Magnus Fröhling

Sustainable supplier management – a review of models supporting sustainable supplier selection, monitoring and development

In the last two decades, pressure from various stakeholders has forced many companies to establish environmental and social improvements both in their company and their supply chains. The growing number of journal publications and conference proceedings confirms this change also in academia. The aim of this paper is to analyse and review scientific literature on sustainable supplier management (SSM) with a focus on formal models supporting decision-making in sustainable supplier selection, monitoring and development. For this purpose, a framework on SSM is proposed and a comprehensive content analysis including a criteria analysis is carried out. Beyond this, in total 143 peer-reviewed publications between 1997 and 2014 have been analysed to identify both established and overlooked research fields. Major findings are the rapidly growing interest of this topic in academia in recent years, the predominance of Analytic Hierarchy Process, Analytic Network Process and fuzzy-based approaches, the focus on the final evaluation and selection process step and the rare investigation of social and quantitative metrics. This review may be useful for practitioners and scientists as it outlines major characteristics in this field, which can serve as a basis for further research.

Integrated planning of transportation and recycling for multiple plants based on process simulation

By-products accrue in all stages of industrial production networks. Legal requirements, shortening of primary resources and their increasing prices make their recycling more and more important. For the re-integration into the economic cycle the scope of common supply chain management is enlarged and so-called closed-loop supply chains with adapted and new planning tasks are developed. In process industries this requires a detailed modelling of the recycling processes. This is of special relevance for operational planning tasks in which an optimal usage of a given production system is envisaged. This contribution presents an integrated planning approach for a real-world case study from the zinc industry to achieve such an adequate process modelling. We consider the planning problem of a company that operates four metallurgical recycling plants and has to allocate residues from different sources to these recycling sites. The allocation determines the raw material mix used in the plants. This blending has an effect on the transportation costs and the costs and revenues of the individual technical processes in the recycling plants. Therefore in this problem transportation and recycling planning for multiple sites have to be regarded in an integrated way. The necessary detailed process modelling is achieved by the use of a flowsheet process simulation system to model each recycling plant individually. The models are used to derive linear input-output functions by multiple linear regression analyses. These are used in an integrated planning model to calculate the decision-relevant input and output flows that are dependent upon the allocation of the residues to the recycling sites. The model is embedded in a decision support system for the operational use. An example application and sensitivity analyses demonstrate and validate the approach and its potentials. The approach is transferable to other recycling processes as well as to other processes in process industries.

A Material Flow‐Based Approach to Enhance Resource Efficiency in Production and Recycling Networks

Resource and energy efficiency are key strategies for production and recycling networks. They can contribute to more sustainable industrial production and can help cope with challenges such as competition, rising resource and energy prices, greenhouse gas emissions reduction, and scarce and expensive landfill space. In pursuit of these objectives, further enhancements of single processes are often technologically sophisticated and expensive due to past achievements that have brought the processes closer to technical optima. Nevertheless, the potential for network‐wide advancements may exist. Methods are required to identify and assess the potential for promising resource and energy efficiency measures from technical, economic, and ecological perspectives. This article presents an approach for a material flow‐based techno‐economic as well as ecological analysis and assessment of resource efficiency measures in production and recycling networks. Based on thermodynamic process models of different production and recycling processes, a material and energy flow model of interlinked production and recycling processes on the level of chemical compounds is developed. The model can be used to improve network‐wide resource efficiency by analyzing and assessing measures in scenario and sensitivity analyses. A necessary condition for overcoming technical and economic barriers for implementing such measures can be fulfilled by identifying strategies that appear technologically feasible and economically and ecologically favorable. An exemplary application to a production and recycling network of the German steel and zinc industry is presented. From a methodological point of view, the approach shows one way of introducing thermodynamics and further technological aspects into industrial planning and assessment.

Fuzzy approach for production planning and detailed scheduling in paints manufacturing

Due to growing competition, small- and medium-sized companies face within supply chains the challenge of providing short and reliable throughput times while coping with uncertainties, especially concerning time parameters, in production planning and detailed scheduling. The application of fuzzy scheduling is an adequate way to model these uncertainties in a supply chain. The paper presents an approach for the fuzzy scheduling of hybrid flow shops based on the general multi-mode resource-constrained project-scheduling problem. The approach is validated in a case study of a small- and medium-sized enterprise producing paints in a batch production process.

