From the sustainability point of view, the evolution of sustainable manufacturing has gone through four main phases, namely, traditional manufacturing, lean manufacturing that targeted only waste reduction, GM which implemented the 3R strategy (reduce, reuse, and recycle), and finally sustainable manufacturing implementing the 6R strategy (reduce, reuse, recycle, recover, redesign, and remanufacture).^1,19 Jaafar et al.²⁰ and Jayal et al.²¹ explained each of the 6R terms as follows: The term “Reduce” is associated with the first stages of the product’s life cycle and is concerned with the activities related to simplifying the product’s design and reducing the materials and resources used to facilitate post-use utilization. This may include the reduced use of resources, energy, materials, waste, etc. “Reuse” refers to the reuse of the same product or its components for a new lifecycle after the end-of-life of the first one. This minimizes the use of new raw materials and is considered an activity with the lowest environmental impact as it involves fewer processes. “Recycle” is a term that refers to the activities implemented to convert the current products or components that would otherwise be thrown away into new useful products (e.g., shredding, smelting, and separating). “Recover” refers to the activities of dismantling, collecting, and preparing the components at their end-of-life to be part of subsequent lifecycles of another product. “Redesign” is more related to “Reduce” where it targets redesigning products to simplify future uses after their end-of-life. One of the techniques that apply the redesign concept is the Design for Environment, or DfE. “Remanufacture” is the manufacturing that is not performed for the first time on the same material to restore the material or product to its original state. Implementing the 6R strategy in the product’s life cycle was predicted to help keep the continuous flow of raw materials for a longer time and minimize the environmental footprint.²⁰ The 6R system involved in sustainable manufacturing is also believed to maximize the value of a product which enhances the potential for better profit.¹ Figure 3 illustrates how the 6R approach increases the product’s value and enhances the benefits for stakeholders compared to GM (which is based on only 3Rs) and the earlier approaches.

In 2018, Kishawi et al.¹⁷ further extended the sustainable manufacturing concept and required it to also include the interaction among three levels to cover the required sustainability target; those levels are product, process, and system. The product level involves the 6R approach instead of the 3R approach to cover multiple lifecycles and to achieve the closed-loop paradigm. The process level focuses on reducing energy consumption and eliminating hazards and wastes via effective process planning. Finally, the sustainable system is achieved by using an efficient supply chain system that covers all the stages of the lifecycle.

Recently, research in the field of green production and sustainable manufacturing has been increasing dramatically. The following Figure 4 shows the number of published documents covering this field from the year 1982 to the year 2024, with China coming on top based on the number of publications as shown in Figure 5 and with approximately double the number of publications of the following country (the United States).

Figure 6 displays the number of published documents related to green production and sustainable manufacturing per subject area, an information that was extracted from the Scopus Database using keywords (“Sustainability” AND “Green” AND “Technology” AND “Manufacturing” OR “Production”).²²

It shows Environmental Engineering coming ahead with 18% of all publications followed by Engineering with 12%, and then Energy with 11%.

This section discusses some of the previously adopted strategies in the literature that aim to achieve sustainable manufacturing. It shows that these strategies are not isolated efforts, but parts of integrated efforts of different community sectors to achieve sustainability via exploring, developing, and adopting intelligent technologies. It also shows that sustainable manufacturing is not a passive effort, but a practical and dedicated to finding a smarter, eco-friendly, and sustainable future.¹¹

Lean manufacturing was first introduced by the Toyota production system,²⁶ which adopted the strategy of constant improvement. The term “Lean” implies eco-efficiency as well as circularity. Lean management paradigm focuses on maximizing efficiency and improving working conditions, which eventually results in minimizing waste and improving operational performance.^26,27 It divides activities inside an organization into either value-adding activities that customers are willing to pay for or non-value-adding activities that are considered waste as the customers are not interested in.²⁶ Lean manufacturing is simply “use less of everything,” which by necessity means minimum materials, labor, space, and investments in machinery and tools.²³ Recent updates to lean manufacturing include enhanced product quality along with reducing cost and lead time.²⁸

