Livestock and Urban Waste Research Team
Departments of 1Agriculture and 2Health Sciences
Illinois State University
Normal, Illinois, U.S.A.
Introduction
Improper disposal of animal mortalities, tissues and related wastes (including those potentially infected with disease agents) poses a substantial risk to worker health and safety, public health and safety, and environmental quality (e.g., air, water, soil and food quality) in the United States and worldwide. Recent outbreaks of Avian Influenza, Bovine Spongiform Encephalopathy (BSE), Foot and Mouth Disease, Chronic Wasting Disease (CWD) and other infectious diseases in harvested domestic and wild animal populations illustrate the need for proper disposal of animal mortalities, tissues and related wastes in a manner that minimizes the potential for disease spread to workers, the public and other animals in a manner that is environmentally responsible (thereby minimizing the potential for air, water, soil and food contamination). Natural disasters such as floods and tornadoes, and catastrophic emergencies such as power failures in Confined Animal Feeding Operations (CAFO) may also generate substantial numbers of animal mortalities and amounts of related wastes that must be disposed of quickly, yet responsibly. It should be emphasized that there is currently no proven satisfactory method to dispose of animal mortalities, tissues, and related wastes associated with a catastrophic disease outbreak or other emergency conditions in a safe, environmentally-responsible manner. This is exemplified by the December, 2003 BSE discovery in Washington State and the subsequent necessary transport and disposal of 450 cattle. Thermal destruction is capable of effective, efficient and responsible treatment of these wastes, but requires modification and evaluation to ensure that it does so in a manner that minimizes risks to worker, public and environmental health.
On-site thermal destruction of animal mortalities, tissues, and related wastes minimizes the potential risks for worker, public health and environmental health as compared to those risks posed by transport of these waste materials to another location for their ultimate disposal (e.g., handling, leaks, accidents, etc.). Thermal destruction is capable of reducing the volume of combustible materials by up to 90%, substantially reducing the amount of space required for ultimate disposal (e.g., burying ash on-site or landfill disposal). Propane fuel also significantly reduces the ash volume/weight generated relative to wood fuel due to the lack of generation of wood ash. Regular operation of safe, environmentally-responsible thermal destruction systems is needed to prepare personnel in proper emergency response procedures in the event of a large-scale infectious disease outbreak or other natural disaster requiring disposal of large volumes of animal mortalities, tissues and related wastes. The safety aspects (relative to personnel, property and the environment) of the proposed thermal destruction process will be assessed through application of rigorous analytical techniques, which may include preliminary hazard analysis, hazard and operability (HAZOP) studies, fault tree analysis, event tree analysis, and cause-consequence analysis. These techniques will be applied to the proposed systems at critical points during the system life cycle (e.g., installation, start-up, normal operation, maintenance, emergency shutdown, decommissioning, etc.).
This project proposes to design, construct and evaluate a propane-fueled, production-scale, on-site thermal destruction system to responsibly dispose of animal mortalities (including spent layer hens), tissues (e.g., potentially infected materials and rendering wastes) and other related wastes in a manner that minimizes worker health and safety, public health, and other environmental health risks (e.g., air, water, food quality protection). The design and construction of this system will be accomplished through contractual agreements with manufacturers already familiar with efficient design, construction, operation and maintenance of similar thermal destruction systems; although substantial modification and/or adaptation of existing air curtain wood-fueled designs is anticipated to be necessary to minimize associated health and safety risks. The design, safety, feasibility, and efficiency of the proposed thermal destruction process will be evaluated through system safety analysis of equipment/procedures and testing of air emissions (e.g., for toxic organic compounds), fly and bottom ash (e.g., for toxic metals and other elements), survival of microbiological disease agents (pathogens and/or their indicators).
Literature review
The most relevant study appears to be a USDA/Texas Dept of Animal Health study conducted at Pilot Point, TX in 1994. This study suggested that wood or coalfueled air-curtain thermal destruction was a viable alternative to other less acceptable methods such as open pyre burning, burial, rendering, and composting.
