This is the fifth Special Issue on Design and Manufacturing for Environmental Sustainability. The first Special Issue on this topic was issued in 2009, and the previous one was in 2018. The acceptance of sustainability has been increasing, as evidenced by the United Nations’ Sustainable Development Goals (SDGs), various carbon neutral movements, and, among others, the gradual recognition of potential impacts of the EU’s “Circular Economy,” which promotes circulation-based businesses to increase the employment and market competitiveness of the EU. This increase in acceptance has brought with it increased activity in the research area of design and manufacturing for environmental sustainability, with the result that this fifth Special Issue includes seventeen well-written papers, a significant increase over the six that appeared in the fourth.
The first paper “Potential Impacts of the European Union’s Circular Economy Policy on Japanese Manufacturers” overviews the EU’s Circular Economy and points out key enabling technologies. To approach environmental sustainability, we should promote various technologies related to ecodesign, process technologies, business strategy, and digital technology. At the same time, we must focus on life cycle design and management, an indispensable technology which synthesizes a sustainable circulation system by integrating the technologies mentioned above. Accordingly, this Special Issue covers both aspects, with the seventeen manuscripts in it organized as follows. The first three papers, authored by Y. Umeda et al., K. Halada, and M. Kojima, give overviews and discuss requirements for technological development. The next two manuscripts by K. Fujimoto et al. and Y. Kikuchi et al. discuss modeling, simulation, and assessment of circulation systems. Papers six to eight, written by W.-H. Chung et al., S. Yamada et al., and K. Yoda et al. develop life cycle design methods. The remaining manuscripts advance fundamental technologies. Manuscripts nine to eleven, by R. Yonemoto et al., T. Samukawa et al., and Y. Yaguchi et al., deal with sustainable manufacturing. Finally, six manuscripts by C. Tokoro et al., K. Tsuji et al., A. Ogawa et al., A. Yoshimura et al., T. Hiruta et al., and S. Nasu et al. are about life cycle processes; recycling technologies and product use phase such as car sharing and maintenance.
Most of the papers, revised and extended in response to the editor’s invitations, were originally presented at EcoDesign 2019: the 11th International Symposium on Environmentally Conscious Design and Inverse Manufacturing, held in Yokohama, Japan.
The editor sincerely thanks the authors and reviewers for their devoted work in making this Special Issue possible. We hope that these articles will encourage further research into design and manufacturing for environmental sustainability.
While the European Union’s (EU) Circular Economy policy package includes various aspects, such as waste treatment, plastics recycling, reduction of food waste, and remanufacturing, it is essentially an industrial and employment promotion policy. In regard to the promotion of circular businesses, including remanufacturing, product-service system (PSS), and digital platforms, this policy may change the shape of the EU market and the core of market competition. However, many Japanese manufacturers are not aware of the difference between the circular economy and the traditional 3R (reduce, reuse, and recycle) policy and are unfamiliar with the impacts on business competition. The objectives of this paper include an analysis of the EU’s Circular Economy (CE) policy and its potential impacts on the Japanese manufacturing industry (as a representative of a non-EU manufacturing industry). First, we summarize the EU’s CE Policy and analyze its meaning. Second, as examples of CE implementation, we introduce Ecodesign Directive “Directive 2009/125/EC” and the European companies, Siemens and Veolia. Then, we discuss the implication of EU’s CE policy; its double-layered structure, the different attitudes toward CEs among European and Japanese companies, and some notes taken from a CE that may be of importance to Japanese manufacturers. Companies are suggested to be proactively integrate sustainability with their main business activity. Finally, this paper points out key enabling technologies. While there are a lot of technologies related to ecodesign, process technologies, business strategy and planning, and digital technology, an indispensable technology for realizing a CE, is life cycle engineering, which synthesizes a sustainable circulation system, by integrating the technologies mentioned above. We also illustrate a hypothetical scenario in which the traditional manufacturing industry transforms into a life cycle value creating industry.
“The Forum of Global Multi-Value Circulation” is the name of forum on Circular Economy in Japan. This forum was launched at June 2018 to discuss and exchange the information on the movement towards the circular economy. Companies that handles production, supply, distribution, and circulation in Japan join the Forum of Global Multi-Value Circulation. In addition, leading universities and national research institutes also join it. The first part of this paper introduces the concept of Global Multi-Value Circulation. In addition, as results of the discussion of the forum, the focus of attention in the concept of Circular Economy are reviewed. The importance of resource efficiency through the boundary between the Eco-sphere and the Techno-sphere, along with retained value, servicizing and platform, has been insisted.
