Multivariate insights of bulking agents influence on co-biodrying of sewage sludge and food waste: Process performance, organics degradation and microbial community

As a prerequisite additive, bulking agent played an essential role on organic wastes biodrying by affecting the organics degradation and microbial consortia. In this study, a series of experiments were conducted to explore the relationships among the type of bulking agents, organics degradation and microbial community evolution. In line with the excellent physiochemical properties, corncob was found to be more desirable for biodrying with more water removal (62.13% vs. 53.70% for sawdust and 51.72% for straw) and higher energy efficiency. Furthermore, different bulking agents showed different biodegradability and affected co-existed organics degradation. In detail, corncob upgraded the amylase and lipase activities, thus promoting the degradation of readily degradable carbohydrates and lipids in feedstocks, which accounted for >60% of the bio-heat sources for water evaporation. In addition, pyrosequencing analysis revealed that Bacillus (>50%) and Ochrobactrum (>40%) were the dominant genera in thermophilic and cooling phases, with degradation capacities of readily degradable substrate and lignocellulose, respectively. And the pathogens, e.g., E. coli and K. pneumonia, were seriously inhibited by high matrix temperatures in corncob trial. These results not only suggested the corncob was a promising bulking agent, but the potential microbial mechanisms for organics degradation were also revealed.