Resilient and sustainable closed-loop supply chains (CLSCs): a research agenda

In the past, products were designed for efficient and cheap manufacturing processes without considering the end use of products. Supply chain management in this era was focused on the network design and co-ordination of suppliers, producers and the delivery of goods to the end user. This model of “take-make-consume-dispose” is the linear supply chain (Geissdoerfer et al., 2018). Environmentally, the linear supply chain faces challenges because of the depletion of non-renewable resources, the shortage of incineration space, the emission of greenhouse gases into the atmosphere leading to climate change. In terms of operations, the growth of e-commerce and outsourcing activities has led to an inevitable flow in the supply chain, the reverse flow of products because of customer returns and product recalls. This has been termed the reverse supply chain. The reverse flow of goods in a supply chain can either be voluntary or non-voluntary. A voluntary reverse supply chain is when a manufacturer has agreements with a customer to return their products of servicing and repair in the form of warranty claims or when a manufacturer collects their own products to protect some technology from competitors. In the non-voluntary scenario, customers return products to the original equipment manufacturer (OEM) that are defective, or products get recalled from the market when they fail to meet specific quality standards. The most common reason for product returns are laws put in place that mandate the OEMs to be responsible for the after-use activities of their products, that is, extended producer responsibility. For this reason, an OEM must collect used products from customers, encouraging the reverse supply chain.

While other manufacturers had no use for these returned products, some OEMs made business from used products. In the electronics, products were disassembled, and some components and modules reused in new products while in the apparel industry, OEMs sold these used products to another market that can still use them as they are. The disposition of used products by various OEMs defined two types of reverse supply chains, the open-loop supply chain and the closed-loop supply chain. In the open-loop supply chain, an OEM collects used products, but they do not go back to their original forward chain, instead they are sold to another supply chain or OEM who has need of the product (Prahinski and Kocabasoglu, 2006) and (Vegter et al., 2020). In a closed-loop supply chain (CLSC) products return to their original supply chain, and they are sometimes sold in the same markets as the OEM’s new products. A CLSC is a supply chain network that considers forward and reverse flows simultaneously (Govindan et al., 2015).

CLSCs are beneficial for most organizations as they make a product valuable for its entire life (Guide and Van Wassenhove, 2009). This means that the closed-loop supply chain is not only a means for minimizing costs, but it is a way of gradually increasing revenue for the manufacturer. Wells et al. (2005) realized the CLSC as a means for realizing the circular economy (CE) and minimizing resource input, waste emissions and energy leakage through remanufacturing, reuse, refurbishing and recycling of products. This reverse logistics of used products means that an OEM has two classes of the same product, new and remanufactured products and they must find ways of marketing and distributing these two classes of products.

The reverse supply chain is here to stay. This means that products that were once designed for disposal are now being redesigned to account for end-of-use activities such as remanufacturing, recycling and refurbishing. In addition to conserve natural resources, products are now being redesigned to last longer. This consideration of end of use activities and natural resources in product design converts a linear supply chain to a “sustainable linear supply chain”. A sustainable linear supply chain consists of products that are easy to disassemble to enable them to be remanufactured, using environmentally friendly packaging, avoiding harmful by-products and waste and making the distribution of the product sustainable (Schreiber et al., 2022).

Sustainable business practices have been a topic of interest in the past decade. Sustainable business practices focus on economic, social and environmental aspects while trying to increase their profits (Shekarian et al., 2022). The term sustainability on its own has been associated with a lot of definitions. From a supply chain perspective, incorporating environmental and social considerations into conventional supply chains that are known to focus mainly on maximizing profits and reducing costs defines a sustainable supply chain. Profits in a sustainable supply chain are usually improved by the reduction of risks and the improvement of the public image and customer loyalty (Rafigh et al., 2021). Sustainability has also gained attention from researchers because of globalization, supply chain disruptions and demand uncertainties. (Pourmehdi et al., 2020). As a result, implementing sustainable supply chain management (SSCM) has been identified as a key enabler for organizations to reduce their environmental impacts whilst increasing social and economic benefits.

Although both sustainable supply chains and closed loop supply chains are beneficial, it is quite unclear as to the relationship between sustainability and closed loop supply chains. Mohammadi et al. (2020) and Maheswari and Kavitha (2020) argued that the two have similar objectives. Quariguasi Frota Neto et al. (2010) observed that the primary objective of CLSCs is to improve the economic benefit from end of use products, thus, CLSCs are assumed to be sustainable supply chains. While CLSCs have been considered from and environmental and economic perspective Das (2020) and Fathollahi-Fard, Hajiaghaei-Keshteli and Mirjalili,(2018) added that reverse supply chain activities are labour intensive compared to the traditional forward chain on its own, thereby creating more job opportunities and addressing the social aspect of sustainability.

While sustainability has always been the goal for almost all supply chains, Fahimnia and Jabbarzadeh (2016) argued that considering only sustainability in a supply chain is not enough given the increasing number of disruptions over the years and their significant impact on supply chain networks. To encourage organizations not to view sustainability as a brake in achieving resilience, Miller and Engemann (2019) developed a framework that mutually addressed possible scenarios where supply chain resilience categories intersect with categories related to sustainability with the goal of developing a frame of reference to address potential conflicts and to create solutions, that are resilient and sustainable. The authors concluded that “resilient and sustainable supply chains do not need to result in zero-sum type trade-offs, but rather are mutually reinforcing, and go hand-in-hand”. Disruptions can negatively affect reverse logistics activities and their environmental and economic benefits. This is why it is necessary to consider resilience in CLSCs. The COVID-19, highlighted the importance of supply chain resilience(Ivanov and Dolgui, 2020). Sustainability and resilience have become two important concepts in supply chains in the past years as “sustainability is focused on the long-term survival of the system and resilience prolongs the firm’s lifespan by tackling the disruptions”- (Mehrjerdi and Shafiee, 2021).

