Search

Aim The aim of this study was to determine the prevalence of microbial pathogens in manure of dairy lagoons in California. Methods and results To determine pathogens in dairy manure stored in anaerobic lagoons of dairy farm, an extensive field study was conducted across California to sample manure from 20 dairy farms. Samples were analyzed to determine the prevalence of indicator Escherichia coli , Shiga toxin producing E. coli (STEC), Salmonella , and E. coli O157: H7. To test the E. coli , STEC, and Salmonella , we used agar culture-based method followed by polymerase chain reaction (PCR) method. In addition, a real- time PCR based method was used to determine the presence of E coli O157: H7. Study demonstrated that the prevalence of Salmonella in manure sample is lower than E. coli. The presence of Salmonella was found in 2.26% of the samples, and both the culture-based and PCR methods yielded comparable outcomes in detecting Salmonella. Moreover, ∼11.30% of the total samples out of the 177 were identified as positive for STEC by qPCR. Conclusion These findings demonstrate that indicator E. coli are abundantly present in anaerobic lagoons. However, the presence of STEC, and Salmonella is substantially low. [ABSTRACT FROM AUTHOR]

This study quantifies the financial and environmental impacts of a microalgal bioenergy system that attempts to maximize circular flows by recovering and reusing the carbon, nutrients, and water within the system. The system produces microalgal biomass using liquid digestate of an anaerobic digester that processes 45 metric tons of food waste and generates 28.6 m3 of permeate daily in California, and three energy production scenarios from the biomass are considered: producing biodiesel, electricity, and both. In all scenarios, the resulting energy products delivered only modest reductions in environmental impacts as measured by carbon dioxide equivalent emissions. The carbon intensities (CIs) of biodiesel from this study were 91.0 gCO 2 e/MJ and 93.3 gCO 2 e/MJ, which were lower than 94.71 gCO 2 e/MJ of conventional petroleum diesel, and the CI of electricity from this study was 70.6 gCO 2 e/MJ, lower than the average electricity grid CI in California (82.92 gCO 2 e/MJ). The economic analysis results show that generating electricity alone can be profitable, while biodiesel produced via this system is not cost competitive with conventional diesel due to high capital expenses. Thus, generating electricity in lieu of biodiesel appears to be a better option to maximize the use of waste flows and supply lower-carbon energy. [Display omitted] • Permeate from a digester had sufficient nutrients for microalgae cultivation. • Combining anaerobic digestion and microalgae limitedly reduced environmental impacts. • Electricity generation better than biodiesel financially and environmentally. [ABSTRACT FROM AUTHOR]