Volker Stich

Ulrich Brandenburg

Julian Krenge
email: julian.krenge@fir.rwth-aachen.de

Energy Simulation for the Integration of Virtual Power Plants into Production Planning

Keywords: Energy-Efficiency, Energy Simulation, Production Planning and Scheduling, Virtual Power Plants

Germany pushes its energy industry towards renewable energy sources which results in an increase of distributed energy generation. Therefore, energy supply will fluctuate more and more and companies need to react to higher and volatile prices as well as to a fluctuating supply of energy. One reaction is to reactively consider these changing prices and supply of energy within production planning and control (PPC). PPC therefore acts as a control unit to integrate volatile energy supply into the production process. Within this paper a scenario is considered where a virtual power plant (VPP) combines different types of distributed energy generation. Energy simulation is then used to demonstrate how fluctuating energy prices can be considered within PPC.

Introduction

The results of the climate change and the global warming are becoming more visible every day [START_REF] Kara | Unit process energy consumption models for material removal processes[END_REF] [START_REF] Branker | Greenhouse gases emitted in manufacturing a product-A new economic model[END_REF]. Inefficient electricity energy consumption accounts for 80% of all greenhouse gases (GHG) emission in the EU. As a result, the EU has been committed to a new plan (known as 20/20/20) to fight global warming. According to the plan, by 2020 the EU will have cut greenhouse gas emissions by 20% from 1990 levels, increased renewable energy usage by 20%, and cut energy consumption through improved energy efficiency by 20% [START_REF]Saving our energy[END_REF].

As Europe shifts away from fossil fuels, electricity will become an even more important energy sector, and more than 29 European countries have targets for a share of renewables of 5-33% until 2020. Achieving these goals is vital for the EU internal energy market. The implementation of more intelligent and active transmission, distribution and supply systems in the form of Smart Grids is central to the success of such a development. Smart Grids are essential for the integration of distributed energy generation in the power grid, which results in a number of benefits from a sustainability point of view [START_REF] Diaz-Elsayed | Assessment of lean and green strategies by simulation of manufacturing systems in discrete production environments[END_REF].

On the downside, along with the increasing share of renewable energies in the electricity network, the supply uncertainty and the volatility increase. One possibility to react to this situation is called demand-side-integration which focuses on increasing the demand flexibility of energy consumers. As the manufacturing industry is one of the major consumers of energy there is a need for companies to play a vital role in this transition process. This can be done by proactively integrating fluctuating energy sources such as wind, solar and water into production planning [START_REF] Reinhart | Energieflexible Produktionssysteme. Einführungen zur Bewertung der Energieeffizienz von Produktionssystemen[END_REF].

2

Terminology and scope of the study

Terminology

Production logistics focuses on ensuring a better delivery capability and reliability while minimizing logistics and production costs. Therefore, production logistics improves the productivity in a network by organizing material flow through the producing process. Because production logistics strongly influences the important performance indicators delivery capability and delivery reliability, much effort is taken in industrial application and scientific research on this topic [START_REF] Nyhuis | Fundamentals of production logistics[END_REF].

Production planning and control (PPC) is a key function to every producing company. As a value adding part of the company's organization, the main task is the holistic optimization of the production system. Part of this is the (mathematical) optimization of the production program, the material requirements and the production order [START_REF]Grundlagen der PPS[END_REF].

Virtual Power Plants (VPP) unite different types of energy generating units, collectively controlled in order to behave like a conventional power plant. Through the use of various energy generation technologies, a continuous, controllable power generation is enabled as it would not be possible at individual power plants working with renewable energy. Connected are for example photovoltaic, wind and hydro power plants. The usage of Virtual Power Plants is an attempt to use the benefit of the usage of renewable energy but still minimize the fluctuations in the power supply [START_REF] Fang | Smart Grid -The New and Improved Power Grid: A Survey[END_REF].

Simulation is the method of evaluating the performance of an existing or proposed system in order to simulate its behavior under different configurations [START_REF] Banks | Discrete-event system simulation[END_REF]. Since energy costs will rise continuously, optimizing the energy consumption becomes an interesting opportunity to reduce costs. Simulation can be broadly divided as Mathematical methods and Numerical computer-based simulation. Mathematical models involve the use of various theories for reaching a conclusion. They use a few number of parameters but can reach a very precise result. The draw-back of this system is that it sometimes may prove to be very tedious and almost impossible for complex systems. Therefore for solving complex systems and to provide simple solutions, numerical computer-based simulations are used [START_REF] Banks | Discrete-event system simulation[END_REF]. More specifically, within Energy Simulation the energy flow and consumption is simulated taking into account the material flow process. To optimize the energy efficiency of a production system or parts of the system, the results of these simulations may be used e.g. to determine the optimum batch size and the production sequence. [10]

2.2

Scope of the Study

The study concentrates on discrete manufacturing systems (e.g. Automotive and mechanical engineering). Products to be considered are multi-part products comprising of a simple structure that are being manufactured in small to medium batch-sizes. There is more than one value-added step to the product meaning that each product passes at more than one value-adding element within the production system. The production system is organized as a job shop production therefore machines of the same production technology (e.g. milling, drilling etc.) are set in the same area. The study solely focuses on the area of production excluding interactions with technical building systems (heating, air-conditioning etc.). Additionally, the study focuses on a shortterm examination (weeks) therefore factory layout planning etc. is not considered. As type of energy, solely electrical energy is considered as this type of energy is provided by VPPs.

State-of-the-art

In order to include the energy and resource efficiency as a target value into production planning systems, it is necessary to know and understand which factors can influence efficiency and how sophisticated production planning can improve it. Several works have been published in the field of energy consumption of production machines.

The first of these approaches, which has been used by several authors is to analyze the energy consumption of machine tools using high resolution power measurements and assigning specific loads to each operational state of the machine [START_REF] Duflou | Critical comparison of methods to determine the energy input for discrete manufacturing processes[END_REF], [START_REF] Li | Eco-efficiency of manufacturing processes: A grinding case[END_REF], [START_REF] Weinert | Methodology for planning and operating energy-efficient production systems[END_REF].

Weinert et. al. introduced a methodology for planning and operating energy efficient production systems. The key element of this methodology is the knowledge of the power consumption profile of individual machines and the subsequent approximation of the production systems' power consumption using EnergyBlocks. The power consumption profile for the machines used in Weinert's method does not explicitly differentiate the subsystems of a production machine but it represents a machine specific consumption profile. The power consumption profile is approximated by Ener-gyBlocks and divided in time-variable, production dependent elements and nonvariable elements. All elements are analyzed and the dependence on each other is described [START_REF] Weinert | Methodology for planning and operating energy-efficient production systems[END_REF]. Fig. 1. Energy Blocks method according to [START_REF] Weinert | Methodology for planning and operating energy-efficient production systems[END_REF] Abele et.al. present a simulation-based method for the prediction of the energy consumption of a running machine [START_REF] Abele | Energieeffizienz in der Fertigungsplanung. Frühzeitige Abschätzung des Energieverbrauchs von Produktionsmaschinen in der Mittel-und Großserienfertigung[END_REF]. A key finding of their approach is that 43% of the specific energy consumption results from the base load of the machine. Therefore, the production process is not very significant for the prediction of the total energy consumption. Once again the machine's base load and dynamic power components are identified as the main drivers behind the energy consumption. Their determination is a key element in assessing the consumption of a machine tool.

Schrems et. al. propose a methodology for designing an energy and resource efficient process chain. A decision-based model was developed in order to identify the preferred production alternative out of several possibilities. The method implements a multi-criteria decision system, weighing ecological, technological and economical parameters to generate the result [START_REF] Schrems | Methodology for an Energy and Resource Efficient Process Chain Design[END_REF].

Bruzzone et. al. [START_REF] Bruzzone | Energy-aware scheduling for improving manufacturing process sustainability: A mathematical model for flexible flow shops[END_REF] also propose a mathematical model. This model integrates energy-aware scheduling (EAS) through an advanced planning and scheduling (APS) system. Key to Bruzzone's proposal is an incorporated model that controls the power peaks for a given schedule on the shop floor level. The EAS operates sequentially with the APS. Both share the same optimization criteria and their output is a feasible schedule regarding the main objectives: job-completion-time, cycle time and delayminimization, additionally the power peak target has been added as a criterion.

Pechman and Schöler [START_REF] Pechmann | Optimizing Energy Costs by Intelligent Production Scheduling[END_REF] present an E-PPC system that is able to create a 24h energy consumption forecast using a similar technique as proposed by Weinert [13]. This technique allows the user to identify upcoming energy peaks in the phase of production planning, therefore allowing him to reschedule accordingly. With a detailed consumption forecast the company has benefits when negotiating the supply [START_REF] Weinert | Methodology for planning and operating energy-efficient production systems[END_REF] contract with the power utility.

