The videos below show how to make mini wood stoves from cans. Three interesting things here:
1) The stoves seem to use fuel extremely efficiently
2) The stoves produce little or no smoke
3) Since they come from old cans, they are cheap
You can see four designs in this video:
This video shows a typical burn, using a tiny amount of fuel:
These are technically known as wood gasification stoves. The idea is to use the "jets" to inject air right into the smoke column so that all the smoke burns instead of escaping.
Learn more about smoke here: Why does smoke come from a fire?
These stoves would obviously be useful for camping. But there's a bigger picture pointed out in this article:
From the article:
Half of humanity cooks over woodfires -- the poorer half. Nearly half the world's wood supply is used as fuel...
For most, there's little alternative to burning wood -- wood energy is here to stay.
In fact burning wood is no bad thing: the efficient use of wood fuel is much more eco-friendly than more efficient and convenient fuels like kerosene and natural gas (LPG). LPG emits 15 times more CO2 (carbon dioxide) per kg than wood, and kerosene nearly 10 times as much. CO2 is the main source of global warming.
And as long as wood burning is sustainable and doesn't cause deforestation, its CO2 emissions are neutral -- the CO2 released in the fire simply gets recycled back into more trees.
These mini stoves give people a way to use wood far more efficiently. In this paper, you can see cross-sections showing why wood gasification stoves work so well, and instructions for construction: