Modern high intensity agriculture focuses on the production of one kind of crop at a time, be it hogs, cattle, corn or soybeans, on a very large scale.  This has huge efficiencies of scale – and huge inefficiencies.  We use energy to pull nitrogen out of the air and extract other minerals from the ground to dump on our fields, a significant fraction of which run off to pollute water, as I’ve shown you.  We feed the grain grown in this way to animals raised at a very high density, commonly in closed structures.  These animals generate a great deal of waste rich in plant nutrients, which often itself becomes a pollutant.  Organic farming is a return to older farming approaches in which animals provide the fertilizer for plants.  The principle of reintegrating nutrient flows in a sound one, but unfortunately organic farming as it is currently practiced under an arbitrary set of rules is simply inefficient, which is why organic produce costs so much more than produce grown by what have become convention modern farming methods.  Indeed, the notion that we could feed a world of 7 billion, much less 9 billion, with organic agriculture is simply wishful thinking.  But my view is that we should keep the principle, but use the most up-to-date science we can find.  Let me share one example of a system that integrates aquaculture with vegetable growing.