∑ 𝑠𝑡𝑜𝑐𝑘 𝑖 𝑛 𝑖=1 𝑛 𝑤𝑖𝑡ℎ 𝑖 = 𝑝𝑜𝑖𝑛𝑡 𝑖𝑛 𝑡𝑖𝑚𝑒 𝑜𝑓𝑠𝑎𝑚𝑝𝑙𝑖𝑛𝑔 𝑛 = 𝑠𝑖𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑡𝑖𝑚𝑒 𝑖𝑛 ℎ𝑜𝑢𝑟𝑠
According to the efficiency definition energy efficiency is considered as a ratio between input and output. In order to account for fluctuating energy prices the input ration is defined as the energy costs that arise per part. The output can be defined as the value-added per part which can be simplified by production costs.

VPP are represented by a volatile energy price function that accounts for the fluctuating feed in of renewable energy sources. Within production planning orders from different sources (customers etc.) are transformed into production orders. For those production orders lot sizes and production sequences are planned based on energy prices and availability, delivery dates etc. The simulation period is considered to be 4 weeks with a weekly interval of releasing production orders into the job shop. Within the job shop a detailed sequencing for each production capacity (machines or groups of machines) is conducted. Therefore, energy prices are considered to be changing every hour. Additionally, energy prices are considered to be known in advance for the following day of production. Within the simulation model elements of the production system are modelled such as machines, buffers and transportation systems. For each element in the system energy data in different states can be defined in order to obtain the energy consumption profiles. According to the principle of discrete-event simulation the material flow pattern generates different operational states of the model such as producing, waiting, failure, setup, standby, etc. according to the arrival rate of products. After conducting the simulation runs, the output data is analyzed. Based on the parameter settings for lot-sizes, production sequence and order release all of the target values are calculated. Then feasible production plans are selected and communicated towards the operator of the VPP.

Conclusion and Outlook

Rising and volatile energy prices due to an increase of renewable energy sources causes producing companies to strive for integrating VPPs into their production. Within this paper an approach for integrating volatile energy sources into production planning and control was presented. First results of the simulation run are promising that integrating volatile energy prices without compromising productivity can be achieved. The next step will be to implement the results within a real system and validate the results from the energy simulation. Consequently, the results will be used to develop a concept for collaborative production planning within a VPP network. Based on the results from the real system the energy simulation can be used to forecast the energy consumption for a given production plan. This information can then be shared with the VPP provider. The first results suggest that rough planning in production (weeks/months) can be used to secure on-time delivery for critical orders due to its high-priority for the customers of producing companies. Once a production plan is validated and the energy consumption is forecasted and communicated to the VPP operator the detailed planning has to ensure that the energy forecast will be realized. Therefore, production sequencing will be very crucial for achieving a high energyefficiency on the shop-floor level. Once the new concepts for energy-efficient production planning are validated within a real production system consequently Enterprise-Ressource-Planning-systems and Manufacturing Execution Systems (MES) have to be adapted in order to support energy-efficient production planning.

Table 1 .

 1 Target values within Energy Simulation

	Name	Definition
	Energy Efficiency	∑𝐸𝑛𝑒𝑟𝑔𝑦 𝐶𝑜𝑠𝑡𝑠 𝑝𝑒𝑟 𝑝𝑎𝑟𝑡
		∑𝑉𝑎𝑙𝑢𝑒 -𝑎𝑑𝑑𝑒𝑑 𝑝𝑒𝑟 𝑝𝑎𝑟𝑡
	Capacity Utilization	∑𝑇𝑖𝑚𝑒 𝑜𝑓 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝑢𝑠𝑎𝑔𝑒
		𝐷𝑢𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑠𝑖𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛
	Lead time	𝑇 𝑜𝑢𝑡𝑝𝑢𝑡 -𝑇 𝑖𝑛𝑝𝑢𝑡 𝑤𝑖𝑡ℎ
		𝑇 𝑖 = 𝑟𝑢𝑛𝑛𝑖𝑛𝑔 𝑡𝑖𝑚𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑖𝑚𝑢𝑙𝑎𝑡𝑖𝑜𝑛
		𝑎𝑡 𝑝𝑜𝑖𝑛𝑡 𝑖𝑛 𝑡𝑖𝑚𝑒 𝑖
	On-time delivery	∑𝑜𝑛 -𝑡𝑖𝑚𝑒 𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑖𝑒𝑠
		∑𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑖𝑒𝑠
	Production costs	� 𝑒𝑛𝑒𝑟𝑔𝑦 𝑐𝑜𝑠𝑡𝑠, 𝑚𝑎𝑐ℎ𝑖𝑛𝑖𝑛𝑔 𝑐𝑜𝑠𝑡𝑠
	Work-in-progress
	(WIP)

adfa, p. 1, 2011. © Springer-Verlag Berlin Heidelberg 2011

Acknowledgement

The authors wish to thank the Finesce Consortium for their input and their support. The Finesce project is funded by the EU grant FP7-2012-ICT-FI.

Energy Simulation

The main objective of the energy simulation is to demonstrate how volatile energy sources represented by a VPP can be integrated into producing company without compromising the productivity of the production system. The software used for this study is called PlantSimulation by Siemens PLM Software which contains an Energy Analyzer module. Therewith, it is possible to model machine profiles according to the EnergyBlocks methodology proposed by Weinert [START_REF] Weinert | Methodology for planning and operating energy-efficient production systems[END_REF], [START_REF] Wolff | Simulating Energy Consumption in Automotive Industries[END_REF]. Fig. 2 illustrates the system under study defined in the scope in 2.2. The modelling of the system is done in accordance to März and Weigert and consists of a model of the production system, actuating variables within PPC, input data and target values [START_REF] März | Simulationsgestützte Optimierung[END_REF].

Fig. 2. Energy Simulation model for integrating VPP

The target values have been derived from production logistics such as lead times, capacity utilization and production costs while integrating a target value for energy efficiency. The following target values Z int,dyn are defined:


Mélanie Despeisse

Doroteya Vladimirova

Decision Making for Sustainability: Review and Research Agenda

Keywords: Decision making for sustainability, Decision-making framework, Manufacturing strategy, Sustainable manufacturing

Manufacturers are failing to maximise the benefits from their own sustainability ambitions. Their decision-making methods and tools have not evolved to allow the non-financial dimensions of sustainability to be accounted for. Non-financial information is not systematically used in decision making as manufacturers do not yet know how to value qualitative benefits, opportunities and challenges. This paper reviews current challenges and the literature on decision-making for sustainability in manufacturing. The paper presents the need for a decision-making framework for sustainability and a research agenda for developing such a framework and delivering a supporting tool.

Background and Problem Statement

It is argued that manufacturers are missing sustainability improvement opportunities because it is not fully understood how decisions are made outside the traditional value system based on short-term financial value purely [START_REF] Porter | Creating Shared Value: How to reinvent capitalism-and unleash a wave of innovation and growth[END_REF][START_REF] Lavery | Next Manufacturing Revolution[END_REF]. Manufacturers find it difficult to consider the medium-and long-term benefits for short-term decision-making for immediate actions, because they seek to monetize all the benefits in developing business cases focused on short-term profit. Additionally, even when there are financial benefits, sustainability activities are not necessarily undertaken [START_REF] Tsui | On Compassion in Scholarship: Why Should We Care?[END_REF].

Many manufacturers will already have a sustainability vision and strategy, yet they struggle to bring these into their day-to-day operational decisions [START_REF] Epstein | Sustainability in action: Identifying and measuring the key performance drivers[END_REF][START_REF] Lueneburger | The Change Leadership Sustainability Demands[END_REF]. Decisionmaking for sustainability is a growing research area as it has been recognised as a vital ingredient for success in modern businesses [START_REF] Arvai | Decision-Making for Sustainability: A Systematic Review of the Body of Knowledge[END_REF]. Decisions can be of different scale and frequency, e.g. new factory location vs. cleaning process sequence. Some successes have been achieved when the social and environmental dimensions have been monetized [START_REF] Turner | Valuing nature: lessons learned and future research direction[END_REF]. The traditional view of manufacturing companies' value capture regards the profit which is made when the goods and services are sold in relation to the cost of producing and delivering them, thus decisions are made purely based on financial profit (Fig. 1).

However the value created and potentially captured is not necessarily in the form of financial benefits. Industry is calling for more "useful" information for sustainability decision-making. Useful information can be defined as information that widens and specifies options to enable better results from implementation and to achieve desired objectives. The challenge manufacturers are facing is to monetize the benefits of long-term innovative sustainable solutions, such as organisational learning, knowledge exchange across disciplines and sectors, collaborative business models, closedloop and resilient industrial systems, or first mover advantage, even when useful information about these solutions are available.

Fig. 1. Decision-making system for short-term financial benefits

In the context of today's increasing interconnectedness, complexity and multidimensionality of business operations and management, it is reasonable to assume that the benefits would become more interdependent and multifaceted as well. To reflect this multidimensionality, organisational decisions around sustainability have been depicted using the triple bottom line of people-planet-profit [START_REF] Elkington | Cannibals with Forks: The Triple Bottom Line of 21 st Century Business[END_REF]; each dimension considered separately by experts and later on brought together. The difficulty is to combine these three dimensions for making final decisions [START_REF] Gibson | Beyond the Pillars: Sustainability Assessment as a Framework for Effective Integration of Social, Economic, and Ecological Considera-tions in Significant Decision Making[END_REF]. As a result, decisionmaking is still dominated by a single index based on financial metrics and short-term thinking which do not adequately account for qualitative benefits. In other words, we have under-performing decision-making systems when it comes to industrial sustainability improvements.

