Which half? One day when I was a junior medical student, a very important Boston surgeon visited the school and delivered a great treatise on a large number of patients who had undergone successful operations for vascular reconstruction. At the end of the lecture, a young student at the back of the room timidly asked, "Do you have any controls?" Well the great surgeon drew himself up to his full height, hit the desk, and said, "Do you mean did I not operate on half of the patients?" The hall grew very quiet then. The voice at the back of the room hesitantly replied, "Yes, that's what I had in mind." Then the visitor's fist really came down as he thundered, "Of course not. That would have doomed half of them to their death!" God, it was quiet then, and one could scarcely hear the small voice ask, "Which half?" E.E. Peacock Jr., Seeing With Fresh Eyes science
Turn them into cycles Permaculture systems seek to stop the flow of nutrient and energy off the site and instead turn them into cycles, so that, for instance, kitchen wastes are recycles to compost; animal manures are directed to biogas production or to the soil; household greywater flows to the garden; green manures are turned into the earth; leaves are raked up around trees as mulch. Bill Mollison, Introduction to Permaculture Two CyclesAn ecological cycle ecosystemsrecyclinggardens