Composting Practices and Pathogen Reduction Joan Jeffrey, Extension Veterinarian University of California School of Veterinary Medicine VMTRC---TULARE, CA

Composting Heat generated by microbial activity Application of heat over time kills mesophilic bacteria and favors thermophilic bacterial population Bacteria in mature compost compete against and inhibit pathogen regrowth

Composting methods Passive Aerated Static Piles or Windrows Stacked Pile Aerated Stacked Pile Windrow Enclosed System Containerized Systems (Aerated Static Piles in a box)

Methods applicable to non-green waste Non-green waste = food, dairy products, raw/cooked meat, dead animals (cows, poultry, fish)

Methods applied to poultry carcasses Two stage bin composting Refers to 2 heating cycles Containerized system Reference FS 717; U. of Maryland

Methods suitable for blood/feathers Windrow Most common method for green waste/manures >3000 facilities in USA Rows = 8 ft high x feet wide Approved by EPA for pathogen destruction if windrows are turned 5x in 15 d and temperatures stay > 131 F (55 C) Aerated Static Pile Piles 7 to 9 feet high connected to blowers Approved by EPA for pathogen destruction Requires 131 F (55 C) for 3 days

Federal guidelines for pathogen destruction in compost For windrows—15 days, turned no less than 5 times, temperature of 131 F (55 C) For aerated static piles—3 days at temperature >131 F (55 C) Governed by Code of Federal Regulations 40, CFR Part 503, 1993

Killing of pathogens during composting Temperature (thermal kill) Ammonia (chemical kill) Microbial antagonism

Rate of microbial decomposition A function of surface area i.e. whole carcasses would compost at a slower rate than tissues like blood or feathers

Temperature-Time relationships for pathogen reduction D-values: time required for 1 log reduction in a pathogen at a given temperature Can compare hardiness of different organisms Used to establish pathogen elimination criteria

Poultry pathogens addressed by specific studies Senne, D. A., et al. (1994) Highly Pathogenic Avian Influenza virus and EDS-76 Adenovirus Compost Bin method used with poultry carcasses Two-stage Turned after 10 days Average temperatures C 1/20 tissues positive for adenovirus at d 10 0/20 tissues positive for virus at d 20

Poultry pathogens addressed by specific studies Conner, D. E. et al. (1991) Fungi and coliform, aerobic, anaerobic, thermophilic and thermotolerant bacteria were represented S. enteritidis, S. typhimurium, S. seftenberg, L. monocytogenes, E. coli, P. multocida and Aspergillus fumigatus Used wheat straw, peanut hulls and other materials Pathogens placed into carcasses No bacteria after stage I of composting No fungal spores after stage II of composting

Poultry pathogens addressed by specific studies Murphy, D. W. et al. (1990) Newcastle disease virus Infectious Bursal Disease virus Bin compost method for carcasses Two stage composting method

Other pathogens addressed by specific studies M. tuberculosis (Morgan & McDonald ’69) Salmonella, Shigella, poliovirus, enterovirus, parasite cysts (Gaby ’75) Coliforms, Salmonella, Ascaris ova (Hay ’96) Salmonella, bacteriophage (Epstein ’76 and others)

Potential problems Recontamination by equipment, other vectors Regrowth Only possible for bacteriaa Studies cite salmonella and coliforms as most likely to regrow These organisms are used as indicators of pathogen elimination

Use of indicator organisms to ensure pathogen destruction Sampling for indicator organisms is conducted to validate composting processes (temperature/time) (USEPA 40) Temperatures are then verified for each compost pile or windrow Microbial sampling is generally not required for every batch assuming consistent feedstock and processing

USEPA standards for Class A biosolids Fecal coliform level of < 1000 MPN per gram of dry solids, OR Salmonella spp. level of < 3 MPN per 4 gram of dry solids

Conclusions Composting methods for pathogen destruction are well documented Monitoring of the composting process is a valid substitute for microbiologic testing

Conclusions Studies addressing major poultry pathogens have been conducted Due to greater surface area, blood, feathers and processing waste should compost more rapidly and uniformly than carcasses