We destroy Nature=we destroy Ourselves
Biological Nutrients are organic materials that, once used, can be disposed of in any natural environment and decompose into the soil, providing food for small life forms without affecting the natural environment. This is dependent on the ecology of the region; for example, organic material from one country or landmass may be harmful to the ecology of another country or landmass.
A major constraint in the optimal recycling of materials is that at civic amenity sites, products are not disassembled by hand and have each individual part sorted into a bin, but instead have the entire product sorted into a certain bin.
This makes the extraction of rare earth elements and other materials uneconomical (at recycling sites, products typically get crushed after which the materials are extracted by means of magnets, chemicals, special sorting methods, …) and thus optimal recycling of, for example metals is impossible (an optimal recycling method for metals would require to sort all similar alloys together rather than mixing plain iron with alloys).
Cradle to Cradle utopia
Disassembling products is not feasible at currently designed civic amenity sites, and a better method would be to send back the broken products to the manufacturer, so that the manufacturer can disassemble the product. These disassembled product can then be used for making new products or at least to have the components sent separately to recycling sites (for proper recycling, by the exact type of material). At present though, few laws are put in place in any country to oblige manufacturers to take back their products for disassembly, nor are there even such obligations for manufacturers of cradle-to-cradle products. One process where this is happening is in the EU with the Waste Electrical and Electronic Equipment Directive.
In the cradle to cradle model, all materials used in industrial or commercial processes—such as metals, fibers, dyes—fall into one of two categories: “technical” or “biological” nutrients. Technical nutrients are strictly limited to non-toxic, non-harmful synthetic materials that have no negative effects on the natural environment; they can be used in continuous cycles as the same product without losing their integrity or quality. In this manner these materials can be used over and over again instead of being “downcycled” into lesser products, ultimately becoming waste.