Jose Arturo Garza-Reyes

Gabriela Winck Jacques
email: gwjacques@hotmail.com

Ming K Lim
email: m.lim@derby.ac.uk

Vikas Kumar
email: vikas.kumar@uwe.ac.uk

Luis Rocha-Lona

Lean and Green -Synergies, Differences, Limitations, and the need for Six Sigma

Keywords: DMAIC, Environment, Green, Lean, Six Sigma, Sustainability

Historically, profitability and efficiency objectives have been the prevailing interest for organisations. However, the move towards green operations has forced companies to seek alternatives to combine these with green objectives and initiatives. Green lean is the result of this combination. The purpose of this paper is to critically discuss the green lean approach and the potential benefits of integrating Six Sigma to enhance its effectiveness. The paper is based on a literature review that discusses the synergies and differences of lean and green, and its main limitations. Departing from the limitations identified, the paper then proposes Six Sigma, and specially its problem solving methodology DMAIC, as an approach that may help in overcoming the limitations of green lean. Thus, the paper conceptually proposes Green Lean Six Sigma. It intends to offer academics, researchers and practitioners interested in lean and green with some initial conceptual ideas regarding their possible integration with Six Sigma.

Introduction

Recently, with the rise of lean manufacturing and the increasing concerns for the environment, the market dynamic has changed. Historically, productivity has been the dominant concern for manufacturing organisations [START_REF] Mohanty | Work Study Managing Green Productivity: A Case Study[END_REF]. However, with the growth of quality management tools and increase in customers' demands for better prices, besides environmental regulations, companies have been forced to rethink how they manage their operations and processes. Since the 1950s lean manufacturing has been gaining fame in a wide range of industries all around the world, disseminating the concept of waste reduction [START_REF] Chauhan | Measuring Parameters of Lean Manufacturing Realization[END_REF]. On the other hand, green initiatives have been adopted as a requirement to comply with environmental regulations and meet market and social demands [START_REF] Digalwar | Green Manufacturing Performance Measures: An Empirical Investigation from Indian Manufacturing Industries[END_REF]. The combination of both seems logical, but two main questions arise from this: Can lean and green in fact work together? and Is their integration enough to effectively achieve positive productivity and green results at the same time?

As lean manufacturing aims at the elimination of waste in every area of production, design, supplier network and factory management [START_REF] Chauhan | Measuring Parameters of Lean Manufacturing Realization[END_REF], the combination of lean and green seems natural. Lean is a management approach that has helped companies to improve competitiveness and operational results [START_REF] Herron | The Transfer of Selected Lean Manufacturing Techniques from Japanese Automotive Manufacturing into General Manufacturing (UK) through Change Agents[END_REF]. Green, on the other hand, is an initiative that emerged from the concern for the environment and the rise of new regulations, norms, and standards on pollution prevention and control [START_REF] Digalwar | Green Manufacturing Performance Measures: An Empirical Investigation from Indian Manufacturing Industries[END_REF]. According to Dües et. al. [START_REF] Dües | Green as the New Lean: How to Use Lean Practices as a Catalyst to Greening your Supply Chain[END_REF], the combination of lean and green to form an integrated approach has only been discussed by a handful of experts and researchers. For example, Dües et. al. [START_REF] Dües | Green as the New Lean: How to Use Lean Practices as a Catalyst to Greening your Supply Chain[END_REF] carried out a study that aimed at exploring and evaluating, from a conceptual point of view, the existent relations between lean and the green concept. Similarly, Carvalho et al. [START_REF] Carvalho | Lean, Agile, Resilient and Green: Divergences and Synergies[END_REF] investigated the synergies and divergences between the lean and green paradigms, and their contribution towards a more sustainable and competitive supply chain. Also, Duarte and Cruz-Machado [START_REF] Duarte | Modelling Lean and Green: A Review from Business Models[END_REF] examined how different business models can contribute to modelling a lean and green approach for an organisation. Mollenkopf et al. [START_REF] Mollenkopf | Green, Lean, and Global Supply Chains[END_REF] investigated the relationship among green, lean, and global supply chain to provide a foundation for future researchers to build upon the company strategies. Hajmohammad et al. [START_REF] Hajmohammad | Lean Management and Supply Management: Their Role in Green Practices and Performance[END_REF] tried to help understanding the roles of lean and supply management in relation to improving the firm's environmental performance. For this, Hajmohammad et al. [START_REF] Hajmohammad | Lean Management and Supply Management: Their Role in Green Practices and Performance[END_REF] proposed and tested a conceptual model which suggests that the magnitude of environmental practices mediates the relationship between lean and supply management with environmental performance.

In general terms, these studies investigate the relationship between lean and green by highlighting the synergies and divergences between the two, their impact on supply chains' performance, and some of their theoretical implementation aspects when tried to be deployed seamlessly. Although the study presented in this paper also reviews and considers the synergies and divergences of lean and green, its main objective is to identify the possible limitations of the "green lean" paradigm as an integrated approach, and provide some research direction as to how these may be overcome. In light of this objective, the working methodology followed by this paper is based on a systematic review of the existent literature and exploring, analysing, and evaluating the information reviewed.

Literature Review -What is Green Lean?

Nowadays lean manufacturing is considered the most influential new paradigm in manufacturing [START_REF] Garza-Reyes | An Empirical-Exploratory Study of the Status of Lean Manufacturing in India[END_REF] as empirical evidence suggests it improves the competitiveness of organisations [START_REF] Wahab | A Conceptual Model of Lean Manufacturing Dimensions[END_REF] by reducing inventories and lead-times, and improving productivity and quality [START_REF] Hines | Learning to Evolve: A Review of Contemporary Lean Thinking[END_REF]. However, recently other concerns have emerged besides productivity, quality and cost. Today, sustainability has increasingly become important to organisations, as a result of concerns over environmental and social responsibilities [START_REF] Sezen | Effects of Green Manufacturing and Eco-Innovation on Sustainability Performance[END_REF]. These environmental concerns and the effectiveness of lean manufacturing contributed to the integration of the lean and green paradigms.

Synergies of lean and green

According to Mollenkopf et al. [START_REF] Mollenkopf | Green, Lean, and Global Supply Chains[END_REF], lean companies, which deploy continuous improvement techniques, seem to be more likely to accept environmental innovations. As lean tends to emphasise waste reduction, it provides a better atmosphere to deploy green philosophies, initiatives and tools. In this scenario, the similarity between the two seems logical, waste reduction. However, green goes beyond waste reduction as it is also concerned with process efficiency, reduction of material consumption and recycling, and similarly as all the quality improvement approaches, one of its ultimate objectives is to improve customer's satisfaction. From this view, it is possible to identify several synergies between the lean and green concepts, these being: waste reduction, lead time reduction, and use of different approaches and techniques to manage people, organisations, and supply chain relations [START_REF] Dües | Green as the New Lean: How to Use Lean Practices as a Catalyst to Greening your Supply Chain[END_REF][START_REF] Mollenkopf | Green, Lean, and Global Supply Chains[END_REF].

According to the literature [START_REF] Dües | Green as the New Lean: How to Use Lean Practices as a Catalyst to Greening your Supply Chain[END_REF][START_REF] Carvalho | Lean, Agile, Resilient and Green: Divergences and Synergies[END_REF][START_REF] Duarte | Modelling Lean and Green: A Review from Business Models[END_REF], waste reduction has different meanings in lean and green. For the lean management philosophy, waste refers to any activity that does not add value to the product while for the green concept waste is related to the wasteful consumption of water, energy or any natural resource [START_REF] Duarte | Modelling Lean and Green: A Review from Business Models[END_REF]. Despite their difference, non-value added activities can also be considered part of wasting energy and natural resources. For example, unnecessary or excessive transportation of products and/or raw materials is not only one of the seven wastes defined by lean but also a waste of non-renewable natural resources. Thus, both practices aim for less transportation in order to save cost (lean) and reduce the consumption of natural resources and CO 2 output (green) [START_REF] Carvalho | Lean, Agile, Resilient and Green: Divergences and Synergies[END_REF]. Another example is excessive inventory, which according to lean it is considered waste due to, in most of the cases, it increases lead time, prevents the rapid identification of problems, and discourages communication [START_REF] Hines | The Seven Value Stream Mapping Tools[END_REF]. Excessive inventory also requires storage space and needs to be lighted, and sometimes heated or chilled, which from the environmental point of view may be considered a waste of energy if the lighting, heating and/or chilling is not done efficiently [START_REF] Franchetti | Lean and Green: Industrial Engineering Methods are Natural Stepping Stones to Green Engineering[END_REF]. In this way, it is possible to relate all the seven lean wastes to those considered and defined by green initiatives. This indicates that lean can serve as a catalyst for green, facilitating companies the deployment of environmental policies and practices. In this way, a new strategy and management form can be defined through the compatibility between these two "cultures". However, there are still some areas in which lean and green cannot be combined as well as there are still some limitations when considering green lean as an integrated approach. The divergences between lean and green are discussed below.

