Many current uses of natural resources are wasteful because the resources are used in a "once through" fashion.

And industrial system may ignore potential efficiences; for example, when a metal is mined, processed into a product, used, and discarded as waste, instead of being recycled and reused.

More efficient industrial processes that reuse and recycle materials -- metals, paper, plastics, even construction materials -- thus point the way toward redudcing the environmental effects of natural resource use and preserving them for future generations.

Not everything can be recycled, however. Some current uses of natural resources are inherently dissipative or irreversible.

• When coal, petroleum, and natural gas are used a fuels, they can only be burnt once, and the resulting carbon dioxide is dispersed to the atmosphere.
• Soil eroded from fields is transported elsewhere by wind or water.
• Some toxic materials, such as those contained in pesticides, are deliberately dispersed in the course of use.

These examples are not trivial exceptions.

• Fossil fuels represent betwen 26 and 46 percent of the Total Materials Requirement (TMR)