Planning departments tend to be suspicious, neighbors don't like the smell of manure, and vacant lots have to be thoroughly tested for toxic substances. City farmers outside the United States have a much easier time of it, and the field is flourishing. Hong Kong, for example, the most densely populated city in the world, produces two-thirds of its own poultry and nearly half its vegetables. In Brazil, slum dwellers raise iguana and guinea pigs to supplement protein-poor diets. Urban farmers in the United States do enjoy some advantages over their country cousins.
Urban farmers have much more ready access to organic waste.
From the 'Hood works because the people who grow the food are also there selling it. Urban farmers are well situated to profit from shifts in consumer tastes. The increasing demand for fresh, organic produce is easy to meet from gardens around the corner, but antithetical to the industrial food system. Major supermarkets have designed themselves around produce that can be grown in huge quantity, shipped long distances, held on the shelf for ages, and consequently sold for a song, and are poorly equipped to do anything else. It's about taking back the ability to produce food for ourselves.