Divergences of lean and green

Green initiatives can no longer be ignored by companies [START_REF] Dües | Green as the New Lean: How to Use Lean Practices as a Catalyst to Greening your Supply Chain[END_REF]. As it is discussed in the previous section, it is easier to deploy green initiatives in lean oriented companies, and the opposite is also valid. However, there are some objectives of both approaches that may not be possible to combine, for example: their focus, what are considered wastes, the customer, manufacturing strategies, and some practices adopted by organisations [START_REF] Dües | Green as the New Lean: How to Use Lean Practices as a Catalyst to Greening your Supply Chain[END_REF][START_REF] Mollenkopf | Green, Lean, and Global Supply Chains[END_REF]. For this reason, despite the several synergies identified in the previous section, lean and green cannot perfectly be combined, they are concurrent and thus can effectively work together, but there are still some points that deserve attention when deploying both initiatives simultaneously.

According to Duarte and Cruz-Machado [START_REF] Duarte | Modelling Lean and Green: A Review from Business Models[END_REF] the main difference between lean and green lies in how waste is defined, this divergence is also identified by Dües et al. [START_REF] Dües | Green as the New Lean: How to Use Lean Practices as a Catalyst to Greening your Supply Chain[END_REF]. As defined in the previous section, in lean, waste is any activity that does not add value to the customer while for green is the inefficient use of natural resources. Despite both meanings take the approach of working to improve processes at an operational level, lean focuses on workforce reduction, space reduction, increase capacity utilisation, higher system flexibility, and the use of standard components [START_REF] Duarte | Modelling Lean and Green: A Review from Business Models[END_REF][START_REF] Pettersen | Defining Lean Production: Some Conceptual and Practical Issues[END_REF]. Whereas green ranges from practices like reduce, reuse and recycle (3Rs), rework, return, and remanufacture [START_REF] Duarte | Modelling Lean and Green: A Review from Business Models[END_REF]. Another clear difference between lean and green is the type of customer [START_REF] Dües | Green as the New Lean: How to Use Lean Practices as a Catalyst to Greening your Supply Chain[END_REF]. Lean focus on cost and lead time reduction to satisfy customers [START_REF] Carvalho | Lean, Agile, Resilient and Green: Divergences and Synergies[END_REF] while in green, customers are more concerned as to whether the product that they are purchasing is helping them being more environmentally friendly [START_REF] Dües | Green as the New Lean: How to Use Lean Practices as a Catalyst to Greening your Supply Chain[END_REF][START_REF] Mollenkopf | Green, Lean, and Global Supply Chains[END_REF]. Also, the green customer would not mind paying more for an environmental friendly product, which would not occur with lean customers.

So it is clear that lean and green are not completely compatible, there are still some areas in which they cannot be combined. However, those areas do not undermine or block the utilisation of lean and green simultaneously as an integrated management approach, contrariwise it gives the opportunity to improve both methods in a way that they can perfectly match. However, even as an integrated approach the green lean concept may still find some limitations that require attention, these are discussed in the following section.

Limitations of Green Lean as an Integrated Approach

There is little empirical evidence of the extent of adoption and effectiveness of green lean. However, based on the extensively documented success and expansion of lean into other industries different to manufacturing [START_REF] Garza-Reyes | An Empirical-Exploratory Study of the Status of Lean Manufacturing in India[END_REF], and the fact that it is now accepted as a best practice for many organisations all around the world [START_REF] Forrester | Lean Production, Market Share and Value Creation in the Agricultural Machinery Sector in Brazil[END_REF], it may be assumed that green lean will also be able to help organisations in achieving improvements that are not only financial and operational but also environmental oriented.

Nevertheless, despite this assumption, the integrated green lean approach may suffer from the same limitations as the individual lean and green philosophies. In the case of lean, Salah et al. [START_REF] Salah | The Integration of Six Sigma and Lean Management[END_REF] think about it as a toolbox that is comprised of methods and tools that are directed toward the reduction of waste. These methods and tools were not all invented with this methodology, but they have been systematically used in a structured manner to form lean [START_REF] Salah | The Integration of Six Sigma and Lean Management[END_REF]. Limitations of the pure lean approach include the fact that (1) none of its methods or tools control and monitor a process using statistical data, (2) they do not scrutinise variations in processes, which are utilised for making decisions, and (3) there are no practices associated with the use of quality and advanced statistical/mathematical tools to identify further problems still remaining in processes after waste has been eliminated [START_REF] Devane | Integrating Lean Six Sigma and High-Performance Organizations: Leading the Charge toward Dramatic, Rapid, and Sustainable Improvement[END_REF][START_REF] Lee | A Comparative Study of the Implementation Status of Lean Six Sigma in South Korea and the UK[END_REF]. Thus, Assarlind et al. [START_REF] Assarlind | Multi-faceted Views on a Lean Six Sigma Application[END_REF] suggest that lean organisations do not extensively utilise data in decision-making and that they should employ methodologies that promote a more scientific approach to quality. In this context, the lack of a data driven approach to process improvement makes lean less accurate and precise [START_REF] Hilton | A Conceptual Model for the Successful Deployment of Lean Six Sigma[END_REF]. Also, despite lean being an operational approach that focuses on fulfilling customer's needs [START_REF] Chauhan | Measuring Parameters of Lean Manufacturing Realization[END_REF], it does not present a structured approach to control processes, solve problems, and/or systematically conduct improvement projects. The lack of a systematic approach to conduct improvements may also complicate the definition of wastes as previously discussed in Section 2.

On the other hand, in the case of green, although decision support and expert systems as well as design for environment (DfE) methods are available to support this approach, Chan et al. [START_REF] Chan | Green Manufacturing Using Integrated Decision Tools[END_REF] comment that their application to solve green problems is limited. For this reason, unlike lean, green cannot be thought as a toolbox but as an initiative underpinned by the utilisation of a single tool, life cycle assessment. This will result in the green concept not being able to "lend" lean, if integrated with it, methods and tools that could help overcome the lean drawbacks previously discussed. Thus, the limitations of lean will be inherited by the green lean approach.

Following the same reasoning, an integrated green lean approach will not only confront the limitations of lean but also the limitations and challenges of the green approach. From the discussion of Nunes and Bennett [START_REF] Nunes | Green Operations Initiatives in the Automotive Industry: An Environmental Reports Analysis and Benchmarking Study[END_REF] on environmental management systems (EMS) and green operations, it is possible to imply that the main limitations of green are not related to operational but strategic aspects. For example, Nunes and Bennett [START_REF] Nunes | Green Operations Initiatives in the Automotive Industry: An Environmental Reports Analysis and Benchmarking Study[END_REF] suggest that although there is clear and strong reasons as to why organisations should implement green (i.e. through environmental management practices), it is still unclear to them how to make green decisions when a company faces a challenging strategic decision regarding where to make the investment when there are involved various possibilities (i.e. in facilities, manufacturing, logistics, marketing, process and product design, etc.). Another strategic challenge of green is how to implement its initiatives in a way in which they also meet corporate goals of profitability and other business requirements [START_REF] Nunes | Green Operations Initiatives in the Automotive Industry: An Environmental Reports Analysis and Benchmarking Study[END_REF]. This is because in some cases, green activities will not return a profit from individual initiatives or be matched with corporate objectives.

Besides these strategic challenges, green can also present operational limitations. Joseph [START_REF] Joseph | The Disadvantages of Going Green for a Corporation[END_REF] comments that two of the most common include conversion expense and more expensive products. For example, it can be expensive for an organisation to go green initially as new energy saving equipment (i.e. solar panels) may need to be bought and installed. Unfortunately, cost reductions in energy savings gained by going green are not always enough to offset the initial capital conversion costs [START_REF] Joseph | The Disadvantages of Going Green for a Corporation[END_REF]. In addition, moving into the use of more environmentally friendly products can lead to more expensive products for consumers.

Similarly as with the inheritance of the lean limitations by the green lean approach, the limitations and challenges of the green concept will also be passed on to the integrated green lean approach, without lean being able to contribute to overcome some of them. For instance, in terms of prioritising strategic green investment decisions, lean lacks of a prioritisation approach [START_REF] Bendell | A Review and Comparison of Six Sigma and the Lean Organisations[END_REF] to support a decision of this type. In addition, since lean lacks of a project-based approach to improvement and thus a planning phase, it may not help in aligning the green lean initiatives to corporate goals of profitability as well as to other business requirements. This lack of a projectbased approach may also contribute to lean not being able to specifically focus and dedicate a project to identify the most cost effective and environmentally friendly equipment and raw material, which could offset and/or limit the negative impact on operational and product costs that these may have.

The individual limitations and challenges of lean and green, also inherited by the integrated green lean approach, and the lack of methods and/or tools from the "other" concept (i.e. lean or green) to overcome these, calls for the integration of additional methods and tools capable of contributing to the reduction or elimination of these challenges and limitations. These "other" methods and tools can come from Six Sigma.

Green Lean Six Sigma?