However, the co-existence of resilience and sustainability in a supply chain is questionable. For example, Negri et al. (2021) carried out a review on the co-existence of resilience and sustainability in general supply chains. Their review argued that in the face of a global pandemic such as COVID-19, the co-existence of sustainability and resilience in a supply chain is questionable since the two have conflicting objectives. For example, reducing inventories in a supply chain to improve its efficiency might lower its responsiveness in the face of a supply chain network disruption. This review considered other opinions by other authors on the interrelationships between sustainability and resilience in a supply chain. These opinions state that:

• Sustainability is a resilience antecedent and that sustainability practices may positively impact resilience. Jain et al. (2017) suggested that an improved understanding of what constitutes the sustainability of an organization helps in making better quality decisions and decreases the risks in the network. In a similar way, Closs et al. (2011) insisted that having a sustainable supply chain reflects a firm’s ability to respond and recover from global disruptions. An explanation of how Walmart made investments in environmental and social sustainability practices to reduce supply chain disruptions from its 50,000-supplier base in China was provided by Gouda and Saranga (2018) as a way of illustrating how sustainability improves resilience in a supply chain.

• The two are related but not necessarily correlated. Strategies to improve the other do not improve the other as well. This was based on an argument by Mehrjerdi and Shafiee (2021) that as each industry is subject to some risks and limitations, the extend of interaction between sustainability and resilience may differ based on the industry’s characteristics.

• Resilience is a driver for sustainability effort. Shin and Park (2019) argued that resilience improves sustainability by improving supply network relationships and competitive advantages.

The main objective of the review is to understand how sustainability can be integrated with resilience in CLSCs by identifying the tactical, operational and strategic issues that are affected by this integration. The review will also identify trade-offs associated with integrating sustainability and resilience in CLSCs and identify research gaps and future research directions to help improve sustainability and resilience of CLSCs in the face of disruptions. Sub-objectives of the review include:

• define sustainability and resilience in the context of CLSCs;

• identify relationships between sustainability and resilience in CLSCs;

• investigate the levels (i.e. strategic, tactical or operational) of decision-making involved when integrating sustainability and resilience in a CLSC;

• identify popular resilience strategies and sustainability objectives used in CLSCs; and

• discuss gaps in current research and identify future research directions to help in the integration of sustainability and resilience in CLSCs.

To meet these objectives, the review asked the following questions:

It should be noted that the review only focused on CLSCs.

There has been an increase in research on CLSCs, sustainable supply chains and supply chain resilience. A lot of reviews have been carried out on the topic.

One review that investigated the integration of sustainability and resilience in supply chains was carried out by López-Castro and Solano-Charris (2021). In the review, the authors classified the literature according to the levels of supply chain network design, levels of decision-making (i.e. strategic, tactical and operational), resilience and sustainability criteria, solving approach, objective criteria, contributions to the Sustainable Development Goals (SDGs), and real-world applications. However, in integrating sustainability and resilience, the review did not specifically consider CLSCs which makes it different from this review.

Other reviews on reverse logistics and CLSCs were carried out by Tombido and Baihaqi (2022) and Mishra et al. (2022). However, these reviews focused on other aspects of CLSCs. Tombido and Baihaqi (2022) focused on CLSCs with dual and multiple channels of selling, collecting and recycling used products while Mishra et al. (2022) looked at CLSCs from the perspective of the circular economy. The rest of the reviews focused on either sustainability [Shekarian et al., 2022; Joshi, 2022) or resilience (Emenike and Falcone, 2020; Shishodia et al., 2021; Rha, 2020; Rahman et al., 2022; Aldrighetti et al., 2021). These are not close to this research as they only focus on one aspect and not both. They also did not specifically focus on CLSCs. However, the increase in reviews on supply chain resilience should be noted. Table 1 summarizes the most recent literature reviews on sustainable supply chains and supply chain resilience.

Based on the information in Table 1, the main contributions of this paper are as follows:

• A simultaneous consideration of resilience and sustainability in CLSCs. Previous research focused on the integration of sustainability and resilience in supply chains, but they did not focus specifically on closed-loop supply chains.

• An exploration of other supply chain issues associated with sustainability and resilience in closed-loop supply chains.

• Interrelationships between resilience and sustainability in closed-loop supply chains. It has not been clear as to the relationship between resilience and sustainability in supply chains.

• Identifying gaps in integrating resilience and sustainability in CLSCs.

The rest of the paper is structured as follows: Section 3 describes the systematic review methodology while applying it to the current topic; Section 4 analyses the literature and identifies gaps according to how the literature is classified; and Section 5 provides the conclusions and suggestions for future research.

Denyer and Tranfield (2009) defined a systematic review as “a specific methodology that locates existing studies, selects and evaluates contributions, analyses and synthesizes data and reports the evidence in such a way that allows reasonably clear conclusions to be reached about what is and what is not known”. In addition, Thomé et al. (2016) listed the four main stages in conducting a systematic review. These stages will be explained in the following sub-sections.

In this stage, the scope of the review is defined. The scope will look at the focus, goals, perspective, coverage and organization of the review. The objectives and research questions asked by the review have been explained in the introduction.

In this review, four methods were used in searching for literature:

1. The citation databases, Web of Science and Scopus. Scopus and Web of Science are two of the largest abstract and citation databases, in the fields of science, technology, medicine, social sciences and arts and humanities. Web of Science and Scopus house peer-reviewed journals from publishing houses such as Elsevier, Emerald, Informs, Taylor and Francis, Springer and Inder-Science among others.

2. Keyword search on an unrestricted timeline. Search results depended mainly on the use of the Boolean operators AND and OR. Three search statements were used: resilience AND closed-loop supply chains OR sustainability AND closed-loop supply chains OR resilience AND sustainability AND closed-loop supply chains. The search was conducted on 12 December 2022, and the initial search resulted in 196 papers.

