Evolution of microbial communities in biomass stacks during the self-heating process and their influence on fuel properties

Biomass industry development requires large-scale storage of biomass feedstock, but microbial growth in biomass stacks may result in self-heating, smouldering, and safety risks. The 16S rRNA/ITS high-throughput sequencing was employed to investigate the bacterial and fungal community evolution with rice husk and wheat straw. The dominant bacterial and fungal communities were identified based on the relative abundance and alpha diversity analysis. The results showed that the bacteria in the initial biomass samples were mainly Actinobacteriota , Proteobacteria , and Firmicutes . The fungi were mostly Ascomycota and Basidiomycota . Both samples' species richness went down with the increasing stacking time. Field emission scanning electron microscopy (FESEM), biomass fraction analysis, calorific value testing and thermogravimetric-differential scanning calorimetry (TG-DSC) were used to examine the impact of microbial life activities on the microstructure and chemical composition of biomass fuel. The findings indicated that microbial life activities had significant effect on microstructure damage of biomass materials. Hemicellulose was more vulnerable to microbial degradation than cellulose and lignin. Rice husk and wheat straw 's gross calorific value declined by 9.35 %, and 22.35 % in the 7 days stacking, respectively. Fuel analysis revealed that wheat straw was more susceptible to self-heating and spontaneous combustion than rice husk. • The bacterial and fungal community evolution analysis was conducted. • The microbial species richness went down with the increasing stacking time. • Microbial life activities damaged the microstructure of biomass materials. • Hemicellulose was more vulnerable to microbial degradation than cellulose and lignin. • Wheat straw was more susceptible to self-heating than rice husk.