There have been many efforts and initiatives to value ecosystem services [START_REF] De Groot | Challenges in integrating the concept of ecosystem services and values in landscape planning, management and decision making[END_REF], to link CSR and firm value [START_REF] Edmans | The Link Between Job Satisfaction and Firm Value, with Implications for Corporate Social Responsibility[END_REF], to develop a three-dimensional framework assessment [START_REF] Hacking | A framework for clarifying the meaning of Triple Bottom-Line, Integrated, and Sustainability Assessment[END_REF] based on the triple bottom line [START_REF] Elkington | Cannibals with Forks: The Triple Bottom Line of 21 st Century Business[END_REF]. There are also numerous tools like SWOT (Strengths-Weaknesses-Opportunities-Threats) [START_REF] Rowe | Strategic Management: a methodological approach[END_REF], Environmental Impact Analysis (EIA), Strategic Environmental Analysis (SEA) and Cost-Benefit Analysis (CBA) [START_REF] Hundloe | Cost-benefit analysis and environmental impact assessment[END_REF] which are well-established and widely used for analysis, but the non-financial (yet useful) information is not systematically used in decision-making because we do not know how to value qualitative benefits, opportunities and challenges [START_REF] Mcnie | Reconciling the supply of scientific information with user demands: an analysis of the problem and review of the literature[END_REF].

There is a gap in knowledge and a need in business practice to make the transition from the traditional decision-making thinking (Fig. 1) to a more holistic approach (Fig. 2) which (1) integrates the multiple dimensions of sustainability into business decision-making in a more balanced manner, (2) considers the benefits and implica-tions of today's actions on the long-term, and (3) expands the scope of decisionmaking to include the wider society and the natural environment.

Fig. 2. Decision-making system for sustainability

This paper identifies and scopes the research problem around decision-making for sustainability, presents a set of research questions and proposes a research agenda to address the identified deficiencies.

Research Questions and Deliverables

We propose a research project that will help to develop the competencies manufacturers need as they move towards sustainability, for purposes of decision-making as well as value non-financial benefits, building resilience and organisational learning. The research aim is to better integrate sustainability into decision-making. This project will deliver a tool to support top-management in doing so: decision-making tool for sustainability (DMT4S).

We will address the following four research questions (RQ):

RQ1. What are the specific challenges when bringing sustainability into manufacturing decision-making? RQ2. What dimensions should form part of sustainability decision-making in manufacturing? RQ3. How to integrate these dimensions into sustainability decision-making tool? RQ4. What happens when the DMT4S is used?

The principal deliverables of this research are:  A better understanding of sustainability decision-making in manufacturing.  A theoretical framework that will identify a set of key themes and dimensions for sustainability decision-making. This will make a contribution to the scholarly literature on industrial sustainability strategy and decision-making.

 A decision-making tool for sustainability, or DMT4S. The tool will support the inclusion of sustainability considerations for better decision-making.

 Evidence of performance from multiple applications.  A user guide to support companies in using the DMT4S. The tool will be professionally packaged to ensure user-friendliness.

 Workshops throughout the project as well as after its completion.

Methodology and Project Plan

The project will deliver a tool to support sustainability decision-making. The objectives are to better understand complex organisational problems in order to address the real-world problem of the integrating sustainability into decision-making, and to access superior opportunities and maximise performance, competitiveness and learning while accounting for the cost and risk involved.

Given the old dichotomy of theory and practice, a wider and deeper form of engagement between researchers and practitioners is needed in the co-production of knowledge [START_REF] Pettigrew | Management research after modernism[END_REF]. Therefore we will adopt a strategy of engaged scholarship [START_REF] Van De Ven | Knowledge for theory and practice[END_REF][START_REF] Van De Ven | Engaged Scholarship: A Guide for Organisational and Social Research[END_REF] as a means of knowledge production and collaborative inquiry between scholars and practitioners. Exploratory expert interviews will be conducted during the first year in phase 1. More intensive engagement will occur at key points such as phases 2 and 4 which will require extensive testing planning and analysis as well as exploitation planning. The core team will also meet bi-annually with the industrial collaborators for phases 2 and 3. This will be done in workshops to be chaired by the principal investigators to gain industry guidance. This participative form of research will obtain the perspectives of key stakeholders (researchers, users and practitioners) to understand a problem of decision-making [START_REF] Van De Ven | Engaged Scholarship: A Guide for Organisational and Social Research[END_REF] and make research relevant to practitioners by bridging the gap between theory and practice [START_REF] Barge | Engaged Scholarship and the Creation of Useful Organisational Knowledge[END_REF]. Linkages to other relevant teams will be strongly maintained. We will share our findings at an early stage and update them regularly as empirical research proceeds to ensure that any assistance needed by other teams is provided.

The following sub-sections outline the work plan for the three research phases, deliverables and tasks allocation.

Explore and plan

This first phase aims at understanding current decision making for sustainability to address RQ1 and RQ2. We will review the literature and existing tools for decision-making in industrial sustainability at three levels to identify the strengths and weaknesses of decision-making at these different levels: best practice (eco-efficiency), technology solution (eco-factory), and business model. A vast body of management literature exists that provides a number of decision support tools but very little in support of sustainable industrial systems. There is a clear gap in knowledge about decision-making for sustainability. We will draw on the well-established stream literature on decision-making in organisations [START_REF] Weber | The Theory of Social and Economic Organization[END_REF][START_REF] Miller | Decision-Making in Organizations[END_REF] to strengthen the theoretical foundation of our work. We will identify concepts and constructs from this established literature and apply them to an emerging body of knowledge on decisionmaking for sustainability. In addition, we will conduct expert interviews with thought leaders in the area of industrial sustainability. Working closely with industry will allow us to strengthen and validate the theoretical framework and address an industry problem [START_REF] Van De Ven | Engaged Scholarship: A Guide for Organisational and Social Research[END_REF].

Tasks:

 Background review: Primarily review industrial sustainability and organisational decision-making literature. Review other relevant fields of research such as organisational learning, risk management, supply chain resilience, and corporate social responsibility.  Existing tool review: Review existing tool in use by companies as well as tool recently developed for supporting sustainable business practices.  Translate initial findings into specific questions and guidelines for structured interviews with industrial collaborators to learn from best practice.  Theory building: Establish a theoretical framework for the decision-making tool.

Develop and learn

In this second phase, we will develop a prototype tool for sustainability decisionmaking, identify and overcome weaknesses of the proposed tool through targeted testing (fast prototyping) to address RQ2 and RQ3. Through the use of fast prototypes, we will test the framework and tool from early stages of development to continuously test and refine the tool. Each fast prototype will focus on specific elements of the tool to insure their validity. We will use lessons learnt from these prototype applications to develop and refine the final DMT4S.

Tasks:

 Define tool specifications based on the theoretical framework and interview results from phase 1.  Develop the initial tool and use targeted testing (fast prototypes).  Continuously test and refine the framework and tool using data captured during phases 2 and 3.

 Use lessons learned from the fast prototype applications to inform the DMT4S development.

Use and prove

In this third phase, we will test the prototype tool and final DMT4S to deliver results and evidence of performance to address RQ3 and RQ4. We will first test the fast prototypes to validate various elements of the prototype tool before approaching industrial collaborators through our established network. Central to engaged scholarship is building relationships between academics and practitioners through the creation of joint forums, researcher/practitioner gatherings and focus groups that consider issues of concern to both academics and practitioners [START_REF] Bartunek | Academic-practitioner collaboration need not require joint or relevant research: toward a relational scholarship of integration[END_REF]. We will use workshops to test the usability of the tool and create a user guide. Finally we will package the tool (e.g. website, software development, user guide printing, etc.) to facilitate the dissemination of our findings through the use of the tool.

Tasks:

 Use fast prototype applications to review the validity of the framework.  Use fast prototype applications to test the performance of the tool.  Analyse tool use and synthesise users' feedback to refine the tool.  Finalise the DMT4S and user guide based on lesson learnt from use.  Assess the overall performance and quality of the tool.  Package and distribute the DMT4S.

Project Outcomes and Implications

Globalisation of manufacturing has resulted in an increasing number of emerging economies competing for a limited pool of resources. In order to remain competitive, manufacturers will need to improve their resource efficiency and improve the resilience of their supply chain against disruptions. Although there is ample knowledge about these issues, manufacturers are still struggling to concretely address them and integrate them into their decision-making. Industry and the environment have long been opposed: industrial improvements for the environment are considered as a cost, although it is not necessarily the case [START_REF] Porter | Creating Shared Value: How to reinvent capitalism-and unleash a wave of innovation and growth[END_REF]. Manufacturers are often reluctant to take action because they fear it will be at too high a cost in the short-term and result in uncertain generalised benefits in the distant future. To develop more sustainable industrial systems, industrialists and policy makers need to better understand and take decisions on how to respond to environmental, social and economic challenges and transform industrial behaviour accordingly leveraging appropriate investment and implementation of new tools and approaches. Important issues and opportunities around sustainable manufacturing can be addressed by improving decision-making.

