Un Enfoque Híbrido de Agrupamiento y Optimización Entera Mixta para el Problema de Servicios de Recolección Selectiva de Residuos Sólidos Domésticos

 Context:  Waste generation is causing profound negative impacts on our natural environment. Because of that, processes related to waste collection, transportation, transformation and final disposal have increased its importance and major efficiencies are is desirable. We propose a Mixed Integer Programming model and clustering approach for waste collection and transportation process.Method: An optimization model, inspired on Bogotá context is proposed, to maximize the amount of waste collected, considering real-life aspects of this activity in the city. For large instances in which there is a big computational cost, we proposed an alternative solution of two stages, firstly a clustering step and then a routing step. Results: In small instances of up to 1453 collection sites grouped in 13 blocks and 51 corners, the model result in an overall collection covering of 100%. For large instances, there are variations between the results of each clustering method. The results suggests that the sweep algorithm is better to clustering the collection sites.Conclusions:  Our proposed model is able to find a solution the waste collection problem in Bogota case considering the vehicle capacity, maximum workday duration and the planning horizon of two days according with the collection process in Bogota. We test three clustering methods in order to group the collection sites and to reduce the complexity of the problem, and then we solve the model using a commercial solver. For the small instances, our model run very fast but in the large instances the computational time was increased. Future work will focus in the validation and search of solution methods improving the performance with the proposed model.Contexto: La generación de residuos está causando profundos y negativos impactos en nuestro ambiente. Por esto, procesos relacionados con la recolección, el transporte, la transformación  y la disposición final de residuos han ganado importancia y se propende a su eficiencia. Un modelo de programación entera mixta y de agrupación es propuesto para los procesos de recolección  y transporte de residuos.Método: Se propone un modelo de optimización, inspirado en el contexto de Bogotá, cuyo objetivo es maximizar la cantidad de residuos recolectados teniendo en cuenta las características reales de esta actividad en la ciudad. Para instancias grandes en las que el costo computacional es muy alto, se proponen una alternativa de solución de dos etapas, clusterizar primero y rutear después. ´Resultados: En pequeñas instancias de hasta 1453 puntos de recolección  agrupados en 13 bloques y 51 esquinas, nuestro modelo logro el cubrimiento total de la recolección. Para grandes instancias,  existen variaciones entre los resultados de cada método de agrupación.Conclusiones: Nuestro modelo propuesto es capaz de encontrar una solución al problema de recolección de residuos en caso de Bogotá considerando la capacidad de los vehículos, la duración máxima de una jornada de trabajo y el horizonte de planificación de dos días de acuerdo con el proceso de recolección de Bogotá. Probamos tres métodos de agrupación para agrupar los sitios de recolección y para reducir la complejidad del problema, y luego se resuelve el modelo usando un paquete comercial. Para instancias pequeñas, nuestro modelo es rápido, pero en grandes instancias se aumenta el tiempo de cálculo. Los trabajos futuros se centrarán en la búsqueda y validación de métodos con el propósito de encontrar aquel que tenga un mejor desempeño con el modelo propuesto

The smart waste collection routing problem: alternative operational management approaches

Waste collection is nowadays an increasingly important business. However, it is often an inefficient op- eration due to the high uncertainty associated with the real waste bins’ fill-levels. To deal with such uncertainty the use of sensors to transmit real time information is seen as possible solution. But, in order to improve operations’ efficiency, the sensors’ usage must be combined with optimization procedures that inform on the optimal collection routes to operationalize, so as to guarantee a maximization of the waste collected while also minimizing transportation costs. The present work explores this challenge and studies three operational management approaches to define dynamic optimal routes, considering the access to real-time information on the bins’ fill-levels. A real case study is solved and important results were found where significant profit improvements are observed when compared to the real operation. This shows the potential of the proposed approaches to build an expert system, which can support the operations manager’s decisions.info:eu-repo/semantics/acceptedVersio

Optimizing the inventorying and distribution of chemical fluids: An innovative nested column generation approach

Vendor-managed-inventory is a successful business practices based on the cooperation between a supplier and its customers in which demand and inventory information from the customers are shared with the supplier. This practice is gaining popularity in the chemical industry and relies on the inventory-routing-problem, which integrates inventory management, vehicle routing, and delivery scheduling decisions. This one is a difficult combinatorial optimization problem both theoretically and practically. However, because of the large expenses involved in distribution and inventorying of chemical products, it is attractive to make use of optimization tools for exploiting as many degrees of freedom as possible with the goal of minimizing both distribution and inventorying costs. Consequently, we propose a nested column generation algorithm for solving an inventorying and distribution problem that models the delivery of several chemicals fluids. The approach is building on a column generation & incomplete branch-and-price algorithm in which for each delivery route, the delivery patterns of fluids are also determined by column generation. We detail the implementation and provide computational results for realistic test instances.Fil: Coccola, Mariana Evangelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Mendez, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Dondo, Rodolfo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

Propuesta de actualización de plan de rutas de barrido manual y recolección de residuos sólidos domiciliarios del distrito de Oyotún

La presente investigación realiza el diagnóstico del estado actual de la recolección de residuos sólidos del distrito de Oyotún a la vez se busca optimizar el recorrido que debe realizar el vehículo recolector de residuos sólidos por el casco urbano del municipio de dicho distrito, con lo anterior se diseñaron rutas de recolección que abarcan la totalidad de los usuarios de las localidades, considerando variables socioeconómicas dentro del diseño que permiten maximizar los beneficios económicos y ambientales para la ciudad. Se realizó acompañamiento en las jornadas de trabajo para la Georeferenciación, se usó la técnica de observación directa y registro de información para el diseño de las rutas al igual que el uso de la información obtenida en las encuestas a fin de obtener un esquema de recolección más equitativo e incluyente, que permitiera maximizar la cantidad de residuos recogidos, lo cual representa mayor eficiencia y menos impacto ambiental. El desarrollo de la investigación se realizó con el apoyo de la Municipalidad Distrital de Oyotún a través del gestor territorial de la localidad.Tesi