From the mid-1990s to 2017, China was a major importer of recyclable waste, including plastic waste, e-waste, wastepaper, and copper scrap. However, after experiencing pollution from the recycling process and improper disposal of imported waste, at the end of 2017, China prohibited the import of certain types of waste, including household plastic waste and waste fiber. Consequently, some types of recyclable waste were rerouted to Southeast Asia. However, after receiving contaminated recyclable waste imports, Southeast Asian countries also tightened import restrictions on recyclable waste. These restrictions hindered the international recycling initiatives of certain manufacturers, which were model cases of the voluntary application of extended producer responsibility. When producers initiate recycling programs, they must compete with other recyclers to secure waste supplies and compete with other producers of the same kind. To compete in the waste and product markets, they must minimize recycling cost. To do so, some producers established international recycling systems; however, trade restrictions in some countries are forcing them to stop these programs. This paper reviews the impact of recyclable waste trade restrictions on recycling activities and producer-organized international recycling systems and argues that there is a need for an appropriate trade policy to facilitate environmentally sound recycling.
Systematic lifecycle design and management are promising approaches for constructing sustainable product lifecycle systems. Lifecycle simulation (LCS) has been used to evaluate a product lifecycle in the design phase from both the environmental and economic perspectives. Based on material flows through each process of the product lifecycle, the LCS calculates the time variation in environmental loads, cost, and profit. In each process of the LCS model, functions that regulate the behaviors of the process, called behavior functions, are set, and these functions control material flows. Previously, we proposed a data-assimilated LCS method that combines data assimilation (DA) with LCS to realize adaptive management based on actual states of the product lifecycle. In this previous development, the DA mechanism modified the material flows of an entire lifecycle in the simulation model based on actual flows observed in each process at the time of the DA. However, because process behaviors were not modified, the gap between material flows predicted by the simulation and the flows of the actual lifecycle increased over time. To overcome this limitation, in this study, we propose a new DA mechanism that modifies the behaviors of un-observed processes based on observed material flows. The proposed DA mechanism uses the response surface methodology to estimate the behaviors while tracing the causal relation in the LCS model in reverse. A case study on a photovoltaic panel reuse business showed that the DA mechanism successfully merged the observed data into the process behaviors in the LCS model including the processes where no data were observed, thereby improving the accuracy of the simulation for future prediction. Systematically analyzing the current and future process states of the product lifecycle can support decision-making in lifecycle management.
Since the enactment of the “Feed-in Tariff” scheme in 2012, the solar power generation capacity in Japan has been steadily growing. Therefore, in the near future, the demand for the mass processing of spent photovoltaic (PV) panels is expected to increase. Secondary batteries, especially lithium-ion batteries (LiBs), have become important products for vehicles and mobile devices. The production of LiBs is also expected to significantly increase in the near future. In this study, we address the design of recycling systems for such emerging technologies. From life cycle perspectives, the requirements for the assessment of these technology systems are carefully defined through a bibliometric analysis of technology assessments, critical reviews of current research and developments in the recycling of PV panels and LiBs, and analysis of the intensities of life cycle impacts (such as greenhouse gas emissions and resource use). The necessities for life cycle assessments, material flow analyses, and other assessment methods are clarified, along with the conditions to be examined using these assessment methods.
With the growing applications of information technologies, consumer electronics products are being widely used in our daily life and at our workplaces. However, most consumer electronics packaging is one-time consumption and produces tremendous environmental impacts. Different package designs affect not only logistics efficiency, but also environmental performance. Here, various package designs for a consumer electronics product are studied and a packaging evaluation method is proposed. The method evaluates package designs mainly based on package characteristics information to avoid the inclusion of too much subjective human judgment. The criteria of the evaluation consider five aspects: marketing, logistics, cost, user convenience, and environment, including protection and containment, stackability, volume, and weight efficiency, product information, packaging cost, packaging waste, etc. The case of computer mice is used to illustrate the proposed method. The preliminary results show that different package designs of a consumer electronics product have a significant impact on logistical, marketing, economic, and environmental performance. Based on existing data of package designs, the proposed method can provide valuable information for improvements in package design, supply chain efficiency, and environmental impact.