3. Review of selected abstracts to make sure that articles properly meet the inclusion and exclusion criteria. Items that were included were those that focused specifically on sustainability and resilience in closed-loop supply chains. Those that were excluded focused on general supply chains and some of them were not written in English. For the sake of quality, the search was limited to journal articles and excluded books and conference proceedings. Articles with in-press-corrected proof status were also included.

4. Forward and backward searches. Articles obtained mostly from Elsevier always come with recommendations. These recommendations were used for forward searches. Each article that fits the inclusion criteria was also read and the list of references at the end of the article checked to identify more articles associated with the topic. This is a form of backward search.

A summary of the review procedure is provided in Table 2 which shows the review protocol. As a result of the exclusion criteria and snowballing, 56 articles remained and were included in this review.

The distribution of the articles in the common journals is shown in Figure 1.

The “others” bar shows journals with only one publication. Most of the articles are scattered across different journals as shown by the “Others” bar having the largest number of articles. The Elsevier Journals, Journal of Cleaner Production and Computers and Industrial Engineering had the highest number of publications on sustainable and resilient closed-loop supply chains. Other popular journals on this topic include the Springer Journals, Environment, Development and Sustainability and Environmental Science and Pollution Research. The Journal of Cleaner Production, Environmental Science and Pollution Research and Environment, Development and Sustainability are three journals that mostly focus on sustainability research. However, the journal Computers and Industrial Engineering is popular because of the research methodologies used and because this topic is popular in the Industrial Engineering domain.

The last two stages, literature synthesis and analysis and reporting of results in the systematic review, will be explained in the next sections of the paper.

In the literature Synthesis and Analysis stage, individual publications are broken down into smaller components for understanding and their relationship with other publications on the same topic established. Synthesis and Analysis is usually made up of Descriptive analysis and the Thematic analysis.

The trends in the publication of research on resilient and sustainable CLSCs is shown in Figure 2.

The general trend is an increase in the number of publications on resilient and sustainable CLSCs. Publications on this topic started in 2014, however, the topic was not very popular until after 2019. The COVID-19 pandemic made resilience of supply chains an interesting topic. This can be seen from Figure 2 as it shows significant increases in publications after 2019. The sharp decrease in the year 2023 is because this article was written at the beginning of 2023.

A distribution of these publications according to the year of publication is shown in Figure 3.

Publications on sustainable closed-loop supply chains started as early as 2014, however, publications on resilient CLSCs started around 2017. Combinations of resilience and sustainability in CLSCs started appearing after 2019 after the COVID-19 pandemic. This is shown by the increase in the number of publications termed “resilience + sustainability” and those termed “resilience + sustainability +others” in Figure 3. The Figure also shows how the COVID-19 had a strong impact on sustainability and resilience research. The year 2022 saw the growth in research on sustainable and resilient CLSCs as it not only has the highest number of publications but also the largest variety in terms of classifying publications according to resilience and sustainability. Sustainable CLSCs continue dominating the number of publications in most of the years, showing how important the topic is becoming. Sustainability seems to be a more important topic in CLSC research compared to resilience, based on Figure 3.

Although there are studies not focusing on specific products, most of the studies were empirical, focusing on the reverse logistics of specific products. The list of products common in research on this topic is represented in Figure 4.

Most research on resilient and sustainable CLSCs focused on waste electrical and electronic equipment (WEEE) and the automotive industry. WEEE and the automotive industry are still common products for research on CLSCs. This is because for some products, remanufacturing and refurbishing are not possible and they end up in open loop supply chains where products are sold to other parties. However, for research on resilient and sustainable CLSCs, it is interesting to note the interest in other manufacturing industries, for example tires, glass, plastics and face marks. The introduction of products such as face masks and their closed-loop supply chains have been influenced by the COVID-19 pandemic and the shortages of PPE associated with it. Research also investigated mining and processing industries, for example copper, stone quarries and steel. It is interesting to note that research on resilient and sustainable CLSCs has a more diversified product and industry focus.

The next section will carry out a thematic analysis of the literature on resilient and sustainable CLSCs.

This section will review literature on resilient and sustainable CLSCs based on the categories identified in Figure 4.2. Although six categories of research were identified, only 4 categories are explored in this publication; 1. Resilience, 2. Sustainability, 3. Resilience + Sustainability and 4. Resilience + Sustainability + Others. Each of these categories will be explored in the next sub-sections. In carrying out the thematic analysis, there were some issues of importance. These included:

• The level of decision-making

• Common resilience strategies

• Common key performance indicators under social, economic and environmental dimensions.

The level of decision-making was necessary to determine at which level sustainability and resilience decisions are incorporated in the supply chain. Supply chain network design is one of the most expensive and irreversible strategic level decisions of the supply chain. Return policies also fall under the strategic level of decision-making. According to Yu and Solvang (2020), supply chain network design is made up of first-level decisions that determine the optimal network configuration through locating facilities with different functions and second-level decisions that determine the optimal use of the network structure through allocating customer demand to different facilities and formulating the transportation strategy on each itinerary. Table 3 summarizes the levels of decision-making in supply chain network design problems was adopted from Yu and Solvang (2020), Sheriff et al. (2012) and (Ivanov et al., 2010).

Table 3 shows that most of the CLSC decisions such as disposition strategies and waste treatment and transportation fall under the tactical level of decision-making.

Another important issue when carrying out the thematic analysis was the consideration of different risks as well as resilience strategies in CLSCs. Supply chains face two classes of risks (Vali-Siar et al., 2022):

1. Operational risks that are rooted in the inherent uncertainty in the supply chain such as uncertainties in supply, demand, delivery time, transport time and costs. The probability of these disruptions is usually high; however, their negative effects are usually low and transient.