Circular economy is a business model that involves reusing, repairing, remanufacturing, and recycling technologies to enhance sustainability.³ Circular economy is also opposite to linear economy that encompasses a make-use-dispose strategy. Circular economy points out a manufacturing system that adopts the idea of having no waste, which means that a product’s waste is another product’s raw material.^3,10

In the closed-loop manufacturing system, Jaafar et al.²⁰ involved all the 6R elements: reuse, recover, recycle, redesign, reduce, and remanufacture to cover all the phases of a product’s lifecycle. The author explained the closed-loop system approach in the following Figure 7. It can be noticed that the circular economy and closed-loop manufacturing system are targeting the same thing and applying almost the same strategies.

Closed-loop manufacturing system targets solving the rising problem of waste by dealing with them as raw materials for other products. Chowdhury et al.²⁹ discussed the serious issue of untreated plastic waste that will eventually lead to “a grave pollution crisis.” Tomic and Schneider,³⁰ on the other hand, emphasized the possibility and opportunity of turning plastic waste into energy in a process that may acquire more profit gains than the traditional manufacturing paths. For example, one of the innovative approaches of implementing the closed-loop principal is turning waste plastics into hydrocarbon fuel in a process known as upcycling.¹¹

Challenges accompanying circular economy and closed-loop systems involve complexity and short lifecycle of products, abundance of materials, and the inconsistent conditions of the end product.³

Myer Kutz²⁵ defines the Design for Environment (DfE) as “the systematic consideration of design performance with respect to environmental, health, and safety objectives over the full product and process life cycle”. DfE focuses on the design aspects associated with the impact on health and safety, hazardous materials minimization, disassembly, waste, compliance with regulations, recycling, and recovery. Tools that can be useful in the application of the DfE include guidelines and checklists, design matrices for each product, environmental effect analysis, and lifecycle analysis.²⁵ In their research, Kudz pointed out Black & Decker as a successful example of applying and benefiting from the DfE. It is noted that the DfE approach covers only one aspect of the TBL, that is the environment.

Traditional supply chain management is the systematic process of converting raw materials into final products in addition to the following processes including delivery to consumers.¹¹ GSCM, on the other hand, is a concept that integrates environmental concerns with supply chain management and focuses on two main targets: mitigating environmental impact and eliminating adverse effects on public health.³¹ GSCM is sometimes known in literature by different names such as Green Logistics, Environmental Logistics, Supply Chain Environmental Management, and Sustainable Supply Network Management.¹¹ GSCM covers a wide range of operations starting from the early lifecycle stages such as sustainable procurements and vendor management across all the other phases to waste management, market distribution, marketing, and green outbound logistics. It interconnects economic success and environmental responsibility.¹¹

The research by Ahmad et al.³² is considered one of the successful attempts that study the significance of GSCM on the sustainability performance of 384 organizations covering three different industries (i.e., textiles, automobiles, and tobacco). The study focused on five dimensions of the GSCM, namely: GM, green purchasing, cooperation with customers, eco-design, and green information systems. It confirmed the significant positive impact on sustainable performance in all dimensions except for the cooperation with customers, which had no impact. In their research, the authors concluded that the incorporation of GSCM practices in the manufacturing organizations will enhance the environmental performance along with the economic performance.

Hijazi et al.,³³ on the other hand, confirmed the significance of eco-design and enriched the landscape of the GSCM by adding corporate environmental management and customer participation as additional significant dimensions.