Initiated by Motorola in the 1980s, Six Sigma is now considered one of the most important developments to process improvement of the last decades [START_REF] Garza-Reyes | An Empirical Application of Six Sigma and DMAIC Methodology for Business Process Improvement[END_REF]. Since then, Six Sigma has gained wide popularity among organisations worldwide, with most Fortune 500 companies using it [START_REF] Garza-Reyes | An Empirical Application of Six Sigma and DMAIC Methodology for Business Process Improvement[END_REF] not only to improve their financial and operational performance but also customer satisfaction through the reduction of defective products and services. Six Sigma is a systematic, data and statistical driven problem solving and improvement methodology that intends to contain defects to 3.4 per every million opportunities, achieving with this lower costs and competitive operations. Garza-Reyes et al. [START_REF] Garza-Reyes | A DMAIRC Approach to Lead Time Reduction in an Aerospace Engine Assembly Process[END_REF] suggest the define, measure, analyse, improve, and control (DMAIC) cycle as one of the Six Sigma's distinctive and essential approaches to problem solving and process improvement. The DMAIC model indicates, step by step, how problems should be addressed, grouping quality and statistical tools, while establishing a standardised routine to solve problems [START_REF] Garza-Reyes | A DMAIRC Approach to Lead Time Reduction in an Aerospace Engine Assembly Process[END_REF].

The systematic, data and statistical driven characteristic of Six Sigma could complement the green lean approach and contribute in overcoming the limitations and challenges of this concept highlighted in Section 3. For example, the use of the DMAIC model could provide green lean with a more specific and holistic project based orientation to the implementation and achievement of green initiatives, which could then be continuously improved through kaizen. Thus, the Six Sigma's DMAIC methodology could be generalised as the umbrella under which green initiatives are implemented, managed, sustained and improved, see illustration in Figure 1. In this context, DMAIC will provide a unique characteristic of sequencing and linking lean and Six Sigma's methods and tools during the five stages of DMAIC when conducting a green project. In this way, lean and Six Sigma will contribute with the provision of methods and tools to help identify, define, prioritise, conduct, manage, achieve, sustain, and improve green initiatives.

In particular, the Define phase of DMAIC consists in identifying, prioritising and selecting the right project as well as clarifying the project's scope and defining goals [START_REF] Garza-Reyes | An Empirical Application of Six Sigma and DMAIC Methodology for Business Process Improvement[END_REF][START_REF] Garza-Reyes | A DMAIRC Approach to Lead Time Reduction in an Aerospace Engine Assembly Process[END_REF]. Thus, at a strategic level, the Define phase of DMAIC could help an organisation to objectively prioritise green initiatives and investments in order to determine in which organisational activity/function (i.e. facilities, manufacturing, logistics, marketing, process, and product design) they should be deployed first, and/or in terms of which parameters (i.e. energy consumption, CO 2 emissions, water consumption, etc.) should be targeted. Specific tools promoted by Six Sigma to achieve this may include Pareto analysis, project ranking matrix, project selection matrix, quality function deployment, project assessment matrix, Pareto priority index, cost benefit analysis, analytical hierarchy process (AHP), theory of constraints, etc. This scientific and data driven approach to defining and prioritising green initiatives would also ensure the selection of the right projects and investments, as well as it will aid in clarifying the objectives, scope, and resources of the green initiatives. This will also ensure their alignment with corporate goals.

The Measure stage of DMAIC consists in establishing reliable metrics to help monitoring key process characteristics, the scope of the parameters considered, and their performance in order to understand their progress towards the objectives [START_REF] Basu | Implementing Quality -A Practical Guide to Tools and Techniques[END_REF]. At an operational level, the Measure phase of DMAIC will "force" an organisation, as an initial step, to identify the similarities, unify, and thus define the lean and green wastes (i.e. excessive CO 2 emissions, water consumption, energy consumption, raw material consumption, inventory, transportation, etc.) into those that will be targeted for reduction/elimination. In addition, specific metrics (i.e. for electricity: KWh, green energy coefficient, energy reuse factor, carbon usage effectiveness, etc.; for CO 2 emissiontonns/week, etc.) for every waste will also need to be determined and agreed. Once that wastes and their metrics have been defined, current lean value stream studies can be conducted to identify the sources of waste and establish the scope of the parameters, as well as their current performance. Based on the DMAIC approach, the latest will be used to help monitoring progress towards the objectives established in the Define phase. This phase of DMAIC will start helping in overcoming the "lack of a data driven approach" limitation of green lean as quantitative data will be collected, analysed, and used as a comparative improvement base.

Fig. 1. Overcoming the green lean limitations through the integration of Six Sigma

The Analyse phase of DMAIC involves evaluating and identifying key causes and process determinants [START_REF] Basu | Implementing Quality -A Practical Guide to Tools and Techniques[END_REF]. If integrated with green lean, this phase of DMAIC will contribute in determining the root causes of wastes in the parameters monitored. Six Sigma methods and tools based on inferential statistics such as scatter plots, analysis of variance (ANOVA), hypothesis testing, regression analysis, design of experiments (DOE), among others, will provide a quantitative-scientific base for the analysis. Other less quantitative, but still effective and systematic, methods that may include cause-and-effect diagrams and "5 whys" could also be used in this stage to uncover wastes and the excessive (i.e. unnecessary) use of energy, water, raw material, CO 2 , etc.

The Improve phase of DMAIC consists of proposing, testing, and implementing creative solutions to eliminate the root causes of problems [START_REF] Garza-Reyes | An Empirical Application of Six Sigma and DMAIC Methodology for Business Process Improvement[END_REF]. Methods and tools such as 5S, brainstorming, corrective action matrix, poka-yoke, among others, can be used to stimulate the development of solutions to reduce/eliminate the wastes identified in the Measure phase. In many cases, the solutions to tackle wastes could be as simple as, for example, installing occupancy sensors to turn lights off in offices when not needed, and reprogramming thermostats to avoid the unnecessary use of heating. Although determining the need to carry out improvements of this type may not require the systematic implementation and conduction of green initiatives, the Six Sigma's DMAIC approach will provide a platform to take decisions and courses of action based on real and scientific facts. Once embedded within the organisation's culture, this fact and scientific driven approach to decision-making will not only be used for green initiatives but also as part of the entire managerial approach of the organisation.

Finally, the Control phase involves setting the mechanisms for ongoing monitoring and institutionalising improvements [START_REF] Forrester | Lean Production, Market Share and Value Creation in the Agricultural Machinery Sector in Brazil[END_REF]. After the objectives set in the Define stage have been achieved, methods such as Statistical Process Control (SPC) may help to monitor critical environmental parameters such as energy, water and raw material consumption, CO 2 emissions, etc. In this case, SPC control charts will aid in statistically setting specification limits based on the maximum, average, and minimum consumption of the parameters monitored. This will allow differentiating the common and inherent variation in the consumption and use of these parameters from excessive uses due to assignable causes. In this context and based on the SPC methodology, investigations and corrective actions will be taken, specially, if the consumption of energy, water and raw material, or CO 2 emissions exceed the maximum specified limit. SPC will also help to scrutinise and thus understand the degree and causes of variation in the consumption/use of these, which will help organisations in decision-making and assisting in the diagnosis of problems. The formal documentation of all the improvement actions taken and best practices, as suggested by the Control stage of DMAIC, will ensure that all employees perform the processes in a uniform manner, which will contribute to the reduction of variability in the consumptions of the green parameters considered.

Conclusions

Environmental sustainability is one of the strategic imperatives that nowadays must be aligned to the traditional organisational priorities of profitability and efficiency as well as customer satisfaction, quality, and responsiveness. The green lean approach has been proposed with the intention of achieving such alignment. However, conceptual and empirical studies regarding green lean are limited, and those conducted have focused on investigating aspects such as the synergies and divergences between the two, their impact on supply chains' performance, and some of their theoretical implementation issues. This paper has mainly focused on discussing the possible limitations of green lean as an integrated approach, which have been determined to be inherited from the individual limitations of every approach, and the fact that the "other" is unable to contribute in overcoming them. For this reason, the paper conceptually proposes and argues the integration of Six Sigma as a possible solution to address these limitations, complement the green lean approach, and enhance its effectiveness.

The paper has provided some initial discussion as to how integrating Six Sigma and creating a green lean Six Sigma unified approach could benefit green lean, but further research can be directed towards the proposal of a conceptual model for their integration, followed by its test and investigation into its empirical relevance to and effectiveness in industry.


Fabio Papalardo
email: fabiopapalardo@gmail.com

L Claudio Meirelles

José B Sacomano

Jayme De Aranha Machado

Small and Medium Enterprises in Brazil: A Comprehensive Study of the Manager's View of the Business

Keywords: Small ad Medium Sized Enterprises 1, Sustainability Factors 2, Cultural Factors 3

Small and Medium Enterprises (SME) in Brazil are factors of great economic importance, for they represent employment for more than fifty six million people. When we consider the country's overall population of two hundred million inhabitants we can understand the magnitude of such economic segment, and it means that it is responsible for the sustainability of the employment structure. As in any economic activity, it depends on efficiency and that means specialized management, low costs, low waste, high competitiveness: these factors assure the sustainability of such enterprises in the market. Apart from these factors, which are internal to the management, there are external factors that influence the enterprises' performance, such as policies to foster development, financial cost, qualified work force, the tax burden, value of local currency weighted against foreign currencies, and other factors. Management compliant with this matrix of factors is dependent upon the managers' vision. This comprehension by the managers about the different internal and external factors that influence the enterprise shall define the organizational culture that will prevail in this type of enterprises. For this study, we have researched the vision of SME's managers as far as internal and external factors that influence the management of enterprises.