Combined scheduling and capacity planning of electricity-based ammonia production to integrate renewable energies

Economic assessment of energy-related processes needs to adapt to the development of large-scale integration of renewable energies into the energy system. Flexible electrochemical processes, such as the electrolysis of water to produce hydrogen, are foreseen as cornerstones to renewable energy systems. These types of technologies require the current methods of energy storage scheduling and capacity planning to incorporate their distinct non-linear characteristics in order to be able to fully assess their economic impact. A combined scheduling and capacity planning model for an innovative, flexible electricity-to-hydrogen-to-ammonia plant is derived in this paper. A heuristic is presented, which is able to translate the depicted, non-convex and mixed-integer problem into a set of convex and continuous non-linear problems. These can be solved with commercially available solvers. The global optimum of the original problem is encircled by the heuristic, and, as the numerical illustration with German electricity market data of 2013 shows, can be narrowed down and approximated very well. The results show, that it is not only meaningfulness, but also feasible to solve a combined scheduling and capacity problem on a convex non-linear basis for this and similar new process concepts. Application to other hydrogen based concepts is straightforward and to other, non-linear chemical processes generally possible.

Freight transportation planning considering carbon emissions and in-transit holding costs: a capacitated multi-commodity network flow model

To mitigate climate relevant air emissions from freight transportation, policy makers stimulate the application of intermodal freight transport chains. The evaluation and selection of intermodal routes based on the key objectives, i.e., greenhouse gas emission, transportation cost and transit time improvements, are the main challenges in the design of intermodal networks. It is the aim of this paper to provide decision support in intermodal freight transportation planning concerning route and carrier choice in transport service design and the assessment of emission abatement potentials. Core of this approach is a capacitated multi-commodity network flow model considering multiple criteria and in-transit inventory. Thereby two processes are modeled, i.e., the transport and transshipment of full truckloads (FTL), to define the material flow of goods through the network. The objective function of the developed network flow model minimizes the number of transported and transshipped FTL assessed by the weighted and normalized criteria (i.e., CO2-equivalents, cost, time) taking into account tied in-transit capital and the distance traveled. Thereby, the model regards carrier and terminal capacities, the option to transfer or either shift the mode and/or change the carrier at predefined terminal transshipment points. The model is incorporated in a decision support system and applied in an example application with industry data from an automotive supplier to demonstrate its application potentials. Within the application among others the potential benefits of the developed optimization model in comparison to a status quo are analyzed. Different criteria weightings and the influence of various levels of in-transit holding costs are investigated. In addition, the introduction of new transportation means such as the Eurocombi is assessed.

Demontageplanung und -steuerung mit Enterprise-Resource- und Advanced-Planning-Systemen

In this paper we discuss, using SAP® R/3® as an example, whether it is possible to implement specific data structures for dismantling planning and control (DPC) in ERP systems, and by that enable the use of ERP systems for DPC. Therefore we initially outline the tasks of DPC. Afterwards requirements concerning modelling and implementation of master data for DPC are formulated and their possible implementation into the data structures of SAP® R/3® is analysed. Concluding an outlook on possibilities of dismantling planning and control with a combined usage of ERP- and Advanced Planning Systems is given.

Demontageplanung und -steuerung mit Enterprise-Resource- und Advanced-Planning-Systemen@@@Dismantling planning and control with enterprise resource and advanced planning systems

In this paper we discuss, using SAP® R/3® as an example, whether it is possible to implement specific data structures for dismantling planning and control (DPC) in ERP systems, and by that enable the use of ERP systems for DPC. Therefore we initially outline the tasks of DPC. Afterwards requirements concerning modelling and implementation of master data for DPC are formulated and their possible implementation into the data structures of SAP® R/3® is analysed. Concluding an outlook on possibilities of dismantling planning and control with a combined usage of ERP- and Advanced Planning Systems is given.

Comparison of Heuristics Towards Approaching a Scheduling and Capacity Planning MINLP for Hydrogen Storage in Chemical Substances

The need for scheduling and capacity planning of electricity and energy storage technologies has risen in line with growing feed-in of intermittent wind and solar power. Hydrogen-based storage technologies usually feature non-linear as well as non-differentiable operating characteristics. This paper discusses different approaches towards integrating consumption figures derived from engineering simulations into scheduling and capacity planning problems. The comparison of best-fit functions to a heuristic-based approach of using comparably rapidly computable functions in addition with adjustment calculations shows, that reduction in complexity and calculation time leads to discrepancies at cost and furthermore at scheduling and capacity size level. Cost effects can be minimized by the heuristics, but different scheduling and capacity choice remains.

Erhöhung der Energie- und Ressourceneffizienz und Reduzierung der Treibhausgasemissionen in der Eisen-, Stahl- und Zinkindustrie (ERESTRE)

Aufgrund der zunehmenden Verknappung von Rohstoffen und der Emissionen klimarelevanter Gase, wurden in den letzten Jahren verstarkte Anstrengungen zur effizienten Nutzung von Ressourcen und Energie in der Eisen-, Stahl- und Zinkindustrie unternommen. Zielsetzung dieses Forschungsvorhabens ist die Untersuchung der Auswirkung von internen und externen Verwertungsmasnahmen zur Steigerung der Ressourceneffizienz unter Beachtung der Energieeffizienz, CO2-Emissionen und Wirtschaftlichkeit.