Effect of co-composting cattle manure with construction and demolition waste on the archaeal, bacterial, and fungal microbiota, and on antimicrobial resistance determinants

Citation

Holman, D.B., Hao, X., Topp, E., Yang, H.E., Alexander, T.W. (2016). Effect of co-composting cattle manure with construction and demolition waste on the archaeal, bacterial, and fungal microbiota, and on antimicrobial resistance determinants. PLoS ONE, [online] 11(6), 1-21. http://dx.doi.org/10.1371/journal.pone.0157539

Plain language summary

Agricultural operations often produce large amounts of manure which if applied directly to agricultural land can have a negative effect on soil, water, and air quality through contamination, odour and gas emissions, and nutrient leaching. Manure is also a reservoir of antimicrobial-resistant bacteria and the levels of resistant bacteria in feces can increase following administration of antimicrobials to livestock. If left unattended, the levels of resistant bacteria in feces or manure can increase over time, resulting in greater concentrations compared to freshly deposited material. The composting of manure results in a product that is more nutrient-stable and free of microbial pathogens and phytotoxins. Furthermore, composting may also decrease the concentration of excreted antimicrobials, resistance determinants, and resistant bacteria. In Alberta, approximately 25% of total municipal solid waste is comprised of construction and demolition. Previously it was demonstrated that the addition of construction and demolition waste to feedlot cattle manure resulted in composted manure with a higher sustained temperature, lower water content, higher pH, and altered mineral contents. However, the effect that these changes have on the antimicrobial-resistant bacteria and prevalence of pathogens was not examined. Therefore, the objective of this study was to investigate the dynamics of the archaeal, bacterial, and fungi microbiota composted feedlot cattle manure to determine what microbiological effect the addition of construction and demolition waste had during composting. It was observed that the concentration of 10 out of 12 antimicrobial resistance genes in the compost mixtures decreased significantly over a 99 day period of composting, regardless of compost ingredients. In addition, the amendment of construction and demolition waste did not affect the persistence of antimicrobial resistance genes or community structure, including pathogens, of the compost microbiota. Therefore co-composting construction and demolition waste with cattle manure offers a safe, viable way to divert this waste from landfills.

Abstract

Agricultural operations generate large quantities of manure which must be eliminated in a manner that is consistent with public health guidelines. Meanwhile, construction and demolition waste makes up about 25% of total solid municipal waste. Co-composting of manure with construction and demolition waste offers a potential means to make manure safe for soil amendment and also divert construction and demolition waste from municipal landfills. Therefore, the archaeal, bacterial, and fungal microbiota of two different types of composted cattle manure and one co-composted with construction and demolition waste, were assessed over a 99-day composting period. The microbiota of the three compost mixtures did not differ, but significant changes over time and by sampling depth were observed. Bacillus and Halocella, however, were more relatively abundant in composted manure from cattle fed dried distillers' grains and solubles. Proteobacteria and Bacteroidetes were enriched at day 0 and Firmicutes at day 99. The fungal genus Kernia was the most relatively abundant overall and was enriched at day 0. The concentration of 12 antimicrobial resistance determinants in the compost mixtures was also determined, and 10 of these determinants decreased significantly from days 0 to 99. The addition of construction and demolition waste did not affect the persistence of antimicrobial resistance genes or community structure of the compost microbiota and therefore co-composting construction and demolition waste with cattle manure offers a safe, viable way to divert this waste from landfills.