Hunsinger's comment, "new resources are created and new uses are found both for old materials and new waste." refers to one of the cardinal rules of chemical engineering: increasing cost of a resource leads to increased value of other resources having the same end use. Also from Chem E comes the concept of a feedstock: used crankcase oil is waste that is the principle input to the re-refining industry. As to Mathieu's comment on waste, the value and useability of waste depends to a large extent on its 'purity.' There is a sort of entropy factor at work here, the more heterogeneous waste is the less value it has. So decreasing entropy is increasing value in most cases, that is, refining makes waste a more usable resource. -- Charles Hendricksen, PhD