Energy limits on recycling

Increasing efficiency of resource use is a major ecological-economics goal. Opportunities for large efficiency increases have been found in every area carefully investigated. What are the limits? Energy analysis: offers power ful insights. Ayres has argued that, even with unlimited available energy, over time it becomes necessary to have ever-more dilute waste reservoirs. I f correct, this would significantly limit the potential of a hypothetical s ustainable spaceship, and of a 'spaceship economy'. However. we know the wo rld is self-contained and long lived, and that stable laboratory microcosms have been built. Thus, this assertion appears to violate reality. I argue that the alleged problem does not exist. Given available energy, there is n o concentration limit on sustainability. My result is consistent with the w ork of Georgescu-Roegen and others. I estimate some numerical examples to s how that present systems are extremely far from theoretical limits. For a l ong time to come, there will be vast opportunities to improve efficiency. T he paper includes a classification schema for recycling based on chemical b onding and thermodynamic considerations. (C) 2001 Elsevier Science B.V. All rights reserved.