Effect of biochar on generic and antibiotic resistant bacteria in dairy cattle manure composting

Authors: Agga, Getahun; NETTHISINGHE, ANNESLY - Western Kentucky University; STRUNK, WILLIAM - Western Kentucky University; WOOSLEY, PAUL - Western Kentucky University; Sistani, Karamat

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: 3/18/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Biochar dairy manure amendment before composting may enhance its effectiveness as a preharvest food safety measure to reduce foodborne bacteria. We evaluated the effect of composting dairy manure amended with 0%, 2%, 4%, and 10% (w/w) biochar on the concentrations and prevalence of generic (E. coli and enterococci), and antibiotic resistant strains (extended spectrum beta-lactamase producing (ESBLs) E. coli, 3rd generation cephalosporin resistant [3GCr], tetracycline resistant E. coli [TETr], and TETr enterococci. Fresh manure was mixed with the appropriate amounts of saw dust and biochar; the mix was then placed in the tumblers. The field experiment was set up in individual tumblers, replicated four times, and composted for six months. Samples collected from the manure mix (n=16) and from the final compost (n=16) were cultured for the enumeration of the bacterial strains. Data were analyzed by Poisson regression model to assess the effects of biochar concentrations and composting phase (manure and compost) on bacterial concentrations. Composting significantly reduced generic E. coli concentrations on a dose-response manner (P=0.02); the highest effect observed with the 10% biochar. Composting also significantly (P=0.015) reduced the concentration of generic enterococci, with no significant (P=0.304) dose-response relationship with respect to percent biochar. TETr E. coli were not enumerable from compost samples and TETr enterococci were enumerable only from a single compost sample obtained from 0% biochar. 3GCr-and ESBLs-E. coli were detected from raw manure mix and not from any compost sample. Composting effectively removes antibiotic resistant bacteria, while also significantly reducing concentrations of generic strains from dairy manure. Biochar amendments to dairy manure significantly reduced generic E. coli concentration in a dose-response manner. Biochar did not modify the effect of composting on the concentrations and detection of other bacterial strains. Other potential benefits of biochar such as compost duration and quality should be assessed under field conditions.