7-17 La Carbonera: Fun With Pit Kilns
Pacific Views, Natasha, July 21, 2006

So I need some charcoal for my project. I wanted it to be made of one type of local wood that would grow fast and also made good char. On the recommendation of several sources, we selected guaba wood, an Inga spp. After two or three years of growth, the trees can be pushing two stories high and are a popular species for shading coffee crops, so trimmings or full trees would be relatively easy to get.

It didn’t work. While the story of how it didn’t work might be interesting for anyone planning to build a pit kiln, my advice at this point would be not to.* At least not if you don’t have time to fail dismally in the beginning.

For those of you who didn’t get a chance (and why not, for pity’s sake!) to read my 13 page paper on man-made Amazonian soils whose high charcoal organic matter gave them particularly long-lasting properties beneficial to agricultural activities, here’s a brief rundown. The carbon left over after a low-oxygen, slow burning fire is high in super-stable aromatic carbon chains that hold onto nutrients and water. Also, you usually retain 30-50% of the original wood biomass instead of the usual 3% left over after a fire that burns the wood to ash. If you don’t then use that charcoal as fuel, it can be added to soil to improve properties like nutrient and water retention, tilth, drainage in clay soils and certain types of biotic activity. So.

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