An upgradable product is a product in which the valuable life is extended by exchanging or adding components. An upgradable product is both environmentally and economically advantageous compared with products requiring replacement because its functions can be improved by adding only a few components. Therefore, the design and sale of upgradable products represent effective methods for attaining a sustainable society. Previous studies of upgradable product design methods have assumed that products have a modular architecture, in which all components are functionally independent. However, actual products have both integral architectures and modular architectures. Achieving high-performance products through component optimization is easier with an integral architecture than with a modular architecture. However, the integral architecture makes it difficult to disassemble and replace individual components. It is difficult to achieve high levels of performance in products with modular architecture, but it is easy to disassemble and replace components. Therefore, upgradable product design must determine the most appropriate product architecture. Hence, this paper focuses on the product architecture of upgradable products and proposes a decision support method that yields the appropriate combination of product architecture and upgrade cycle. In addition, the authors propose evaluation models for the environmental load, cost, and customer dissatisfaction, as well as a comprehensive evaluation index based on these models. The overall model, which gives the evaluation index, considers the differences in the evaluated values resulting from differences in the product architecture and the number of upgrades. The proposed method was applied to a motherboard module design problem for a laptop computer. The results of this case study confirm that the proposed method successfully supports the designer during upgradable product design by deriving the most suitable combination from a set of product architectures and upgrade cycle candidates.
In order to cope with the issue of depletion of natural resources, expectations for economical designs of the closed-loop supply chains of products that include remanufacturing in their lifecycle have recently significantly grown. However, since disassembly of a product to remanufacture it is costly due to high labor costs, the lifecycle option of remanufacturing an end of life product by disassembly and reassembly needs to be established environmentally as well as economically. In this study, we propose a remanufacturing option selection method that takes recovery rates and profits into account. First, a bill of materials of a product is prepared to create data for remanufacturing. Next, its remanufacturing option selection is formulated by using the 0-1 integer programming. Lastly, the proposed remanufacturing option selection method is verified by analyzing the sensitivities of the recovery rates and selling prices of the remanufactured products using the ϵ constraint method. The proposed method that takes remanufacturing into account has demonstrated a generating larger profits than a conventional method maintaining high recovery rates at the same levels in a case study.
Energy savings and reduction in environmental burdens are necessitated to enhance sustainable manufacturing performances. Not only should energy consumption in the factory be visualized, but also a mechanism, by which in-process production and energy-related information measured in the shop floor are fed back into planning/scheduling decision-making, must be established to improve the energy efficiency during manufacturing execution. This study addresses the effect of scheduling on the improvement of energy efficiency in manufacturing by connecting a developed measurement and control platform with a real manufacturing system. The manufacturing system testbed utilized in this study forms a simple flow-type flexible manufacturing system composed of automated manufacturing cell with a CNC lathe, material-handling manipulator, and vertical machining center. We focus on the task scheduling of the material-handling manipulator, which yields a job sequence, and the effect of task scheduling of the manipulator on the energy efficiency and productivity of the entire manufacturing system.
Prediction of energy consumption in the entire production system is crucial for managing production and pursuing environmentally friendly manufacturing. One critical issue that must be addressed to realize green manufacturing is to construct a method for predicting the electric power consumed by each manufacturing device. To address this problem, we have proposed a regression-based power consumption model to predict in-process power consumption based on the strong correlation between MRR and SEC. This study is an extension of our previous work, and here, we conducted face milling experiments by utilizing ten different materials to demonstrate the applicability and generalization capability of the model. We focused on the face milling process and measured the power consumption of the machine tool during the milling process. We also determined the characteristics of the in-process power consumption in face milling from the viewpoint of SEC and MRR and the influence of the work material on SEC. The prediction accuracy of the proposed model is demonstrated by comparison with a conventional model. It was revealed that the proposed model can describe the influence of the entire machine tool on power consumption depending on the characteristics of the work materials.
