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Catastrophic Mortality Composting: Is It Safe and Effective?

Posted on: Sunday, 3 July 2005, 03:00 CDT

Primary Audience: Flock supervisors, Veterinarians, and Researchers

SUMMARY

Catastrophic composting can be an effective disposal method. This is especially true for destruction of viral disease agents. However, further research needs to be completed to verify safety and efficacy of composting mortalities as the result of other infectious diseases. Although mortality composting does show promise, burial will be the major disposal method used in mass mortality situations. Exceptions will be when limitations of shallow ground water or frozen ground in winter months prevent its use.

Key words: catastrophic, composting, mortality, poultry, disease

2005 J. Appl. Poult. Res. 14:414-416

DESCRIPTION OF PROBLEM

Composting of animal mortalities has increased in popularity in recent years due to decreased availability and increased costs associated with the traditional animal rendering industry. With increasing foreign animal disease and transmission concerns, composting has received considerably more attention as a potential method for mass mortality disposal. Disposal of mass mortalities has traditionally been completed through burial or burning of carcasses. However, burning of mortalities raises concerns with airborne infectious agents. Burial is currently the main option supported by many state agencies as the preferred disposal method in catastrophic mortality events. However, other disposal options must be available when limitations of carcass burial are present in areas of shallow ground water or in winter months when soil may be frozen.

Composting Process

Composting is the natural decomposition of organic materials by aerobic (oxygen-dependent) bacteria and fungi. However, microorganisms require certain conditions to effectively breakdown materials. The main conditions that must be present to potentially reduce or eliminate pathogens in diseased animals will be discussed briefly.

Carbon and Nitrogen. Microorganisms use carbon and nitrogen for energy, growth, and reproduction, and ideally require a carbon:nitrogen ratio of 25 to 30:1. Fibrous materials (straw, corn stalks, silage, hay bales, wood shavings, and newsprint) can be used as cover materials because they have high carbon:nitrogen ratios (60 to 850:1). Because many of these products have carbon levels that are higher than that needed by microorganisms, poultry litter (10.8:1) or manure from feedlots (10 to 20:1) can be blended in the covering mixture. The source of carbon is not as important as the availability during a catastrophic event.

Moisture. Moisture levels of the cover mixture should range between 50 to 60%, because active composting slows when it falls below 40% or can totally cease (<15%). If the level is greater than 65%, pores for oxygen transfer may become blocked, and odor emissions can increase. Some form of moisture should be added in most cases to cover mixtures because solid manure and carbon sources usually have levels below the preferred range. Wells, ponds, lagoons, or liquid manure from containment facilities can be used depending on availability. As a rule of thumb, the compost is too wet if water can be squeezed out of a handful and is too dry if the handful does not feel moist to the touch.

Temperature. Microorganisms responsible for effective composting require an optimum range of 40 to 65.6C for maximum efficiency. Millner [1] estimated that over 99% of pathogens and parasites are killed when heated to 55[dagger]C for 3 consecutive days.

Also weed seeds can be killed by the heat generated (62.7[dagger]C) during composting. When composting normal materials, the composting pile should be turned when temperatures reach above 65.6[dagger]C, which can kill the composting microorganisms. Conversely, a pile below 40[dagger]C may indicate an inadequate oxygen level, and it should be turned. If the temperature fails to rise adequately, the pile should be allowed to finish composting for at least 1 mo, or other corrective action should be taken. The compost temperature can be monitored with a thermometer having a long probe that can be inserted to the center of the compost pile.

Application. Although the above conditions would be considered ideal when composting mortalities in catastrophic situations, producers especially need to do the best job possible because they have a short time to create the conditions for composting. Regular management practices in creating the ideal composting conditions, such as turning the pile to help regulate temperature, oxygen levels, and mixing of the materials, may be limited due to exposure of carcasses to open air. However, depending on the organism that needs to be eliminated, this may still be a safe practice as long as adequate temperatures have been maintained prior to turning of the pile.