Introduction

Small and Medium Sized Enterprises (SMEs) represent 99% of the Brazilian enterprises [1]. They are responsible for 20% of the Gross National Product (GNP) with 320 billion Dollars and generate 60% of all formal employment posts in Brazil, that is, 56.4 million. These data are by themselves relevant for the Country's economic and social development.

The vision of SMEs managers, the way they see the market, the way they face administration, the importance of these enterprises and above all, the factors necessary to their sustainability, show the possibility of analyzing the segment, as far as its consol-idation in the market, according to the time of permanence or survival in the market.

In Brazil the mortality level is around 25%, after two years of existence [1]. In the worldwide landscape, Brazil is faring well; best levels are: Slovenia 22%, Austria 24%, followed by Spain 31%, Italy 32%, Portugal 49% and Holland 50%. Of course, these countries have different markets, with their characteristics and particularities.

Our analysis takes into account factors that influence the performance of SMEs in two aspects, internal factors, that relate to their operations, divisions and functions; as well as external factors, as public policies, the financial market, among others. The managers' vision are indicative of how they understand the real aspects of SMEs, but not necessarily how SMEs should be managed, and how they understand the policies for development and sustainability of such an important economic sector, as the SMEs are.

Theoretic Foundation

Studies about Small and Medium Sized Enterprises are frequently conducted, due to their importance in the development of countries and regions. Studies report differences of management in large enterprises and SMEs.

The administration of a SME has its particularities; the greatest difference between large enterprises and SMEs is that the SMEs are concerned with day-to-day operational activities, but large enterprises follow strategic planning [1]. Managers do not realize the economic potential of being responsible to the social issues, to the environment and, as particularly it was studied in the research, to the health of the employees. Although the first responsibility of a manager is generating profits, companies can at the same time contribute to social and environmental objectives, through integrating corporate social responsibility as a strategic investment into their core business strategy, their management instruments and their operations [START_REF] Bakos | Decision-making and Managerial Behaviour Regarding Corporate Social Responsability in the Case of Small and Middle-sized companies[END_REF]. Another particularity of SMEs is the cultural difficulty of cooperation and the establishment of Local Production Consultations, which, a relationship of cooperation among SMEs would ease up access to resources one does not have, as well as would strengthen up one´s own resources and increase the potential of an enterprise's strong aspects. Besides, cooperation between enterprises can represent a manner of developing SMEs competitive advantage and such may become a link to competitiveness [START_REF] Gonzáles | Asociación Significativa entre los Modos de Conversión de Conocimiento y los Modelos de Decisión en las PYMEs de Cali-Colombia[END_REF].

The funds raised are used by small and medium companies in their development, the most innovative, counseling and training staff. In the development of business by SMEs are most helpful database consulting, sample manuals for obtaining financial support and to promote innovation. The current business environment is referred to as hyper-competitive and global. If there are any changes in it, these will be permanent rather of the crisis character than towards certainty and possibility prediction of future development [START_REF] Pellešováa | Position of Small and Medium Companies in Poland and Results of Research in Selected Areas[END_REF].

Informational barriers are the core bottleneck inhibiting energy efficiency improvements in SME sector. Financial and organizational barriers also influence a company's energy saving activities. Data point out three additional barriers to energy saving activities: the role of family ownership structures, lax enforcement of govern-ment regulations and the absence of government support as well as a lack of skilled labor [START_REF] Kostkaa | Barriers to Increasing Energi Efficiency: Evidence from Small and Medium-sized Enterprizes in China[END_REF].

All these factors form a picture that must be studied in all its particularities, so that policies and management systems may be implemented.

Methodology

The methodology presented used the comprehensive method, the comprehensive analysis encourages the integration of the largest possible number of elements and connections. This method identifies opinions of managers of small and medium sized enterprises, as far as their sustainability in the Brazilian market [START_REF] Alvarado | La innovación en Entornos Económicos Poco Favorables: El Sector Auto Partes[END_REF]. The research, of exploratory character, used the study of a case with data collection through a non structured interview with questions and answers. Non structured interviews identified the factors the managers considered relevant for the administration of small and medium sizes Brazilian enterprises. The theme of this proposal represents a contribution to the ways a manager of a small and medium sized Brazilian enterprise evaluates a business. The research was conducted using the Likert measuring scale for relevant sustainability factors of the enterprise in the market, as well as an evaluation after attributing points 0 to 10 applicable to the enterprise's sectors, depending on each sector importance for administration and performance.

As far as the Likert scale, the number of possible answers is five, keeping in mind that the possibility of answers can be odd or even: an odd answer allows the respondent, for any reason, to keep himself neuter; an even answer does not allow itthe respondent has to take a position. This diversity has the objective of avoiding any regional aspect to the research.

Results and Discussion

Fifty seven enterprises were researched in the four regions, and the companies were classified as wholesalers, retailers, industry and services. We can see that, according to the vision of the managers, to have a product of competitive performance is the most important factor, with 7.89 points in a 0 to 10 scale. The second factor is sales, with 7.75 points, followed by the business administration with 7.52, purchases 7.51, costs 7.32, planning 7.25 and production 6.76.

A detailed vision per region (Table 1). The preponderant external factor is to be well prepared to remain in the market, followed by the cooperation and support of class entities, the SMEs importance in the national scenario, employment posts generated by SMEs, capacitating of SMEs' labor, and support by the financial establishment.

Analysis and Discussion

With reference to the internal factors that influence the sustainability of the SMEs, the products to be offered to the market are the main factor, and this leads to a competitive market, as far as the product's performance; however factors like costs and production and delivery times were not mentioned by the participants in the research. This brings up the commercial nature of the SMEs. Quite obviously, the objective of having a competitive product is to make sure it will be sold well, and that appears as second in importance in the research. Even services and industries show this type of focus. The numbers also show that to administration and purchasing is assigned quite well the same importance, and actually the ones interviewed believe that to buy efficiently is synonymous to administer efficiently. Costs are considered a consequence of purchasing, and here it means the buying of materials and labor. The planning factor is viewed as something operational, rather than strategic, and to production the same reasoning is applied. Commercial activities, as an end in themselves, are important for SMEs' performance and sustainability in the market, but these activities add no value. Considering that the SMEs are responsible for the structural employment in Brazil, activities that add no value have the tendency of forcing the market into imports, and it would focus the economy's sustainability exclusively on the country's internal consumption. Among external factors, the one of least importance is the expected support from the financial establishment. Due to high financial burdens, enterprises do their best to remain as capitalized as possible. Also, as a low importance factor, is the expectation of help from public policies aimed at SMEs; actually a degree of skepticism is noticed as far as this question is concerned. On the other hand, class associations, support from institutions as SENAI and SESC are recognized as of great usefulness to the SMEs and a real factor of development, even though the technical training supplied by these institutions many a time is not considered by managers as of relevant importance. This reasoning derives from the fact that managers do not see collaborators as SMEs development agents; they consider that only their own capacitating and expertise are decisive factors for the development of SMEs. These findings open a gap for further research, enabling a better understanding of the characteristics of these factors, pointing the need of the development of public policies towards new strategies of business enterprises in these sizes.

Fig. 1 .

 1 Fig. 1. Profile of the Researched Enterprises

Fig. 2 .

 2 Fig. 2.. Internal Factors Importance for the Sustainability of SMEs

Fig. 3 .

 3 Fig. 3.External Factors classified by their importance to the SMEs.

  Region of Fortaleza and Juazeiro do Norte, in the State of Ceará; the region of Montes Claros and the region of Araxá, in the State of Minas Gerais. The regions of Araxá and Montes Claros, although they both are in the State of Minas Gerais, have different characteristics as far as entrepreneurial culture: Araxá is in the Triângulo Mineiro, an area under the influence of the Southeast Region, and Montes Claros is in the northern part of the State of Minas Gerais, culturally connected to the Region of the Sertão Mineiro and Southern Bahia. The region of Fortaleza and Juazeiro do Norte has cultural aspects typically of the Northeastern Region.

The format was: 1 -Of no relevance; 2 -Of some relevance; 3 -Relevant; 4 -Of much relevance; 5 -Necessary. Research was conducted in four areas:

Table 1 .