Recently, biodegradable plastic materials that can be decomposed by living organisms have attracted significant attention because of the great demand for the safe disposal of plastics. Recycling has failed to provide a practical solution for plastic waste disposal (60% of all plastics produced are discarded). It is difficult to achieve both durability and biodegradability in biodegradable plastics. In additive manufacturing processes, polylactic acid (PLA), one of the biodegradable plastics, is typically used, but it presents strength and durability problems. We developed novel additive manufactured biodegradable composite plastics by inserting continuous natural fibers (cotton, hemp, jute, etc.) into fabricated layers of PLA. The composite had a greater strength than normal additive manufactured PLA materials and could be used like a normal PLA filament in fused deposition modeling to create free-form three-dimensional objects. In this study, we performed experiments to evaluate the durability and biodegradability of the composite (PLA as matrix and hemp fibers as reinforcement). Specimens made from the composite were exposed to a normal indoor environment and to severe environments that products might encounter during use (presence of water and UV light (300–400 nm)). The decrease in strength over time was compared with that of PLA, and the durability was evaluated. The results indicated that the strength of the manufactured composite material exceeded that of PLA under all conditions. Whereas the stiffness of PLA exposed to UV light reduced significantly, that of the composite material remained constant, suggesting the significant effect of fiber reinforcement. In addition, test specimens were buried in a simulated soil environment, and their biodegradability was evaluated. The strength of the composite material decreased rapidly, and the biodegradability was confirmed to be at an acceptable level.
The volume of spent photovoltaic (PV) panels is expected to grow exponentially in future decades. Substantial material resources such as silver (Ag), copper (Cu), aluminum (Al), silicon (Si), and glass can potentially be recovered from silicon-based PV panels. In this paper, we targeted the recovery of Cu and Ag from a cell sheet separated to a glass panel from a spent PV panel. The technical feasibility of a novel electrical dismantling method was experimentally studied. This method employed a pulsed power technology that releases high energy in a short time. It allowed a selective separation of the Cu/Ag wires from the sheet once per discharge in water. The experimental results indicated that 95.6% of the total Cu and 17.2% of the total Ag in the sample were successfully separated from the cell sheet using a 3.5-kJ capacitor bank circuit. Moreover, 3.66% of the total Si in the sample was contaminated by the separated Cu/Ag particles from the cell sheet, mainly by shockwaves generated by plasma expansion, and some of them formed a compound with Cu and Ag by eutectic melting, resulting in low liberation. At the lower energy of 3.5 kJ, eutectic melting of Cu and Ag with Si was more suppressed than 4.6 kJ, and 94.3% of Cu and 77.5% of Ag in the separated particles were liberated, which would be acceptable for further wet gravity and/or shape separation of Cu and Ag.
Sustainable production and consumption are categorized as target 12 in the United Nations’ Sustainable Development Goals. The “sharing economy” has been developing globally as a new consumption style, and it is often recognized as being environmentally friendly by both consumers and service providers. Several aspects of the practice, such as the avoidance of new production, can reduce the impact to the environment. However, additional factors, such as the expansion of consumption, namely rebound effects, can increase the impact to the environment. Although many variables exist to determine the total impact of sharing services on the environment, additional and rebound effects and the uncertainty of influential variables have not been well considered. In this study, we aim to reveal the conditions that car-sharing practices place in increasing or decreasing environmental loads, and to identify the significant influential factors on the environment imposed by car-sharing services. We analyze the CO2 emission of car sharing by considering various influential factors and their distributions. Furthermore, we consider differences in car size, fuel type, ownership condition, and several other factors in the simulation. The distribution of each variable is determined, and a Monte Carlo simulation is conducted. The CO2 emissions from the production and operational stages over a 10-y period are estimated. The simulation is conducted with sensitivity analysis to identify the variables that contribute significantly to the total CO2 emission. In some cases, the CO2 emission involved in car sharing exceeded cases in which car sharing is not practiced. Among those cases, although the main contributor to the total CO2 emission is in the operational stage, CO2 emission from the production stage increased the amount of emission. It is discovered that the number of cars increased significantly during the target 10 y after sharing is introduced in some cases. These results indicate a high probability that car sharing can achieve CO2 reduction, but the increase in CO2 emission can occur under certain conditions. Additionally, the sensitivity analysis shows that the main determinants of CO2 emission are the ratio of people who eliminated their private cars, degree of rebound effect, and increasing ratio of number of cars introduced to car-sharing practices. This suggests that whether car sharing becomes environmentally friendly depends substantially on consumer behavior and the manner in which sharing services are operated.
