A lyfe cicle

Resources, Conservation and Recycling 51 (2007) 792–826

A life cycle based multi-objective optimization model for the management of computer waste
Poonam Khanijo Ahluwalia ∗ , Arvind K. Nema 1
Department of Civil Engineering, I.I.T. Delhi, New Delhi-110016, India Received 24 October 2006; received in revised form 9 January 2007; accepted 10 January 2007 Available online 15 February 2007Abstract The accelerating pace of waste generation from used electrical and electronic equipment is of growing global concern. Within this waste stream, computer hardware is quite significant in terms of both volume and risk to the environment because of the hazardous materials within it. The waste management hierarchy of prevention, reuse, recycle, treatment and disposal in landfill is accepted as auniversal guideline for waste management. The contemporary concept of integrated solid waste management is very complex comprising of not only the environmental aspects or the technical aspects of the waste management hierarchy, but also incorporating economic, institutional, perceived risk and social issues in the context of complete life cycle of waste. Moreover, when to shift from one stage ofhierarchy to another, is an involved decision warranting inclusion of several case specific issues. This paper presents a life cycle based multi-objective model that can help decision makers in integrated waste management. The proposed model has been applied to a case study of computer waste scenario in Delhi, India, which apart from having computer waste from its native population receives largequantities of imported second hand computers. The model has been used to evaluate management cost and reuse time span or life cycle of various streams of computer waste for different objectives of economy, perceived risk and environmental impact. The model results for different scenarios of waste generation have been analyzed to understand the tradeoffs between cost, perceived risk andenvironmental impact. The optimum life cycle of a computer desktop was observed to be shorter by 25% while optimizing cost than while optimizing impact to the environment or risk perceived by public. Proposed integrated approach can be useful for determining the optimum life cycle of
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Corresponding author. Tel.: +91 11 26490907; fax: +91 11 26581117. E-mail addresses: poonamkahluwalia@yahoo.co.in(P.K. Ahluwalia), aknema@civil.iitd.ac.in (A.K. Nema). Tel.: +91 11 26596423; fax: +91 11 26581117.

0921-3449/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.resconrec.2007.01.001

P.K. Ahluwalia, A.K. Nema / Resources, Conservation and Recycling 51 (2007) 792–826

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computer waste, as well as optimum configuration of waste management facilities, for urbancenters where computer waste related issues are of growing concern. © 2007 Elsevier B.V. All rights reserved.
Keywords: Computer waste; Integrated waste management; Multi-objective optimization; Life cycle analysis; Perceived risk

1. Introduction It is estimated that obsolete personal computers (PC’s) were around 2.25 million units in India in 2005, which are expected to touch a figure of 8 millionobsolete units by the year 2010 at an average annual growth rate of approximately 51% (Boralkar, 2005). Considering an average weight of 27.18 kg (Toxics Link, 2003) for a desktop/personal computer approximately 61,155 tonnes of obsolete computer waste would have been generated in India in 2005, which would increase to about 217,440 tonnes by the year 2010 at the projected growth rate. Computerhardware would appear to have up to 3 distinct product lives: the original life or first product life (when it is being used by the primary user) and up to 2 further lives depending on reuse. Fig. 1 depicts the flow of computer hardware units from point-of-sale to the original purchaser and on to the reuse phases. The duration of the product’s first life is estimated to be between 2 and 4 years for...