LCA is an evaluation process that measures and analyzes the environmental performance along different stages of a product’s lifecycle.^25,34 Traditional LCA usually covered only the cradle-to-grave lifecycle phases. The cradle-to-cradle lifecycle, however, implements recycling, recovery, and reuse and is formally known as the Design for Sustainability DfS concept.²⁰ This approach is a systematic way to analyze and mitigate the manufacturing process impact on the TBL dimensions at the lifecycle’s early stages. It has already been promoted through educational and training programs in a step to be fully implemented in the near future.²⁰ Although LCA is a time-consuming process and cannot be used to improve the environmental impact of current products, it might be a good tool to measure the improved environmental performance of a current product when redesigned to be more environmentally benign.²⁵

Lee et al.³⁵ performed a thorough review research analysis and confirmed that the growing trends in sustainable manufacturing are following the digital revolution, which resulted in the fourth industrial revolution, or what is known as Industry 4.0 (I4.0). In their review, they predicted that deep learning and big data, with their huge processing capabilities, will be utilized in the digital transformation and the creation of decision-making algorithms in the field of sustainable manufacturing. They also anticipated that technologies with older trends such as additive manufacturing and electronic devices will most likely continue to strengthen.

According to Sartal et al.,²³ I4.0 has emerged as a new trend during the last decade and was associated with sustainable manufacturing as a way of enhancing the industrial value. ElMaraghy et al.³ confirmed the information and added the Internet of Things (IoT) as another trend and added that both of them are capable of extending the product’s lifecycle which can boost its value and support a sustainable economy.

Bag and Pretorius³⁶ integrated the concept of sustainable manufacturing with I4.0 and circular economy. Their study extended the theoretical model created by Dobey et al.³⁷ in several of their previous studies to cover not just the significant role of implementing big data and predictive analysis in improving organizational performance, but also how they take part in sustainable manufacturing and integrate circular economy. For instance, the cyber-physical system (CPS) is one of the embedded systems that are used to control physical devices in a system using digital communication and is one of the system examples that is mainly networked with IoT.³⁸ The integration of such systems can assist in job scheduling and will help in cost and resource minimization.³⁶ I4.0 is based on some principles including interoperability, decentralization, virtualization, real-time capabilities, modularity, and service orientation.³⁶

In literature, CPS, I4.0, Industrie 4.0, and smart manufacturing systems (SMS) are sometimes used interchangeably as they share many similar features.³

Research for sustainable materials has always been one of the most important steps toward achieving sustainability. An example is the utilization of biodegradable materials, which has emerged as one of the effective approaches for attaining sustainability. Rice husk, for example, is one of the extensively studied materials for sustainable materials due to its abundance, good mechanical properties, and richness of useful compounds such as cellulose, lignin, and silica that can be extracted and utilized in other useful applications.³⁹ According to Morimoto et al.,³⁹ in 2020, the global rice production reached 756 million tons, which means a huge yield of rice husk. Utilizing this huge amount of byproduct material in industry instead of burning, as it is the case in some countries, is indeed a huge step forward towards achieving sustainability.

Sustainable composites are another example of materials derived to support sustainable manufacturing and sustainability in general. For example, for several years scientists have been working on developing sustainable solutions for construction composite materials. In their research, Hegyi et al.⁴⁰ offered a promising development of raw-clay-based construction material. The developed material offers several advantages such as minimized environmental impact, improved indoor air quality, high capacity of heat storage and release, and improved energy efficiency in addition to other qualities.

Sustainability assessments help in testing and monitoring sustainability across the different phases of manufacturing lifecycle activities. This is an important step in monitoring the environmental, economic, and social influences to facilitate solving problems and the continuous improvement process. Despite the efforts done in this area, research in the past two decades has mostly focused on the evaluation tools of only the environmental aspect.⁶ However, with the rising awareness of the TBL, more researchers started covering the three sectors simultaneously. This section addresses the topic of sustainability assessment and covers its definition, historical overview, common tools and types, and challenges.