 1 Values assigned to Internal Factors, per Region.

	Company	Montes	Fortaleza	Juazeiro	Araxá	Total
	sectors	Claros		do Norte
	product	8.43	9.00	7.75	6.38	7.89
	sales	8.13	8.31	7.00	7.54	7.75
	administration	8.00	7.95	7.00	7.15	7.52
	purchasing	6.50	8.25	7.67	7.62	7.51
	costs	7.50	7.75	7.50	6.54	7.32
	planning	8.14	7.71	6.00	7.15	7.25
	production	5.50	6.63	7.67	7.23	6.76
	Enterprise's sectors: products, sales, administration, purchasing, costs, business plan-
	ning, production, others, none; average.
	The second half of the research shows external factors, which, according to the vision
	of the managers, affect the performance and sustainability of the enterprises.
	They are:
	Public policies for development and growth of Small and Medium Sized Enterprises.
	The financial establishment banks and credit institutions the serve the Small and Me-
	dium Sized Enterprise.
	Academic or technical education for the workers at Small and Medium Sized Enter-
	prises.

Table 2 .

 2 Multiple Choice questions concerning External Factors to SMEs

	Of no	Of some	Relevant Of much	Necessa-
	rele-	relevance	relevance	ry
	vance
	The SMEs importance
	in the economic
	growth and develop-
	ment is:
	Public policies for the
	growth and develop-
	ment SMEs are:
	Posts of employment
	generated by SMEs in
	the national scenario
	are:
	Contribution from non
	governmental agen-
	cies, for the growth of
	SMEs are:
	Academic and tech-
	nical education at the
	SMEs is considered:
	To be competitive in
	the market is:
	Financial System con-
	tribution for SMEs is:

Table 3 .

 3 Values assigned to External Factors according to Regions

		Montes	Fortaleza	Juazeiro	Araxá	Average
		Claros		do Norte
	To be prepared	4.58	4.57	4.50	4.33	4.50	15.51%
	for the market
	Contributions	4.42	4.43	4.33	4.33	4.38	15.11%
	from entities
	SMEs develo-	3.73	4.43	4.83	4.33	4.33	14.49%
	pment
	Employment	4.31	4.30	4.17	3.94	4.18	14.42%
	posts generated
	Technical train-	3.92	4.22	3.67	4.33	4.04	13.92%
	ning
	Public policies	4.08	9.96	4.00	3.50	3.89	13.41%
	Financial Sys-	3.25	3.52	3.50	4.44	3.68	12.69%
	tem


Meirelles L Claudio
email: claudiolirameirelles@baumannconsultancy.com

Sacomano B Jose

Papalardo Fabio

The concept of sustainability in view of micro, small and medium Brazilian companies

Keywords: Sustainability 1, Micro, Small and Medium Enterprise 2, Social Responsibility 3

The present moment in enterprises scenario show a triple crisis in financial, ecological and social aspects, forcing companies to revise their strategy to make a stand with sustainably in the market. Micro, small and medium organizations (MSMEs) are 99% of companies in the world, main source of employment and are having difficulties to adapt to this moment because of the lack of public policies, knowledge and innovation capacity . The objective is to show what the brazilian MSMEs understand about sustainability, using a descriptive approach, with mixed procedures and survey method in the cross-sectional. The research identified that the factor with more impact in the profitability of the firm, such as cost, is considered the main factor in ensuring the sustainability of the company. And the factors, social and environmental, aren`t considered important to achieve this sustainability, to conclude that these businessman see their business in the short time.

Introduction

Present business world is having a triple crisis following to financial, ecological and social areas, forcing companies to show a new approach of governance that allows developing a set of performance indicators to measure the sustainability of these three aspects at the company level [START_REF] Ozcure | The sustainable company and employee participation as a part of the solution to triple crisis in the European Union and Turkey: Exemple of OMV Samsun Elektrik[END_REF].

Increasing sustainability enters in the corporative agenda, forcing them to include this theme in their strategies and to create sustainable strategies. However, in practice, the lack of segmented information, discussing issues of sustainability face some difficulties, mainly because this new reality requires a vision in product level, strategic and tactic [START_REF] Egels-Zanden | Sustainable strategy formation at a Swedish industrial company:bridging the strategy-as-practice and sustainability gap[END_REF].

At one side, the new legislation is emphasizing social responsibility, corporation image and client awereness and, on the other side, consumers are getting more interested in products and services related to economic viable practices, that are socially just and environmentally correct. This makes the producers worry about producing goods that do not hurt the environment and recycle products after their usage. In this context, sustainable development policies wich benefit companies will be important to local economics dynamics. But it can`t be forgotten that it is necessary for the present policies not to compromise future development [START_REF] Faccio | Susteinable SC through the complete reprocessig of end-of-life products by manufacturers: A traditional versus social responsibility company perspective[END_REF][START_REF] Musson | The build-up of local sustainable development politics: A case study of company leader in France[END_REF][START_REF] Sebrae | O que pensam as micro e pequenas empresas sobre sustentabilidade[END_REF].

This situation is changing the business models and economic relations that are based in sustainable development as a competitive factor. In this context, it is necessary to adapt micro and small firms according to the importance of job creation, wealth distribution and ability to innovate [START_REF] Sebrae | O que pensam as micro e pequenas empresas sobre sustentabilidade[END_REF].

The micro and small companies have competitive advantage to be next to the consumer, making it possible to anticipate competition on observation and adjustment of demands on sustainable practices for their stakeholders. It is important to understand that micro and small organizations as being considered the main source of development and employment in most countries, representing approximately 99% of companies in the world, but also stand out as a source of pollution of nature, approximately 30% of the total, due to the difficulty to implement other innovative methods or not to use cleaner technology [START_REF] Hoof | Cleaner production in small firms taking part in Mexico`s sustainable supplier program[END_REF].

SMEs in the European economy are the main sources of employment, entrepreneurship and innovation, representing 66.7% of the jobs in the European Union. In Brazil the micro and small organizations are responsible for 99% of establishments, 51.6% of private formal jobs in the country, no agricultural, and almost 40% of salaries [START_REF] Sebrae | O que pensam as micro e pequenas empresas sobre sustentabilidade[END_REF][START_REF] Hoof | Cleaner production in small firms taking part in Mexico`s sustainable supplier program[END_REF][START_REF] Sadaba | Project risk management methodology for small firms[END_REF].

The commerce is the activity with the greatest number of MSEs, accounts for over 50% of total Brazilian MSEs. The services sector is the second area with the greatest number of MEPs, representing 33.3%, followed by industry with 10.7% and 4.5% of the construction sector. The participation of MEPs in total export companies in 2011 reached 61.5%, and 27.0% in the micro and 34,5% in the small firms. The Industrial sector represents about 60% of total exports made by MPE, against a percentage of 80% corresponding to the larger firms. The commercial sector, in contrast, has more important role among the MPE than among larger firms [START_REF] Sebrae/Diesse | Anuario do trabalho na micro e pequena empresa[END_REF][START_REF] Sebrae | As micro e pequenas empresas na exportação brasileira 1998 -2011[END_REF][START_REF] Sebrae | Boletim estudos e pesquisas[END_REF].

Small and medium companies are limited in resources, human capital and technology; they have difficulties in managing new projects. A solution for these firms is business network, as was the case in the autoparts industry in Mexico. Firms that get to improve their capacity to compete are those that reinvent the way to do business, creating a sustainable scenario [START_REF] Sadaba | Project risk management methodology for small firms[END_REF], [START_REF] Alvarado | La innovcion em entornos econômicos poço favorables: El sector auto partes maxicano[END_REF].

The main elements of sustainable business are: a multidimensional concept of sustainability as a central principle of the company, easy comprehension of communication, formulating sustainability concrete goals and detailed strategy for achieving these objectives, the alignment of management incentives intraorganizations and the involvement of stakeholders and, in particular, the employees in the process [START_REF] Ozcure | The sustainable company and employee participation as a part of the solution to triple crisis in the European Union and Turkey: Exemple of OMV Samsun Elektrik[END_REF].

Thus, considering the importance of this issue for the competitiveness of companies, one wonders how micro and small businesses understand what sustainability is. To answer this problem, this paper has as main aims to show what the most important concept of sustainability in the MSMEs is.

Methodology

With the objective and the research problem chosen, this study used descriptive approach with quantitative and qualitative procedures, methods survey in a cross-sectional. The decision of using descriptive study systems from the claim to identify a population, or subgroups of a population, situations, events, attitudes or opinions arising from certain phenomenon [START_REF] Freitas | Método de Pesquisa Survey[END_REF][START_REF] Gil | Como elaborar um projeto de pesquisa[END_REF][START_REF] Yin | Estudo de caso: Planejamento e Métodos[END_REF]. The procedures were defined from the research objective, which aims to understand the vision of sustainability by a population at a determined moment, using structured techniques for data collection.

Planning the research

To operationalize the research, defined data sources, collection method, structure and data processing.

Data source

The choice of data to be analyzed has as its base in the objective of the research, bearing in mind the constraints and difficulties in collecting. This study in particular, defined as a micro, small and medium size research, and the first decision was to choose which method of classification of the size of the companies was going to be used.

