Industrial Nutrients

The term industrial nutrients refers to materials used in manufacturing, the use and disposal of products, and emphasizes the fact that materials often discarded as waste can be reused or recycled, thus becoming useful new inputs or nutrients to sustain the industrial system, analogous to the nutrients that humans ingest to sustain their bodies. Additionally it emphasizes the fact that industrial nutrients can cycle through the industrial ecosystem just as nutrients such as water and carbon cycle through the natural ecosystem. The industrial nutrient approach to manufacturing facilitates the design of the manufacturing process in order to maximize sustainability and minimize harm to the ecosystem by reusing materials or returning them to the environment in useful forms.

The industrial nutrient concept is integral to analyses of industrial metabolism, as advocated by Robert Ayres, which trace the life cycle of materials through industrial systems. It is also a vital component of the cradle-to-cradle (C2C) approach to manufacturing, which offers an alternative to the cradle-to-grave system that theorists such as William McDonough and Michael Braungart argue is no longer sustainable. The cradle-to-grave approach is based on continually taking raw materials, such as coal and iron ore, into the industrial system, and disposing of the resulting wastes outside the system, without much consideration about causing harm to the environment or the possibility that the supply of raw materials may not be unlimited. This type of approach to the industrial process is often referred to as a linear flow of materials (because the materials move in only one direction, from their raw state through manufacturing to waste) or an open-loop system (because materials are taken in from and return to locations outside the system). The C2C system, in contrast, is a circular or closed-loop system in which the end products of the manufacturing process, including waste, are seen as potential inputs to the same or other processes, that is, as nutrients to feed the process. In the cradle-to-grave approach, raw materials are used only once and discarded, while in the C2C approach, materials are seen as the source of nutrients that can be reused or recycled in further industrial or biological processes, ideally with no degradation of quality or ecological harm.

Braungart and McDonough classify industrial nutrients as either technical nutrients (synthetic materials such as plastics and metals that can be used over and over again without [Page 327]degradation) or biological nutrients (organic materials that will decompose in the appropriate natural environment). In a C2C system, both kinds of nutrients flow through the manufacturing and use processes in a closed loop that minimizes the amount of raw materials which must be taken in and the amount of waste discarded. Ideally, products made from technical nutrients will be designed so they can be reused or recycled more or less endlessly, while those made from biological nutrients will be designed so they can be completely returned to the environment without harm (meaning, for instance, that they must not contain toxic chemicals).

In Braungart and McDonough's conceptualization, products made from biological nutrients are called products of consumption because they are not intended to last forever, and are designed to break down in the natural environment after use. One example is the Climatex® Lifestyle fabric developed by Rohner Textil and DesignTex (in conjunction with the Environmental Protection Encouragement Agency and McDonough Braungart Design Chemistry), which is made from natural fibers, including wool and ramie, and can safely be returned to the environment as a biological nutrient. Another example is the Trigema Compostable T-shirt, which contains no toxins or heavy metals, and will biodegrade in a household compost heap.

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