Research has shown that the Amazonian compost worm Pontoscolex corethrurus consumes particles of char after fires.1 2 These particles are ground together with organic matter, minerals, and bacteria in the worm's digestive tract. The char particles are likely reduced in size when they are ground against each other. It is therefore hypothesized that worms played a role in the formation of Terra Preta soils. Since Terra Preta is exceedingly fertile and stable, it is also suggested that vermicomposting organic matter and biochar together has the potential to form a very fertile substrate.
Experiments in biochar vermicomposting with northern hemisphere composting worms, particularly Eisenia fetida, have been successful.3 An 8% addition of biochar to wood feed based in sewage sludge increased the production of cocoons by 66%.4
In sum, biochar improves the health and reproductivity of the worms, creating a more efficient and productive vermicomposting system, and it improves the fertility of the vermicompost by promoting aggregation and retaining more of the available mineral nutrients in the vermicompost.