> Those three billion people don't live in too close proximity. Apologies if I misunderstood your point but I would think many of those people do live in close

> Those three billion people don't live in too close proximity. Apologies if I misunderstood your point but I would think many of those people do live in close proximity. My view is from anecdotal evidence not research, but its common to see wood/charcoal/dung fires when you see how people cook in slums all over the world. These people are tightly packed and very much using wood or similar to cook alongside gas/metho type stoves.