Describe the concept of cradle-to-cradle in sustainability.

Cradle-to-cradle is a sustainable business strategy that models industrial processes on natural processes, focusing on waste-free production.

The cradle-to-cradle concept is a biomimetic approach to the design of products and systems. It views materials as nutrients circulating in healthy, safe metabolisms. The term itself is a play on the phrase "Cradle to Grave," implying that the C2C model is sustainable and considerate of life from start to finish.

This concept was popularised by William McDonough and Michael Braungart in their book "Cradle to Cradle: Remaking the Way We Make Things". They argue that if factories and products are designed properly, the things we make can be continuously recycled, providing nutrients for nature and industry. This would eliminate the concept of waste altogether, creating a circular economy where waste is food for another process.

The cradle-to-cradle design framework is based on three principles derived from nature: everything is a resource for something else; use clean and renewable energy; celebrate diversity. Products are designed from the outset so that, after their useful life, they will provide nourishment for something new. They can be composed of technical nutrients (non-toxic, synthetic materials that can be used in continuous cycles) or biological nutrients (organic materials that can be composted or consumed).

In the cradle-to-cradle model, all used materials in commerce are seen as valuable, circulating in closed-loop cycles of production, use, and recycling, and systems thinking is applied throughout. Businesses following the cradle-to-cradle model enjoy economic benefits such as reduced materials and waste handling costs, increased brand equity, and the ability to offer high-quality products and services while supporting environmental and social wellbeing.

The cradle-to-cradle concept is a radical shift away from the traditional, linear model of 'take, make, waste'. It offers a new way of thinking about how we design, make, and use everything, with benefits for people, the planet, and economies.