We propose a research project that will explore a concrete issue in the manufacturing industry: decision-making for the sustainability transition towards resource efficiency, circular economy, resilience, and organisational learning. The work will provide a better understanding of the multi-dimensionality of corporate decision-making for sustainability and advance the academic fields of industrial sustainability and organisational decision-making. It will also contribute to knowledge in the areas of corporate social responsibility, strategic planning, resilience, uncertainty and risk management. The tool developed will support the sustainability transformation of manufacturing companies in a novel manner and provide a contribution to academic literature, disseminated via journal papers and conference presentations.

This project fits with the need to strengthen the manufacturing sector in a forwardlooking and sustainable manner. A greater focus on long-term impact of decisionmaking will help firms increase resilience and reduce costs. For sustainability improvements to take place, constant efforts are needed in resource efficiency and innovation. Organisations making these efforts will be rewarded with strong performance improvements. This project will involve best practice leaders with high visibility aiming to encourage the rest of the manufacturing industry to follow their lead.


R S Wadhwa

Synergizing lean and green for continuous improvement

Keywords: Six Sigma, Systems Engineering, SME

For many years small-medium enterprises (SMEs) have attempted to improve their manufacturing and environmental operation performance in a view to achieving competitiveness and operational excellence. This paper looks at the literature in order to investigate the relationship between lean and green management and their relationship to one another while keeping in mind their simultaneous implementation at a foundry SME. Separate literature streams have arisen to address issues in green and lean using systems engineering tools but research has largely neglected the intersection of the two. The presented research synthesizes the literature addressing the intersections of green and lean and suggests a research agenda to address gaps. Suggestions for implementing environmental management systems for sustaining continuous improvement activities have also been provided.

Introduction

Today's SMEs (Small-to-Medium sized Enterprises) need to address the increasing global competition, decreasing product life cycles and increasing customer demands. SMEs require more financial and technical assistance when compared to OEMs (Original Equipment Manufacturers) when moving from reactive measures for the end use of products to a more proactive consideration within environmentally benign continuous improvement in plant operation. [START_REF] Bey | Drivers and barriers for implementation of environmental strategies in manufacturing companies[END_REF] Improving environmental performance while keeping regulatory costs down is one of the key challenges affecting the future competitiveness of casting foundry SMEs.

Metalcasting produces a number of liquid, gas and solid waste streams, many of which could have an adverse affect on the environment. On the other hand, it also produces some positive impacts on the environment by preventing landfills of large amounts of scrap metal. In the US the foundry industry spends over $1.25 billion/year to comply with federal, state and local government regulations, although this number does not include some smaller foundries, certain categories of environmental compliance costs from captive foundries reported under different industry classifications. [START_REF]Energy and Environmental profile of the US metalcasting industry[END_REF] About 40% of compliance costs are used for control, treatment, and disposal of air pollutants and related sludge. Solid and hazardous waste disposal-sand bags and slagaccount for about 33% of the compliance costs. (Figure 1) Environmental compliance costs are currently estimated to be 2% of the cost of a casting, which is expected to increase to 5% in the near future. Sand casters face major environmental issues related to treatment and disposal of spent sands that may be contaminated with toxic wates.

Fig. 1. Environmental cost by media

Manufacturing is a dominant sector in the European economy as well. The economic importance of this sector is evident: it provides jobs for approximately 34 million people; and produces an added value in excess of €1 500 billion from 230 000 enterprises with 20 or more employees [START_REF] Flegel | MANUFUTURE Strategic Research Agenda. Report of the High-Level Group[END_REF]. However, it is widely perceived to be facing serious challenges. This is particularly true of the manufacturers located in the highcost regions.

Lean production is often described as both a philosophy and a set of working practices with the goal of achieving high levels of customer satisfaction through increased quality, reduced costs and world-class delivery performance. While there are sepa-rate streams of established research on green and lean issues, few authors have addressed the intersection of these in industrial SME scenarios. This is a critical oversight because firms may be missing synergies available through improved concurrent implementation; they may also be failing to address important trade-offs that may arise when there are incompatibilities between strategic initiatives. For example, lean and green strategies are often seen as compatible initiatives because of their joint focus on waste reduction. The ISO-9000 quality standard has been shown to be highly correlated with the adoption of ISO-14000 environmental standard. There is evidence of this relationship across both lean interfaces, but quality improvement has not been explored at the conjunction of all two strategies. The relationship yet to be explored at the interface of the two strategies. Green initiatives focus on reducing pollution, while this is not a priority driving lean. Managers in companies find it difficult to simultaneously implement these three strategies. For example, buyer-supplier alignment is addressed differently across the three interfaces. Buyers often focus on low costs, whereas suppliers may incur greater costs while attempting to provide more environmentally re-sponsible or higher quality products. Lack of development may be due to the exploratory nature of research regarding the relationships between green and lean.

Environmental management may also represent an untapped avenue for further reduction of manufacturing costs through more efficient use of natural resources [START_REF] Hart | A natural-resource based view of the firm[END_REF] [START_REF] Florida | Lean and green: the move to environmentally conscious manufacturing[END_REF]. The issue, however, of how to address the environmental management practices of vendors may prove to be a costly endeavour if not managed taking into consideration a number of important economic factors. To date there has been only limited anecdotal discussion of the legitimate incentives for SMEs to extend environmental management beyond their immediate boundaries.

The paper is organized as follows. Section II presents the research methodology followed by the industrial use case in section III. Section IV describes the suggested plan for continuous improvement and environmental performance management at SMEs and finally, the summary is presented in section V.

Research Methodology

Common drivers and barriers lead to both complementary and conflicting arguments across green and lean strategies. Synthesizing the literature in the areas of green and lean allows the researchers to draw inferences about a combined green and lean strategy. Four major factors motivate firms to adopt some combination of these strategies: cost reductions, customer demands, international standards such as ISO-9000 and ISO-14000, and risk management. Toyota is a good example of a firm that has successfully integrated a green and lean strategy in a global setting. The company's commitment is evident through its ISO certifications and financial investment into quality and environmental research and development. [6][7]

Lean and Green manufacturing

Lean manufacturing is based on the principles and working processes of the Toyota Production System, and has been defined as doing more with less [8]. Lean manufacturing's most distinguishing principle is the relentless pursuit of waste [START_REF] Åhlström | Sequences in the Implementation of Lean Production[END_REF]. It has been most prominent in discrete, repetitive assembly--type oper-ations. Liker [START_REF] Liker | The Toyota Way: 14 Management Principles From the World's Greatest Manufacturer[END_REF] suggests that the goals of lean manufacturing are highest quali-ty, lowest cost, and shortest lead time. It can be described as a multi--dimensional approach that encompasses a wide variety of management practices, including Just--in--Time (JIT), quality systems, work teams, cellular manufacturing supplier management, etc. in an integrated system [START_REF] Shah | Ward Lean manufacturing: context, practice bundles, and performance[END_REF]. Distribution and transportation operations networks are important operational characteristics that will affect green manufacturing value stream. [START_REF] Srivastava | Green supply-chain management: A state-of the-art literature review[END_REF] With the rapid increase of long--distance trade, supply chains are increasingly covering larger distances, consuming signif-icantly more fossil--fuel energy for transportation and emitting much more car-bon dioxide than a few decades ago. [START_REF] Venkat | Is Lean Necessarily Green[END_REF] Lean manufacturing value streams typ-ically have lower emissions due to reduced inventory being held internally at each company, but the frequent replenishment generally tends to increase emis-sions. As distances increase, it is quite possible for lean and green to be in con-flict. Lean may be green in some cases, but not in others. The reverse logistics focuses primarily on the return of recyclable or reusable products and materials into the forward supply chain. [START_REF] Shah | Lean manufacturing: context, practice bundles and performance[END_REF] To reintroduced recy-cled materials, components and products into the downstream production and distribution systems, it is necessary to integrate reverse material and infor-mation flows in the supply chain. Due to the reverse material flow, traditional production planning and inventory management methods have limited applica-bility in remanufacturing systems. Therefore, it is necessary to consider the existence of the returned items that are not yet remanufactured, remanufactured items and manufactured items.

Lean for Better Environmental Management

Some researchers have established links between the occurrence of practices that support manufacturing sustainability and firms adopting lean manufacturing strategies. This work attributes the mutual benefits between lean production and environmental management practice to the reduced waste and continuous improvement philosophies of lean.

The objective of lean is to generate a system that is efficient and well organised and devoted to continuous improvement and the elimination of all forms of waste. The potential for a benefit to manufacturing SMEs environmental management practice is high. The practices that support lean manufacturing are similar to the practices that support environmental performance. Lean production is broadly described as an integrated approach to the management of a manufacturing organisation, that encompasses a wide variety of practices, including JIT, quality systems, work teams, cellular manufacturing and supplier management. The lean production philosophy focuses on avoiding seven forms of waste and on respecting customers, employees and suppliers [7][8] [32]. A sizeable body of empirical work supports the capacity of the lean system to remove continuously multiple forms of waste, smooth production flow, improve understanding of human resource management issues, maintain quality and increase customer service, while also yielding a significant competitive advantage.

