From the Tree Hugger web site:

Products As Nutrients: A Key Environmental Concept

We should be designing products to be nutrients. This is a key environmental concept today. It is a goal of changing the fundamental ways we make products and do business. The idea has been put forward by theorists such as William McDonough, in his Crade to Cradle proposal, and Paul Hawken, in his book Natural Capitalism. But what does "making a product a nutrient" really involve? It means structuring a business and it's manufacturing processes so that they are actually beneficial to the envrironment and profitable to the business too. Specifically, products should be made of biodegradable components, so that they can be returned to soil, and enrich it, or alternatively, they should be "technical nutrients", meaning they can be recovered and recycled to produce the same product again and again.

McDonough summarizes the idea this way:

Utilizing biological nutrients and technical nutrients allows a company to eliminate the concept of waste and recover value, rather than creating a future solid waste problem and relinquishing material assets by delivering a product to a customer.

But beyond the products themselves, the businesses themselves should be operating as biological nutrients. This means that all the energy and fuels that are used by businesses, should be renewable. It means factories and office buildings should be made with local, renewable, non-toxic materials. Moreover, all office supplies, cleaning supplies, and other goods should be biodegradeable and come from renewable sources. Water should be dealt with strategically, either by capturing rainwater, or by recycling the water in a closed-loop cycle.

Clearly these changes cannot be achieved by companies instituting small "green initiatives" to show that they are concerned about the environment. Instead, what is required is a change in the fundamental DNA of a business, a complete shift in their strategies and operations. The result of this shift, is that businesses become more profitable, consumers get non-toxic, better supported products, and the environment is not polluted but instead is benefited by the operation of businesses.

:: See also the books Cradle to Cradle and Natural Capitalism and Treehugger's challenge to create a Cradle To Cradle Umbrella.