Exploring the relationship between Lean and Green for further research

Abstract

Purpose

Exploring the Lean and Green relationship goes back to the beginnings of Lean manufacturing. Most cases established that companies implementing Lean have Green results. However, there are Lean practices with a higher impact on Green, but others with less impact. Therefore, this paper presents research that explores the relationship between Lean and Green in manufacturing companies and aims to determine whether Lean practices have a higher association with Green aspects.

Design/methodology/approach

A survey was conducted amongst manufacturing firms to determine their Lean Index (LI). The internally related elements of the Lean construct determined each firm’s LI, whilst Cronbach alpha determined internal LI consistency. The survey also identified firms developing six Green aspects: International Organisation for Standardisation (ISO) 14001, ISO 50001, general Green aspects and the specific aspects of materials, energy and water. An individual sample t-test shows different LI levels of association for each Green aspect. Binomial logistic regression shows the LI element association for each Green aspect.

Findings

LI is higher at firms reporting the inclusion of Green aspects. More than half of LI components have a statistically relevant association with the six Green aspects. In general, Ishikawa diagrams had the highest association with Green aspects whilst the lowest was seen in workers as improvement initiators. By grouping the LI elements into their categories, the Lean practices related to controlling processes have a higher association, whilst the involvement of employees has the lowest.

Research limitations/implications

Further research found in this paper identifies the possibilities for investigating the specificities of each Lean tool to develop Green aspects in companies.

Practical implications

Practitioners learn that Lean and Green are not separate issues in business. This article provides evidence that Lean practices in place at companies are already associated with Green aspects, so integration may already be happening.

Originality/value

This paper provides specifics on the relationship between each Lean practice and developing Green aspects. Thus, this paper specifies the Lean practices that contribute most to Green efficiency to support the joint development of both themes.

Citation

Martinez, F. and Jirsák, P. (2024), "Exploring the relationship between Lean and Green for further research", Journal of Manufacturing Technology Management, Vol. 35 No. 9, pp. 73-93. https://doi.org/10.1108/JMTM-05-2023-0165

Quick value overview

Interesting because: This manuscript addresses a research gap between the Lean–Green relationship. The theoretical and global aspects of this relationship have existed since the advent of Lean Manufacturing. Moreover, there is a lack of research on the association of specific Lean practices with Green aspects. This study aims to fill this gap by reviewing their association.

Theoretical value: This research solidifies the Lean–Green relationship with new empirical evidence. Each association opens a unique line of research, offering the potential to uncover insights into how a Lean practice can foster Green aspects. For example, the “Cause and Effect” diagram (Fish/Ishikawa) has the highest association with Green aspects, representing an opportunity to delve into applying this practical tool for Green solutions.

Practical value: This article offers a valuable resource for managers and promoters of Lean in organisations. It provides a comprehensive list of Lean practices – already implemented by organisations – but with the added insight of their association with Green aspects. This knowledge is a tangible, proven tool to advance the company’s Green objectives.

Introduction

Lean manufacturing introduces a management approach to improve the efficiency of organisational operations (Womack et al., 1990). Similarly, environmental thinking calls for efficiency in operations, which opens the debate on the relationship between Lean and Green (Verrier et al., 2016). The early connection between Lean and Green inspired research into the opportunity to include Green in the modernisation of factories (Florida, 1996) and the establishment of a relationship between the implementation of International Organisation for Standardisation (ISO) 9001 and ISO 14001 norms (King and Lenox, 2001).

Nevertheless, research also found evidence that this relationship is relatively weak, contrary to expectations (Hallam and Contreras, 2016). Their work shows that Lean practices push Green outputs as reducing waste can be seen as lower emissions of environmental waste. However, this is still a conversation about a dichotomy. Green and Lean implementation are separate organisational efforts that must be integrated (Hegedić et al., 2018; Hallam and Contreras, 2016).

In later years, the discussion moved into the relationship between Lean and Green practices, concluding that implementing both practices separately influences the environment. However, integrating both approaches provide better results (Kleindorfer et al., 2005). Furthermore, an in-depth case study analysis concluded the use of quality control tools in manufacturing systems helps to implement Green initiatives (Singh et al., 2022).

Nevertheless, a research gap remains in the need for more empirical evidence to establish the relationship between Lean and Green (Caldera et al., 2017; Hallam and Contreras, 2016; Kleindorfer et al., 2005; Verrier et al., 2016), but most importantly into the specific Lean practises than facilitate Green outputs (Hegedić et al., 2018; Inman and Green, 2018; Rothenberg et al., 2001). Thus, this paper presents research that explores the relationship between Lean and Green in manufacturing companies, aiming to determine which Lean practices have a higher association with improving Green efficiency and to identify the practices that facilitate the integration of both management approaches.

The paper establishes the current relationship between Lean and Green from a review of literature. Then the question is posed: Do Lean practices have an association with Green aspects? Furthermore, the research establishes a Lean Index (LI) implementing the Lean production construct (Shah and Ward, 2007). The data collected from the survey determines the LI of each firm and notes the presence of six Green aspects at each firm. Then, the hypotheses are determined and tested to discover the relationship between Lean and Green and later the association that each implemented Lean concept (ILC) has with each Green aspect. The results of the hypotheses testing contribute to enhancing the relationship between Lean and Green and the possibilities of their integration through specific Lean practices.

Literature review – Lean and Green

The relationship between Lean and Green has been explored from different perspectives. Lean manufacturing pursues the increase of value to the customer by reducing the waste of the operation in a context of continuous improvement (Browning and de Treville, 2021; Hopp and Spearman, 2021; Martinez, 2019; Shah and Ward, 2003; Stone, 2012; Womack et al., 1990).