Industrial Use Case

DMAIC Methodology

There are two major methodology approaches that have been reported in the literature for implementing lean, the DMAIC (Define-Measure-Analysis-Improve-Control) and the DMADV (Define-Measure-Analysis-Develop-Verify) [37] [START_REF] Wadhwa | Implementing Manufacturing Process Automation in Metalcasting Facilities[END_REF]. The DMAIC approach is recommended for analyzing and improving the existing product or process, while the DMADV approach is appropriate for designing new product or process.

An exploratory six sigma case study conducted at the parent company based on the five phases of the methodology: Define, Measure, Analyze, Improve and Control (DMAIC) is described shortly. The DMAIC approach is described which was used to dig deeper into the non-conforming components received by the parent company from two tier-one suppliers. This exploratory case study were conducted within the energy industry in order to examine the nature of the complex interactions between the two major constructs lean and environmental sustainability at the parent company and its first tier vendor. Interviews were conducted with key purchasing, production and environment staff within the parent company and case study conducted with one firsttier parts vendor. Interviews with at parent company (government owned, around 15000 employees worldwide) were selected from a sample that represented major groups of responsibility and decision making.

At the first tier vendor (privately owned, around 220 employees, supplies foundry and special sub-assembly components, supplies about 80 per cent of their business to the parent company) two-to three-hour semi-structured interviews were conducted with the operations manager, production supervisor and quality/environment manager. A site tour was conducted to look specifically at shop floor layout, warehouse and receiving inspection areas. The relevant stakeholders completed a self-assessment questionnaire at the completion of the site visit.

DMAIC Process A. Problem Definition

Defining the problem is the most important step in Six-Sigma project since better understanding of the problem at this stage will help at the later stages of the project. In order to define the objectives of the project, manufacturing company's claims were investigated. The management needed to resolve the problem of long process lead time. The relevant KPIs were be identified, linked and then measured.

The critical-to-quality (CTQ) indicator was defined as below: CTQ= Identified Defects / Shipment Flex Hoses per year The company claimed that reducing the hose non-conformance issues by 50% would help the company save USD17,629.

B .Measuring the scope of problem

During the measure phase, the various non-conformance issues with the incoming components from the vendor were identified and measured in scope using company proprietary software. The top root causes were identified against the parent company's requirements and standards. The detailed product hierarchy and its relation to the final product assembly is confidential.

The attribute agreement analysis was conducted using data from the company's SAP system which also had the appraisers within the company which were needed to make the assessment. The questionnaire was provided to the appraisers from the company in free-text format.

The operational definitions of defect and opportunity defined by the company are shown in a flowchart in Figure 2. The measurement system for defect and opportunity was capable as the Kappa values in the test exceed the allowable value of 0.7.

Fig. 2. Operational definitions

C. Analyze the causes

After the first two phases of DMAIC approach, it was decided to focus on the improvement plan to reduce the non-conformances. It was important to further study the potential causes/key input variables (KPIVs) of the non-conformances using 4M (man, machine, material, method) categorization method. Additional cause and effect matrix analysis was conducted in which key output variable (KPOVs), nonconforming product/incoming shipment was selected as the performance measure. A hypothesis test was conducted to compare the capability of the two vendors for the commodity resulted in a P-Value = 0.768 which demonstrated no significant difference in the capability between vendors. One of the vendor related issues uncovered were, for example, missing incorporating the purchase order requirements from the parent as a part of the vendor's internal assembly .

D. Improve the exiting processes

The improve phase consisted of several activities organized to address the nonconformance causing factors. Onsite vendor meetings were organized to discuss engineering drawing requirements, company and industry-wide standards and the importance of compliance to the requested specifications. With the agreement of internal company stakeholders processes were updated to incorporate the suggested improvements.

E.Control

The control phase is the last stage for the DMAIC approach. A control plan was design and introduced to the production line. The plan provides a summary of the control application which aims to minimize the process variation and ensures producing top quality products. In addition, the control plans guarantees that the proposed solution is properly implemented and monitored. It was reported that as a result of the recommendations, the customer claim rate was reduced by 55%.

Results : Parent Company

At the parent company the following early results were obtained:

• Greater than 80 per cent of respondents believed that the greatest influence of the parent company over the vendor's environmental management practices occurred during sourcing and to a lesser extent (but still possible) during production trials. Greater than 70 per cent of respondents did not believe that it was possible for the parent company to influence or develop a vendor's environmental management practices during ongoing production.

• The majority agreed that the following situations would encourage them to discuss with, monitor and assess a vendor's environmental performance: if it presented a risk to the parent company's production system; and if it was a well documented, resourced and standardized aspect of their purchasing.

Tier-one Vendor Company

The vendor had undergone a lean transformation with the direct assistance of the parent company. The vendor had not obtained ISO 14000 certification. The following early observations were gathered at the vendor:

• The commitment to ongoing process improvement an meeting the requirements of the customer at this plant was high. The customer's requirements for environmental performance were a more important driver for change than the regulatory environment. • The culture for improvement at the vendor was strong, with worker involvement high and worker attitude towards change, highly positive. Resources committed to the environment were very low however, and the SME appeared to be just keeping up with its lean transformation and its significant growth during the year.

When developing the kaizen implementation plan associated with the future state value stream map, it was noticed that continuous improvement events on certain processes may require special attention to EHS issues.

Summary

The current literature is abundant with discussion on the individual strategies, but has thus far not addressed how firms can implement these strategies concur-rently. A thorough examination of the individual bodies of literature was used as a means to guide future research at the intersection of green and lean strategies. The future research agenda addresses gaps in the current literature, and suggest relevant framework from which to explore this phenomenon. The agenda pre-sented in this paper allows for future research that begins to meet the call for potential work.

In terms of limitations, this research paper makes use of only one case study.

Though the case study demonstrate useful insight into working through quality processes and integrating environmental concerns into already in place quality management system; this is simply the start. Research investigating this integra-tion with other manufacturing models outside of the energy business is planned in the near future.


Handson C Dias Pimenta
email: handson.pimenta@ifrn.edu.br

Peter D Ball
email: p.d.ball@cranfield.ac.uk

Environmental and social sustainability practices across supply chain management -a systematic review

Keywords: Environmental sustainability practices, social responsibility, supply chain management

This paper explores the sustainable manufacturing knowledge in the field of supply chain management in order to understand the best practices to diffuse sustainability across supply chain network. A systematic literature review was conducted, covering six databases by combinations of key-words between the periods of 1992 to November of 2013. A total of 92 peer-reviewed papers in English are reviewed. A lack of integration of the core SCM activities (purchasing, performance and collaboration) was found in the diffusion of environmental and social sustainability practices across supply chain. Thus, more studies are needed to cover the adoption of environmental and social practices into supply chain management activities and the process to diffuse them across the supply network. In addition, environmental issues have received more attention than social ones in both upstream and downstream supply chain management activities. Using the outputs of the literature review, a conceptual framework is proposed covered: 1) the interrelationship between the core upstream SCM activities (purchasing, suppliers´performance assessment and collaboration with suppliers) and 2) the effect of internal cross function in upstream SCM activities.

Introduction

Sustainable supply chain management (SSCM) is a broad subject itself; hence it covers three dimensions of sustainable development, i.e. economic, environmental and social. In addition, the diversity of activities involved in the cross-organisational functions as well as inter-organisational processes in supply chain management become the subject more complex regarding to promote sustainability. Despite the growth in the body of SSCM knowledge, it is still difficult to understand the effect of sustainability practices involved in supply chain activities to engage suppliers and to promote improvements.

Seuring and Müller [START_REF] Seuring | From a literature review to a conceptual framework for sustainable supply chain management[END_REF] is one the first papers that covered a full view of sustainability (triple bottom line -environmental, social and economic dimension) across supply chain management (SCM). They focused on triggers and barriers for SSCM and presented a framework including strategies for suppliers' management of risks and performance and for sustainable products. However, there was less attention on specific supply chain management activities and on sustainability practices.

A comprehensive view of the purchasing process is presented by Igarashi et al. [START_REF] Igarashi | What is required for greener supplier selection? A literature review and conceptual model development[END_REF]. This covered a specific activity of the SCM and takes some environmental sustainability practices and focused on one dimension of sustainability (green). Govindan et al. [START_REF] Govindan | Multi criteria decision making approaches for green supplier evaluation and selection: a literature review[END_REF] also described some environmental practices, such as Environmental Management System (EMS) and Design for environment (DFE), from papers that involved multi-criteria decision making for supplier evaluation and selection. Zhu et al. [START_REF] Zhu | Green supply chain management: pressures, practices and performance within the Chinese automobile industry[END_REF] conducted a survey in 89 Chinese automotive supply chain companies and assessed one particular company responsible for engines by interviews with key-managers. Even though this study covered plenty of SCM activities (purchasing, cooperation with customers and cross-functional cooperation), environmental practices (e.g. ISO 14001, DFE, audits) were the main focus in this study.

Therefore, there has been no review of SCM activities involved in the adoption and diffusion of environmental and social sustainability practice across supply chain. This paper addresses the gap by examining environmental and social practices adopted in supply chain activities. In this context, sustainable manufacturing knowledge in the field of SCM will be explored in order to understand the practices to diffuse sustainability across supply chain network.

