Environmental effects of physical life span of a reusable unit following functional and physical failures in a remanufacturing system

Abstract

Reuse of product components is an effective way to conserve natural resources. Likewise, remanufacturing is a new trend in the field of environmentally friendly products. A product undergoes functional failure or physical failure in a remanufacturing environment, where the former failure is equivalent to the state in which the product cannot be used because of functional insufficiency or obsolescence and the latter failure is equivalent to the state of malfunction or breakdown of a product. A unit intended for reuse should be designed to be durable for a period equal to at least two functional lives through remanufacturing. Utilization of excess materials-for example, for improvement of unit strength-can enable a reusable unit to endure over a period equal to at least two functional lives. However, if the environmental impact of such excessive use of materials is taken into account, a strong doubt arises as to whether such a method truly reduces the environmental load from the viewpoint of lifecycle design. In order to analyse this issue, the present study examines the optimal physical life span of a reusable unit and its effect on the environment. A mathematical model of a remanufacturing system is constructed, taking into account functional and physical failures of a product. A minimization problem of the incurred total environmental impact per unit time for a reusable unit is formulated under the decision variables of a design parameter vector of the unit and the maximum number of times of reuse. The design parameter vector is closely related with physical life span. The maximum number of times of reuse can cause environmental loss if a product has a long residual physical life span brought on by the small number of times of reuse. The effects of physical life span of a reusable unit on environmental impact are analysed to show the potential value of the developed model by means of varying stochastic characteristics and the parameters of the remanufacturing environment.

The Environmental Impacts of Reuse: A Review

“…Design strategies that increase the reusability of a product or component (greater durability, modularity, or standardization) will often require the use of additional material and so increase the initial impacts in production. This has been recognized by Okumura and colleagues () and examined by Skelton and Allwood (). They model the life cycle emissions associated with a product that takes account of embodied energy, use‐phase efficiency, and life span.…”

State of the art review of quality, reliability and maintenance issues in closed-loop supply chains with remanufacturing

“…In addition, the author proposed some guidelines as safety measures for the third party suppliers and users when replacing OEM parts. Okumura, Morikuni, and Okino (2003) proposed a life design method for remanufacturing durable products, by which each reusable part/unit is assigned an appropriate physical life span and its environmental impact is evaluated. A stochastic model formulation of the environmental performance cost, which is defined as the ratio of the expected environmental impact to the expected time span of product usage, is provided and used for decision-making at the design stage.…”

A hierarchical end-of-life decision model for determining the economic levels of remanufacturing and disassembly under environmental regulations

“…They proposed the reusability of a component to evaluate the time dependent reusability of components and products on the basis of reliability theory. Okumura et al (2003) classified two types of failures e functional and physical failures e and examined the optimal number of reuse in terms of environmental impacts. Galbreth and Blackburn (2006) provided optimal sorting and acquisition policies of a remanufacturer by considering the variability of returned products when acquisition cost is linear.…”