Jatta Charcoal Retort, The Gambia
My retort is in my back yard. It is a drum with a fairly tight lid and a piece of pipe letting volatile gasses take over the initial firing in the firebox underneath. The drum is enclosed in a rock and soil and lime plaster wall. For a quick start I surrounded the drum with small branches or crop waste before covering the top with a scrap iron sheet with a gap for smoke to escape in the beginning. The drum costs money, the rest is labor.
The biomass is crop waste and or tree trimmings. Some material is up to 50 mm thick and still chars all through. Like was stated on the list, the char appears to be about 40 %. After initial smoke, the volatiles take over and burn with a roaring sound. Sorry, no analysis of the off gasses, but I trust I am not a poluter beyond the normal CO2. With adequate investment the excess gas or heat can be utilized, not likely an easy option for most third world farmers.
Where does all the biomass come from? Plant it! People still get rid of lots of it to clear roadsides and farms here. OTOH, I am planting more biomass every year and my soil is improving in the process. My mini climate is improving too as many of the trees retain their leaves during the dry season . Jatropha curcass is a soil improver and wind break. Not useful for char, but it makes great fuel oil for lamps and soap making. The oil cake makes good methane gas for cooking. The digester effluent is mixed with the bio char before it put in the planting holes on the field. Soil improver, energy and soil micro-organism inoculant.
Is it economic? What is the meaning of that? Maybe, when I get a good harvest, which depends on many other factors, like rain, etc. After all, food prices are going up because of increasing scarcity. Maybe some people think they can eat their economic gain in the form of money. During the last world war money could not buy food that was not there! You think the government is going to regulate food production to assure economic gain and sustainability? Or the market place will be regulating the climate in a timely fashion so that harvests will be reliable. My conclusion is that the real value is the food and other resources provided by the life of the plant springing from the soil.
Why am I doing this? I think it is a usefull thing to do. There was a quotation that I recognized as true: 'The Spritual precedes the material'
The economic consideration will not bring a solution. It has in fact been the cause of the problem!
So, considering economic criteria, maybe no present value seen yet , but the net value will be having a future worth having at all. It is a choice and it better be a collective choice. If it does not do all as expected, do we lose anything?
Bwiam village, WR