In their disposable cups

WHILE greens have been carping themselves hoarse against the "throwaway" culture, a scientist at the University of Victoria in Canada has calculated that disposable cups -- polystyrene or paper -- may be more ecofriendly after all (Nature, Vol 369, No 6473).

Comparing the energy consumed in manufacturing reusable ceramic cups and disposable cups, Martin B Hocking has discovered that moulded polysterene foam cups consume the least total energy per piece.

The mathematics are a bit involved. He says that if a reusable cup is used between 10 and 70 times, then the energy required to manufacture the cup per use is equivalent to the energy cost of making a disposable one. However, if the energy used to wash and sanitise a reusable cup is factored in as well, to get your energy's worth you would have to use a reusable cup 1,006 times to make it as energy efficient per use as a polystyrene cup.