A search of general literature on waste thermal destruction identified several references each for prior studies concerning thermal destruction of laboratory wastes, including veterinary school waste (Thompson, 1997, Thompson, et al., 1996, Rosencraft, 1974), medical waste (Gordon, et al., 1992, Brunner and Brown, 1988), crematory waste in Japan (Takeda, et al., 2001, 2000), poultry carcasses (Blake and Donald, 1992, Great Britain Ministry of Agriculture, 1982), and municipal waste (Zhang et al., 2001a,b). Schaffner, et al., (1979) investigated the use of livestock waste as a fuel source, while Ohio State University (1971) investigated the feasibility of pyrolitic ("anaerobic") thermal destruction of livestock waste. Two studies identified (Schecter, et al., 1991 and Ahlborg and Victorin, 1987) investigated the potential affects of dioxins and other trace organic emissions generated by thermal destruction on worker health and public health, respectively. Chemical contaminants of environmental health concern generated by thermal destruction identified and considered in these studies included metals and other elements in the ash generated (cadmium, barium, selenium, magnesium, arsenic) and organic compounds in the ash and gases generated (e.g., polychlorinated biphenyls [PCB's], polychlorinated dibenzo-pfurans [PCDF's], and polychlorinated dibenzo-p-dioxins [PCDD's]). Responsible livestock waste management has been the focus of a number of comprehensive studies, including those by Iowa State University (1971), New York State College of Agriculture and Life Science (1970), and Cornell University (1970). Woodfired, portable thermal destruction systems with air-curtain technology have been used in the destruction of large-scale animal mortalities, including turkeys in Shenandoah Valley (avian influenza, April 2002), Hurricane Floyd-related animal kills in North Carolina, (September/October 1999).
Results of these and other studies indicated that while there are significant worker health, public health, and other environmental health concerns associated with thermal destruction of waste that properly designed, constructed, controlled, and monitored thermal destruction systems are capable of safe and efficient disposal of animal wastes, including mortalities, animal tissues, and related wastes. Propane-fired thermal destruction offers an alternative that potentially offers easier process (e.g., temperature) control, as compared to wood-fired thermal destruction. Data presented at the Fall, 2003 Midwest Carcass Disposal Conference suggested that the rendering industry does not have the capacity to quickly destruct large numbers of diseased livestock. Thermal destruction is a viable alternative, but alternate fuel sources/designs must be developed where wood-fueled thermal destruction is impractical. It should also be noted that wood-fueled thermal destruction also significantly increases the amount of ash that must ultimately be disposed of in an environmentally-responsible manner.
The urgent need for a safe, environmentally-responsible thermal destruction as an alternative to previously used burial or open mass-pyre burning of animal mortalities cannot be over-emphasized. Mass burial of infected or potentially infected animal mortalities is an unacceptable disposal option, due to the potential for groundwater contamination and other concerns. Open mass-pyre thermal destruction of animal mortalities as occurred during the Hoof-and-Mouth disease outbreak in the United Kingdom would also be unacceptable to a majority of the U.S. general public, primarily due to air pollution and infectious agent transfer potential concerns. Existing air-curtain incinerator systems cannot provide the process control necessary to minimize environmental health and safety risks. It is anticipated that cost of safe, environmentally-responsible thermal destruction may exceed the cost of these and other currently unacceptable disposal methods. However, it is anticipated that the indirect costs of worker health problems, public health problems, environmental degradation and associated long-term liability will far outweigh the higher initial costs of responsible thermal destruction. Demonstration that propane-fueled, on-site thermal destruction can serve as a responsible, yet economically-viable alternative to these and other unacceptable disposal options is a primary goal of this project.
