<p><pre><code>   The city has a ring of waste disposal 
   sites around it. Many of them are fully 
   unregulated and illegal. Basically a 
   catastrophe in the making.
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This is not a problem of big cities as such but one that Beijing (and China more generally) has because it has only recently transitioned from a developing country. Indeed, modern sustainable waste disposal becomes more economical for bigger cities.<p><pre><code>    They grow like cancer in the outskirts
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I&#x27;m afraid I can&#x27;t follow your argument here. Land consumption is inversely correlated with density. Compare Hong Kong with Los Angeles. As I said in another answer, all the world&#x27;s population would fit Texas if Texas was as densely populated as London.  The tendency for suburban sprawl we observer around big cities can be counteracted with appropriate legislation.<p><pre><code>   the quality of life is really really amazing
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I&#x27;m happy to believe this, but it&#x27;s not sure this is scalable to and sustainable for  the projected 10 Billion population.