Despite the recent wide and intensive research during the past decades, until the year 2012, the U.S. Federal Trade Commission listed “sustainability” as one of the concepts that would not be addressed in the “Green Guide” due to the unavailability of a clear perception about the term and that the “Commission lacks sufficient evidence on which to base general guidance” as stated in their report.⁴⁵ The number of interpretations related to sustainability has increased, and there has not been a unified definition yet. This acted as a hurdle that delayed implementing sustainability in organizations due to the lack of a clear image and practices related to sustainable manufacturing.²³

In addition, despite the recent research clearing the vision regarding the issue of sustainability, the potential risks of the lack of effective activation, and the emergence of potential practical tools, there are still some barriers impeding the full application. For example, challenges associated with the full implementation of a circular economy involve high initial investment costs, weak cooperation between businesses, a complex supply chain, inaccurate information about the product’s design and manufacturing processes, a lack of competent talents, compromised quality, and a long and expensive disassembly process.³⁶

Regarding sustainability assessments, challenges are usually characterized by several complexities (such as the different values of the decision-makers), in addition to uncertainties, vagueness, and the inclusion of many factors which make them challenging to manage.⁴⁶In real life, sustainability indicators are affected by several uncertainties and randomness, and it was found that the majority of researchers overlooked both of them.⁶

The guidelines for the social sector evaluation of the TBL were only provided by the United Nations Environment Programme in the year 2009,⁴⁷ which means that earlier developed research did not include the social dimension in the assessment methods, which was confirmed by several researchers.^11,48 This has led to most of the researched sustainable manufacturing assessment tools not including the three dimensions of the TBL and being limited to the energy analysis or lifecycle assessment and the environmental impact assessment methods. This resulted in a limited number of assessment indicators that lacked experts’ validation.⁶

Scharmer et al.⁹ were able to spot several other gaps including the lack of a holistic sustainability view where most of the developed models were limited to focusing on specific parts, layers, or industries, which was confirmed by this research author. They concluded that the previous research often: (a) overlooked one or more aspects of the TBL approach, especially the social sustainability aspect; (b) lacked details covering sustainability factors in manufacturing; (c) disconnected the shop floor from the company’s overall sustainability; and (d) missed the concept of cross-sector sustainability.

Regarding the existing sustainable manufacturing approaches, lean manufacturing, for example, targets only waste reduction and creating value. It focuses on producing small lot sizes which in turn increases the amount of GHG emissions. GM, on the other hand, targets minimizing the exploitation of natural resources and the minimization of environmental wastes and thus implementing large lot size strategy which requires a large storage spaces.

To enhance the integration and implementation of the best-mixed strategy, organizations are recommended to be aware of the complementary and conflicting natures. In addition, integrated tools and strategic steps are required to be considered such as targeting lead-time reduction, people engagement in the decision-making process, and organizational and supply chain relationships.²⁶

To have a convenient application of sustainability with all its dimensions (environmental, social, and economic), Lin and Hao⁴⁹ also recommended going in three directions to achieve sustainable manufacturing: (a) public awareness: where the ideas of traditional manufacturing are gradually replaced with the environmental protection ideas that are represented by sustainable manufacturing; (b) solving current products’ environmental problems; and (c) activation of legal penalties and promoting good management and improved personnel quality.

It is also recommended by Punj et al.¹¹ that the new concept of modern eco-designs has evolved and broadened to cover not only technological advancements but also to implement relationships across suppliers, customers, recyclers, and government entities. And in order to overcome the gap in the sustainable manufacturing assessment tools that occurred due to the limited resources available covering all the sustainability dimensions, Ahmad et al.⁶ suggested some future directions to enhance current methods and to make them more inclusive. These directions include adding extra effort in integrating the economic and social dimensions, in addition to employing weighted, validated, and applicable indicators.

Finally, there is an increasing need for a gradual empirical validation of the proposed assessment tools and indicators mentioned in the literature to extract the most useful and convenient ones and to provide credibility and variability to these tools across various sectors and industries. It is recommended to perform a comprehensive study on the human-machine interaction to enhance the operability, minimize the information asymmetries, and boost the overall organizational performance when integrating the revolutionizing I4.0 tools.⁵⁰ On the governmental level, to enhance the effective adoption of sustainable manufacturing technologies, especially in critical fields such as water, energy, and food resources, effective tools such as environmental certificates, stringent ecological regulations, and penalties against violations can be of great help.⁵¹