Animal mortalities and tissues generated
Approximately 63 billion pounds of animal mortalities and byproduct wastes (including cattle, swine, sheep and poultry) are generated annually by the livestock industry in the U.S. Approximately 14 billion pounds of this total are generated by the swine industry alone (2002 USDA slaughter data). A substantial percentage of these wastes are utilized by the rendering industry to generate products such as meat and bone meal that may then be incorporated into animal feed. However, during the late 20th and early 21st centuries, concerns raised by animal infectious disease outbreaks such as Bovine Spongiform Encephalopathy (BSE) suggested that infectious disease agents might be transmitted through these products. There is also concern that companion (pet) animal carcasses might be processed to generate animal feed for other companion animals, a prospect that was not acceptable to pet owners. Recently, pet owners appear to have moved toward choosing pet foods that contain non-animal protein sources (e.g., soybean meal). As a result of these and other economic pressures, the percentage of feed mills in the U.S. accepting meat and bone meal has declined by approximately 50% during the period of 1999-2002 (Feed Management, 2003). Therefore, the rendering industry is currently investigating alternative uses for the products generated. Among the alternative options considered have been soil amendment, ethanol and industrial oil production. However, these options have not yet been proven economically feasible. Therefore, responsible on-site thermal destruction may provide an alternative option at a reasonable cost compared to current disposal techniques such as air-curtain incineration technology, landfilling, rendering, composting or burial (United Kingdom Department of Health, 2001 and Canadian Food Inspection Agency, 2003).
Potential system uses
The poultry industry has also been recently investigating alternative disposal options for spent (egg) layer hens. Some currently used methods have been criticized for insensitivity to animal cruelty concerns, including the use of wood chippers to destroy and grind live animals. The poultry industry generates approximately 17 billion pounds of mortalities and byproducts annually (2002 USDA slaughter data). Humane euthanasia followed by responsible propane-fueled thermal destruction may provide an economical alternative to current disposal methods. The use of carbon monoxide and dioxide generated from thermal destruction may also provide a method for humane euthanasia of animals to be thermally destroyed.
Veterinary clinics throughout the U.S. also generate companion animal (pet) mortalities that are disposed of by a variety of methods other than rendering, including small thermal destruction units and burial. Responsibly controlled onsite thermal destruction may provide an economical alternative to current disposal methods.
Energy use
As a fuel for combustion of animal carcasses, wood generates approximately 6,000 BTU/lb dry weight (U.S. Department of Energy). Propane generates 21,000 BTU/lb., is cleaner burning (generating only CO2 and H2O as combustion products), is more readily available in many part of the country, is easily transportable, and allows more precise control of a thermal destruction process (e.g., more even temperature distribution). Since 0.5-1.5 lb. of wood is generally needed to completely combust one pound of animal carcass, and each destruction unit is capable of processing carcasses at the rate of approximately 10,000-12,000 pounds per hour it is anticipated that the propane usage for the proposed thermal destruction system will be in the range of 1430-4290 lb./hr. This is calculated to be roughly equivalent to 350 to 1,265 gallons of liquid propane per hour of operation for each unit. Recent emergency events have required the simultaneous operation of 6-10 units.
Methodology
The LUW Research Team proposes to design, construct, site-evaluate and implement a propane-fueled thermal destruction system incorporating modified existing air-curtain technology that will be capable of safe, environmentally-responsible disposal of infected or potentially-infected animal mortalities, tissues and other related wastes under both lower-volume routine operation and higher volume emergency operation conditions. This system will be designed and built upon existing industry thermal destruction technology while adapting and modifying this technology to meet the needs for responsible thermal destruction of these specific types of wastes. This will allow for more efficient development of a safe, environmentally-responsible thermal destruction system. Design and construction of a production-scale system will also allow for modification and evaluation without the need for the additional time and cost requirements of an interim pilot-scale system. Modifications to existing designs will be based on the relevant physical, chemical, and biological characteristics of these wastes (e.g., moisture content, combustion characteristics, toxic contaminants, etc.). An important biosecurity component of this system will be its mobility for on-site operation, eliminating the need for transporting these wastes and the associated risks.
Phase I of the proposed project includes the design and construction of a production-scale research unit that will then be transported to an appropriate test site (e.g., a local rendering plant and/or the ISU farm) and operated at capacities designed to mimic both lower routine daily operation and higher emergency operation conditions. Phases II-IV will promote the implementation of this proven system regionally and nationally and continued evolving needs. The ongoing development and implementation of an ISU Thermal Destruction Institute as described below will take place during all four phases of the project.
Thermal destruction institute (TDI)
Development of an Thermal Destruction Institute (TDI) located at Illinois State University is proposed to provide oversight, education, training and demonstration in the proper design modification, construction, installation, maintenance, operation and monitoring of thermal destruction technology, including the proposed system, to ensure responsible operation and implementation on a regional and national basis. The Director of this Institute will coordinate the development of the Institute and operation of its education, training and demonstration functions. Other academic and industry personnel will provide appropriate expertise and experience as needed.