We evaluated the feasibility of waste-generated heat using a 100-kW digestion gas engine at the Karatsu City Water Purification Center by evaluating its disaster resilience through four indicators. We achieved the best outcome, i.e., a power generation rate of 1,122 kW and a power self-sufficiency rate of 22% when two or more digestion gas engines were installed to supply waste-generated heat to the absorption chiller/heater of a water-pool. Additionally, we evaluated the environmental and economic aspects of a Mechanical Biological Treatment (MBT) system installed in Karatsu City. The results suggested that by installing an MBT system, the annual cost could be reduced by ∼100 million Yen and the power generation capacity could be increased to 4,310 kW; this could also help reduce 19,000 tons of annual CO2 emissions with increased power generation. The environmental and economic feasibility assessment tool developed here is configurable; hence, applicable to other regions.
We conducted experiments using unit processes to prove the feasibility of the concept of an environmentally sound Au recovery process from waste electrical and electronic equipment (WEEE) using organic aqua regia, i.e., a propylene carbonate (PC) solution containing CuBr2 and KBr. First, the WEEE samples (memory card and mobile phone board) were finely ground. The samples were then carbonized and oxidized to decompose the polymers and oxidize the base metals. The leaching of Au from the oxidized samples was then carried out in a PC solution with 0.2 M of CuBr2 and 0.2 M of KBr over 353–373 K, followed by biphasic separation with sulfuric acid. The dissolved Au in the PC phase was recovered via ascorbic acid reduction. The mass balance of Au in the leaching was investigated. The maximum recovery ratios of Au from the memory card and mobile phone board were 79% and 83%, respectively. The cost of leaching was preliminarily estimated.
A key aspect of life cycle management for pursuing sustainability is machine condition prognosis, which requires a condition monitoring system that estimates machine system deterioration to assist engineers in determining which maintenance actions to take. Conventional data-driven methods such as machine learning, have two issues. One is data dependency. The accuracy of a data-driven method depends on the data volume because a data-driven method builds a classification model on the basis of historical data as training data. However, it is difficult to acquire enough data on all deterioration modes, which requires a long time, because deterioration modes are diverse, and some of them rarely happen. The other issue is interpretability. When a condition monitoring system using a data-driven method sends the degree of deterioration (DoD) of the machine system to maintenance engineers, they have difficulty in understanding the results because the method is a black box. The objective of this paper is to address these two issues. We propose a model-based method that simulates machine system deterioration with a cyber physical system (CPS). Model-based methods address these issues in the following manner. First, the methods can simulate the progress of deterioration from an initial condition to failure to estimate the DoD. Second, the methods employ mathematical models that represent machine systems. Engineers create such mathematical models (which we call “physical models”) by referring to various kinds of knowledge like design information and the result of failure mode and effects analysis. A physical model allows us to reason about a machine system to address interpretability. For dealing with machinery that has multiple operation modes, we introduce a state space to clarify the relationship among input, observable state variables, and DoD in a physical model. The CPS estimates DoD by comparing observed data with simulated data in the state space. In our case study, we evaluated our proposed method with a hydraulic pump of a mining machine. First we created a physical model with Modelica, which is a multi-domain modeling language. Then, the method constructed the state space by simulating deterioration with the physical model given all combinations of inputs and DoD. After that, we showed that the estimated DoD tended to increase until the hydraulic pump was replaced, using the observed data from an actual mining machine. As a result, the experimental results revealed that the proposed method succeeded in identifying the DoD with observed data of the hydraulic pump of a mining machine.
An advantage of solar-powered houses is the concurrent generation and consumption of power. However, the simultaneous power consumption of a solar-powered house tends to be lower than its actual load consumption. We aim to design a multi-agent system for exchanging the power value information within a solar-powered house and neighborhood in order to maximize simultaneous solar-derived power usage. This study purposes a priority order to determine the simultaneous solar-derived power usage procedure. Using the measurement data of a next-generation solar-powered house on a sunny day, we evaluate the estimation result of the domestic power balance and analyze the time series of each of the power variabilities. From the result, the three types of power usage are classified, and the four phases of the power capacity allocation are defined. We clarify the specific calculation procedure and indicate the availability of simultaneous solar-derived power usage by finding the optimum combination of the power capacity and the usage volume per hour. Finally, we estimate that the total value of available simultaneous solar-derived power usage is approximately 80% of the capacity in the solar-powered house and four hypothetical neighborhood houses, contributing to a drastic reduction in surplus power.
