Otto Rentz

Modeling reverse logistic tasks within closed-loop supply chains: An example from the automotive industry

In this contribution, the peculiarities of establishing a closed-loop supply chain (CLSC) are presented, based on an example considering the end-of-life vehicle (ELV) treatment in Germany. Different design options for a CLSC are put up, concentrating on how reverse material flows can be handled with regard to reintegrate them into their genuine supply chains. Reverse logistics aspects are modeled with vehicle routing planning. Introducing a problem-tailored algorithm, results of several CLSC scenarios are discussed which are based on real case data, depicting measures from German ELV stakeholders.

Closed-Loop Supply Chains for Spent Batteries

In Germany, a battery decree prescribes measures for collecting and recycling spent batteries. We developed a hybrid approach to establishing a closed-loop supply chain for spent batteries that combines an optimization model for planning a reverse-supply network and a flow-sheeting process model that enables a simulation tailored to potential recycling options for spent batteries in the steelmaking industry. Our results show that almost complete recycling of spent batteries can be achieved by transforming the current structure into a modified recovery network.

Using quality function deployment for technique selection for optimum environmental performance improvement

Abstract The paper tackles how a given process or technique can be improved to qualify as an environmentally-conscious one at a given budget constraint. The use of quality function deployment (QFD) for the improvement analysis of selected “Best Available Techniques” is discussed. A modified version of QFD is developed and applied to determine the emissions which need to be analysed further for environmental performance improvement. The critical emitted substances with consideration given to environmental impact potential and cost budget are reported. The target specifications used are the environmental benchmarks obtained from the comparison of emission values of the techniques. Sinter production is used as an illustrative example to apply the proposed House of Ecology and the linear mathematical model. QFD could be applied to the continuous improvement of any process or technique with some modifications.

Flowsheeting-based simulation of recycling concepts in the metal industry

Abstract This paper presents a methodology for the planning of integrated recycling concepts taking into account the peculiarities of process engineering in the process industries. Process models for certain unit operations simulated with a flowsheeting program allow to calculate mass and energy balances considering the technical characteristics and performance of a single process or a combined process chain. Based on principles of thermodynamics, this approach allows an assessment of integrated recycling strategies considering techno-economic as well as ecological criteria. The approach is illustrated with an example from the iron and steel making industry where the injection of plastic waste into a blast furnace is investigated.

Environment-oriented project scheduling for the dismantling of buildings

Abstract. This paper presents a case study for the environment-friendly dismantling and recycling of buildings. Based on material-flow management it is shown how the dismantling on the construction site can be improved using resource-constrained project scheduling. Computational results show that strict environmental requirements like high recycling quotas and the reduction of harmful substances in recycling materials can be satisfied. Moreover, a comparison with results in practice indicates that project scheduling helps to achieve economic advantages for environment-friendly dismantling and recycling strategies.Zusammenfassung. Im vorliegenden Beitrag wird eine Fallstudie zur umweltorientierten Projektplanung beim Rückbau und Recycling von Bauwerken vorgestellt. Aufbauend auf einer Stoffstromanalyse wird gezeigt, dass sich durch Anwendung der ressourcenbeschränkten Projektplanung die Demontage auf Baustellen erheblich effizienter gestalten lässt. Ergebnisse belegen, dass einerseits strenge Umweltschutzanforderungen wie beispielsweise hohe Recyclingquoten oder eine weitgehende Schadstoffentfrachtung von Baustoffen erreicht werden können. Vergleiche mit Beispielen aus der Praxis verdeutlichen zudem, dass sich durch ressourcenbeschränkte Projektplanung derartige umweltschutzorientierte Ziele auch ökonomisch vorteilhaft realisieren lassen.

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.

Scheduling of deconstruction projects under resource constraints

In many countries a large part of the building stock will have to be maintained, renovated, rehabilitated or even removed in the next few decades. Although profitability will be one of the major requirements to be met when these works are carried out, there will be more and more emphasis on the environmental requirements to be respected. To make the modernization of the building stock more efficient, dismantling with the aim of producing high quality recycling materials at reasonable costs is a promising approach. This paper presents an integrated approach to deconstruction site management that focuses on both economic and environmental goals. As a first step, material flow management aims at the closed-loop recycling of various construction materials. In a second step, resource constrained project planning models are used to evaluate strategies for optimized deconstruction site management. The approach offers high flexibility and can be adapted readily to different conditions. Results show that time and cost for deconstruction can be reduced by more than 50%, together with recycling quotas of more than 90%. Even when resources are strictly limited or when strong budget and time restrictions have to be respected, tremendous improvements in deconstruction site management can be achieved.

Integrating Spent Products’ Material into Supply Chains: The Recycling of End-Of-Life Vehicles as an Example

Economic, ecological and legal forces are emphasizing the need to recycle spent products in an enhanced way, i.e. reprocessing material in production processes. Hence, increasing reverse material flows are to be coordinated in the next few years. However, this coordination task, also known as ‘reverse’ supply chain management, has not yet been discussed as extensively as supply chain management objectives. Though ‘reversing’ the supply chain is possible to some extent, the main obstacle for transferring supply chain management knowledge to take-back processes is the degree of uncertainty regarding the composition and the amount of discarded products. Especially in the design stage of a reverse supply chain, continuous adaptations in these fields have to be taken into account.

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.

Fuzzy Scheduling for the Dismantling of Complex Products

In this paper, an approach is presented for the solution of decisionmaking problems in short-term dismantling planning. Weak data resulting from uncertain dismantling time parameters are modeled as fuzzy sets and integrated into a scheduling model that supports deriving optimal work plans. Case studies from the construction industry and the electronic scrap recycling show the application of the approach.