The overarching design framework we exist within has two essential elements: mass (the Earth) and energy (the sun). Nothing goes in or out of the planetary system except for the heat and the occasional meteorite. Otherwise, for our practical purposes, the system is closed, and its basic elements are valuable and finite. Whatever is naturally here is all we have. Whatever humans make does not go “away”.
If our system contaminate Earth’s biological mass and continue to throw away technical materials (such as metals) or render them useless, we will indeed live in a world of limits, where production and consumption are restrained, and the Earth will literally become a grave.
If human are truly going to be prosper, we will have to learn to imitate nature’s highly effective cradle-to-cradle system of nutrient flow and metabolism, in which the very concept waste does not exist. To eliminate the concept of waste means to design things – products, packaging, and systems – from the very beginning on the understanding that waste does not exist. It means that the valuable nutrients contained in the materials shape and determine the design: form follows evolution, not just function. We think this is a more robust prospect than the current way of making things.
As we have indicated, there are two discrete metabolisms on the planet. The first is the biological metabolism, or the biosphere – the cycles of nature. The second is the technical metabolism, or technosphere – the cycles of industry, including the harvesting of technical materials from natural places. With the right design, all of the products and materials manufactured by industry will safely feed these two metabolisms, providing nourishment for something new.
Products can composed either of materials that biodegrade and become food for biological cycles, or of technical materials that stay in closed-loop technical cycles, in which they continually circulate as valuable nutrients for industry, In order for these two metabolisms to remain healthy, valuable, and successful, great care must be taken to avoid contaminating one with the other. Things that go into the organic metabolism must not contain mutagens, carcinogens, persistent toxins, or other substances that accumulate in natural systems to damage effect. (Some materials that would damage the biological metabolism, however, could be safely handled by the technical metabolism.) By the same token, biological nutrients are not designed to fed into the technical metabolism, where they would not only be lost to the biosphere, but would weaken the quality of technical materials or make their retrieval and reuse more complicated.
Fonte: Cradle To Cradle: Remaking the Way We Make Things por William McDonough & Michael Braungart