The coal fired brick may indeed not be sustainably produced,but the coal is going to be burnt anyway,and the energy derived therefrom mostly used to produce steel used in cars,or run electric lighting and so forth-not in sustainable activities.

I unhappily will never be able to travel to China,but being acquainted with the habits of poor but fairly self sufficient people here in the mountians of the American south,I would bet that those overengineered bricks are still in use hundreds of years from now if they are as good as the ones commonly used here.

Given the fact that the coal WILL be burnt,I can't immediately think of a better use of it.

I expect to see the solar stoves in common use here in the states in poorer communities within a few years.

As to the health hazards of fires in tents,it seems to be well established that smoke inhalation is a major source of health problems when people live in similar structures.One good friend of mine died of CO poisoning inside a modern house a a result of a leaky flue and a furnace located under a faily tightly sealed den.It seems unlike that a traditional yurt or other movable structure would be THAT airtight.