I stumbled across this forum while surfing my favourite subject area. I found your ideas regarding charcoal/wood gasification interesting because this is almost exactly the same road that I want to
go down. This link http://six6.region-stuttgart.de/sixcms/media.php/773/ABS-61-Jesper-Ahrenfeldt.pdf
contains information regarding the thesis from Jesper Ahrenfeldt regarding a 2 stage gasifier with partial oxidation of the pyrolysis gases to reduce the tar content. This link is also on the GEK site. This gasifier was built around 2005 so these ideas are not new. There is also book from 1907 called "A Treatise on Producer-Gas and Gas-Producers" which gives a good insight into the technology available at the end of the 18th century. I personally found the Riche Double-Combustion Wood Gas-Producer very close to the kind of gasifier design I would like to make (but a little bit smaller!!). We have the advantage nowadays of much better materials technology with greatly reduced costs. Maybe these connections give you a little food for thought.