There are two ways to classify the size of the companies. One adopted by BNDES, other banks and governments, which considers the gross income as a form of analysis , and the other adopted by IBGE and SEBRAE, which takes under consideration the number of employees, this classification was chosen for the research. This criterion can be seen in Table 1 [START_REF] Sebrae | Critérios de classificação de empresas: EI-ME-EPP[END_REF].

Population and sample

For the research 50 companies were selected; they are associated in the FCDL-CE and FEDERAMINAS, with segments, locations and different sizes. At the request of the companies names will be preserved.

The Interviews were conducted with representatives of the companies that were in the author`s presentation this journal, being mostly socio-directors of organizations.

Although the strict representativeness of the used sample may not be proved, as generally occurs in sample obtained by accessibility, it may be supposed that treat it is feature of the Northeast region of Brazil, where the research was performed.

Data collection

Data collection in selected companies for research was conducted through a structured questionnaire, composed of closed question about research questions.

According to Martins, the questionnaire "is an important tool for data collection for social research, and it is formed by a set of questions about situations and variables to be measured or described". The same author explains that the interview is required to be a research technique for gathering information, data and evidence to get information from the interviewee that were not collected before [START_REF] Martins | Metodologia da investigação científica para ciências sociais aplicadas[END_REF].

For this article, a part of the collection instrument that is being used for the development of the PHD thesis of the author and presented in Table 2.

Results and Discussion

Results obtained in the study observed the following information.

In the city of Montes Claros, Minas Gerais state, 11 companies that met the classification of companies understood as a source of research, micro, small and medium firms, and with different activities, services, commerce and industry were interviewed.

Business managers were interviewed and after the data charting from the questionnaires, which can be seen in figure 1, arrived at the following results: 1 -Cost and profit are the most relevant to the organization's sustainability factors, both with 25.81% of the votes; 2 -Social Development is the least relevant to the company's sustainability factor, with 3.23%; 3 -Environment with 6.45% of the indications is the seventh factor less weight to corporate sustainability among eight possible options. ENT In the city of Araxá, in the state of Minas Gerais, 18 companies that met the classification of companies understood as a source of research, micro, small and medium firms, and with different activities, services, commerce and industry were interviewed.

Business managers were interviewed and after the tabular data from the questionnaires, which can be seen in figure 3, arrived at the following results: 1 -Social Development is the most relevant factor for the sustainability of the organization with 21.95% of the votes 2 -Stability in the market is less relevant to the company's sustainability factor with no indication; 3 -Environment with 14.63% of the votes is the fourth factor with less weight to corporate sustainability among eight possible options. ENT In the city of Fortaleza, state of Ceará, 16 companies that met the classification of companies understood as a source of research, micro, small and medium firms, and with different activities, services, commerce and industry were interviewed.

Business managers were interviewed and after the tabular data from the questionnaires, which can be seen in figure 5, arrived at the following results: 1 -Welfare is the most relevant factor for the sustainability of the organization with 21.74% of the votes; 2 -Production is less relevant to the company's sustainability factor with 1.45% of the votes; 3 -Environment with 10.14% of the votes is the sixth factor less weight to corporate sustainability among eight possible options. In the town of Juazeiro, in the state of Ceará, five companies that fell into the classification of companies understood as a source of research, micro, small and medium firms, and with different activities, services, commerce and industry were interviewed.

Business managers were interviewed and after the tabular data from the questionnaires, which can be seen in figure 7, arrived at the following results:

MINAS GERAIS

MINAS GERAIS Figure 10. Search results in the state of Minas Gerais Analysis of consolidated results of all companies surveyed, representing organizations classified as micro, small and medium sized regions of the Northeast and Southeast, the following results are shown in the figure 11: 1 -Cost is the most relevant to the organization's sustainability factor with 18.06% of the votes; 2 -Production is less relevant to the company's sustainability factor with 5.16% of the votes; 3 -Environment with 11.61% of the votes is the sixth factor less weight to corporate sustainability among eight possible options.

MG CE

MSMEs

Conclusions

Sustainability is an important topic in academia and nowadays. Even with the broad debate on what would be a sustainable company, this condition may result from better management practices, adjustments in operating procedures or the use of more efficient technology, the environmental factor stands out , which is related to the demands of the market and society to a company to be sustainable in the long term [START_REF] Ozcure | The sustainable company and employee participation as a part of the solution to triple crisis in the European Union and Turkey: Exemple of OMV Samsun Elektrik[END_REF], [START_REF] Egels-Zanden | Sustainable strategy formation at a Swedish industrial company:bridging the strategy-as-practice and sustainability gap[END_REF], [START_REF] Sebrae | O que pensam as micro e pequenas empresas sobre sustentabilidade[END_REF], [START_REF] Hoof | Cleaner production in small firms taking part in Mexico`s sustainable supplier program[END_REF], [START_REF] Estadao | Sustentabilidade[END_REF].

Micro, small and medium companies have considerable impact on world economies, mainly by employing a significant number of hand labor with lower qualification is necessary to understand how to position in this segment before this new reality [START_REF] Sebrae/Diesse | Anuario do trabalho na micro e pequena empresa[END_REF].

Whereas only 10.7 % of companies are MSEs of the industrial sector and 89 % of companies have activity as trade , service and construction sector it is an evident characteristic of the non-manufacturing sector , which resulted in the search result as that found factor of greatest relevance to the sustainability of the company "cost " and less relevant , "production " [START_REF] Sebrae/Diesse | Anuario do trabalho na micro e pequena empresa[END_REF].

Different than reported in the media and academic papers, highlighting the "environment " as the main factor for sustainability of companies, the survey found that this factor is not seen as a relevant for achieving sustainability in organizations [START_REF] Ozcure | The sustainable company and employee participation as a part of the solution to triple crisis in the European Union and Turkey: Exemple of OMV Samsun Elektrik[END_REF], [START_REF] Egels-Zanden | Sustainable strategy formation at a Swedish industrial company:bridging the strategy-as-practice and sustainability gap[END_REF], [START_REF] Musson | The build-up of local sustainable development politics: A case study of company leader in France[END_REF], [START_REF] Sebrae | O que pensam as micro e pequenas empresas sobre sustentabilidade[END_REF], [START_REF] Hoof | Cleaner production in small firms taking part in Mexico`s sustainable supplier program[END_REF], [START_REF] Estadao | Sustentabilidade[END_REF].

Given the results presented, conclude that the factor in MSMEs that directly impacts the profitability of the company, such as cost, is considered as a major factor in ensuring the sustainability of the enterprise market. The characteristics of being faithful service and commerce sectors as representing most companies in these sizes.

Having the factors, social and environmental, not considered as important factors for achieving sustainability in the market even before new legislation and consumer requirements, leading to the conclusion that these entrepreneurs understand and plan their business in the short term.

These findings open a gap for further research, enabling a better understanding of the characteristics of these factors, pointing the need of the development of public policies towards new strategies of business enterprises in these sizes.

Figure 2 .

 2 Figure 2. Result graph in the city of Montes Claros -MG

Figure 4 .

 4 Figure 4. Result graph in the city of Araxá -MG

Figure 6 .

 6 Figure 6. Result graph in Fortaleza -CE

Figure 7 .Figure 8 .

 78 Figure 7. Search results in the town of Juazeiro -EC

Table 1 .

 1 Classification criteria for companies (Source: adapted Sebrae, 2012).

		INDUSTRY
	Micro	< = 19 employees
	Small	20 -99 employees
	Medium	100 -499 employees
	Larger	> 500 employees
	COMMERCE AND SERVICE
	Micro	< = 9 employees
	Small	10 -49 employees
	Medium	50 -99 employees
	Larger	> 100 employees

Table 2 .

 2 Instrument for data collection (Source: the author).

	Environment	Social development
	Costs	Employee welfare
	Production	Profit
	Productivity	Market stability

In your opinion what concept (or concepts which) is more relevant sustainability of your company?

1 -

 1 Environment and Social Development are the most relevant to the organization's sustainability factors, both with 21.43% of the votes; 2 -Production and productivity are less relevant to the company's sustainability factors with no indication;

	JUAZEIRO DO NORTE -CE
		ENT 1 ENT 2 ENT 3 ENT 4 ENT 5		Total	Porc.(%)
	environment	1	1	1		3	21,43%
	cost		1	1		2	14,29%
	production productivity social development	1	1	1	frequency	0 0 3	0,00% 0,00% 21,43%
	employee welfare	1	1			2	14,29%
	profit		1	1		2	14,29%
	market stability		1	1		2	14,29%

  Search results in the state of CearáAnalysis of consolidated results of the cities of Montes Claros and Araxá, representing the state of Minas Gerais in the Southeast region, the following results are shown in the Figure10:1 -Cost is the most relevant to the organization's sustainability factor with 22.22% of the votes; 2 -Stability of the market is less relevant to the company's sustainability factor with 2.78% of the votes; 3 -Environment with 11.11% of the votes is the fifth factor with less weight to corporate sustainability among eight possible options.