On the other hand, the concept of Green pertains to the understanding of sustainability (D’Amato et al., 2017; Sun et al., 2023; United Nations, 2015), which in turn is a rather broad concept that has been debated and analysed since the 1970s, reaching operationalisation in the form of the sustainable development goals (SDGs) (United Nations, 2017). Under this framework, the conceptualisation of Green manufacturing (environmental scope) focuses on reducing the environmental impact of operations and improving environmental efficiency by also successfully meeting other business objectives, including financial ones (Garza-Reyes, 2015). Certifications such as ISO 14001 look at environmental aspects to reduce their impacts, which ISO claims is a practical way to meet many of the SDGs (ISO, 2016), and it is an initial step for the development of a sustainable strategy (MacDonald, 2005). Thus, understanding the Green concept as the reduction of the impact of a manufacturing system on the environment is in line with higher concepts such as the SDGs and certifications such as ISO 14001 that see this approach as fundamental and practical to developing robust, sustainable strategies (D’Amato et al., 2017; Garza-Reyes, 2015; ISO, 2016; MacDonald, 2005; Sun et al., 2023). Therefore, Green comprises all activities aimed at reducing the impact of environmental aspects (Garza-Reyes, 2015). Consequently, the reduction of waste is an essential link with the environmental approach as the increase in effectiveness reduces the consumption of the input mix (i.e. materials, energy and water), and therefore, the expectation is to reduce the impact on the environment (Caldera et al., 2017; Corbett and Klassen, 2006; Dieste et al., 2019; Dües et al., 2013; Garza-Reyes, 2015; Verrier et al., 2016).

Current knowledge includes academic papers that seek to establish the relationship between Lean and Green. There is evidence of Lean models with a contribution to sustainability (Caldera et al., 2017); the establishment of the relationship between Lean and Green using waste (Verrier et al., 2016); the applicability of Lean tools in a Green context (Kleindorfer et al., 2005); the possible integration of both approaches (Hallam and Contreras, 2016); and even proposing conjectures between them (Corbett and Klassen, 2006). A positive relationship between Lean and Green has been established in these publications. However, there is still a need for empirical evidence to confirm that relationship in the pursuit of their integration.

Singh et al. (2022) explore the relationship of Lean/Green through formal interviews with experts. Their research establishes the integration barriers for this relationship. Using experts from a specific context, such as small and medium industry (SMI), provided understanding and proposed models for integrating these two perspectives within that specific field (Amrina et al., 2021). On the other hand, cases and multi-cases constantly show the existence of the Lean/Green relationship and how Lean tools become a natural bridge for the integration of both perspectives within an organisation’s operational strategy (Galeazzo et al., 2014; Kurdve et al., 2014; Mårtensson et al., 2019; Ng et al., 2015; Piercy and Rich, 2015; Pinto and Mendes, 2017). Nevertheless, there is still a need to determine the practices that allow or facilitate the integration of both perspectives.

Existing empirical research shows evidence of how Lean practices influence the environment and environmental management. The beginning of research into this relationship uses innovation in production to increase efficiency as the bridge to verify the impact of these innovations on the environment (Florida, 1996). Similarly, ISO certifications are the tool to investigate whether organisations with quality certification are more likely to obtain environmental certification (King and Lenox, 2001). The work from Inman and Green (2018) confirms the positive Lean/Green relationship through Lean practices. Similarly, Hegedić et al. (2018) found the relationship between Lean practises and the environment; and the work from Rothenberg et al. (2001) confirmed that influence. Nevertheless, the research gap remains as to which Lean practices have a higher association with the development of Green aspects.

In conclusion, the research gap in current knowledge remains the scarcity of empirical evidence confirming the Lean/Green relationship and, more importantly, the lack of evidence on which specific Lean practices have greater potential to develop Green aspects in the organisation (see Table 1). Bridging this gap provides practitioners with knowledge of tools that better integrate both perspectives.

Lean practices

The Lean production system is one of the most relevant manufacturing paradigms. Its conceptualisation emerges from a better understanding of the automotive industry (Womack et al., 1990). The success of this production perspective has been exceptional and many of its tools, concepts and practices have been implemented in several contexts outside manufacturing, going beyond its original industrial scope (Amaro et al., 2021; Bhamu and Sangwan, 2014; Stone, 2012).

Given this diversification, the definitions and conceptualisation of Lean have become a challenge in recent years (Åhlström et al., 2021). Browning and de Treville (2021) explore a definition of Lean from the perspectives of efficiency, the dichotomy of Value vs. Waste, its predecessor the Toyota Production System (TPS) and a synthesis of overlapping of definitions, amongst others. They claim it is impossible to turn Lean philosophy and Lean thinking into specific concepts. However, they retrieve some general practices proposed by Cusumano (1994) to determine when a system is Lean (Browning and de Treville, 2021).

Hopp and Spearman (2021) also point out discrepancies between the understanding of Lean amongst industrial practitioners and academics. In their work, they propose the tenets of Lean that cover its essence, which creates a structure to see the presence of Lean in any organisation.

Nevertheless, this exploration of concepts, definitions and theories yields three main elements of Lean: increasing customer value, reducing waste and continuous improvement (Amaro et al., 2021; Bhamu and Sangwan, 2014). Additionally, efficiency is a common idea across all definitions of Lean, especially Lean production (Bhamu and Sangwan, 2014; Browning and de Treville, 2021; Hopp and Spearman, 2021; Puram and Gurumurthy, 2021; Shah and Ward, 2003). Thus, when efficiency is considered a goal, it is possible to find specific activities in a manufacturing system that evidence the implementation of Lean concepts (Hopp and Spearman, 2021; Shah and Ward, 2003; Womack et al., 1990). Additionally, Lean manufacturing is a more specific term that includes a series of practices and elements that characterise a Lean system within a manufacturing firm (Shah and Ward, 2003, 2007).

Thus, a Lean practice is an activity or set of activities reflecting the application of a Lean concept that pertains to a component of Lean manufacturing (Cusumano, 1994; Shah and Ward, 2007; Vinodh and Chintha, 2011). In other words, the performance of these activities is the Lean practice that evidences the implementation of Lean manufacturing. The construct created by Shah and Ward (2007) describes specific activities performed in a manufacturing system and their relationship with Lean production (Åhlström et al., 2021; Browning and de Treville, 2021; Hopp and Spearman, 2021). This construct reflects Lean manufacturing, avoiding the discussion of its relevance in other Lean implementations outside this context (Vinodh and Chintha, 2011). The Web of Science shows this construct has been cited more than a thousand times (1,155) and used 21 times as a reference to determine a measurement of leanness. For example, the construct facilitates the determining leanness by identifying the most representative supply chain management (SCM) practices (Chardine-Baumann and Botta-Genoulaz, 2014). Also, the construct helps to determine the relationship between suppliers and customers to develop leanness (Lotfi and Saghiri, 2018). Furthermore, the construct determines the level of Lean in case studies (Fahimnia et al., 2015). Thus, the implementation of the construct as an instrument to measure leanness has several examples (Narayanamurthy and Gurumurthy, 2016; Vinodh and Chintha, 2011), which is a solid background to determine a manufacturing firm’s leanness – or LI – from specific Lean practices (Tortorella et al., 2022; Ghobakhloo and Fathi, 2020; Hu et al., 2015).

Green aspects

A Green aspect is an element that shows a system is striving for practices that help reduce the system’s impact on the environment. The most robust current approach to pursue these aspects is the 17 SDGs (United Nations, 2015). These are important targets that includes not just the Green components but embrace all aspects of sustainability (Amrina et al., 2021; Mårtensson et al., 2019).

The perspective of environmental social responsibility (ESR) (Siegel, 2009), as an extension of corporate social responsibility (CSR) is a collection of reasons for ESR implementation only under the circumstances of the firms' strategic and economic performance. It explores Green aspects as strategic and managerial approaches rather than specific practices implemented on the shop floor (Siegel, 2009).

A practical approach to Green aspects is the environmental management system (EMS) under ISO 14001. It is a certification norm that claims to include 12 out of the 17 SDGs (ISO, 2015), which makes it relevant for current sustainability issues. The norm does not list specific Green practices. On the contrary, it encourages firms to identify environmental aspects and their respective environmental impacts to develop specific practices that reduce their impact on the environment (ISO, 2015; King and Lenox, 2001).

Another certification related to Green aspects is ISO 50001, which governs energy management systems (ISO, 2018). The energy-saving predictions for its implementations are significant (McKane et al., 2017). A capability model based on plan-do-check-act (PDCA) further validates the positive impact of ISO 50001 on energy savings (Jovanović and Filipović, 2016). Although the implementation of certification is rare, firms with the certification report a positive impact on energy aspects. Besides, it is an excellent complement to ISO 9001 and ISO 14001 (Zimon et al., 2021).

Each of these perspectives possesses different aspects for evaluation. However, three Green aspects are repeatedly mentioned throughout the literature and are considered the minimum basis for considering Green manufacturing systems. These Green aspects relate to reducing the consumption of three elements: material, energy and water (Elshkaki, 2019; Green et al., 2012; Smith and Ball, 2012). Reducing material consumption, reducing the energy used to manufacture and reducing water consumption in the manufacturing process are the three primary aspects used to determine whether a system is Green. Thus, reducing the consumption of these three Green aspects allows the organisation to reduce its environmental impact (Zimon et al., 2021; Elshkaki, 2019; ISO, 2015; Green et al., 2012; Smith and Ball, 2012). Additionally, a manufacturing system certified with ISO 14001 and ISO 50001 proves the organisation develops specific activities to reduce its environmental impact and increase energy efficiency. Then, the research of these six Green aspects (ISO 14001, ISO 50001, general Green aspects and the specific aspects of materials, energy and water) constitute a base to determine the Green aspects in place at a company.

The literature review – Lean and Green – notes it is still necessary to establish which Lean practices have the strongest association with Green aspects (see Table 1) and that empirical evidence is still needed. Therefore, empirically investigating a company’ level of leanness as a result of applying Lean practices and comparing them with evidence of Green aspects in organisations will allow for a better understanding of which Lean practices have a stronger relationship with Green aspects. Therefore, the research question of this investigation is: Do Lean practices have an association with Green aspects? The objective is to determine the association of Lean practices with Green aspects and to determine those with stronger associations. Firstly, the LI determines the firm’s leanness level based on the Lean production construct (Shah and Ward, 2007). Then, the research examines whether the mean LI amongst firms implementing each Green aspect is higher than amongst firms without such an implementation. Finally, the research examines each Lean practice association level with each Green aspect to answer the research question.

Materials and methods

The research aims to find the level of association between Lean practices and Green aspects. A survey was implemented to gather data and determine the LI of manufacturing firms and to establish the existence of the six Green aspects at each firm. The LI implements the Lean production construct (Shah and Ward, 2007). This construct has been used many times for similar assessments (Åhlström et al., 2021; Browning and de Treville, 2021; Chardine-Baumann and Botta-Genoulaz, 2014; Fahimnia et al., 2015; Hopp and Spearman, 2021; Lotfi and Saghiri, 2018; Narayanamurthy and Gurumurthy, 2016; Vinodh and Chintha, 2011), providing a solid basis for developing a manufacturing company’s leanness index, or LI (Tortorella et al., 2022; Ghobakhloo and Fathi, 2020; Hu et al., 2015).

The research surveyed 145 manufacturing firms in spring 2022 as part of the European Manufacturing Survey (EMS) (Fraunhofer Institute for Systems and Innovation Research ISI, 2022). The only enterprises contacted were manufacturing companies listed under NACE codes 10000 to 33,200 (European Commission, 2015) of different size (20–49 employees, 50–100, 100–249, 250–499, 500–1,000, 1,000+). A contracted specialised research agency contacted the firms via telephone (Data Collect, 2022), locating the operations manager of the manufacturing system to conduct the survey and obtain the relevant data.

The EMS collects information on technological and non-technological aspects of European manufacturing companies. The introduction and use of organisational concepts such as Lean management, environmental management, technical modernisation of production processes and product and process innovation (as well as others) are consolidated in this periodic survey that is carried out approximately every four years (Fraunhofer Institute for Systems and Innovation Research ISI, 2022). Data collection was done telephonically by seeking out the operations managers of the factories. The survey queried these operational managers about their ILCs. Each ILC directly relates to Lean practices from the Lean production construct (Shah and Ward, 2007), which has been used successfully in several publications as explained in the Lean Practices chapter of this text (Chardine-Baumann and Botta-Genoulaz, 2014; Fahimnia et al., 2015; Ghobakhloo and Fathi, 2020; Hu et al., 2015; Lotfi and Saghiri, 2018; Narayanamurthy and Gurumurthy, 2016; Tortorella et al., 2022; Vinodh and Chintha, 2011). This Lean manufacturing construct includes three sections (Shah and Ward, 2007): Supplier-related activities, the involvement of the customer and finally internal-related constructs. The last incorporates the constructs of Pull, Flow, Low setup, Controlled processes, Productive maintenance and involved employees. The construct permits posing questions to assess the presence of each construct element within the manufacturing system. Thus, the assessment of Lean practices through this construct allows for the assessment of the leanness of a manufacturing system.

The operations managers review each ILC within their factories on a five-level Likert scale. This provides a value for each Lean Practice (x_i) at its correspondent (ILCx_i) and a total value for each company (respectively, a total value of each Lean Practice across all companies) as shown in the following equation:

LI=∑1ixii

Each x_i represents one specific Lean Practice related to one firm’s ILCx_i. Each x_i obtains its value based on the five-level Likert scale. Therefore, the sum of all Lean Practices (x_i) divided by the total number of Lean Practices determines the LI, which is a number for each company and each ILCx_i. Then, the Cronbach alfa determines the LI internal consistency (see Table 2).

In addition to the ILC data, the survey collects information on six Green aspects. The Green variables result from asking about the existence of any organisational concepts for Green development. Next, the survey includes specific questions on efficiency improvements in three Green aspects: materials, energy and water. Finally, the survey of operations managers explicitly asks whether their system is ISO 14001 or ISO 50001 certified.

The literature review determines the research question: Do Lean practices have an association with Green aspects? The objective is to determine the association of Lean practices with Green aspects and ascertain those with a stronger association. In the previous step, the study determines the LI based on the Lean production construct (Shah and Ward, 2007). In this next step, the research examines whether the mean LI amongst companies implementing each Green aspect is higher than amongst firms without such implementation. In other words, if a firm has a high LI, then it has a higher presence of these six Green aspects. Therefore, the hypotheses for this step are:

H1.

The mean LI amongst companies with ISO 14001 is higher than the mean LI amongst companies without it.

H2.

The mean LI amongst companies with ISO 50001 is higher than the mean LI amongst companies without it.

H3.

The mean LI amongst companies implementing any Green aspect is higher than the mean LI amongst companies without implementation.

H4.

The mean LI amongst companies implementing material reduction efficiencies is higher than the mean LI amongst the companies without implementation.

H5.

The mean LI amongst companies implementing energy consumption efficiencies is higher than the mean LI amongst companies without implementation.

H6.

The mean LI amongst companies implementing water consumption efficiencies is higher than the mean LI amongst companies without implementation.

The theoretical implications of the hypothesis are related to the research gap. As explained in the literature review, there are several examples in the literature that establish the relationship Lean/Green from different perspectives (Florida, 1996; Hegedić et al., 2018; Inman and Green, 2018; Kleindorfer et al., 2005; Rothenberg et al., 2001). However, evidence remains inconclusive about which specific Lean practice has a stronger association with environmental issues (see Table 1). These hypotheses allow us to again test whether the association between Lean and Green exists, but more importantly what is the level of association of each Lean practice with the Green aspects, which is still unclear in the current literature. By finding these associations, we seek to determine the Lean practices that have more significant Green development potential in companies.

An independent sample t-test of mean variation is used to test these hypotheses. It aims to determine whether the average LI amongst companies that apply any efficiency from the six Green aspects (ISO 14001, ISO 50001, Green, material, energy and water) is higher than the average LI amongst companies that do not apply them (Bell et al., 2022; Vanichchinchai, 2020). Box plots allow us to graphically verify if there is a difference between the average LI amongst companies that apply Green efficiencies and those that do not (Assef et al., 2018; Sun and Genton, 2011). The research uses SPSS, Jamovi, Excel and Minitab to perform these tests.

The next step examines each of the Lean practices for their level of association with each Green aspect to answer the research question. It determines which ILC is associated with each Green aspect. Therefore, an individual analysis of each LI (ILC) component is studied in association with each Green aspect. The aim is to find associations between each ILC and each Green aspect. Each Green aspect is represented as an equation where f(x) is the Green aspect and each xi is an ILC.

f(x)=f(x1,x2,x3,x4,…x24)

Binomial logistic regression allows us to demonstrate the association of each x_i with x, which is how each ILC is associated with each Green aspect (Hoffmann, 2016). ILCs with the lowest p-value have the highest association with Green aspects. Respectively, a high p-value represents a lower association with the Green aspect. The research also considers a p-value higher than 0.5 not to be associated with the selected Green aspect (Hoffmann, 2016).

A similar analysis searches for the association between the construct categories and the Green aspects (Shah and Ward, 2007). Each category c_i represents: c₁ = Pull; c₂ = Flow; c₃ = Low setup; c₄ = Controlled processes; c₅ = Productive maintenance; c₆ = Involved employees (Shah and Ward, 2007). In this instance, each Green aspect is represented as an equation in which f(x) is the Green aspect, but each c_i is a category of the construct. The analysis seeks to establish whether there is an association between the categories c_i and each x.

f(x)=f(c1,c2,c3,c4,c5,c6)

Similarly, the research implements binomial logistic regression to demonstrate the association of each ci with x. Here, it seeks to determine the association of each category with each Green aspect (Hoffmann, 2016). If the category has a low p-value, it will have a higher association with the Green aspect. Correspondingly, higher p-values will represent a lower association with the Green aspect. When the p-value is greater than 0.5, the same consideration applies and the research considers that the category is not associated with the selected Green aspect (Hoffmann, 2016).

The following diagram graphically summarises the different stages of the research (see Figure 1).

Results

The LI is created from the operations managers' responses to the survey. The internal consistency of the LI is high. The Reliability Analysis of the LI determines a Cronbach’s alpha of 0.910. Thus, the construct determines an index with high internal consistency. The LI mean is 2.37 with a median of 2.38. The standard deviation is 0.706, the maximum LI is 4.58 and the lowest is 1.00. The Confirmatory Factor Analysis loadings are statistically significant, with p-values lower than 0.001 and magnitudes greater than 0.4, confirming a solid construct to build the LI (see Table 3)

The number of companies implementing the Green aspect of ISO14001 is 25%, but only 5% in the case of ISO50001. In general, 50% of the companies implemented efficiency practices in one of the three Green aspects (seen as Green in Table 4). However, the analysis per Green aspect shows that 36% of the enterprises implemented efficiency initiatives to reduce material and 34% in energy efficiency, whilst water efficiency was only 13%.

The individual sample t-test of variation of the mean for each hypothesis assumes Ha 0 < 1. All the p-values have statistical significance, with the highest p-values are related to material reduction (see Table 5).

The following Box Plot graphs illustrate the statistical output of the variation of the LI for each Green aspect (see Figure 2).

All hypotheses are thus accepted. The mean of the LI amongst the companies implementing any Green aspect efficiencies (ISO 14001, ISO 50001, Green, material, energy, water) is higher than the mean of the LI amongst firms without implementation.

The following Table 6 includes the p-values determining the association level of each ILC with each Green aspect.

Since the number of firms that had ISO 50001 was just 5% of the sample, the binomial logistic regression output indicated that all p-values were 1 (see Table 6). Therefore, it is impossible to review the level of association of each ILC with the Green aspect of ISO 50001. On the contrary, 75% of LI elements have a p-value lower than 0.5 in the Green aspect ISO 14001. In the case of the three Green aspects, this percentage is 46%. Material is at 63%, but energy is only 38% and water 54%. Thus, it is possible to review their association with ILCs.

The individual analysis of the LI components showed that for ISO 14001, ILC22 (maintenance) was the LI element with the highest association with this Green aspect and ILC16 (process capability analysis) was the ILC with the lowest association. For all three Green aspects, ILC15 (Ishikawa diagrams) had the highest contribution, whilst ILC13 (statistical methods) had the lowest contribution. Considering just material, ILC05 (products grouped with similar processing requirements) had the highest contribution, whilst ILC18 (workers in the plant drive the improvement program) had the lowest. For energy, ILC04 (Kanban) had the highest contribution, whilst the lowest contribution was in ILC18 (workers in the plant drive the improvement program). Finally, for water, ILC01 (production is started by receiving a customer order) had the highest contribution, whilst ILC18 (workers in the plant drive the improvement program) was once again found to have the lowest contribution. The average of all six p-values showed the highest contribution from ILC15 (Ishikawa diagrams) and the lowest contribution was again ILC18 (workers in the plant drive the improvement program).

Table 7 shows the association level of each category of ILCs with each Green aspect.

When grouping LI elements by their categories (Shah and Ward, 2007), it is important to notice the binominal analysis based on categories gives a better result for ISO 50001, contrary to the analysis by each LI element when all the p-values were 1. Furthermore, it is possible to see “pull” practices having a higher association with ISO 14001, whilst “low setup” had the lowest for this Green aspect. “Productive maintenance” had the highest association with ISO 50001 and “flow” had the lowest. In the case of Green, “controlled processes” had the LI element with the highest association, whilst “low setup” had the lowest. “Controlled processes” had the highest association with “material”, whilst “flow” had the lowest. For energy, “controlled processes” had the highest association and the lowest was “flow”. Finally, for water, the highest association was found in “low setup” and the lowest in “involved employees”.

Discussion

Lean practices contribute to the development of Green aspects (see Table 1). Previous publications explore this relationship in models (Caldera et al., 2017), conjectures (Corbett and Klassen, 2006), measures (Dieste et al., 2019), practices (Kleindorfer et al., 2005) and integration (Hallam and Contreras, 2016). Early research understood Lean only as a general approach to include efficiency in modernising manufacturing systems (Florida, 1996) or just as a ISO 9001-certified company (King and Lenox, 2001). Later research claimed the relationship is weak because Lean and Green developed separately (Kleindorfer et al., 2005). Furthermore, other research concluded that only quality control tool practices pursue Green (Singh et al., 2022). Another element in the literature is the integration of Lean and Green (Galeazzo et al., 2014; Ng et al., 2015) and the review of practises (Hegedić et al., 2018; Inman and Green, 2018; Rothenberg et al., 2001).

