Consistency of biochar properties over time and production scales: A characterisation of standard materials

Users of biochar in the field require this product to reliably meet its declared specifications. For the first time, this work investigated, whether these specifications could be reproducibly obtained as a sole function of the thermal history of the biomass feedstock during slow pyrolysis, irrespective of the type and scale of the production unit. Using volatile matter content as a proxy for a wider set of biochar quality parameters, biochar from units at scales from grams to hundreds of kilograms, representing three main types of slow pyrolysis units (fixed bed, screw reactor and rotary kiln) were investigated. For the first time we showed that comparable biochar could be produced by these very different pyrolysis units, with good reproducibility within individual as well as among separate production runs.