I think the yield differences in a dedicated charcoal retort vs an imbert gasifier would be fairly significant. This is why All Power Labs had a different version of their GEK that was used for biochar production—BEK. That being said, an imbert might be a good choice if viewed from a financial aspect… i.e. it might be good enough, especially if you already own an imbert gasifier.
A charcoal retort with a dedicated heat exchanger is a very interesting proposition. This was why I believe in charcoal gasification so much. The basic premise being that we simply split gasification into two groups… drying / pyrolysis happens in the retort, and oxidation / reduction happen in the gasifier… This versatility lends itself well to market opportunities.
In fact, the only way we can compete on a philosophical level when comparing biomass to charcoal gasification, is if we are capturing the left over BTUs during pyrolysis… Any time there is a chimney or radiator involved in the equation, there is wasted heat that is blowing off to atmosphere… So, with my example above, the chimney is there due to my laziness in drawing a heat exchanger
I personally hated tar so much that it drove me towards the dark side… I was thrilled to never, ever have to deal with it again… And, in my experience, the performance with gasification was more consistent with charcoal vs biomass (especially on start up).
So, if the dedicated retort can be specialized for heat capture, AND is superior in char production, to me, I feel like I’m on the right path.
With all this being said, there is the “hassle” factor with char… And for many, this is a turn off. i get it… It’s all good.