#physics **Poop Cabbage** Physics tells us that the root membranes are effectively 'Reverse Osmosis Filters' Nothing gets by them. At our cottage (summer hut) we have a compost toilet and all the compost goes to growing 'Poop Potatoes'. I have this huge thermal compost bin in the back and it's hot even in the winter. I put all the dog poop in it. However, I also put in Miraclegro for the nitrogen. The physics error in the article is that there is not enough natural fixed nitrogen in the world to feed us.