Using the outputs of the literature review, a conceptual framework is proposed. The novelty of this conceptual framework is the inclusion of the interrelationship between the core upstream SCM activities of purchasing, suppliers´performance assessment and collaboration with suppliers. The effect of internal cross function in upstream SCM activities for diffusion of environmental and social sustainability across supply chain network is also taken into account in the conceptual framework.

Method

A Systematic Literature Review (SLR) was conducted based on Tranfield et al. [START_REF] Tranfield | Towards a Methodology for Developing Evidence-Informed Management Knowledge by Means of Systematic Review[END_REF] and Denyer and Tranfield [START_REF] Denyer | Using qualitative research synthesis to build an actionable knowledge base[END_REF]. SLR enables the researcher both to map and to assess the existing intellectual territory and to specify a research question to develop the existing body of knowledge further [START_REF] Tranfield | Towards a Methodology for Developing Evidence-Informed Management Knowledge by Means of Systematic Review[END_REF]. This systematic review follows a protocol made up of four steps: planning, searching, screening, and content analysis, as described below.

The following research question guided this SLR: how might a focal company diffuse environmental and social sustainability practices across the supply chain and in which context?

In order to encompass a representative number of materials more related to the research question, two groups of key-words in line with social and environmental sustainability issues "sustainab*", "environment*", green, "closed loop", "industrial ecology", "social responsibility", reverse, governance) and SCM ("supply chain", "value chain", network, relationship, "collaborat*", "co*operation", performance, purchasing, procurement) was used to construct search strings with the Boolean connectors "and". The strings were then used to search materials between the periods 1992 to 2013 in electronic databases. Six databases were selected, namely Scopus, Web of Science (Isi), EBSCO (Business Source Complete, Environment complete and GreenFILE) and ABI. The main criterion to choose a database was that it needed to be related to the field of manufacturing, sustainability and supply chain management and index well-rated journals.

Between October and November 10th 2013, papers were searched using the "all fields". This search was based on all possible combinations between those two groups of keywords in order to take into account papers more representative with the research question. 20,059 papers were found. Taking into account the high volume of materials it was considered reasonable to narrow the search due to quality of contribution just to include only peer-reviewed scientific papers in English, resulting in 10,814 papers. Removing duplicates reduced the papers found to 4,131.

The title and abstract were read using explicit inclusion and exclusion criteria in order to select relevant papers. Specifically, the paper needed to provide any insight to the relationship between the focal company and member(s) of the supply chain of the manufacturing base in terms of the diffusion of environmental and social sustainability practices. Papers were excluded when they did not cover this relationship within SCM domain. Other exclusion criteria were: ethical and humanity issues, opinion of stakeholders on sustainability and outsourcing, public purchasing and services supply chain (bank, hotel, supermarket, hospital, education, supply of water, e-market) and supply chain security.

A total of 80 papers were resulted from the screening process. Finally, cited references were used as a secondary source (Citation tracking). A further 12 papers were included. Therefore, these three approaches resulted in a total of 94 studies, which were then coded and analysed. Thus, the final sample was 92 papers.

In order to identify the relevant issues related to sustainability across supply chain network, the content of papers selected was analysed, taking into the following aspects, namely: the dimension of sustainability covered (e.g. TBL, Green or Social), the scope of SCM (e.g. upstream -focus on suppliers, downstream -focus on clients, life cycle view) and SCM activities involved.

3

Results and discussion

Environmental and social sustainability practices across supply chain management

The body of the literature covered in this systematic review is still a young field; hence the majority was released in the last 10 years. According to Seuring and Muller [START_REF] Seuring | From a literature review to a conceptual framework for sustainable supply chain management[END_REF] and Srivastava [START_REF] Srivastava | Green supply-chain management: A state-of-the-art literature review[END_REF], the most research related to SSCM has been published after 1990. In this context, the start year was chosen based on these facts. By 2000, a total of seven papers were published. The first paper identified was done by Roy and Whelan [START_REF] Roy | Successful recycling through value-chain collaboration[END_REF]. From 2001 to 2010, 47 papers were released. Finally, more than 40% of the papers identified (38 papers) were published between 2011 and 2013, showing a significant interest in environmental and social sustainability practices across supply chain. Indeed, this subject received great attention mainly in the first 9 months of 2013, when 20 papers were published.

Although it is expected that the three dimensions of sustainability (e.g. economic, environmental and social) integrally work together, it is more common to find research covering just one or two aspects, i.e. just environmental or environmental and economic issues or just social (e.g. [START_REF] Seuring | From a literature review to a conceptual framework for sustainable supply chain management[END_REF][START_REF] Ahi | A comparative literature analysis of definitions for green and sustainable supply chain management[END_REF]). This is confirmed in this systematic literature review, with 53 papers (57%) focusing just on environmental dimension of sustainability. Triple bottom line (TBL) and society are covered in 15 and 11 papers, respectively. In addition, there was some overlap between environmental and society (nine papers), environment and economy (three papers) and society and economy (one paper). Papers on pure economic issues across supply chain are not included in this literature review.

To date various authors have investigated different ways to diffuse sustainability across supply chain. These approaches include both direct and indirect activities of SCM. The selection of supplies that achieve minimal requirements and the collaboration with existing or new suppliers in order to reach higher levels of sustainability are identified by several authors as a direct action of SCM activities responsible for diffusing sustainability (e.g. [START_REF] Vachon | Environmental management and manufacturing performance: The role of collaboration in the supply chain[END_REF][START_REF] Hollos | Does sustainable supplier co-operation affect performance? Examining implications for the triple bottom line[END_REF]). Another study suggests indirect actions [START_REF] Kogg | Environmental and social responsibility in supply chains: The practise of choice and interorganisational management[END_REF]. In this approach a focal company can implement measures that are not directly related to its own sourcing or management, such as supporting of NGO´s, philanthropy, or compensation schemes.

Direct actions are wide and cover a plenty of issues. Not only cross-functional aspects (internal function integration) are involved in diffusing environmental and social sustainability across supply chain but also cross-organizational (external integration -direct actions with suppliers and other partners located in downstream). Both integrations are essential for environmental and social collaboration addressed for competitive advantage [START_REF] Gold | Sustainable Supply Chain Management and Inter-Organizational Resources[END_REF]. In this regard, this systematic literature review found 64 papers that focused on upstream, seven papers focused on downstream and 12 papers both upstream and downstream. In addition, six papers took into account the perspective of lifecycle view though life cycle assessment (LCA) or carbon footprint studies (Figure 1). Considering the papers that covered upstream SCM activities, the majority were related to purchasing (44%) (e.g. [START_REF] Baden | The effect of buyer pressure on suppliers in SMEs to demonstrate CSR practices: An added incentive or counter productive?[END_REF]), followed by supplier's performance assessment (14%) (e.g. [START_REF] Shaw | Developing environmental supply chain performance measures[END_REF]) and collaboration (14%) (e.g. [START_REF] Brockhaus | Where Do We Go From Here? Progressing Sustainability Implementation Efforts Across Supply Chains[END_REF]).

To diffuse sustainability across the supply chain it is necessary to adopt the appropriate performance measurement system to identify what actions are needed [START_REF] Gimenez | Extending sustainability to suppliers: a systematic literature review, Supply Chain Manag[END_REF]. In this context, suppliers´performance management allows focal companies to evaluate a supplier's performance, compare it with the performance of other suppliers, and provide suppliers with direction for improvements [START_REF] Simpson | Use the supply relationship to develop lean and green suppliers, Supply Chain Manag[END_REF]. Finally, there is a huge variance of environmental and social KPI's to assess supplier´s performance. Some environmental and social sustainability practices are adopted in collaboration with suppliers were observed. The focus given was to implement some improvements into process, product and general activities. Pollution prevention and EMS -ISO 14001 were the most common practice reported with focus on process. In terms of collaboration with focus on product, LCA and DFE were substantially reported. Finally, training with purchasing staff of focal company and suppliers staff was a common practice in general activities. Interestingly, social sustainability practices were only briefly mentioned, specifically SA 8000 and code of conducts.

