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In-house Pasteurization of Broiler Litter

by 5m Editor
23 October 2006, at 12:00am

By Theresia K. Lavergne, Matthew F. Stephens, David Schellinger and William A. Carney Jr., Ph.D., and published by Louisiana State University - Poultry production is the largest animal agricultural industry in Louisiana, second only to forestry production in total generated income. The Louisiana broiler industry produces almost 1 billion pounds of meat each year.

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Table of Contents

  • Introduction
  • Methods
    • Initial Litter Moisture Requirements
    • Initial Windrow Treatments
    • Subsequent Trial Windrow Maintenance
    • Analyses and Monitoring
  • Results and Discussion
    • Appropriate Moisture: Dewar Flask Trial
    • Effects of Moisture: On-Farm Trial
    • Effects of Moisture in On-farm Trials
    • Effects of Poultry Litter Age on the Pasteurization Processes
    • Effects of Pasteurization on Pathogenic Microorganisms and Plant Nutrient Dynamics
      • Pathogenic Microorganism Reduction
      • Plant Nutrient Dynamics
  • Conclusions

Introduction

In current management systems, used poultry bedding material called litter is typically land applied on pastures or hay fi elds after removal from poultry houses. Investigations in midwestern states and more recently in Louisiana have determined that mismanagement and misuse of animal manures from animal feeding operations (AFOs) such as feedlots, dairy farms or poultry farms can contribute to nonpoint source water pollution.

The potentially large quantity of litter generated from the poultry industry in Louisiana has raised concerns with environmental regulators and poultry industry integrators about proper use and management of poultry litter. As a result, poultry growers are becoming more environmentally conscious about how poultry litter is used and handled and have developed “environmentally friendly” alternatives to conventional litter management. Many poultry producers re-use the litter from previous fl ocks to help reduce the amount of litter for disposal and to help defray production costs.

Poultry litter contains uric acid. When exposed to moisture, air and microbiological degradation, the uric acid is converted to volatile ammonia that increases pH in poultry litter (near pH 8.5). As poultry litter dries, the pH becomes more neutral (near pH 7). The highest concentration of ammonia in a poultry house is experienced within a few inches above the litter surface where chicks are susceptible to its detrimental effects on eyes and lungs. Coupled with elevated relative humidity levels in houses and the high moisture contents of litter in houses cleaned after a previous fl ock, ammonia can have a devastating affect on the health of chicks. Most poultry losses occur soon after chicks are introduced to the houses because of respiratory tract damages or illnesses, such as pneumonia, that may result in death.

To reduce the potential effect of ammonia on chick health when re-using poultry litter, poultry producers have depended on chemical litter treatments that reduce the ammonia loss from litter when chicks are most vulnerable to high ammonia concentrations. Poultry litter treatments acidify litter, a condition under which ammonia is not volatile, and chemically bind some ammonia. This condition, however, is short-lived but can reduce losses of chicks in early growth stages. The two commonly used chemical treatments in Louisiana are Al+Clear and PLT.

Salmonella spp., Escherichia coli, Clostridium spp., Campylobacter spp., Staphylococcus aureus and other microorganisms are pathogenic to humans and also may be pathogenic to poultry, causing serious infections that may lead to death. Most pathogenic microorganisms cannot withstand the high pH and high ammonia concentrations common in poultry litter. However, Salmonella spp. and Clostridium spp. are two examples of organisms able to survive the adverse environments of poultry litter. These bacteria are able to endure for long periods under adverse conditions and can repopulate. Chemical poultry litter treatments make claims that the acidic conditions created after application to litter can reduce pathogenic microorganism populations in addition to reducing ammonia concentrations.

