Rapeseed cake (RSC) as a novel bulking agent for accelerated biodrying of dewatered sludge

Rapeseed cake (RSC) was first used as a bulking agent for the biodrying of dewatered sludge (DS) in this study. Results showed that adding straw (Trial A), corncob (Trial B), and RSC (Trial C) achieved 47.68%, 32.45%, and 61.71% water removal within 15 days. Especially in Trial D using the mixtures of straw and RSC (1:1, w/w) as bulking agents, the moisture content (MC) in the matrix decreased from 72.53 wt% to 53.01 wt% within 6 days. Proteins and lipids were the main organic matter (OM) components contained in the RSC trial and contributed a high percentage of volatile solids (VS) consumption (51.56%) and bioheat generation (71.77%). Especially, Trial D achieved the maximum calorific value of final products with the low heating value (LHV) of 5843 kJ/kg. These results suggested adding RSC with a low proportion could promote the efficiency of biodrying and transform DS into high-quality solid fuel.