, as described earlier in this paper, it is expected that eREM < eRM + eMAN1. As ۦii
is the material flow of remanufacturable and reusable parts, a reduction in newly produced parts can be achieved. With
ۦi-ii (eRM + eMAN1 ) + ۦii eREM < ۦi (eRM + eMAN1) (3)
follows that closed loop production systems have a higher productivity as to embodied energy than throughput systems.
The main challenges for the implementation of Circulation Factories are the uncontrolled fluctuation in the amount of material and products, the diversity of quality condition of the returned parts and the timing variation. These difficulties are mainly caused by the variation on the technology rates of the products, uncertainties of the product lifetime and consumer
disposal. As commonly agreed, the stochastic nature of the returned material flow might not only be difficult to model and describe, but also could affect the stability of the production operations. Another challenge is the mismatch between recovered material and the outgoing product flow due to the push and pull nature of these systems. This may lead to further uncertainty in inventory management. Current research on the assessment and management of the aforementioned uncertainties have been addressed in the state of the research.
Circulation factories will not offer both a remanufactured and a new product; therefore there should not be any risk of cannibalizing the product. However the market of remanufactured products is still immature and the products are still seen as having a lower quality than new products. This might cause business difficulties when competing against forward manufacturers or increase the uncertainty of the demand. In addition, a circular model as the one proposed in this paper can cause instability within the forward supply chain by influencing the sales of a raw material supplier. 5. Exemplary case study: Battery Circulation Factory
For an easier understanding, a Circulation Factory is shown in the example of a lithium ion batteries production. The matrix production and reproduction system is the core feature of the factory. Spent batteries are remanufactured parallel to the manufacturing of new cells. The working stations are capable of performing operations like screwing/unscrewing or cleaning and testing. Every station can carry out its operation either in assembling or in disassembling. The quality testing stations can do so for new parts and for used parts. It is even possible to have flexible automated assembly/ disassembly cells, in which robots perform the assembly and/ or disassembly steps, aided by a video camera system that enables the robot to identify the product and to decide which next operation is needed. Additionally, the reproduction/ production waste as well as waste coming from external sourced can be recycled. This way the old battery cells and the faulty cells from production can be recycled and fed back into the production. All materials that cannot be reprocessed or are not usable in the factory again, e.g. from the casing or the electrolyte, are given to symbiotic partners. The remaining energy, stored in the returned battery systems, is utilized can either feed the electricity back into the grid, store the energy in a remanufactured buffering battery system from which peak demands can be met or the energy can directly be used to charge the new battery systems. This can be achieved by the integration of remanufactured battery systems into the TBS. Potential technology enablers are planned as future research areas of the project.
6. Conclusion
To meet the demands made on Factories of the Future, the proposed Circulation Factories concept gives manufacturing companies the opportunity to enhance their ecological and economic performance. Through an integrated manufacturing
and remanufacturing system with a close coupling of the TBS, the ecological impacts can be reduced and new economic business opportunities can be created.
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