Effect of biodrying of lignocellulosic biomass on humification and microbial diversity

Effect of high corn straw loads on short-chain fatty acid production in semi-continuous rumen reactor

Ruminal microorganisms can efficiently hydrolyze biomass waste for short-chain fatty acid (SCFA) production. However, the continuous SCFA production by ruminal microorganisms at high loads is unclear. In this study, the effectiveness of a rumen semi-continuous reactor at high load for SCFA production was explored. Results showed that SCFA concentration reached 13.3 g/L at 8 % (w/v) corn straw load. The higher the corn straw load, the lower the volatile solid removal. Rumen microbial community composition changed significantly with increasing corn straw load. A significant decrease in bacterial diversity and abundance was observed at 8 % corn straw load. Some core genera such as Prevotella, Saccharofermentans, and Ruminococcus significantly increased. As corn straw loads increased, the expression of functional genes related to hydrolysis and acidogenesis gradually increased. Thus, the 8.0 % load is suitable for SCFA production. These findings provide new insights into high load fermentation of ruminal microorganisms.

Change of core microorganisms and nitrogen conversion pathways in chicken manure composts by different substrates to reduce nitrogen losses

Due to the rapid development of animal husbandry, the associated environmental problems cannot be ignored, with the management of livestock and poultry manure emerging as the most prominent issue. Composting technology has been widely used in livestock and poultry manure management. A deeper understanding of the nitrogen conversion process during composting offers a theoretical foundation for selecting compost substrates. In this study, the effects of sawdust (CK) and spent mushroom compost (T1) as auxiliary materials on nitrogen as well as microbial structure in the composting process when composted with chicken manure were investigated. At the end of composting, the nitrogen loss of T1 was reduced by 17.18% relative to CK. When used as a compost substrate, spent mushroom compost accelerates the succession of microbial communities within the compost pile and alters the core microbial communities within the microbial community. Bacterial genera capable of cellulose degradation (Fibrobacter, Herbinix) are new core microorganisms that influence the assimilation of nitrate reduction during compost maturation. Using spent mushroom compost as a composting substrate increased the enzyme activity of nitrogen assimilation while decreasing the enzyme activity of the denitrification pathway.

The synergistic regulation of sewage sludge biodrying and greenhouse gas reduction by additives

As a dewatering method of high moisture solid waste sludge, biodrying still faces environmental problems such as material loss and greenhouse gas emission in the process of treatment. In this study, biochar and magnesium chloride were used to explore the synergistic effect of enhancing sludge biodrying and reducing greenhouse gas emissions. The highest temperature of biodrying was raised to 68.2 °C within 3 days, extending the longest high-temperature period to 5 days, which reduced the water content to 28.8 % in the single addition of biochar treatment. The complex addition increased the NH4+-N content of materials by 57.49 % and decreased the NO3--N content of materials by 40.62 %. The use of additives significantly reduced the emissions of CO2, CH4, and N2O compared to the no-addition treatment. The increase in dominant Actinomycetes and Chloroflexibacter was the main reason for the reduction in gas emissions.