Evolution Of Microbial Community In Biomass Stacks And Its Influence To Fuel Properties

China has abundant biomass resources,and the effective utilization of biomass energy is of great significance for accelerating the 3060 carbon neutrality goals and building beautiful rural areas.The development of the biomass energy industry requires large-scale storage of biomass raw materials.However,the growth of microorganisms in biomass stacks can lead to heat accumulation and even thermal runaway,causing spontaneous combustion and threatening life and property safety.This paper deeply investigates the evolution of microbial communities during the storage process of biomass fuels and analyzes the impact of microorganisms on fuel properties.This paper investigates the microbial diversity in the self-heating process of biomass stacking,using molecular biology techniques based on 16S rRNA/ITS.Through data processing methods such as species annotation,Alpha diversity analysis,and Beta diversity analysis,the effects of factors such as raw material chemical composition and storage period on the evolution of microbial communities are systematically analyzed.The results show that in the initial biomass sample,bacteria are mainly actinobacteria,proteobacteria,and firmicutes,with relative abundances of 43.22%,33.46%,and 16.36%in the rice husk sample,and 76.58%,12.11%,and 7.28%in the wheat straw sample.The fungi were mainly composed of Ascomycota and Basidiomycota,with relative abundances of 94.79%and 3.67%in the rice husk sample,and 69.33%and 30.08%in the wheat straw sample.With the increase of storage time,the timedependent dominant bacterial community in the biomass includes nutrient-rich Firmicutes(r-type)and nutrient-poor Actinobacteriota and Proteobacteria(ktype).During the early stages of degradation,when the content of cellulose and hemicellulose is high,the r-type bacteria proliferate rapidly and become the dominant community.During the later stages of degradation,when cellulose and hemicellulose are depleted,k-type bacteria and fungi that can degrade and utilize lignin become dominant,and this stage lasts longer.Microbial growth can cause changes in the physical and chemical properties of biomass raw materials.By means of techniques such as field emission scanning electron microscopy,infrared spectroscopy,and calorimetry testing,the impact of microbial activity on the micro structure and fuel characteristics of biomass fuels can be analyzed.The results show that with the increase of storage time,easily degradable polysaccharides and lipids are degraded by microorganisms into small molecules of alcohols and acids.The main chemical components such as lignin,cellulose,and hemicellulose show a decreasing trend in content.In the pine wood samples,the lignin content decreased by 3.96%,the cellulose proportion decreased by 9.9%,and the hemicellulose proportion decreased by 16.9%;in the straw samples,the lignin content remained almost unchanged within seven days,while the cellulose content decreased by 13.8%and the hemicellulose content decreased by 23.2%.Hemicellulose content decreased the fastest,while lignin content decreased the slowest,due to the stable structure of lignin and the fact that lignin-degrading bacteria are mostly k-type bacteria and fungi.The calorific value of biomass materials also decreases to varying degrees with the increase of cultivation time.In the self-heating process,herbaceous biomass materials have a greater loss of calorific value than woody biomass materials.Under the conditions of 40℃ and 50%humidity,the calorific value of pine wood decreased by 8.1%after 7 days,while the calorific value of straw decreased by 20.5%after 7 days.Microbial activity is the main reason for the decrease in fuel calorific value.This paper provides a useful scientific exploration to elucidate the microbiological mechanisms during the storage of biomass and to advance the self-heating safety control of the stack.This is beneficial for reducing the safety hazards of large-scale utilization of biomass.