More than half the worlds population cooks over open fires or small charcoal or biomass stoves. These burn fuel incompletely, producing carbon monoxide and smoke that cause 1.5 million deaths a year. Envirofits Cookstove burns the same easily found wood but does so more completely to cut emissions by more than 80 percent and use half as much fuel. The can-shaped stove has a precisely measured opening that lets in enough air to fan the flames, yet not enough to cool it and slow down combustion. A chimney-like tube inside helps funnel in fresh air, and a ceramic lining insulates the stove to keep the fire hot and burning efficiently.
Looks like they want to charge $15 for that unit through EnviroFit
There are a lot of 'rocket stove' plans on-line. A google search will show quite a few, including some very low tech ones on youtube. Most are very efficient at burning sticks and such. I thought the basket for pellets was a good idea and my try something of the sort with my stove.
A couple commercial ones I have seen that are tough and/or very efficient are the ones by Phoenix Stoves, and the older Stove-tec ones. My brother has the Phoenix stove and uses it a lot camping-he filled the cylinder between the combustion chamber and the cylinder with volcanic ash and it insulates very well for safe handling. Prices have tripled in the past decade on most commercial ones: