[Terrapreta] Clarification about "simple" charcoal devices

[Laurens Rademakers]

Günther, Kevin, Lou, Sean and the others,

It seems like there has been a misunderstanding about the short "warning" I made against simple charcoal kilns. I didn't intend to downplay anyone's efforts to produce charcoal this way. 

I made the warning because to me biochar / terra preta is still tied to a very particular context: that of the tropics, close to forests and carbon-rich ecosystems, the destruction of which can be limited by biochar.

And it is in this context that care must be taken to make the system as efficient as possible. Because your initial biomass feedstock in this environment will often be wood from secondary regrown forest, it is important to make the most of it, else you do not alter the "slash-and-burn" cycle enough and thus your crucial added benefit - that of reducing deforestation - can get lost.

Efficient does not necessarily mean "large". One of the Biochar Fund's goals is precisely to develop a village-scale plant that uses the syngas for power production (capacity smaller than 20kW), and use it in this specific context.

Small kilns or retorts made for use by individuals in other (agroecological) contexts might be quite interesting, provided they don't emit too much methane. So I wasn't warning against this at all. 

Apologies for any misunderstandings.

Regards,
Lorenzo
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