Some microorganisms, however, can survive the chemical poultry litter treatments and, in the absence of competition from other microorganisms, may more easily re-infest poultry litter following chemical treatment. Composting is a term often used to identify the process of using elevated temperatures to kill microorganisms by destroying or denaturing proteins, including genetic materials. Another term is thermal treatment or thermal inactivation. Heat generated during composting (self-heating) is the energy released when microorganisms degrade materials that contain carbon (organic matter). Self-heating and aeration that occurs during composting has been known for many years to kill pathogenic microorganisms. The United States Environmental Protection Agency (U.S. EPA) recognizes composting as a “process to further reduce pathogens” (PFRP) in pre-treated biosolids (Class B) under the 40CFR.503 regulations (503 or Biosolids Rule).

The PFRP relies on a time/temperature relationship under which composting materials are required to exist above 131 F for various periods of time; 72 hours in static piles and invessel composting technologies or 15 days (with fi ve turnings) for turned windrow composting. Moisture loss during the early stage of composting can be signifi cant, and the odor potential of composting materials often decreases signifi cantly as drying occurs. Additionally, chemical changes that occur during composting also enhance emissions of odor-causing chemicals such as sulfi de gasses and ammonia, and neutralization of acidic chemicals such as volatile fatty acids and volatile organic acids. The pH of composting materials usually increases signifi cantly early during the process either because of the release of ammonia from degrading organic matter or from other chemical reactions. Ammonia is not stable under pH conditions above neutral (higher than 7) and becomes volatile, as does many forms of sulfi de gas. Organic and fatty acids are formed from oxidation of other chemicals that are produced by microorganisms when conditions were not aerated as in composting (packed sublayers or cake in poultry houses or cattle barns, or undisturbed piles of manures or biosolids).

Based on the Biosolids Rule, many state regulatory agencies governing use and disposal of agricultural wastes require thermal treatment of animal manures that are to be land applied. Composting has been used successfully for many years to transform raw manures and other forms of organic matter, including poultry litter, to materials suitable for use as soil amendments. Composting is an increasingly important tool in poultry litter management, reducing some nutrient and pathogen contamination of water resources; a key issue affecting Louisiana and other poultry producing states. With the exception of phosphorus, nutrient solubility is signifi cantly decreased in properly composted organic matter. Phosphorus solubility, however, is known to increase with composting. This increase in solubility may be a benefi t to soils and vegetation, allowing increased infi ltration of phosphate to rooting zones of soils, thus reducing the total concentration in runoff water as insoluble or organic forms.

Poultry grower litter management has become the focus of much criticism from environmental researchers and activists. Therefore, reducing the potential for nutrient and pathogenic microorganism contamination of surface and groundwater sources through runoff waters from stored or applied litter would reduce many environmental pressures placed on poultry producers to reduce nonpoint source pollution.

Increasing the cost effectiveness of poultry production is also an important goal nationwide. Extending the longevity of poultry litter as bedding, reducing reliance on chemical litter treatments and decreasing poultry mortality would be of great economic signifi cance to poultry growers. Thus, using composting technology to pasteurize poultry litter between fl ocks may produce results consistent with these goals. The self-heating of poultry litter can kill Salmonella, Escherichia coli, Clostridium, Campylobacter, Staphylococcus aureus and other microorganisms pathogenic to humans and poultry, while fewer volatile emissions and lower litter moisture levels can reduce conditions that lead to signifi cant losses of young birds, thus reducing mortality.

With invaluable cooperation and assistance from poultry producers in northern Louisiana parishes, LSU AgCenter personnel have evaluated the effectiveness of in-house pasteurization of broiler litter by conducting demonstration trials in commercial poultry houses. The main objective of this project was to develop a suitable process to pasteurize poultry litter in-house, between fl ocks, with minimal additional cost or inputs to growers. That would be suffi cient to generate PFRP temperatures for pathogenic microorganism reduction. Secondary objectives were to evaluate the pasteurization technology to reduce litter moisture and ammonia emissions from litter, thus, reducing chick mortality. In addition, the effect of pasteurization on nutrient dynamics over time was a concern.

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September 2006