......What will happen to farm livestock if everybody becomes vegan and what will fertilise the soil for growing vegetables?
A very good question! There are green fertilisers that contain nitrogen fixing bacteria on the rood nodules, and which can be ploughed back in.
One of the reasons I support a vegetarian, rather than a vegan approach is that in an organic high welfare farm system milk and egg production does produce fertiliser, but what do we do with all the make cattle and chickens?
But I like meat.... so in the imperfect world there will still be meat from male animals to eat. I just wish we didn't waste all the male chickens. But they are nasty, brutish things that cannot easily be raised as meat, without castration.
