Doctoral Dissertations

Fei YaoFollow

Date of Award

12-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Environmental and Soil Sciences

Major Professor

Jennifer M. DeBruyn

Committee Members

Shawn Hawkins, Sindhu Jagadamma, Rebecca Tiffany Trout Fryxell, Forbes R. Walker

Abstract

Composting is a widely used method for the treatment of animal waste, but improper management leads to a poor performance. Benefits of biochar have been identified in animal waste composting including reduced odor and greenhouse gas emissions, and improved heating performance. However, the benefits of low amendment rates of biochar addition for composting are unclear. Our research goal was to evaluate the effects of composting, with and without biochar addition, on poultry litter microbial community structure, N-cycling, and pathogens in commercial poultry farm and further determine the effects of temperature and moisture on the presence of pathogens through a laboratory simulated composting experiment. Our research indicates that composting changed bacterial and fungal community structures in poultry litter. Across all the samples from two compost trials, Firmicutes and Acidobacteria were the dominant bacterial phylum. Ascomycota was the predominant phyla in fungal community. Abundance of N-cycling functional genes did not change in the first trial, but three denitrification genes (nirK, nirS and nosZ) and amoA were increased in the second trial. Low amounts of biochar (1%) did not influence microbial community structures or the relative abundance of selected taxa in either of two compost trials, but it increased the abundances of denitrification genes in the first trial.

Marker genes of Salmonella, E. coli O157:H7, C. jejuni and C. perfringens were used to evaluate the pathogen removal in windrow composting and simulated composting. High moisture content and low moisture content poultry litter were tested in a simulated composting experiment. Decreased abundances of Salmonella, E. coli O157:H7 and C. jejuni after composting indicated the benefits of composting for pathogen removal. Biochar addition (1%) did not improve the windrow composting performance. Thermal inactivation decreased total bacterial abundance in simulated composting at 50 °C for high moisture content litter and 62 °C for low moisture content litter. In summary, changes in poultry litter microbial community structure and N-cycling functions were detected during in-house composting, but low amounts of biochar did not increase compost performance or pathogen removal. This study also highlights the importance of initial litter moisture content and heating temperature for pathogen removal.

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