Twenty five years ago, the German chemist Michael Braungart developed a new approach to recycling, now called "Cradle to Cradle" or "C2C" after the book, Cradle to Cradle: Remaking the Way We Make Things, which he and the American architect William McDonough published in 2002.

The amount of nitrogen that is excreted by livestock is directly proportional to the amount it is fed . This is according to Chris Reynolds a researcher in nutritional physiology of ruminants  at  the University of Reading , UK.