Oh, so I take it that you are a big fan of the Agenda 21 and UN Sustainable Development? That is certainly what your post indicates.
Take it from this habitat restorationist for nearly 25 years: You have no idea what is "good for the environment." What you are describing is both an urban prison and the destruction of topsoil.
China is an anthropogenic landscape and has been for thousands of years. For that entire time, the soil received the minerals that people consumed in vegetation. To suddenly pull the people off that land is a horrible idea. What will grow there? Who will weed it? Or are they going mechanize farming, feed it natural gas, and deplete that soil? How are they going to separate out the toxic minerals from that sewer cake while leaving the trace elements for growing food? What makes you think sewage treatment plants are such a good idea compared to composting. Do you know what the THM in that treated outfall will do to their fisheries?
I promise you, a third, at least of the farms in the American Midwest would blow away and turn to sand in three years without additional ammonia. My take is that the same will happen to China once they've used up what has been built.
Worse, once the people are gathered into cities they are ripe for extermination at the throw of a switch unless they obey. So I take it you are a big fan of tyranny and population control as well.
So I suggest you dispense with the popular whiz-dumb as regards what is "good" and start thinking about what is good for topsoil over the long run. It is the most precious resource on earth.
Non-farming Americans have no true understanding of the land, other than a logical expectation of cause and effect.
The concept of urban prisons is wonderful, because after all the taxation and denial to the farmers and red-country folk they will not be so generous when it comes to basic survival. Let the truckers stop rolling for 4-7 days in the US and the cities will be in trouble; a disruption in gas/oil will prevent follow on products and food.
I actually look forward to the day that the cities self consume themselves along with their political clout and socialist mentality; only those individuals and the familys on corporate farms shall remain in this vision.