The combination of these activities was also observed, highlighting -purchasing and collaboration (17%) (e.g. [START_REF] Gimenez | Extending sustainability to suppliers: a systematic literature review, Supply Chain Manag[END_REF]). An example of purchasing and collaboration developed by Sony Corporation was reported by Handfield et al. [START_REF] Handfield | Integrating environmental management and supply chain strategies[END_REF]. This company implemented its green procurement policy to ensure the adoption of minimal requirements by suppliers. However, at same time, designers from key suppliers worked together with Sony engineers to find improvements in products and processes in terms of environmental impact control and disposal solutions. Finally, with respect to sustainability dimension in upstream, the majority of papers covered environmental issues with 52%, followed by TBL and social, 14% and 12%, respectively (Figure 1). The focus of papers that covered downstream activities were related to transportation (two papers) (e.g. [START_REF] Holt | An empirical study of green supply chain management practices amongst UK manufacturers[END_REF]), warehousing (1 paper) (e.g. [START_REF] Chen | Incorporating green purchasing into the frame of ISO 14000[END_REF]) and the management of product end-of-life (4 papers) (e.g. [START_REF] Roy | Successful recycling through value-chain collaboration[END_REF]). Specifically, concerning product end-of-life management, only environmental issues are covered. More attention was given to reverse logistics, product recovery, recycling and remanufacturing. In transportation and warehousing, environmental practices identified aimed to control environmental impacts mainly in terms of energy efficiency (e.g. [START_REF] Holt | Managing the interface between suppliers and organizations for environmental responsibility -an exploration of current practices in the[END_REF]) and GHG emission control [START_REF] Hassini | A literature review and a case study of sustainable supply chains with a focus on metrics[END_REF]. Specifically, in transportation, two particular practice were covered; the design of vehicles to reduce fuel consumption and routing (e.g. [START_REF] Holt | An empirical study of green supply chain management practices amongst UK manufacturers[END_REF]). Finally, with regard to product end-of-life, two main activities are involved: reverse logistics (reuse, dismantled and recycling) (e.g. [START_REF] Chan | A pro-active and collaborative approach to reverse logistics-a case study[END_REF]) and close loop supply chain (remanufacturing) (e.g. [START_REF] Souza | Closed-Loop Supply Chains: A Critical Review, and Future Research*[END_REF]). Social practices with focus on safety issues were identified just in transportation and warehouse activities.

A total of 12 papers encompass upstream and downstream supply chain management. In the papers a diversity of SCM activities, such as performance assessment and purchasing were covered. Two papers highlighted the combination of performance and collaboration. For example, Lee and Cheong [START_REF] Lee | Measuring a carbon footprint and environmental practice: the case of Hyundai Motors Co. (HMC)[END_REF], through a collaboration with 15 key-suppliers, collected in situ details of energy consumption, CO 2 flow and fuel consumption in order to measure the performance and the carbon footprint (raw material, manufacturing and distribution) of a Korean automotive OEM. Finally, the environment was the main sustainability dimension covered by up-and downstreampapers (eight papers), followed by TBL (two papers) and two papers that combined two dimensions of sustainability, one environmental and social and other environmental and economy.

Towards a conceptual framework

As it could be seen in the previous section, in terms of upstream supply chain activities, purchasing (including minimal requirements, final selection and monitoring), supplier´s performance assessment and collaboration have received more attention to diffuse environmental and social sustainability across supply chain. However, these three core activities have been covered separately by the current literature, given more attention on purchasing and performance assessment. In addition, few papers have considered the adoption of environmental and social practices together in specific supply chain management activities. Therefore, few studies simultaneously embrace and integrate these three core SCM activities in order to diffuse environmental and social sustainability practices across supply chain.

In addition, internal departments (e.g operation management, design, R&D, environmental management, quality, etc.) have played an important role to support the definition of specification and select requirements for supplier´s selection as well as metrics for suppliers' performance assessment and alternatives for improvements. In this sense, the rigor of environmental criteria select for suppliers' selection is associated to the maturity level of focal company's environmental management function. However, empirical studies for better understand the relationship between the inclusion of environmental and social practices across supply chain activities and the role of internal functions are poor.

The understanding of the interrelationship between these core upstream SCM activities and the effect of internal cross function might be useful for a better assessment and monitoring of suppliers and identify priority and make sound decisions in terms of spreading environmental and social sustainability.

Therefore, a framework for diffusion of environmental and social sustainability across supply chain network will be presented taking into account these issues. Firstly, upstream supply chain activities, particularly the integration of purchasing, suppli-ers´performance assessment and collaboration with suppliers, will be the focus of the framework. Secondly, the framework will consider the interaction of the internal functions with the upstream SCM activities (Fig. 2).

Fig. 2. Conceptual framework for diffusion of environmental and social sustainability practices across supply chain

Concluding Remarks

This paper has examined works related to diffusion of environmental and social sustainability practices across the supply chain. It has been observed that the diversity of activities involved in the cross-organisational functions as well as inter-organisational processes in supply chain management become the subject more complex regarding to diffusion of environmental and social sustainability. Despite the growth in the body of SSCM knowledge, it is still difficult to understand the effect of sustainable manufacturing practices involved in supply chain activities to engage suppliers and to promote improvements in terms of sustainability. In addition, the body of the literature analysed on environmental and social sustainability practices across supply chain is still a young field. The adoption of environmental sustainability practice is more commonly reported both in upstream and downstream SCM activities than social practices. For example, Environmental sustainability practices have received more attention in collaboration activities than social practices, especially prevention pollution, EMS, LCA and DFE.

In order to understand how to strengthen the relationship with suppliers through spreading sustainability practices, future work might focus on empirical studies of upstream SCM particularly the integration of purchasing, suppliers´performance assessment and collaboration with suppliers. For example case studies can be conducted to validate the conceptual framework.

Fig. 1 .

 1 Fig. 1. Scope of sustainable supply chain concepts.

Acknowledgments

The research is conducted in collaboration with the EPSRC Centre for Innovative Manufacturing in Industrial Sustainability. This work is sponsored by the Brazilian government (CNPq) through the programme "Science without Borders".


Ramesh Roshan

Das Guru

Amin Kaboli
email: amin.kaboli@gmail.com

Rémy Glardon
email: remy.glardon@epfl.ch

The Effect of Coercive Power on Supply Chain Inventory Replenishment Decisions

Keywords: Coercive power, decentralized supply chain, inventory replenishment, power awareness, human decision-making

Supply chains often consist of stakeholders with different power levels collaborating with each other in order to meet customer demand. This imbalance of power along the supply chain is a critical factor that affects its short and long-term behavior, as well as its overall stability and efficiency. The role and the impacts of power in distribution channels have been explored quite extensively in Marketing, but far less so with regard to power in the context of supply chains. This paper explores the effect of power on supply chain functioning by focusing on a specific power type i.e. coercive power. More specifically, the impact of power and power awareness on inventory replenishment human decision-making is investigated. An experimental approach with unknown market demand and local information availability is implemented so as to provide a controlled environment for decision-making. Three different treatments are implemented in order to create situations of balanced power, imbalanced power without awareness and imbalanced power with awareness. Results show that power awareness does play a significant role in the way coercive power is exercised. In particular, a significant increase of the size and variability of order quantity and order time interval is observed in the case of imbalanced power with awareness.

Background

Power in supply chain is the ability of one firm (source) to influence the actions and intents of another firm (target) it deals with [START_REF] Maloni | Power influences in the supply chain[END_REF]. Power in supply chain can be either balanced or imbalanced. Balanced power exists when stakeholders in the chain possess broadly similar levels of power in influencing each other's decisions, while imbalanced power exists when one or more partners (sources) are capable of manipulating decisions of the other partners (targets) because of their power position [START_REF] Muthusamy | Does power sharing matter? The role of power and influence in alliance performance[END_REF]]. The exercising of power in a supply chain can have positive, as well as negative effects on its overall performance. Some of these effects can be visible immediately but most of them emerge out over a longer period of time [START_REF] Hanf | DARK" AND THE "BRIGHT" SIDES OF POWER IN SUPPLY CHAIN NETWORKS[END_REF].

Amongst the various power types defined by [START_REF] French | The Bases of Social Power[END_REF], coercive power is referred to as the ability of a source to punish a target in case of failures. Based on studies done by [START_REF] Yeung | The effects of trust and coercive power on supplier integration[END_REF], coercive power tends to improve supplier integrations, with or without the presence of trust, which is again a positive outcome for the overall supply chain. These authors argue that the exercise of power ends up assuring the congruence in goals and activities of different associated partners, particularly in the absence of a well-specified cooperation agreement.

Most of the time, partners in supply chains are not completely aware of the broad scope of their power dimensions and therefore end up not actively managing their own power bases [Cordon and Vollmann, 2005]. Understanding and awareness of power structure is a crucial factor in management of supply chains and selection of the appropriate reactive or proactive strategy, since it can be easily connected to the dominance and interdependence of partners in the chain [START_REF] Cox | Managing appropriately in power regimes: relationship and performance management in 12 supply chain cases[END_REF]. Thus awareness of power is central since exercising available power is very much dependent on its awareness.

Unlike other attributes of supply chain partnerships, power and its impact cannot be readily measured. Power, as stated earlier, is a mixture of complex social, economic and even psychological factors.

Despite the existence of numerous contributions investigating the role of factors such as trust, commitment and shared meaning, the literature suggests that there is a lack of empirical research examining the effect of power in supply chains. Most of the earlier research works on this topic were done using surveys, interviews and analysis of field data [START_REF] Cox | Power, value and supply chain management[END_REF][START_REF] Maloni | Power influences in the supply chain[END_REF]Benton, 2000: Yeung et al., 2009]. These empirical studies are generally case based, hence restricting the opportunity to develop general conclusions. This scarcity of empirical research examining the impacts of power exercised by partners in a supply chain is the central motivation for this work. Accordingly, the main goal of this study is to investigate the impact of coercive power on inventory replenishment decision. To this end, a controlled experiment is implemented, using a participatory simulation platform. It allows simulating supply chains with balanced and imbalanced power regimes among different players and analyzing the resulting impact on inventory replenishment decisions. The experiment and further analysis aim at answering the main question of this study: How does imbalanced coercive power and its awareness impact on the replenishment decision-making in supply chains?

