Reusable and Disposable Cups: An Energy-Based Evaluation

A group of five different types of reusable and disposable hot drink cups have been analyzed in detail with respect to their overall energy costs during fabrication and use. Electricity generating methods and efficiencies have been found to be key factors in the primary energy consumption for the washing of reusable cups and a less important factor in cup fabrication. In Canada or the United States, over 500 or more use cycles, reusable cups are found to have about the same or slightly more energy consumption, use for use, as moulded polystyrene foam cups used once and then discarded. For the same area paper cups used once and discarded are found to consume less fossil fuel energy per use than any of the other cup types examined. Details of this analysis, which could facilitate the comparative assessment of other scenarios, are presented. Conventional wisdom suggests that multiple uses of a reusable cup produce a lower overall environmental impact per use than a single use of a disposable cup. Disposable cups have a place in applications where breakages and losses of other types of cup are unacceptably high, or where washing and sanitizing of reusable cups is awkward, such as in hospitals, in the entertainment and transportation sectors, and for occasional use by large numbers of people. These circumstances make the convenience and the much lower unit cost of disposable cups attractive. Our previously published study of the life cycle environmental impacts of paper and polystyrene foam cups (Hocking 1991a,b) evoked a lot of interest, most notably in its conclusion that adverse resource and pollution externalities of these cup types were at least similar. Some readers mistakenly interpreted these papers to be recommendations in favor of disposable over reusable cups, which was not the case. However, these misinterpretations, plus evidence of increasing concern about the overall environmental impact of cup selection (van Eijk and others 1992, Fenton 1992, Hocking 1991c, d, 1993) prompted the energy-based evaluation presented here. The basic question is, considering the resource consumption and the total resulting waste stream during use, how many uses of a reusable cup are necessary before its overall impact per use is less than that of a disposable cup? Decision-making by food service operators, legislators, environmental groups, and the public would be served by the answer to this question.