Research

Senne et al. [2] evaluated survival of highly pathogenic avian influenza virus and egg drop syndrome-76 virus during composting. They used tissues from chickens infected with highly pathogenic avian influenza virus and tissues from chickens infected with egg drop syndrome-76 virus distributed among the chicken carcasses. In a compost mixture, they included a ratio of 1 part straw, 1 part carcasses, and 2 parts manure (vol/vol). They tested tissues at d 10 of composting, turned the pile, and then retested tissues 10 d later. The avian influenza virus was not detected after 10 d of composting. The egg drop syndrome-76 virus could be recovered at 10 d of composting but not at 20 d.

Research by Glanville [3| evaluated the potential of composting to control other catastrophic viral disease outbreaks. Briefly, they evaluated pathogen inactivation vaccine strains of poultry viruses placed inside the composting piles in retrievable containers (dialysis cassettes and cryogenic vials). A commercially licensed (B1Lasota) vaccine strain of Newcastle disease virus (NDV) was first used to evaluate the potential biosecurity risks from composting. NDV is a single-stranded RNA enveloped virus that is highly representative of other viruses, such as influenza viruses. Preliminary results indicated that no viruses were detected in either container at d 8 of composting in mixtures of straw-manure, cornstalks, or silage. Also they evaluated if the viruses would escape the composting mixture and affect surrounding poultry. This was done by inoculating and propagating viruses inside chicken eggs and then distributing the eggs (and their contents) throughout the composting test piles before the cover material was added. They used specific pathogen free (SPF) sentinel chickens stationed in cages located 10 ft from all sides of the composting test units. Results indicated that of the 48 caged SPF birds stationed around trials, none tested positive for NDV anti-bodies during the 10- to 12-wk period of blood sampling and testing. In addition, researchers are currently evaluating the effects of a commercially licensed vaccine strain of avian encephalomyelitis (AE) virus that was used to emulate foot-and-mouth (FMD) virus. However, these data are not currently available.

Numerous publications and information from university extension services are available for proper design of mortality composting sites [3, 4, 5]. This information is beyond the scope of this paper. However, sites need to be selected that are not public health risks to air, water, or from direct contact if the infectious agents that are being composted can pose a direct threat to humans and other animals. All activities with composting will require some human activity, which may have direct health concerns if the disease is highly contagious and proper handling procedures are not followed. Mortality composting sites must follow strict biosecurity plans set forth by state or local emergency plans.

CONCLUSIONS AND APPLICATIONS

1. Catastrophic composting can be an effective mortality disposal method.

2. Composting has been shown to be effective in destruction of viral disease agents.

3. Operations need to be prepared with site locations, cover materials, and equipment to effectively compost catastrophic mortalities.

4. Emergency mortality plans and biosecurity protocols may consider including mortality composting as a potential carcass disposal method.

REFERENCES AND NOTES

1. Millner, P. 2003. Composting: Improving on a time-tested technique. Available: http://www.ars.usda.gov/is/AR/archive/aug03/ time0803.htm. Accessed May 25, 2004.

2. Senne, D. A., B. Panigrahy, and R. L. Morgan. 1994. Effect of composting poultry carcasses on survival of exotic avian viruses: highly pathogenic avian influenza (HPAI) virus and adenovirus of egg drop syndrome-76. Avian Dis. 38:733-737.

3. Glanville, T. D. 2004. Emergency livestock mortality composting in Iowa, www.ahe.iastate.edu/catllccomposting/index.asp. Accessed May 25, 2004.

4. Carter, T., K. Andersen, J. Arends, J. Barker, K. Bunton, B. Hawkins, J. Parsons, D. Rives, S. Scheideler, M. Stringham, and M. Wineland. 1996. Composting Poultry Mortality in North Carolina. PS Facts #11. North Carolina Cooperative Extension Service. Raleigh, NC.

5. Keener, H., D. Elwell, and T. Mescher. 1997. Composting Swine Mortality Principles and Operation. Fact Sheet AEX-711. Ohio State University Extension, Columbus, OH.

J. M. DeRouchey,*,1 J. P. Harner,[dagger] and J. P. Murphy[dagger]

* Department of Animal Sciences and Industry, and [dagger] Agriculture and Biolo\gical Engineering, Kansas State University, Manhattan, Kansas 66506-0201

1 To whom correspondence should be addressed: jderouch@ksu.edu.

Copyright Poultry Science Association Summer 2005

Source: Journal of Applied Poultry Research

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