2. Disruption risks caused by disruptions in the supply chain. A disruption is an event that can affect a supply chain network. Disruptions are caused by natural disasters (e.g. floods and earthquakes) and intentional or accidental human actions (e.g. staff strikes, war and terrorist attacks) or technical factors (e.g. equipment failures or information system failures). Disruption risks are a result of the supply chain interacting with its external environment and their effects are more than those of operational risks.

To overcome these risks, several methods were identified and summarized in a review by Tukamuhabwa et al. (2015). The authors identified proactive and reactive resilient strategies. These resilient strategies are summarized in Table 4.

In the thematic analysis, common risks and resilience strategies employed in CLSCs will be employed and compared to the general resilience strategies summarized by Tukamuhabwa et al. (2015).

Finally, for a supply chain to be considered sustainable, it must consider, social, environmental and economic aspects. Economic sustainability has been framed as the “business case” by Dyllick and Hockerts (2002). Dyllick and Hockerts (2002) specified that the economic dimension of sustainability focuses more on economic capital: financial capital (i.e. equity, debt), tangible capital (i.e. machinery, land, stocks) and intangible capital (i.e. reputation, inventions, know-how, organizational routines). The economic dimension of sustainability is the most studied to date as organizations have been focusing more on the minimizing of costs and the maximizing of profits.

In a similar fashion, Dyllick and Hockerts (2002) framed environmental sustainability as “the natural case”. This “natural case” focuses on supply chains that do not engage in activity that degrades eco-system and the environment. Hence, the environmental dimension of sustainability focuses on minimizing the consumption of natural resources, minimizing dangerous emissions to the environment and minimizing activities that degrade or destroy the environment. The environmental dimension of sustainability has also been studied in greater detail and a combination of economic and environmental sustainability is one of the most common topics studied in supply chain management.

The social dimension of sustainability is framed as “the societal case” where companies contribute and add value to the societies that they operate in. Hence, the social dimension of sustainability focuses on community development, for example the creation of jobs and the development of people skills and health. The social dimension has not been looked at much by research and key performance indicators for the social dimension of sustainability are still being discovered.

For the three dimensions of sustainability to be considered, there is a need to have key performance indicators identified for each dimension considered in the supply chain. Common key performance indicators for sustainable supply chain network design were identified from literature and summarized by Joshi (2022) and these are summarized in Figure 5.

In this research, it was necessary to mention the KPIs in Figure 5 as a way of identifying which ones have been applicable to sustainable CLSCs and which ones may need further consideration. Research gaps will also be identified based on these KPIs.

This category defined CLSCs that focused only on supply chain resilience. Publications on resilient CLSCs constituted 20% of all publications. Only seven publications focused on resilient CLSCs.

A summary of the seven publications on resilient CLSCs is shown in Table 5.

From Table 5, most publications on resilient CLSCs focused on disruption risk and only one considered operational risk in addition to disruption risk. The publication by Vali-Siar et al. (2022) focused on network design for a mixed open and closed-loop supply chain. The authors considered the uncertainty in demand as the operational risk.

Most publications on resilient CLSCs focused on strategic and operational decisions, with facility location being the dominant strategic decision for resilient CLSCs. Pricing and inventory decisions were also important operational decisions considered in resilient CLSCs. Supply chain decisions at the tactical level were not common for resilient CLSCs. However, Shoaraye-Nejati et al. (2017) did consider tactical decision-making when they considered the allocation of capacities for various facilities.

Table 5 also shows that most research on resilient CLSCs focused on reactive resilience strategies. Based on the general classification of resilience strategies by Tukamuhabwa et al. (2015) in Table 4, some resilient strategies popular to current CLSC research have been identified and explained in Table 6.

From Table 6, most of the studies on CLSCs focused on the reactive resilience strategies of creating redundancy and demand management. Creating redundancy includes keeping spare capacity and inventory that can be used during a disruption. Common strategies used in creating redundancies include spare stocks, multiple suppliers and extra facilities (Glickman and White, 2006). At the same time, demand management involves influencing customer decisions in the supply chain as a way of managing disruptions. Demand management uses strategies such as dynamic pricing, assortment planning and silent product rollovers (Urciuoli et al., 2014). Some studies, however, did consider proactive resilience strategies when they focused on building security. Building security includes strategies such as fortification of facilities to protect facilities from obvious disruptions such as theft and terrorism (Pettit et al., 2013).

Unique research by Katsoras and Georgiadis (2022) examined system response to a disaster event such as COVID-19. The authors used systems dynamics simulation to develop five business scenario settings for the manufacturer as alternative mitigation policies in responding to the wholesaler’s orders. These scenarios included an inventory management policy which remains constant throughout the planning horizon; the manufacturer adopts a speedy stock replenishment policy and operates with an additional shift in the post-disaster period; the manufacturer adopts a remote inventory policy; the manufacturer satisfies the wholesaler’s demand by contracting with a third-party producer who is not affected by the disaster event; and the manufacturer satisfies the wholesaler’s demand by contracting with a third-party producer who did not operate during the disaster period but has an increased percentage of supply in the post-disaster period. Katsoras and Georgiadis (2022) considered both pre-disaster and post disaster system responses and they considered both pro-active and reactive resilience.

Only one study by Vali-Siar et al. (2022) considered pro-active resilience strategies. Research on resilient CLSCs still provides a huge gap as there are only seven publications on the topic; however, it will be interesting to have studies incorporating pro-active resilience strategies.

Sustainable CLSCs are those that consider the economic, social and environmental perspectives of sustainability. Studies in this category excluded all studies that considered environmental and economic sustainability only, economic and social sustainability only and environmental and social sustainability only. These studies made up most of the research on resilient and sustainable CLSCs. A summary of studies on sustainable CLSCs is provided in Table 7. It should be noted that the classes for the social, economic and environmental KPIs are obtained from Figure 5. The classes for the levels of decision-making are obtained from Table 3 where the strategic level is named class 1, tactical level class 2 and operational level class 3.

