Relationships between Wood Density, Wood Permeability and Charcoal Yield

Abstract

Charcoal yields for woods from different tree species can vary widely. Charcoal is believed to consist of the combined residues of primary wood decomposition reactions and of secondary reactions undergone by volatile products en route to the wood surface. It might be expected that the harder it is for these volatile products to migrate to the wood surface, the more carbon will be laid down as a result of secondary reactions. Two wood properties that could be expected to influence volatiles’ migration rates are density and permeability. Initially, experiments were conducted to establish whether density could be used as a predictor of charcoal yield. Early results seemed promising but extension of the investigation to other woods showed that links between density and charcoal yield were tenuous. A program to study the influence of wood permeability on charcoal yield was then initiated. Early results for samples from several Brazilian grown eucalypts confirmed the lack of a relationship between density and charcoal yield but suggested a stronger link between permeability and charcoal yield. However, extension of the investigation to woods of widely varying densities and permeabilities showed that no straightforward relationships exist between density, permeability and charcoal yield.