Flow and yield stress behaviour of ultrafine Mallee biochar slurry fuels: The effect of particle size distribution and additives

► Polybutadiene-maleate is more effective in increasing the solids loading of biochar slurries. ► Unltrafine biochar slurries in excess of 40 wt% solids have been prepared. ► Yield stress decreases with increasing particle size of the biochar slurries. ► Power law models described the relationship between yield stress and particle size. ► The yield stress-volume fraction relationship of self-similar PSD slurries is also power law.