Project Drawdown - Biochar Production
Project Drawdown defines biochar as: a biosequestration process for converting biomass to long-lived charcoal (and energy) which can be used as a soil amendment. This solution provides an alternative to disposing of unused biomass through burning or decomposition.
Biochar is a carbon-rich, highly stable charcoal soil amendment produced as a byproduct of pyrolysis, a bioenergy generation process. The production of biochar effectively stabilizes photosynthetic carbon by abating emissions that would otherwise occur if biomass feedstocks were allowed to follow their typical decomposition and disposal pathways, particularly for the great quantity of crop residues that are burned today.
Applying biochar to soils further stabilizes its carbon by protecting it from alternate loss pathways and can reduce other soil greenhouse gas emissions (though this emissions reduction impact is not modeled in this study). In infertile soils, such as sandy soils with low cation exchange capacity, biochar can reduce loss of nutrients through leaching.
Biochar is something of a new category and is not precisely replacing a current practice, but can be seen as an alternative to other uses of biomass such as burning.