The next section provides the methodology and experimental approach. Section 3 provides the results and statistical analysis of the experiment. Finally, a discussion and conclusion are given in Section 4.

Methodology

To understand the dynamics and complexity of inventory replenishment decisionmaking, supply chain simulation has been shown to be an appropriate research tool [START_REF] Croson | Experimental economics and supply-chain management[END_REF]. In particular, simulation helps creating a stable and controlled environment that allows reliable observations of the decision maker's behavior over time. In this study, a participatory simulation platform developed at Université Laval, Québec, Canada, called XBG-platform, is used for the experiments with human decision makers [START_REF] Montreuil | Experiences in Using XBeerGame Virtual Gaming for Learning Supply Chain Management[END_REF]]. The XBG-platform mimics the dynamics of inventory replenishment in a decentralized, linear, four echelon supply chain. Order size and order time can be freely chosen; thus any order placement implies a twofold decision about time and quantity. In Fig. 1, filled rectangles represent echelons with human participants, and empty rectangles represent echelons with computer agents. Human participants, thereafter subjects, played the role of the wholesaler and computer agents played factory, distributor, retailer and market roles. The main reason to use an experimental set-up with one single subject is to avoid interaction of human decision-making between echelons. None of the subjects were made aware of the fact that the computer simulated other echelons. The market demand is stable and follows a normal distribution with a mean of 3000 units/day and a standard deviation of 500 units/day, truncated at zero. This daily demand is randomly split into two orders per day. The demand information is unknown to the subjects.

This experiment is divided into three settings based on the power and awareness levels of the subjects. The imbalance of power between the echelons is achieved by varying the level of backorder costs between them. The awareness of power is incorporated with the introduction of contracts, which the player must sign before starting the game. The contract contains information about the business environment and commercial conditions, which makes the player aware of the power he/she holds over his/her supplier. The objective of the subject is to maximize his/her benefit, which is rewarded with a performance-based payment up to 60 CHF. Three different treatments are used to generate the required levels of power and power awareness.

─ Treatment 1: Balanced power. Backorder costs are identical for all echelons, therefore leading to power equilibrium between them. ─ Treatment 2: Imbalanced power without awareness. The backorder cost to be paid by the distributor to the wholesaler (subject) is doubled, but the contract signed by the subject does not mention this fact. All other relations within the supply chain are in power equilibrium. ─ Treatment 3: Imbalanced power with awareness. The backorder cost to be paid by the distributor to the wholesaler (subject) is doubled and the contract signed by the subject explicitly mentions this fact. All other relations within the supply chain are in power equilibrium.

The supply chain parameters considered in the experiments are defined in Table 1. Twenty-four undergraduate and graduate students representing 15 nationalities from EPFL's engineering and business majors participated in the experiment. The subjects consisted of 21% women and 79% men, with 29% of students in their Bachelor and 71% in their Master. To analyze the evolution of decision-making in the span of four months of game duration, the obtained data are divided bimonthly in 8 rounds. Consequently the database consists of a total of 24 subjects x 8 rounds = 192 results; i.e. 64 observations per treatment.

Results and Statistical Analysis

The obtained experimental results are analyzed over the whole game, separately for each treatment T1 (balanced power), T2 (power without awareness) and T3 power with awareness). The values reported for each treatment group (T1 to T3) represent the average of all the subjects in that particular setting throughout the duration of four months of game (64 observations). The statistical significance of all observations is checked using the Mann Whitney test (criterion p<0.05). These aggregated experi-mental results are presented in the next four sub-sections as follows: 3.1 Replenishment decision indicators, 3.2 Inventory indicators and 3.3 Cost components.

Replenishment decision indicators

As described earlier, the replenishment decision in this study involves two indictors, namely ordered quantity (OQ) and order time interval (OT). The results presented in Fig. 2 indicate no significant differences between treatments T1 and T2 but a very significant increase in the magnitude and variability of both OQ and OT in case of treatment T3, i.e. in case of power awareness. The above observations are statistically confirmed by the Mann Whitney test scores, as indicated in Fig. 2.

Inventory Indicators

Two indicators are considered, the on-hand inventory (OI) and the supply line (SL). Fig. 3 shows no significant differences between treatments T1 and T2 but a significant increase in the magnitude and variability of OI in case of treatment T3, i.e. in case of power awareness. With regard to SL, an increase in its variability, but not in its magnitude is noticed for treatment T3.

The above observations on OI and SL are confirmed by the Mann Whitney test scores provided in Fig. 3. For OI, a significant difference is confirmed between treatments T2 and T3. For all other comparisons, including T1/T3, no statistical significance is found (criterion p<0.05).

With regard to SL, the statistical tests confirm also a significant difference between T2 and T3. Although there is an observable difference between T1 and T3, its significance is not confirmed by the Mann Whitney test for the selected criterion of p<0.05.

Cost Components

As defined above, the considered cost components are:

• The operating cost (OC), defined as the sum of the backorder (BC) and inventory carrying (IC) costs (OC=BC+IC), • The total cost (TC), defined as the sum of the operating (OC) and purchasing (PC) costs (TC=OC+PC=BC+IC+PC). Both OC and TC are considered in the analysis of the experimental results and presented in Fig. 4. They indicate no significant differences between treatments T1 and T2, but a significant increase in the magnitude and variability of both OC and TC in case of treatment T3, i.e. in case of power awareness. The statistical analysis by Mann Whitney test scores confirms the results described above (see Fig. 4). For both OC and TC, the differences between treatment T3 versus treatments T1 and T2 are shown to be significant.

Discussions and Conclusion

It is important to recall that the use of a controlled and reproducible experimental environment assures that all observations are strictly due to changes in the human replenishment decision process. Thus, the statistical analysis of the experimental data in the three different settings T1, T2 and T3, with varying power and awareness levels, leads to the following main observations.

─ Observation 1: Holding power without having its complete awareness creates no significant change in ordering behavior, inventory levels and costs compared to a power equilibrium situation (T2 versus T1). ─ Observation 2: Holding power and being completely aware about it leads to a significant impact in inventory replenishment decision, inventory levels and costs when compared to a power equilibrium situation (T3 versus T1).

In particular, the following significant impacts are observed: a) Ordered quantity and Ordering time interval are increased, b) Inventory levels are increased c) Cost components are increased.

As T1 (balanced power) and T2 (imbalanced power without awareness) lead to very similar results, the following discussion is limited to the comparison of two situations: T3 (imbalanced power with awareness) versus T1 (balanced power).

The significant difference observed in the ordering behavior (increased ordered quantity (OQ) and increased ordering time interval (OT) can be considered as being at the origin of the other observations. In particular, the higher inventory level can reasonably be attributed to the larger order quantity. It is interesting to notice that the supply line is not significantly changed, even though the purchase satisfaction is reduced. These suggest that the increased order quantity reduces the reactivity of the supplier (as partial delivery is not allowed) but does not significantly hamper its ability to ship; i.e. increase its backlog.. A first analysis of the global supply chain performances has shown that a significant drop of the total supply chain profit occurs in case of exercising coercive power (T3). This is an indication that coercive power in supply chain has a negative effect on its integration and efficiency.

Through the use of a controlled experimental set-up it has thus been possible to observe that coercive power in supply chains significantly impacts its behavior and performances. It can in particular be concluded that, in a controlled and stable environment, exercising coercive power within a supply chain tends to reduce its performance. The Supply Chain costs are increased and the overall profit reduced, but the final customer satisfaction is not so much affected. A first analysis of the intra-supply chain results indicates also that the reduced total Supply Chain profit is shared in a less even way, which is detrimental to the partner under power dependence. This may ultimately lead to additional intra-chain dissatisfactions, and therefore to further degradation of the Supply Chain performances with time.

Real Supply chains are of course significantly more complex and less stable than the well-controlled experimental environment used in this study. Nevertheless, the obtained results being strictly due to human decision-making, it can be expected that similar tendencies would be observed in practice. Consequently, it means that a strong imbalance of power in a decentralized Supply Chain is adverse.

Fig. 1 .

 1 Fig. 1. Structure of the Supply Chain used in XBG simulation.

Fig. 2 .

 2 Fig. 2. Mean OQ and OT for treatments T1, T2 and T3.

Fig. 3 .

 3 Fig. 3. Mean OI and SL for treatments T1, T2 and T3.

Fig. 4 .

 4 Fig. 4. Mean OC and TC for treatments T1, T2 and T3.

Table 1 .

 1 Summary of the variables

	Variable	Symbol Variable	Symbol
	Ordered quantity	OQ	Purchasing cost	PC
	Ordering time interval	OT	Backorder cost	BC
	On-hand inventory	OI	Inventory carrying cost	IC
	Supply line	SL	Operating cost	OC
			Total cost	TC

Acknowledgement

The authors wish to thank Prof. Benoit Montreuil and his research team at Université Laval for providing the participatory simulation platform XBG and for efficiently supporting its use and maintenance. Thanks are also due to Mr. Marc Matthey for his technical support and to Mrs. Ioanna Paniara for helping with the preparation of this manuscript.