Table 7 shows some blank spaces under the economic dimension KPIs which are classified under supply chain structure. These include technology integration, communication and coordination and quality issues. These have not been explored by sustainable CLSC research. In a similar way, there is a blank column for the social KPIs under social status, mostly location and human rights issues. Almost all the studies focused on maximizing jobs created and the safety and health of workers as social sustainability measures. Additional measures were mentioned by Elfarouk et al. (2022) (job satisfaction and customer satisfaction), Emamian et al. (2021) (social justice), Pourmehdi et al. (2020) (lost working days) and Soleimani (2021) (social service constraints). These measures of social sustainability have not been explored in depth, and it will be more interesting to have more research on them. In addition, the focus of most CLSC research has been on the minimization of costs and greenhouse gases and the creation of jobs. Other KPIs for sustainability have not been addressed. This presents a gap for research.

From Table 7, it can be observed that most of the studies on sustainable CLSCs focused on the strategic decisions of facility location and allocation. Authors such as Tavana et al. (2022) and Nayeri et al. (2020) also focused on supplier selection as additional strategic level decisions of supply chain network design. At the tactical level of supply chain network design, the pricing of products and inventory management were the most investigated topics by all authors. Routing, flow of products and the planning of production were some of the operational decisions that were explored by researchers on sustainable CLSCs. It is also interesting to note that most of the publications on sustainable CLSCs combined different levels of supply network design decision levels. Some authors, for example, Soleimani (2021), Mirzagoltabar et al. (2021), Devika et al. (2014), Rafigh et al. (2021) and Zhalechian et al. (2016) addressed all three levels of supply chain network decision-making in their research. Another interesting point to note is that most research on sustainable CLSCs was empirical focusing on different products, although most of it was limited to one country mostly, Iran.

Research on sustainable CLSCs has been increasing over the years, however, sustainable CLSCs are still a topic of interest because measures for the social dimension of sustainability are still to be discovered and explored at all levels of decision-making in the CLSC.

Furthermore, research on sustainable CLSC can develop by considering the technological aspects of CLSCs. It would be interesting to merge sustainability in CLSCs with technological considerations such as the internet of things and Industry 4.0 among other technologies. In addition, issues such as the pricing of new and remanufactured products have not been investigated much by research on sustainable CLSCs; hence, research can benefit from combining such issues with common issues like facility location and allocation.

Resilient and Sustainable CLSCs combined the resilience strategies mentioned in Section 4.2.1 and the sustainability dimensions in Section 4.2.2. Most of the research with combined resilience and sustainability started in the year 2020 after the COVID-19 pandemic and research on combining resilience and sustainability has been slowly increasing over the years. In this review, only nine publications focused on resilient and Sustainable CLSCs. The nine publications on resilient and sustainable CLSCs are summarized in Table 8.

Like sustainable CLSCs, Table 8 shows gaps in the supply chain structure KPIs and social status KPIs for the economic and the social dimensions respectively. Some of the publications on resilient and sustainable CLSCs do not address the social dimension at all. They focus on the environmental and the economic dimension only. Studies conducted by Yousefi-Babadi et al. (2021) and Yavari and Zaker (2020) did not address the social dimension of sustainability. This shows the need for more research on resilient and sustainable CLSCs. Almost all research on resilient and CLSCs has focused on real world case studies, which is a good thing, however, there is a huge focus on the tire industry. It would be interesting if there was research on other products and on processing industries.

Table 8 also highlights the same resilient strategies mentioned by literature focusing on resilient CLSCs. Two new methods of supply chain resilience were mentioned by Baghizadeh et al. (2021) and Afshar et al. (2022). Baghizadeh et al. (2021) focuses on the importance of reducing supply chain node complexity as a way of improving supply chain resilience. Focusing on reducing node complexity is a resilience strategy that focuses on supply chain network design, and it is a pro-active resilience strategy. In their network design research, Baghizadeh et al. (2021), calculated the optimal locations for distribution centers, secondhand product collection centers and recycling centers and they argued that “if the nodes and paths between the nodes increases, so does the nodes and paths complexity and thus the CLSC flexibility is reduced, and less flexibility leads the network to lose the ability to cope with change. Their research mostly focused on the tire manufacturing industry in Iran. In different research, Afshar et al. (2022) focused more on reactive resilience as they focused more on the repair of damaged facilities to return the system to its optimal operating conditions based on different demand conditions. Although research on sustainable and resilient CLSCs is still new, these two resilient strategies are also worth looking into and reactive resilience presents an interesting research gap.

There is a limited focus on operational risk as well as pro-active resilience strategies. Like the resilient CLSCs, this still presents a significant research gap. Research on resilient and sustainable CLSCs should also consider reactive resilience, where a disruption has already happened, for example the research by Afshar et al. (2022) who considered the repair of facilities after a disruption. It would also be interesting to have research that focuses on both pro-active and reactive resilience in one study.

In terms of the levels of decision-making, it can be seen from Table 8 that most of the integration of resilience and sustainability in CLSCs was carried out at the strategic level of facility location and some inclusion of the operational decision of distribution planning and routing. This is almost like sustainable CLSCs and resilient CLSCs. Most of these decisions have been incorporated at the strategic level of decision-making. However, because there are only nine publications on the topic, one cannot conclude that resilience and sustainability can only be integrated at the strategic level. Research can be expanded by investigating other strategic and tactical decisions such as supplier selection, the level of production technology and route selection. A consideration of operational risks and disruption risks simultaneously is also necessary to expand research on resilient and sustainable CLSCs.

This section considers those studies that did not only consider sustainability and resilience in a CLSC simultaneously, but they also managed to consider other supply chain issues in addition to sustainability and resilience in CLSCs.

