The cradle to cradle books are signs signaling sustainability. C2C is a "technical" nutrient — the entire book is made to be taken back into a production process — the pages are plastic, the ink reclaimable. The Upcycle is instead a biological nutrient, made to decompose and return to the cycles of nature. Paper, ink, binding, is all made to biodegrade… This fully signals the ideology of Cradle to Cradle. (Michael Braungart and William McDonough (with the design Paul Sahre))