W. Bogale, Published in the Ethiopian Journal of Education and Sciences, Vol 5, No 1 (2010)

Mr. Bogale has been working in Ethiopia, and has developed a carbonizer that would allow a small land-holder to make charcoal out of agricultural residues and then dry and package that charcoal either for their own use, or for sale.

His paper has a very good table that helps make the case for the carbonizer, extruder system and it is available online through African Journals Online:
http://www.ajol.info/index.php/ejesc/article/view/56314

the abstract:
Abstract