Further tests while a stove is growing

In these days, as we are gearing up for the next festival where I will be able to organize another biochar making workshop, I have started testing my stove a little bit more closely, with a chronometer and an electronic scale. In this way I hope to get some deeper insight while I size up the Elsa design to burn bigger chunks of wood for a longer time.

  

This is the combustion chamber on the top, all connected using a 5 liters recycled tank, a tomato can and some roofing metal sheet. In my idea, the top "mushroom" chimney it's all going to hold tight together so when I have to open it to do the quenching (possibly again without using water, just by chocking the hot charcoal in a proper airtight container) it's going to be easier and less dangerous...

Detail of the inside of the chimney, with the usual cuts and blades to mix secondary air with the smoke coming from below. 

I have also started weighting how much biomass I put inside and how much charcoal comes out at the end: this is an important proportion to check the whole process and to imagine what to expect while sizing it up. With the present stove, I can load about 60-65 grams of biomass and in a couple of burns I got 9 and 8 grams of biochar, which is less than what I was expecting, but considering that the type of quenching return super light and dry biochar maybe it's alright on these small quantities.

 

Also I have started checking about the speed of the whole process: with the super light biomass that I am using (used chopsticks and small twigs) I can get only to about 10 minutes leaving the primary air always open. In this test I have tried to close the inlet of primary air putting some small rocks all around the base of the stove, where the air comes in from underneath. In this way I was able to arrive to almost 12 minutes and in proportion it's already a good improvement. I have also checked the weight of my biochar volume unit (a tomato can), so that now I know how much biochar I have dumped around in the bush or handed out to some people: it's 35 grams.

  
Now I need to keep producing a bit more biochar and find a good location for a bigger deposit: surely there are many areas nearby that can benefit from it! Keep going on...