Nevertheless, the gap remains in the scarcity of empirical evidence confirming the Lean-Green relationship and, more importantly, the lack of evidence on which specific tools can potentially develop strategic Lean-Green integration (See Table 1). Thus, this research contributes to the discussion about implementing a LI using the Lean production construct (Shah and Ward, 2007). Besides confirming the relationship between Lean and Green, it provides evidence on the specific Lean practices with a higher association with Green aspects. Thus, the fact a manufacturing system implements a Lean practice with a higher association with Green aspects today means the system is already opening the potential to integrate Lean and Green in daily work. Therefore, Lean manufacturing, besides its proven record of efficiency improvements, contains specific practices with a high association with Green aspects that contribute to the environmental aspect of the company.

Interestingly, a traditional tool such as (ILC15) “fish diagrams (Ishikawa diagrams) are used to identify the causes of defects” had the highest association with all Green aspects. A case study showed how the practical implementation of specific Lean management tools contributes to environmental improvements, including fish diagrams (Pinto and Mendes, 2017) or to finding uncertainty factors of pollutants (Velichko and Gordienko, 2009). Thus, in isolated cases the use of Ishikawa shows a relationship with Green. The practical implication of this result relates to the fact that this tool is popular, well-known and widely used, and now we have empirically proven that it has a high association with Green. In other words, from a practical perspective companies already have practices that integrate Lean and Green per se. This is very important because the dichotomous discussion must end, and precise tools must be used to determine Lean-Green integration. Thus, if popular Lean tools with high association with Green are being used on the shop floor today, then these tools should be the ones that lead the strategic Lean-Green integration plan. However, further study is required to determine this root cause analysis tool as a standard in developing Green initiatives.

The practice with the lowest association (ILC18), “workers in the plant drive the improvement program”, is an unexpected finding. All the “involved employees” categories have the worst association with all Green aspects and with the majority of categories except for “Green” and “energy”. Thus, a plausible future research question is whether employee involvement in Lean practices facilitates implementing Green aspects in manufacturing companies. Some research evidences a positive relationship between the Green involvement of employees and their perception of CSR (Srivastava and Shree, 2019) or the role of employee engagement with environmental initiates (Ababneh, 2021). Also, employee involvement relates to performance, and if the quality of the product is amongst business performance metrics, some relationship might be found (Chen et al., 2015). Nevertheless, the relationship between the Lean practice of employee involvement and Green aspects still requires more research.

The “controlled processes” category has the highest association with all Green aspects except for “water”. There are examples of robust control systems that determine the stability of groundwater physicochemical parameters (Arslan et al., 2022). Some perspectives review water pollution and present sophisticated approaches to analyse water contamination for wastewater treatment (Li et al., 2021). Others seek to increase the efficiency of the manufacturing processes of cutting using abrasive water (Zohoor and Nourian, 2012). None of these approaches relates to the environmental aspect of water consumption, with some exceptions such as research on water consumption in the milk industry (Quevedo et al., 2018), or the water-reuse approach in agile manufacturing systems. Thus, water consumption control systems in a Lean environment require further attention and development without considering the type of industry, especially in the manufacturing sector (UN, 2022).

On the other hand, the Green aspects of “material” and “energy” have a higher association with “controlled processes”. Material consumption is highly related to the economic performance of the business (Florida, 1996; King and Lenox, 2001). In the early days, the main reasons for Lean success relate solely to the efficiency of the process where inventories are one of the wastes in the industry (Womack et al., 1990). Even new technologies, such as additive manufacturing or composite materials, are searching for efficiency in their material consumption (Jin et al., 2017; Lunetto et al., 2023). These are usually related to energy consumption as it is also a repetitive component of costs in industry pushed higher today by the global energy situation (United Nations, 2017). Although the number of ISO 50001 firms is low, the relationship between energy consumption efficiency and Lean practices is vital due to the industry’s need for this primary component (Zhou et al., 2016).

In general, the next step to follow from a research perspective is to start reviewing the Green scopes of Lean tools. This research proves there are Lean practices with greater association with Green aspects. Further research should concentrate on the tools with higher association to better understand procedures for their implementation, their limits, barriers and success factors in pursuing a better Lean-Green integration strategy.

Conclusion

The research investigates the association of Lean practices with Green aspects. From the analysis of the current literature about the relationship between Lean and Green, the research establishes a mechanism to measure the leanness of manufacturing systems in combination with the existence of basic Green aspects in that system. Then, a survey facilitates data collection to analyse the relation between Lean practises and Green aspects.

The primary outcomes of the research relate to the fact that there are specific Lean practices that are more associated with Green aspects. For example, finding that Ishikawa diagrams have a good association with Green aspects is energising as it is a popular and easy-to-implement tool. Likewise, it is of concern that worker involvement has a low association with Green aspects. Thus, each of the outcomes in each of the Lean practices becomes a research path to be developed.

The evidence from this research contributes to determining that Lean and Green have a strong relationship. Then, it is necessary to review the implementation of each Lean practice for Green purposes only to establish Lean and Green practices as an integrated approach rather than separate issues in the company.

The individual analysis of each LI element associated with a Green aspect opens specific opportunities for further research. Also, the LI categories comprise a series of research questions to obtain more specific evidence on each relationship. Some of them have strong evidence of a relationship, which begs research on implementing the Lean practice solely for Green purposes. Others have a weaker relationship, which invites determining the reasons behind this lower association. In any case, this further research aims to establish empirical evidence that each Lean practice has a specific and clear role in developing Green initiatives at any organisation. In addition, and considering the specific limits, further research should look for other possible constructs to reaffirm the associations found. Similarly, the number of respondents is always considered a limitation, so further research could expand the number of responses to improve the data presented.