Inventory routing problem with backhaul considering returnable transport items collection

The Inventory Routing Problem (IRP) has been highlighted as a valuable strategy for tackling routing and inventory problems. This paper addresses the IRP but considers the forward delivery and the use of Returnable Transport Items (RTIs) in the distribution strategy. We develop an optimization model by considering inventory routing decisions with RTIs collection (backhaul customers) of a Closed-Loop Supply Chain (CLSC) within a short-term planning horizon. RTIs consider reusable packing materials such as trays, pallets, recyclable boxes, or crates. The RTIs represent an essential asset for many industries worldwide. The solution of the model allows concluding that if RTIs are considered for the distribution process, the relationship between the inventory handling costs of both the final goods and RTIs highly determines the overall performance of the logistics system under study. The obtained results show the efficiency of the proposed optimization scheme for solving the combined IRP with RTIs, which could be applied to different real industrial cases

Developing Model of Flexible Periodic Vehicle Routing Problem (FPVRP) Considering Color Combination Requirements for a Paint Distribution System

The distribution system in paint product’s sector does have some unique complexities. Within a developing technology, paint products are now wider in color range, faster in manufacturing, and better in quality. Even now it is possible to create a desired color instantly using on-spot paint tinting machine technology (One thousand color policy). Flexible Periodic Vehicle Routing Problem (FPVRP) is a tool chosen within planning the paint distribution system. Paint distributor will be able to plan the deliveries on a weekly planning horizon. The model is developed from previous research by adding the multi-product criteria (weighted bill of color consideration) as well as multi-capacity vehicle criteria to help paint distributors in making a better decision of routing. The benefits obtained from FPVRP decision tools is the increased flexibility of routing options considering the visit frequency, routing sequence and also the selection of the vehicle used which save cost up to 59.85%. Nevertheless, as a drawback, this model requires a very long computational time and some unexpected shut down often occurred especially during calculations for bigger data siz

The flexible periodic vehicle routing problem: modeling alternatives and solution techniques

In this thesis the Flexible Periodic Vehicle Routing Problem is introduced and studied. In this problem a carrier must establish a distribution plan to serve a given set of customers over a planning horizon using a fleet of homogeneous capacitated vehicles. The total demand of each customer is known for the time horizon and it can be satisfied by visiting the customer in several time periods. There is, however, a limit on the maximum quantity that can be delivered at each visit. The aim is to minimize the total routing cost. This problem can be seen as a generalization of the Periodic Vehicle Routing Problem which, instead, has fixed service schedules and fixed delivered quantities per visit. On the other hand, the Flexible Periodic Routing Problem shares some characteristics with the Inventory Routing Problem in which inventory levels are considered at each time period, the delivery of product is a decision of the problem and, typically, an inventory cost is involved in the objective function. The relation among these periodic routing problems is discussed and a worst-case analysis, which shows the advantages of the studied problem with respect to the problems with periodicity mentioned above, is presented. Furthermore, alternative mixed-integer programming formulations are described and computationally tested. Given the difficulty to optimally solve the studied problem for small size instances, a matheuristic is developed, which is able to solve large size instances efficiently. Extensive computational experiments illustrate the characteristics of the solutions of the problem and show that, also in practice, allowing flexible policies may produce substantial savings in the routing costs in comparison with both the Periodic Vehicle Routing Problem and the Inventory Routing Problem.: En esta tesis se presenta y estudia el Problema de Ruteo de Vehículos Periódico Flexible. En este problema, un transportista debe establecer un plan de distribución para atender a un conjunto determinado de clientes durante un horizonte de planificación utilizando una flota de vehículos con capacidad homogénea. La demanda total de cada cliente es conocida por el horizonte temporal y se puede satisfacer visitando al cliente en varios períodos de tiempo. Sin embargo, hay un límite en la cantidad máxima que se puede entregar en cada visita. El objetivo es minimizar el costo total de ruteo. Este problema puede verse como una generalización del Problema clásico de Ruteo de Vehículos Periódico que, en cambio, tiene programas de servicio fijos y cantidades de entrega fijas por visita. Por otro lado, el Problema de Ruteo de Vehículos Periódico Flexible comparte algunas características con el Problema de Ruteo de Inventarios en el cual los niveles de inventario se consideran en cada período de tiempo, la entrega del producto es una variable de decisión y, típicamente, un costo de inventario está involucrado en la función objetivo. Se discute la relación entre estos problemas periódicos de rutas y se presenta un análisis del peor de los casos, que muestra las ventajas del problema estudiado con respecto a los problemas periódicos mencionados anteriormente. Además, las formulaciones alternativas de programación entera mixta se describen y se prueban computacionalmente. Dada la dificultad de resolver a optimalidad el problema estudiado para instancias de tamaño pequeño , se desarrolla una matheurística que puede resolver instancias de gran tamaño de manera eficiente. Una extensa experiencia computacional ilustra las características de las soluciones del problema y muestra que, también en la práctica, permitir políticas flexibles puede producir ahorros sustanciales en los costos de ruteo en comparación con el Problema de Ruteo de Vehículos Periódico y el Problema de Rutas de Inventario.Postprint (published version