I first tried burning hulls by simply throwing them in wood stove. It never flamed well. Next, on side of strongly burning woods. The shells next to strong flame burned but never continued to reduce the rest to ashes. I stopped there. I thought it was not possible. Fuel is not the only possible use of cocoa shell anyway.
I gave it a second thought when I saw a video demonstration of rice hull stove. A small fan helps the burning process. I remember seeing a similar setup when I was in Benguet. A strong blower fan facing against a file of large firewood was keeping the flame strong.
The same concept might actually worked for burning cocoa shells. It might work better if I pack it closely in a cylinder, like a charcoal briquette and like a cigarette.
For a really quick and easy work trial. I gathered an empty sardine can. Tightly packed some shells into it. I provided a hole by placing a cardboard tube in the middle.
Time for testing. I placed one end against candle flame to start the ember. Removed it when 50% of surface was red hot. Then placed an electric fan in front. Ember got stronger and almost covered the whole surface after few seconds. I also noticed the ember getting weaker as it goes away from breeze and completely died out few minutes after turning off the fan.
Plenty of white smoke. Thankfully it is not black. I heard from someone that coffee hulls cannot be used as fuel to power electric generators because of its black smoke. It harms the environment I think. The ozone layer maybe. On the other hand, I need sort of mechanism to vent it outside. Else, my house will be like floating in clouds.
I will continue experimenting on this whenever have time.