From a practitioners' point of view, this paper provides information on Lean practices that are more related to Green aspects as it provides evidence that Lean practices used in companies today develop Green aspects. Thus, the strategic Lean/Green integration in an organisation can be better carried out by integrally using Lean practices that express higher association with Green aspects. In this way, the dichotomy between the two perspectives tends to fade. Further studies should improve or modify the steps in specific practices by including the Green aspects from the beginning of implementation when developing the Lean tool.

In any case, being Green in today’s society has gone from being an option to an obligation. Many companies have to include Green processes mandated by legislation. This research provides evidence that Green tools exist in today’s manufacturing processes. Therefore, becoming Green is even more accessible than expected, which helps the sustainability of companies, the environment and society.

Figures

Figure 1

Graphical summary of the research stages

Figure 2

Box plot Lean index per Green aspect

Table 1

Literature review – summary and clarification of the research gap

Citation	Type of research	Perspective	Main findings
Caldera et al. (2017)	Literature review	Models	Identifies Lean models and how each contributes to sustainability
Corbett and Klassen (2006)	Literature review	Conjectures	Develops conjectures that assume how Lean and Green realities will exist and how to investigate them
Dieste et al. (2019)	Literature review	Measures	Most of the literature finds a positive relationship between Lean and Green, but little empirical evidence exists
Kleindorfer et al. (2005)	Literature review	Practices	Finds relationships between some Lean tools and their Green applicability
Hallam and Contreras (2016)	Literature review	Integration	Evidence of the successful integration of Lean and Green is scarce. Lean improves operations and that reduces the impact on the environment
Verrier et al. (2016)	Theoretical	Relationship	Presents relationships between Lean and Green using waste
Singh et al. (2022)	Interviews of experts	Barriers	Identifies the barriers to Lean and Green integration and how to overcome them
Amrina et al. (2021)	Interviews of experts	Integration	Proposes a Lean and Green integration model for small and medium industry (SMI)
Fercoq et al. (2016)	Experiments (DOE) with students	Integration	Using DOE, this work demonstrates that integrating Lean and Green brings better results for the environment
Galeazzo et al. (2014)	Single case study	Integration	Green project development that includes Lean is better, and the results also improve
Ng et al. (2015)	Single case study	Integration	Using Carbon-Value Efficiency, the research demonstrates that shortening lead time reduces the carbon footprint
Pinto and Mendes (2017)	Single case study	Relationship	This case study finds the relationship between specific tools and Green aspects
Piercy and Rich (2015)	Multiple-site case study, interviews	Integration	The work shows Green evolution thanks to Lean implementation
Kurdve et al. (2014)	Multiple-site case study, interviews	Integration	The problem is the lack of an integrated strategy for QMS, EMS, OHS and the administration of that strategy
Mårtensson et al. (2019)	Multiple-site case study, interviews	Relationship	Provides evidence of the Lean and Green relationship, but its existence is incomplete and inconsistent across cases
King and Lenox (2001)	Empirical: large-scale databases	ISO certifications	Organisations adopting ISO 9001 are more likely to adopt ISO 14001
Florida (1996)	Empirical – survey	Environmental	Innovation in manufacturing practices creates incentives to adopt environmentally conscious manufacturing practices
Inman and Green (2018)	Empirical – survey	Practices	Lean practices have a positive association with environmental and operational performance similar to the supply chain
Hegedić et al. (2018)	Empirical – survey	Practices	It was found that Lean practices affect the environment
Rothenberg et al. (2001)	Empirical – survey and interviews	Practices	The use of Lean practices is not enough to become Green

Source(s): The authors

Table 2

List of Lean practices

ILC	Lean practice (xi)	Shah and Ward (2007)
ILC1	Production is started by receiving a customer order	Pull
ILC2	The production lot of a work centre is determined by the previous work centre (internal customer)	Pull
ILC3	We use a PULL production system	Pull
ILC4	Production is controlled by the kanban system	Pull
ILC5	Products are grouped with those that have similar processing requirements	Flow
ILC6	Products are grouped together with a common logistics path	Flow
ILC7	Equipment is grouped to create a continuous flow of products (one-piece flow)	Flow
ILC8	The product families determine the layout of our plant	Flow
ILC9	The workplace rebuild is designed to minimise the ongoing rebuild time	Low setup
ILC10	We work systematically to reduce lead times (workstations, processes) in production plans	Low setup
ILC11	We have low setup times for machines/equipment in our plant	Low setup
ILC12	Most equipment/processes in our plant are currently below SPC	Controlled processes
ILC13	We improve processes by systematically evaluating using statistical methods	Controlled processes
ILC14	Graphs or charts showing defect rates are used as process control tools in the plant	Controlled processes
ILC15	Fish diagrams (Ishikawa diagrams) are used to identify the causes of defects	Controlled processes
ILC16	We conduct process capability studies before introducing a product into mass production	Controlled processes
ILC17	Operators are key employees and routinely part of problem-solving teams in operations	Involved employees
ILC18	Workers in the plant drive the improvement program	Involved employees
ILC19	Employees in the plant are the main initiators of improvements	Involved employees
ILC20	Plant workers receive cross-functional training to gain skills in multiple areas	Involved employees
ILC21	We handle a portion of the daily (autonomous) and scheduled maintenance activities at the facility	Productive maintenance
ILC22	All our facilities are subject to regular maintenance	Productive maintenance
ILC23	We have accurate maintenance records for our machinery and equipment	Productive maintenance
ILC24	We publish and actively share maintenance records of our machines in the workplace with our employees	Productive maintenance