Supply chain responsiveness has been defined by Gunasekaran et al. (2008) as the ability of a supply chain to adjust to changes in customer demand. In addition, Sabouhi et al. (2020) identified different approaches for considering responsiveness in optimization models. The first approach is to define some objective functions like minimizing lateness of delivery, maximizing the fill rate of customers’ demand or minimizing the unmet demand. The other approach defines some constraints in the optimization model, for example constraints on the fulfillment rate of customers’ demand. Vali-Siar and Roghanian (2022) are the only authors who considered responsiveness in their responsive and sustainable CLSC network design, and they modelled responsiveness by imposing constraints on the fulfillment rate of customers’ demand. The fact that only one publication focused on responsiveness makes the topic an interesting gap for further research. In addition, there is a need to explore the other methods for modelling responsiveness in sustainable and resilient CLSC network design problems as mentioned by Sabouhi et al. (2020).

The robustness of a supply chain is also an interesting characteristic that has been explored by other authors to be combined with sustainability and resilience in CLSCs. The difference between supply chain robustness and resilience has always been a topic of debate. However, Brandon-Jones et al. (2014) clarified the two terms and explained their differences. Robustness in a supply chain is when a supply chain can maintain its operations despite changes in its operating environment while supply chain resilience is the ability of a supply chain to return to its original state after a disruption or disturbance. In other words, resilience takes over where robustness fails to absorb the effects of disruption, since resilience is only necessary after a disturbance or disruption has occurred. Lotfi et al. (2021) and Mehrjerdi and Lotfi (2019) modelled the concept of robustness in sustainable and resilient CLSCs using the Mulvey robust scenario-based approach defined by Mulvey et al. (1995) called robust optimization (RO). The concept of robustness is another interesting research gap in the context of sustainable and resilient CLSCs.

The agile strategy in supply chains involves actions taken by a supply chain to adapt to rapidly changing environments (Rosário Cabrita et al., 2016). Such actions include mass customization and postponement as a way of responding to market requirements. A viable CLSC “integrates sustainability, resilience and agility into a circular economy” (Ivanov, 2020). The viable CLSC model was adopted by Lotfi et al. (Lotfi et al., 2022) who adopted agility in their model by assuming that all demands in the model should be satisfied, and no shortages were allowed. In considering agility, Mohammadzadeh et al. (2020) also modelled what they termed a “LARG” CLSC that considered lean, agility, resilience and green strategies in CLSC. In their research, the authors investigated the co-existence of the four strategies in a CLSC, as some of the strategies have conflicting principles. In the LARG model, agility was modelled by considering the facilities’ surplus capacity, scattered facilities and the transportation vehicle. Aghamohamadi-Bosjin et al. (2022) also considered the agility of their CLSC by designing a queue system to reduce the driver and depreciation cost of trucks due to waiting time at the distributors. The queue system also reduced the waiting time of machines in routes due to disruption effects. This was a quick-response strategy derived from the agile manufacturing concept.

A high dependance on Just-In-Time (JIT) means that the lean strategy is aimed at based on cost reduction and flexibility and is focused on eliminating and identifying the various sources of waste. Under this strategy, inventory is a form of waste and must be eliminated. This kind of contradicts with some resilience strategies of having backup inventory. However, it is interesting to note that there are publications that integrated sustainability, resilience and the lean strategy in CLSCs. For example, Aghamohamadi-Bosjin et al. (2022) maintained the leanness of their CLSC by increasing the routing options. In this context, designing a routing problem with various decisions was meant to reduce the number of trips and provide a wider area of routing. In their LARG CLSC, Mohammadzadeh et al. (2020) introduced leanness by aiming at decreasing costs by reducing the number and dispersion of facilities and using the cheapest strategy. It is also interesting to note that the research by Mohammadzadeh et al. (2020) investigated the co-existence of leanness, agility, sustainability and resilience in a CLSC, since the four have conflicting principles.

It is important for a supply chain to be reliable. In a logistics system, reliability is the ability to meet customer demands on time and with the best quality (Warburton, 2004). To achieve reliability in resilient and sustainable CLSCs, the conditional Value at Risk (CVaR) index has been used to achieve reliability through risk reduction by authors such as Mehrjerdi and Lotfi (2019), Lotfi et al. (2021a) and Shabbir et al. (Shabbir et al., 2021). The availability coefficient in capacity constraint was applied by Lotfi et al. (2021) and Shabbir et al. (2021) to represent a reliable facility with disruption.

There is a need to explore resilient and sustainable CLSCs integrated with other supply chain issues. Two such common CLSCs have emerged, the viable and the LARG CLSC have been introduced in literature, yet there is little research on such CLSCs, which makes them an interesting gap for research.

The relationships between resilience and sustainability in supply chains have been disputed by different authors. Shashi et al. (2020) argued that research on supply chains does not link the aspects of resilience to dimensions of sustainability clearly. Because of this several authors have come up with theories regarding the integration of sustainability and resilience in supply chains. For example, Pavlov et al. (2019) and Davoudabadi et al. (2020) mentioned that the increase in risks and disruptions in supply chains require that resources should be reserved to deal with disruptions in supply chains to make them more flexible, redundant and pro-active. However, Roostaie et al. (2019) argued that network redundancies in supply chains require an increase in resource consumption and inventory which violates the basic principle of efficiency in supply chains which represents sustainability. Zahiri et al. (2017) added that supply chain network redundancies significantly impact the social dimension of sustainability because the supply chain would not contract exclusively with local suppliers.

Despite these negative observations regarding the integration of sustainability and resilience in supply chains, Fahimnia and Jabbarzadeh (2016) observed a positive relationship between resilience and sustainability through the interoperability of information systems. Information systems are said to allow visibility and effective information exchange for joint decision-making which makes the supply chain resilient to disruptive events. Fahimnia and Jabbarzadeh (2016) argued that although this generates additional costs, it does create a positive relationship with the social dimension as a continued operation of the supply chain is likely to generate more employment.

Based on these arguments, Marchese et al. (2018) observed that the relationship between sustainability and resilience can take three forms:

1. Sustainability and resilience as separate conceptual objectives meaning that managing sustainability does not contribute to resilience nor does managing resilience contribute to sustainability.