	MG -29 Firms
	Total 10 12 1 9 14 17 8 12 CE -21 Firms Porc.(%) 12,05% 14,46% 1,20% 10,84% 16,87% 20,48% 9,64% 14,46% Porc.(%) 8 11,11% 7 9,72% 11 15,28% 10 13,89% 6 8,33% 12 16,67% 2 2,78% Figure 9. Total frequency frequency 16 22,22%	environment cost production productivity social development employee welfare profit market stability environment cost production productivity social development employee welfare profit market stability	12,05% 14,46% 10,84% 16,87% 20,48% 9,64% 14,46% 11,11% CEARA 1,20% CEARA 22,22% 9,72% 15,28% 13,89% 8,33% 16,67% 2,78%


D Trentesaux
email: damien.trentesaux@univ-valenciennes.fr

V Prabhu
email: prabhu@engr.psu.edu

Sustainability in manufacturing operations scheduling: stakes, approaches and trends

Keywords: Sustainability, manufacturing operations, scheduling, production control

In this paper it is explained how manufacturing operations scheduling can contribute to sustainability. For that purpose, the relevant stakes are first presented. Sustainable manufacturing operations are then characterized. Different forms of sustainability in manufacturing operations scheduling are pointed out and some illustrative contributions are positioned.

Introduction

Several recent literature reviews are available in sustainable manufacturing, but most of the time the studies are led at the strategic levels: supply chain design, layout design, cleaner product and production mean design, construction, recycling process, etc., see for example (Garetti and Taisch, 2012), [START_REF] Gunasekaran | Sustainability of manufacturing and services: Investigations for research and applications[END_REF]. One of the main reasons for the strategic level emphasis is that much of the sustainability efforts have been driven by highest levels within organizations. According to [START_REF] Fang | A new approach to scheduling in manufacturing for power consumption and carbon footprint reduction[END_REF], research on reducing environmental impacts through manufacturing operations control and scheduling has been relatively limited. Early efforts in this direction were applied in the chemical industry [START_REF] Grau | Environmental considerations in batch production scheduling[END_REF]. There has been relatively little effort on energy-aware scheduling of manufacturing operations [START_REF] Bruzzone | Energy-aware scheduling for improving manufacturing process sustainability: A mathematical model for flexible flow shops[END_REF].

Despite this, this paper intends to explain how manufacturing operations can contribute to sustainability, and especially to two of the three pillars in sustainable development: the environmental and economical pillars (the social pillar is not addressed in this paper). The present article aims to review these two pillars at the detailed manufacturing operations level with the intent to provide impetus for further research. For that purpose, the relevant stakes are first presented. Sustainable manufacturing operations are then characterized. Different forms of sustainability in manufacturing operations are pointed out and some illustrative contributions are positioned.

2

Sustainable manufacturing operations: stakes and trends

Three emerging stakes can be identified in the context of sustainable manufacturing operations.

First, despite the fact that machining represents a small fraction of the whole product life cycle, reducing the energy consumed during this phase was recently identified as one of the most important strategies to improve sustainability in manufacturing [START_REF] He | A modeling method of task-oriented energy consumption for machining manufacturing system[END_REF], [START_REF] Pusavec | Transitioning to sustainable production -Part I: application on machining technologies[END_REF]. This is driven by the fact that in the 2010's, the industrial sector accounts for about one-half of the world's total energy consumption. More, the consumption of energy by the sector has almost doubled over the last 60 years [START_REF] Fang | A new approach to scheduling in manufacturing for power consumption and carbon footprint reduction[END_REF]. (Garetti and Taisch, 2012) add that manufacturing is responsible of more than 33% of the global final energy consumption and 38% of direct and indirect CO2 emissions worldwide the remaining are attributed to the transport sector, households and services. Furthermore, energy efficiency of machine tools is generally less than 30% [START_REF] Hu | An on-line approach for energy efficiency monitoring of machine tools[END_REF] combined with dynamic pricing and significant limitations on peak energy will make detailed manufacturing scheduling and control systems will have considerable influence on the energy consumption and associate cost.

Second, manufacturing has a huge impact on the environment and major risk of "unsustainability" comes from the operational levels of the manufacturing phase (pollution, waste, including waste of energy) (Garetti and Taisch, 2012). Some process industry such as chemical, food, refining, paint or metal industries are highly energy consuming and present a high risk to generate important amount of waste or pollution. For example, in [START_REF] Chen | Energy-Efficient Production Systems through Schedule-Based Operations[END_REF] is pointed the fact that during 2000 about 60% of the $700 million energy expenditures in 37 U.S. automotive assembly plants are spent in painting processes. In such a context, a 5% reduction in energy consumption may result in a saving of more than half million dollars per year for each plant. Given the rapidly increasing energy prices during the past ten years, the saving would be even more remarkable in present days while a significant amount of savings could be achieved without any major equipment investment, focusing efforts on operations. Moreover, low margins in such industries make seeking for efficiency a strategic objective [START_REF] Akkerman | Development and application of a decision support tool for reduction of product losses in the food-processing industry[END_REF]. For these kinds of industry, research is also focused on waste management, leading especially to cleaner production. Manufacturing and industrial processes are also known to produce large amounts of C02 but it is difficult for enterprises to consider renewable sources application and emissions reduction when making manufacturing and operation decisions, especially on the production planning and scheduling problem [START_REF] Wang | A low-carbon production scheduling system considering renewable energy[END_REF].

Third, from an industrial point of view, with the successive financial and economic crises, more and more industrial managers face a new kind of problem: their manufacturing systems become oversized compared to the market need and they wonder if they could limit their energy consumption. For example, in [START_REF] Yildirim | Single-Machine Sustainable Production Planning to Minimize Total Energy Consumption and Total Completion Time Using a Multiple Objective Genetic Algorithm[END_REF] is related a study of a Wichita, KS, aircraft small-parts supplier, where it was observed that, on average, in an 8-h shift, 16% of the time, machines stand idle. During these idle periods, there is an opportunity to save at least 13% of the total energy consumption by simply turning them OFF when they are not processing any jobs. The problem may be obvious at a first glance, but some unexpected issues arise, such as: memorization/retrieval of last information before shut-down, re-initialization of robots (programs, parameters and states), re-synchronization of manufacturing processes after restart, etc. [START_REF] Pach | Reactive and energy-aware scheduling of flexible manufacturing systems using potential fields[END_REF].

Therefore even if the manufacturing operation is not a prime driver of sustainability, it is becoming increasingly important to study various ways in which manufacturing operations can contribute globally to sustainability. Prior work has led to an increasing awareness and interest in integrating sustainability considerations when designing manufacturing operations scheduling and control system as can be evidenced by several recent special issues of international journal, dealing with "automation in green manufacturing" [START_REF] Li | Editorial: Automation in green manufacturing[END_REF], "sustainable manufacturing" (Garetti et al., 2012) or "Recent cleaner production advances in process monitoring and optimisation" [START_REF] Klemeš | Recent cleaner production advances in process monitoring and optimisation[END_REF]. These special issues addressed some aspects relevant to sustainability applied at detailed manufacturing operations and some of the papers published in these special issues are reviewed in this article. Moreover, previously released literature reviews have been realized on close topics. They focused for example on a specific kind of manufacturing systems, such as: mixed-models manufacturing processes [START_REF] Neugebauer | Energy-Sensitive Production Control in Mixed Model Manufacturing Processes[END_REF], specific usable tools, such as simulation software [START_REF] Thiede | Environmental aspects in manufacturing system modelling and simulation-State of the art and research perspectives[END_REF], industrial-oriented software, such as manufacturing execution systems [START_REF] Soplop | Manufacturing execution systems for sustainability: Extending the scope of MES to achieve energy efficiency and sustainability goals[END_REF], energy consumption reduction in manufacturing from a technology [START_REF] Park | Energy consumption reduction technology in manufacturing -A selective review of policies, standards, and research[END_REF] or from a processes and systems [START_REF] Duflou | Towards energy and resource efficient manufacturing: A processes and systems approach[END_REF] point of views. All these reviews contain of course some considerations paid to manufacturing operations scheduling and control, but partially.

3

When manufacturing operations scheduling is sustainable?

Several notions are often used to describe similar strategy or philosophy in the context of sustainability in manufacturing: lean, clean, green manufacturing to name a few. In this paper, sustainable manufacturing refers to the set of technical and organizational solutions contributing to the development and implementation of innovative methods, practices and technologies, in the manufacturing field, for addressing the world-wide resources shortages, for mitigating the excess of environmental load and for enabling an environmentally benign life cycle of products (Garetti et al., 2012).

Manufacturing operations refer in this paper to the low-level short-term or even real time decisions applied to manufacturing systems. Upper levels, such as mid-term production planning, supply chain and business levels are not considered in this paper, as well as lower levels dealing with actuators/sensors and physical behaviour are not considered either. We focus on process monitoring, inventory and tool management, machine control, scheduling and maintenance among the main functions of manufacturing operations [START_REF] Trentesaux | Introduction to shop-floor control[END_REF].