Source(s): The authors

Table 3

Confirmatory factor analysis factor loadings

Factor	Indicator	Estimate	SE	Z	p	Stand. estimate
Pull	ILC01	0.696	0.1300	5.36	<0.001	0.479
	ILC02	1.059	0.1226	8.64	<0.001	0.713
	ILC03	0.855	0.1080	7.92	<0.001	0.658
	ILC04	0.643	0.0794	8.10	<0.001	0.673
Flow	ILC05	0.802	0.1220	6.57	<0.001	0.575
	ILC06	0.903	0.1187	7.60	<0.001	0.647
	ILC07	0.917	0.1032	8.89	<0.001	0.706
	ILC08	0.698	0.1114	6.26	<0.001	0.534
Low setup	ILC09	0.994	0.0965	10.30	<0.001	0.766
	ILC10	1.156	0.0938	12.33	<0.001	0.880
	ILC11	0.864	0.1008	8.57	<0.001	0.676
Controlled processes	ILC12	0.415	0.0828	5.01	<0.001	0.420
	ILC13	0.957	0.0789	12.13	<0.001	0.848
	ILC14	0.982	0.0805	12.20	<0.001	0.852
	ILC15	0.602	0.0755	7.97	<0.001	0.626
	ILC16	0.922	0.0958	9.63	<0.001	0.724
Involved employees	ILC17	0.784	0.1009	7.76	<0.001	0.623
	ILC18	0.951	0.0792	12.00	<0.001	0.876
	ILC19	0.705	0.0868	8.12	<0.001	0.647
	ILC20	0.692	0.0835	8.29	<0.001	0.661
Productive maintenance	ILC21	0.871	0.0953	9.14	<0.001	0.710
	ILC22	1.081	0.0933	11.58	<0.001	0.834
	ILC23	1.090	0.0910	11.97	<0.001	0.853
	ILC24	0.694	0.0938	7.40	<0.001	0.605

Source(s): Authors

Table 4

Percentage of firms implementing Green aspects

	ISO 14001	ISO 50001	Green	Material	Energy	Water
No (0)	75%	95%	50%	64%	66%	87%
Yes (1)	25%	5%	50%	36%	34%	13%

Source(s): The authors

Table 5

Independent samples t-test – Lean index per Green aspect

Lean index	ISO 14001			ISO 50001			Green
	Statistic	df	p	Statistic	df	p	Statistic	df	p
Student’s t	−3.80	143	<0.001	−3.57	143	<0.001	−4.18	143	<0.001
Welch’s t	−3.35	49.6	<0.001	−6.61	8.71	<0.001	−4.19	136	<0.001
Mann–Whitney U	1,193		<0.001	89.5		<0.001	1,619		<0.001

Lean index	Material			Energy			Water
	Statistic	df	p	Statistic	df	p	Statistic	df	p
Student’s t	−2.02	143	0.023	−3.91	143	<0.001	−2.67	143	0.004
Welch’s t	−1.91	90.4	0.029	−3.46	71.1	<0.001	−2.15	21.1	0.022
Mann–Whitney U	1884		0.014	1,478		<0.001	732		0.003

Note(s): H_a 0 < 1

Source(s): The authors

Table 6

p-values of each Green aspect

Predictor	ISO 14001	ISO 50001	Green	Material	Energy	Water
Intercept	0.005	1.000	0.002	0.079	0.001	0.010
ILC01	0.115	1.000	0.480	0.151	0.523	0.036
ILC02	0.015	1.000	0.656	0.046	0.296	0.097
ILC03	0.499	1.000	0.171	0.346	0.150	0.947
ILC04	0.013	1.000	0.874	0.043	0.057	0.712
ILC05	0.652	1.000	0.047	0.033	0.730	0.413
ILC06	0.152	1.000	0.564	0.605	0.663	0.860
ILC07	0.556	1.000	0.842	0.584	0.902	0.395
ILC08	0.078	1.000	0.055	0.043	0.769	0.591
ILC09	0.447	1.000	0.256	0.850	0.880	0.793
ILC10	0.751	1.000	0.527	0.294	0.516	0.868
ILC11	0.784	1.000	0.840	0.560	0.302	0.225
ILC12	0.197	1.000	0.853	0.432	0.538	0.636
ILC13	0.480	1.000	0.921	0.988	0.662	0.187
ILC14	0.786	1.000	0.601	0.389	0.561	0.132
ILC15	0.137	1.000	0.020	0.074	0.169	0.064
ILC16	0.796	1.000	0.084	0.322	0.434	0.062
ILC17	0.330	0.999	0.152	0.862	0.561	0.473
ILC18	0.439	0.999	0.900	0.991	0.979	0.966
ILC19	0.206	1.000	0.482	0.771	0.889	0.958
ILC20	0.320	1.000	0.752	0.628	0.822	0.539
ILC21	0.121	1.000	0.522	0.316	0.567	0.081
ILC22	0.004	1.000	0.316	0.151	0.392	0.126
ILC23	0.018	1.000	0.758	0.089	0.405	0.571
ILC24	0.046	1.000	0.240	0.380	0.259	0.081

Note(s): Estimates represent the log odds of “1” vs “0”

Source(s): The authors

Table 7

p-values of each Green aspect by category

Predictor	ISO 14001	ISO 50001	Green	Material	Energy	Water
Intercept	<0.001	0.003	0.001	0.026	<0.001	<0.001
Pull	0.012	0.133	0.541	0.627	0.333	0.965
Flow	0.422	0.650	0.322	0.969	0.506	0.658
Low setup	0.888	0.184	0.633	0.633	0.336	0.134
Controlled processes	0.021	0.237	0.009	0.027	0.055	0.654
Productive maintenance	0.665	0.050	0.161	0.655	0.172	0.219
Involved employees	0.589	0.627	0.315	0.845	0.305	0.990

Note(s): Estimates represent the log odds of “1” vs “0”

Source(s): Authors