2. Sustainability as a component of sustainability means that the goal of the system is resilience, and that sustainability is a process that helps this goal.

3. Resilience as a component of sustainability means that resilience is a necessary precondition for the fulfillment of sustainability considering that businesses are sustainable if their core activities are resilient to disruptions.

Based on the three forms of relationships observed by Marchese et al. (2018) research on resilient and sustainable CLSCs has been investigated to identify relationships as well as trade-offs between resilience and sustainability in CLSCs. Table 9 summarizes these relationships.

From Marchese et al. (2018) classifications, the relationship between resilience and sustainability in CLSCs, has been investigated more from the third form where resilience is a component of sustainability. Most of the studies investigated the impact of introducing resilience on the dimensions of sustainability in CLSCs. In the network design, most of the research has considered CLSCs with the objectives of maximizing their economic, social and environmental impact. However, their networks face disruptions and they must incorporate resilience to an existing sustainability objective, making resilience a part of sustainability. None of the research investigated sustainability as a part of resilience.

In addition, the impact of resilience on sustainability is still unclear as different authors give different conclusions for different sustainability objectives. One thing is clear, however, introducing resilience to a CLSC that already has sustainability objectives will increase the costs during implementation, and this seems to be true no matter what resilience strategy is applied. In the case of applying backup strategies, i.e. backup facilities and backup suppliers, implementing costs will increase then decrease during a disruption. This is in favor of the economic dimension of sustainability. Having backup also creates employment opportunities, this agrees with the argument by Fahimnia and Jabbarzadeh (2016) that resilience improves the social dimension of sustainability. In terms of environmental sustainability, there has been no clear agreement as to the impact of having backup facilities. For example, Fazli-Khalaf et al. (2021) argue that opening more facilities and decentralizing the CLSC could result in more availability and probability shorter paths thereby lowering the carbon dioxide emissions. However, this is a different conclusion by other authors such as Akbari-Kasgari et al. (2022) who argue that having backup facilities increases pollution and energy consumption. The same arguments apply for other resilience strategies such as multiple sourcing.

In terms of trade-offs, the most common trade-off is that of environmental pollution and economic and social benefits. While incorporating resilience seems to benefit a supply chain economically and socially, it increases the pollution to the environment. Supply chain networks need to strike a balance between the economic and social benefits and the amount of pollution they are willing to release to the environment. In addition, the tradeoff between the implementation costs and the economic and social benefits cannot be ignored. Introducing additional sourcing options, opening backup facilities, fortifying facilities and capacity expansion are all examples of resilient strategies that require financial investments and although they have economic benefits in the case of disruptions, a network must consider exactly how much financial investment they are willing to make and weigh that against the benefits.

Research on CLSCs incorporating both resilience and sustainability is still in its early stages. The publications on this topic do not explore all relationships between resilience and sustainability. They just investigate how resilience impacts sustainability but not how sustainability impacts resilience. For this reason, there is a need for more research on resilient and sustainable CLSCs, specifically exploring the interactions and relationships between the two. It is quite possible for a supply chain to be resilient and to incorporate sustainability into an already resilient supply chain. In addition, the research seems to disagree on some aspects, so more research on the benefits, tradeoffs and relationships between sustainability and resilience in CLSCs is necessary to draw more informed conclusions.

The research gaps for each subtopic have been identified and represented in the research framework shown in Figure 6. Figure 6 shows research gaps common to all the subtopics as well as those unique to each subtopic.

There is a need for more research on pro-active resilience strategies. Most proactive resilience strategies fall under the strategic level of decision-making as they cannot be easily changed over time. Issues such as appropriate supplier selection and development, supply chain collaboration, co-opetition, network design and the use of information technology are pro-active and strategic decisions that can also be combined with reactive strategies to make a CLSC more resilient. For the reactive resilience strategies, it would be interesting if more research explored supply chain issues that have nothing to do with the supply chain network structure, for example the demand management options of dynamic pricing of products, assortment plans for products and silent product rollovers and investigating on how these issues contribute to the resilience of the CLSC. Another interesting topic would be the postponement in the manufacturing of products as a resilience strategy in CLSCs.

Research on resilient and sustainable CLSCs should also consider reactive resilience, where a disruption has already happened, for example the research by Afshar et al. (2022) who considered the repair of facilities after a disruption. It would also be interesting to have research that focuses on both pro-active and reactive resilience in one study. More research on resilient CLSCs investigating both proactive and reactive resilience strategies simultaneously in one problem is also needed.

Resilience in CLSCs has been investigated more from the strategic level of decision-making with dominating topics being the location, allocation and the number of facilities, capacity of facilities and vehicle planning. There was very little focus on how the supply chain was coordinated to ensure CLSC resilience. In addition, most of the research was focused on the forward part of the CLSC, there was little or no consideration of the reverse part of the CLSC where issues such as return policies, disposition strategies, hazardous waste treatment and disposal and the collection and the return rates of products, yet these are the main concerns of CLSCs. It would be interesting to have more research focusing also on aspects affecting the reverse chain in a CLSC.

The social dimension has been overlooked in most sustainability research and Akbari-Kasgari et al. (2022) argued that the lack of attention to the social dimension means that a combination of resilience and sustainability will always remain a research gap. Considering the research framework in Figure 6, although the social dimension of sustainability has been explored by all studies, it seems that all of them focused more on the service issues and work environment issues of job creation and the health of employees. The most common social objective by all publications was job creation. This shows that the social dimension of sustainability is still under explored. In the research framework, the social dimension has been categorized into three classes, the social status, service issues and the work environment. The social status which consists of human rights and location has not been explored at all. At the same time, under service issues, culture and gender equality issues have not been explored in sustainable CLSCs. The work environment has more social issues for exploration such as staff satisfaction, skills uplifting, insurance, quality education and infrastructure development. In the development of facilities, infrastructure development can be considered as an objective in the social dimension of sustainability. As a result of all this, the social dimension of sustainability remains under explored and sustainable CLSC are still an interesting gap for research.