This Institute will provide the following benefits:
- Coordination of the design, construction, maintenance and monitoring of the production-scale thermal destruction system to ensure development and operation of a safe, environmentally-responsible, economically-viable, on-site (portable) thermal destruction system.
- Continuing regional/national education and training of appropriate personnel in the proper installation, maintenance and monitoring of thermal destruction systems.
- A clearinghouse function for compilation and dissemination of information related to responsible thermal destruction projects and related research, including sharing of educational materials such as booklets, multimedia presentations and guest speakers.
System design and control
This project includes the development and evaluation of an aboveground portable unit utilizing a refractory lined box (approximately 40 feet long, with a 12-foot by 12-foot cross section) as a thermal destruction chamber (Figure 1).
This system design is anticipated to use a bottom burner system with a grate and air curtain unit to ensure efficient, complete combustion of animal mortalities and related wastes (e.g., a modified air curtain technology). The proposed system will be of sufficient capacity for multiple-unit use during emergency situations in which mortalities may be generated in large quantities (e.g., large disease outbreaks and natural disasters). However, it will also be capable of routine operation to properly dispose of smaller-quantity animal carcasses and tissues (e.g., routine euthanasia of downer livestock no longer approved for human consumption or meat and bone meal production, spent layer hens, routine euthanasia of companion animals such as dogs and cats no longer accepted by rendering plants for meat and bone meal production, and highway animal mortalities). These materials are generated in roughly predictable lower quantities on a more routine basis. This system is anticipated to be portable enough to be moved at short notice, but capable of remaining at a fixed location for as long as necessary to complete proper thermal destruction of the wastes generated on-site. The proposed system (Figure 2) is anticipated to integrate a grinder, steam injection cooking and pre-disinfection system, a primary burn chamber and a secondary burn chamber to ensure complete combustion of the gases emitted and destruction of potentially infectious agents. Temperatures of approximately 1,500 degrees Fahrenheit are expected for the primary combustion chamber and may be as high as 2,500 degrees F. in a secondary combustion chamber. Previous research indicates that temperatures of approximately 2,000 degrees F. should be adequate to destroy contaminants of concern, including prions which may be responsible for BSE. It is anticipated that a continuous-feed process approach will be used rather than batch combustion. It is also expected that multiple units of the system will be required for thermal destruction of large volumes of animal carcasses or for semi-permanent operation to address localized routine needs.
System safety analysis and risk assessment
The safety aspects (relative to personnel, property and the environment) of the proposed thermal destruction process will be assessed through application of rigorous analytical techniques, which may include preliminary hazard analysis, hazard and operability (HAZOP) studies, fault tree analysis, event tree analysis, and cause-consequence analysis (Clemens and Simmons, 1998). These techniques will be applied to the proposed systems at critical points during the system life cycle (e.g., installation, start-up, normal operation, maintenance, emergency shutdown, decommissioning, etc.). The results of these analyses will guide the final design and operation of the system, as well as the preparation of system documentation and operator/maintainer training materials and curricula. Emissions Analysis and Evaluation Air emissions and ash generated by the system will be monitored to evaluate and minimize the risks associated with thermal destruction and ash disposal, both under low- and high-volume operation. Temperature and velocity profiles within the combustion chamber(s) will also be monitored. The input (animal mortalities and tissues and related wastes), air emissions (including gases and fly ash), bottom ash (e.g., metals, pathogen indicators, and other potentially hazardous components), temperature, propane fuel demands, potential need for supplementary combustible materials (e.g., wood chips or sawdust) will be monitored and characterized on a regular basis to first determine, and then minimize, worker health and safety risks, public health and safety risks and other environmental health risks (e.g., air, water, soil contamination).
Summary
The proposed project to develop a propane-fired, air-curtain thermal destruction system will benefit the poultry industry by providing a practical means of disposing of spent layer hens, as well as a means to safely dispose of potentially infectious mortalities, and diseased livestock, while protecting workers, the public, the environment, and the industry.
References are available on request
From Proceedings of the "Midwest Poultry Federation Convention", St. Paul, Minnesota, U.S.A.
