"Reusable vs. Disposable Cups
University of Victoria 1994
This classic life-cycle energy analysis was performed by University of Victoria professor of chemistry Martin B. Hocking. Hocking compared three types of reusable drinking cups (ceramic, glass and reusable plastic) to two types of disposable cups (paper and polystyrene foam).
The energy of manufacture of reusable cups is vastly larger than the energy of manufacture of disposable cups (Table 1). In order for a reusable cup to be an improvement over a disposable one on an energy basis, you have to use it multiple times, in order to "cash in" on the energy investment you made in the cup. If a cup lasts only ten uses, then each use gets "charged' for one-tenth of the manufacturing energy. If it lasts for a hundred uses, then each use gets charged for only one-hundredth of the manufacturing energy."