Almost all aspects of the economic dimension of sustainability have been explored, however, the issues of technology integration, the quality of returned products and communication and co-ordination have not been explored at all. Technology integration is an important objective especially as the operation of CLSCs is now being made simpler by the integration of concepts such as Industry 4.0 to make traceability and visibility in the supply chain easier. Quality is also an important issue in CLSCs. Quality considers two issues, the quality of the returned products and the quality of the recycled or the remanufactured product. For this reason, it is necessary to have research on the economic dimension of sustainability considering technology integration costs and quality costs as well.

Although three dimensions of sustainability have been explored, Santander et al. (2022) argued that “for a system to be sustainable, it should not only include economic, environmental and social dimensions, but it must also consider technological and political aspects and their subsequent sustainability indicators for their evaluation”. In their argument, Santander et al. (2022) mentioned the interest of governments in increasing the recycling rates of products and maintaining a circular economy, for example the Chinese waste embargo that reshaped how plastic exporting companies managed their plastic waste. From a technological perspective, specific recycling technologies may change how industries and supply chains operate and offer specific challenges to CLSC network design. All this needs to be considered in sustainable CLSCs. For this reason, it would be interesting to have new research on sustainable CLSCs considering five dimensions of sustainability and not just a focus on the social, environmental and economic dimensions of sustainability. This is because of the challenges that come about when a reverse chain is integrated into an existing forward chain and the processes and networks become more complex.

To expand research on resilient and sustainable CLSCs, it is also necessary to investigate other strategic and tactical decisions such as supplier selection, the level of production technology and route selection. Most research focused on network design and facility location problems. Research can also be expanded by considering operational risks together with disruption risks.

Research on sustainable and resilient CLSCs did not clarify the interactions between resilience and sustainability. The assumption by most of the research was that resilience is being added to a network that already has sustainability goals, thereby making resilience a tool for achieving sustainability. None of the research investigates how sustainability might be used as a tool to achieve resilience. In terms of benefits and tradeoffs, there are conflicting findings. This means that more research on resilient and sustainable CLSCs is necessary to explore interrelationships and interactions between resilience and sustainability in CLSCs.

In general, research on resilient and sustainable CLSCs is still not much, and there is need for more research on the topic. The social dimension of sustainability continues to be under explored, making the topic very relevant. It would also be interesting to add political and technological aspects as objectives of sustainability in addition to the existing three dimensions of sustainability in resilient and sustainable CLSCs as well. The assumption that remanufactured products are as good as new also needs to be relaxed in resilient and sustainable CLSCs and there is need to explore scenarios where remanufactured products have a secondary market.

The goal of this paper was to systematically review literature on resilient and sustainable CLSCs and come up with a research framework on the topic. The research questions and the inclusion and exclusion criteria managed to find 56 publications from 2014 up to 2023. The review explored CLSCs from different categories including resilient CLSCs, sustainable CLSCs, resilient and sustainable CLSCs, sustainability and others, resilience and others and resilience, sustainability and others CLSCs to come up with the major issues investigated together with resilience and sustainability in CLSCs.

The research started by defining “resilience” and “sustainability” and establishing relationships between the two conflicting topics as concluded by other authors. The research then identified other reviews on resilience and sustainability in supply chain management and explained how they are different from this review. By carrying out descriptive and content analyses, the review managed to explain the review strategies, sustainability goals, research methods and the levels of decision-making mostly explored by research on resilient and sustainable CLSCs. This led to the development of a research framework to identify future research gaps in resilient and sustainable CLSCs.

The findings will be useful for practitioners, allowing them to compare the benefits and trade-offs involved in integrating resilience and sustainability in closed-loop supply chains. Identifying the level of decision-making for resilience and sustainability in CLSCs may also assist practitioners in estimating costs, timelines and investments associated with such changes and updates in supply chain networks. Findings of this research will also be beneficial for researchers interested in investigating interactions between resilience and sustainability in a closed-loop supply chain setting. The relationship between sustainability and resilience is still a debatable issue. It is still necessary to determine whether resilience enhances sustainability or if it is sustainability that enhances sustainability. For this reason, more research is still necessary to understand these relationships. This paper will serve as a map for researchers to identify research gaps that will lead to answers to questions relating to integrating resilience and sustainability in CLSCs.

The research presented a systematic review on literature on resilient and sustainable CLSCs, however, the review focused only on articles from peer reviewed articles and only on publications written in English. The article did not consider book chapters, conference proceedings, reports and other types of literature. This means that the review is not exhaustive of all literature on resilient and sustainable CLSCs. The article also focused specifically on CLSCs, and it did not consider reverse logistics or open loop supply chains where returns do not return to the OEM. This could be a limitation as there are many organizations that have open loop supply chains. The review also ignored articles that did not focus on all three dimensions of sustainability. This means that articles that focused on environmental and economic sustainability only or on economic and social sustainability only or on environmental and social sustainability only were not considered in this research. This also means that there was literature on resilient and sustainable CLSCs that were left out.

Future research can consider technological and political factors in the integration of sustainability and resilience in CLSCs. Future research can also relax the focus on closed-loop supply chains and consider all types of reverse supply chains, including those in which the product does not return to the original equipment manufacturer for disposition. Another issue to consider is the role of third- and fourth-party logistics providers and how they are impacted by integrating resilience and sustainability in CLSCs.

Funding: No funding was provided for this research.

Ethics approval and consent to participate: No ethics approval was required for the review.

Data availability: Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Competing interests: The author reports there are no competing interests to declare.

Author’s contributions: Linda Tombido searched for the articles for the research, classified them according to the themes reported in the research and carried out the literature review. Linda Tombido authored the manuscript and made all the necessary editing. The article only has one author.