Manufacturing operations management in a broad sense, and especially scheduling in manufacturing, has been one of the most studied problems by the operation research and control communities, and this holds also true considering sustainability issues. Scheduling is the allocation of resources (human and technical) to tasks over given time periods and its goal is to optimize one or more [START_REF] Pinedo | Scheduling: Theory, Algorithms, and Systems[END_REF]. In this paper, scheduling is taken in a broad sense, encompassing predictive approaches, dynamic/reactive approaches and real-time control techniques.

The question that arises is then: under which conditions a manufacturing operations scheduling method can be termed as sustainable? From our point of view, the key point is related to the consideration of means in addition to classical time-based (completion times, flow times, tardiness/earliness…) or mixed time/quantity-based (throughput…) production objectives. In the context of sustainable manufacturing operations, two kinds of means can be identified: the input means that enable the realization of a scheduling (energy, machines, inventories, raw materials, tools…) and the output means that are consequences of the realization of the scheduling (waste, scrap, pollution). Due to its specificity, money is not present in the input means list in the sense that it is the driver of all the other input means. As a consequence, from our point of view, the answer is: it is when a method considers in addition to usual production objectives (time-based or time/quantity-based) the optimization of input means and/or output means when computing/constructing these schedules.

This answer guided us to realize our literature review to determine if contributions are relevant or not to sustainability in manufacturing operations scheduling. Thus, in a sustainable context, input/output means have then to be considered as decision variables when computing schedules in a predictive or reactive manner. For example, energy and resources are such typical means and must be seen as tuning/decision parameters. Other approaches, typically for example the ones that consider energy as a fixed cost, which is not a value to reduce as much as possible, cannot be considered as contribution to sustainability. Typically, in such a context, if the energy consumption for a schedule is assumed to be constant, then it can be ignored [START_REF] Yildirim | Single-Machine Sustainable Production Planning to Minimize Total Energy Consumption and Total Completion Time Using a Multiple Objective Genetic Algorithm[END_REF]. It is the same for the numerous contributions in the manufacturing scheduling domain that consider the quantity of available machines as a constraint, not a value to be reduced as much as possible. Typically, the literature review proposed by [START_REF] Hoogeveen | Multicriteria scheduling[END_REF] is out of the scope since the author considered only time-related performance objectives, being mono or multicriteria-based: no attention was paid to input nor output means.

Other numerous works concern the solving a problem known as the resourceconstraint scheduling problem (RCPSP) [START_REF] Brucker | Resource-constrained project scheduling: Notation, classification, models, and methods[END_REF]. Roughly, a RCPSP problem is a project planning problem considering renewable resources (manpower, machines…) and nonrenewable resources (budget, energy) [START_REF] Hartmann | A survey of variants and extensions of the resourceconstrained project scheduling problem[END_REF]. Fundamentally, there exist two ways to optimize a RCPSP problem: either minimizing the project makespan subject to a fixed upper bound on the nonrenewable resource (the budget problem), or at minimizing the total allocation subject to a given bound on the makespan (the deadline problem) [START_REF] Brucker | Resource-constrained project scheduling: Notation, classification, models, and methods[END_REF]. A lot of extensions of this problem have been proposed [START_REF] Hartmann | A survey of variants and extensions of the resourceconstrained project scheduling problem[END_REF]. These works address high-levels in manufacturing system, which is beyond the scope of this paper. Even if these works are not directly related to sustainability, they have inspired numerous studies related to predictive manufacturing operations scheduling considering sustainability.

More precisely, considering input/output means in scheduling enlarges the debate and leads to the consideration of a new performance indicator, efficiency, in addition to the classical effectiveness one: seeking for the best use of means refers to efficiency while seeking for the best results, effectiveness [START_REF] Roghanian | Productivity through Effectiveness and Efficiency in the Banking Industry[END_REF]. Efficiency and effectiveness are commonly performances indicators used in economy, accounting, business and management. Roughly speaking, efficiency is often assimilated as "doing things right" while effectiveness, "doing the right things" [START_REF] Roghanian | Productivity through Effectiveness and Efficiency in the Banking Industry[END_REF]. The ideal sustainable manufacturing scheduling system realizes everything (maximum effectiveness) using nothing (minimum use of means, that is maximum efficiency). In reality, effectiveness and efficiency are conflicting objectives: for example, reducing energy consumption may imply a loss of performances in operations (makespan).

Illustrative works in sustainable manufacturing operations

To illustrate the previous discussion, some contributions from the literature are positioned in this part. This positioning is made according to the addressed means in the sustainable-oriented scheduling models (input, output or mixed). Obviously, the aim is not to provide a complete review.

4.1

Input oriented approaches: energy, inventory, machine, tools Input-oriented scheduling approaches are the most often developed. For this approach, optimal predictive scheduling are mainly proposed. A first type of predictive approach works is focused on the elaboration of a trade-off between effectiveness and input-means oriented efficiency. It has been widely addressed in the literature. It consists in minimizing input resource consumption while maintaining the quality of the schedule as a compromise, aggregation being made using a mono or a multi-criteria aggregation method, see for example [START_REF] He | A modeling method of task-oriented energy consumption for machining manufacturing system[END_REF], [START_REF] Zhang | Dynamic scheduling model in FMS by considering energy consumption and schedule efficiency[END_REF], [START_REF] Vergnano | Embedding detailed robot energy optimization into high-level scheduling[END_REF] or [START_REF] Newman | Energy efficient process planning for CNC machining[END_REF]. Most of these approaches are statically handled, but this tradeoff can be realized in real time, in an opportunistic manner, using for example potential fields [START_REF] Pach | Reactive and energy-aware scheduling of flexible manufacturing systems using potential fields[END_REF]. In a second type, less addressed but promising and innovative, the approach consists in optimizing scheduling effectiveness under input means profile as hard constraints (eg., expressed in terms of money or maximum available power for given time windows, typically in the smart grid, or more simply, a maximum peak power value to be respected). This could lead for example to scheduling mechanisms shortening the makespan if more energy is available while increasing the makespan if less energy is available, see for example [START_REF] Pechmann | Energy Efficient and Intelligent Production Scheduling -Evaluation of a New Production Planning and Scheduling Software[END_REF], [START_REF] Bruzzone | Energy-aware scheduling for improving manufacturing process sustainability: A mathematical model for flexible flow shops[END_REF] or [START_REF] Artigues | The energy scheduling problem: Industrial case-study and constraint propagation techniques[END_REF]. In the last type, the scheduling effectiveness is maintained as the main objective, while the input resource use/consumption is minimized, if possible, see for example [START_REF] Mashaei | Energy Reduction in a Pallet-Constrained Flow Shop Through On/Off Control of Idle Machines[END_REF] or [START_REF] Chen | Energy-Efficient Production Systems through Schedule-Based Operations[END_REF].

Approximate predictive approaches are also proposed [START_REF] Santos | Global optimization of energy and production in process industries: a genetic algorithm application[END_REF], [START_REF] Yildirim | Single-Machine Sustainable Production Planning to Minimize Total Energy Consumption and Total Completion Time Using a Multiple Objective Genetic Algorithm[END_REF] as well as simulation/optimization ones [START_REF] Weinert | Methodology for planning and operating energyefficient production systems[END_REF], [START_REF] Prabhu | Simulation Modeling of Energy Dynamics in Discrete Manufacturing Systems[END_REF].

4.2

Output oriented approaches: waste, pollution, scrap, greenhouse gases

These approaches are less studied, but some contributions are among the first ones in the field. Especially, chemical plants constitute a classical and historical application field of environment considerations in production operations. For example, [START_REF] Grau | Environmental considerations in batch production scheduling[END_REF], (Vaklieva-Bancheva and Kirilova, 2010) and [START_REF] Adonyi | Effective scheduling of a large-scale paint production system[END_REF] proposed optimal predictive approaches in the context of waste and cleanness management.

Mixed approaches

Some mixed approaches, considering simultaneously input and output means have been developed. For example, [START_REF] Fang | A new approach to scheduling in manufacturing for power consumption and carbon footprint reduction[END_REF], [START_REF] Wang | A low-carbon production scheduling system considering renewable energy[END_REF] considered simultaneously energy and carbon footprint. From our review, mixed approaches are then not well developed as for output oriented approaches.

Conclusion and future trends

In this article, the role of scheduling manufacturing operations in a sustainable context was addressed. The research activity is growing but still does not fill the gap between research and industrial needs. Input-oriented approaches are the most studied ones but the field is still nascent (most of the references are after 2012). Output-oriented and mixed approaches are clearly unstudied. Given the future evolutions, scheduling under sustainability constraints should be urgently addressed. From our point of view, future trends concern the development of "means-friendly" systems, being manufacturing execution systems or scheduling systems. This concerns typically: the integration of opportunistic behavior in energy savings, the optimization of greenhouse gases emission in scheduling, and more globally the definition of scheduling benchmarks integrating output means considerations. From our review, it is indeed clear that output and mixed approaches should also be urgently addressed. Innovative approaches and concepts such as cyber-physical systems, intelligent products, product-service systems to name a few can bring some insights to contribute to the development of effective and efficient sustainable scheduling systems. This paper did not considered the social pillar which should be studied to complete the view on the addressed issue.