Additive manufacturing (AM) is recognized as a core technology for producing high value, complex, and individually designed components as well as prototypes, giving AM a significant advantage over subtractive machining. Selective laser melting (SLM) or electron beam melting (EBM) are two of the main technologies used for producing metal components. The powder size varies, depending on the technology and manufacturer, from 20–50 μm for SLM and 45–100 μm for EBM. One of the current barriers for implementing AM for most industries is the lack of build repeatability and a deficit in quality assurance standards. The mechanical properties of the components depend critically on the density achieved; therefore, defect analysis and detection of unfused powder must be carried out to verify the integrity of the components. Detecting unfused powder in AM parts using X-ray computed tomography (XCT) is challenging because detection relies on variations in density. Unfused particles have the same density as the manufactured parts; therefore, detection is difficult using standard methods for density measurement. This study presents a methodology to detect unfused powders in SLM and EBM-manufactured components. Aluminum and titanium artefacts with designed internal defects filled with unfused powder are scanned with XCT and the results are analyzed with VGSTUDIO Max 3.0 (Volume Graphics, Germany) software package. Preliminary results indicate that detecting unfused powder in an aluminum SLM artifact with a 9.5 μm voxel size is achievable. This is possible because of the size of the voids between the powder particles and the non-uniform shape of the particles. Conversely, detecting unfused powder in the EBM-manufactured titanium artifact is less challenging owing to the uniform spherical shape and slightly larger size of the particles.
A method to calculate tool path uniquely for roughing using a flat drill is proposed. A flat drill is a drill with a flat tip. Unlike a square end mill, it cannot feed a tool laterally, but it is suitable for machining to feed a tool longitudinally. The advantage offered by the flat drill is expected to reduce machining troubles, such as tool breakages and chatter vibration, owing to the axial sturdiness of the tool. Furthermore, it can be used to machine lapped holes that cannot be machined with a normal drill owing to its flat tip. Hence, roughing using a flat drill by drilling multiple holes at constant intervals is proposed herein. Furthermore, in this method, a tool path for semi-finishing is generated only on the remaining region. A cutting experiment is conducted to validate the effectiveness of the proposed method. The result of the cutting experiment confirmed the effectiveness of the proposed method based on the machining time and the productivity of machining multiple products simultaneously.
Recently, cubic boron nitride (CBN) cutting tools and high pressure coolant (HPC) have garnered significant attention for high performance machining of difficult-to-cut materials, such as nickel-based super alloy, Inconel 718. In this study, the cutting performance of a low-CBN-content (L-CBN) cutting tool, which is known as a suitable CBN material structure for the high-speed machining of Inconel 718, is investigated under the HPC conditions. The experimetntal results show that, although crater wear is significantly suppressed as the coolant pressure increases, the combination of high cutting speed and high pressure coolant causes severe thermal cracking on the tool rake face of the L-CBN cutting tool. Hence, we evaluate the cutting performance of high-CBN-content (H-CBN) cutting tool which has smaller coefficcient of thermal expansion, compared with the L-CBN cutting tool. A series of cutting experiments shows that changing the material structure of the CBN tool effectively suppressed thermal cracking and that the H-CBN tool is a highly promising option for the high performance machining of Inconel 718.
Electroplating has many applications, including surface hardening and metal thin film manufacturing. In conventional electroplating, the entire workpiece is immersed in the plating solution. Since the whole surface in contact with the solution is plated, a masking operation to remove the unnecessary plating film is required. This is especially applicable to local plating in the case of ornament plating, surface hardening method, among others. However, these additional processes result in substantial increase in processing time and cost. Earlier, we achieved maskless local electroplating with a smooth surface using a suction tool, in which the electrolyte was retrieved by a suction pump through a suction hole. Even so, formation of film on electroplating is yet to be verified by simulations. Herein, we performed experiments and simulations of the local electroplating by varying the processing time before comparing the results. Finally, the validity of the film forming was examined by discussing the results.