Disposal of Swine Mortalities
There is no best way to dispose of swine mortality carcasses. While some methods may work well for managing routine mortalities, the ability to scale them up to handle large numbers can be difficult. These methods may not adapt to times when catastrophic mortalities occur. The optimum system for any particular farm location is based on a number of criteria, including the current state of the protein/oil market, the biosecurity required, the distance to processing sites, the local public’s perception, the government regulations that apply to that location, the environmental conditions, and the ability of the farm to carry out the different procedures.
The death losses at a farm can be classified broadly as one of two types, routine or catastrophic. Routine mortalities represent a small proportion of herd and occur throughout the course of normal production. Catastrophic mortality events involve high death losses within a distinct period of time. These methods can also be used for catastrophic loses but the larger scale in a shorter time frame often increases process intensity. Additionally if losses are due to disease, they have a higher biosecurity risk.
The specific objectives of this fact sheet are to:
- Provide an example Mortality Management Plan.
- Review typical options for swine mortality management.
Four predominant methods of routine swine mortality disposal have been developed, these are: on-site burial, incineration, rendering, and composting. The choice of method will depend on individual farm characteristics, regulatory requirements, operational costs, and farmer preference.
Catastrophic losses present unique challenges due to the large volume of carcasses, the time frame, and the potential of biosecurity concerns. Often times methods used on farm for typical mortality management are overwhelmed when these events occur, as such preparations should include development of emergency mortality disposal plans based on local and regional conditions. The emergency mortality disposal plan is to provide a response map to both you, and your employees. Critical information includes contact names and numbers for each disposal option, numbers for state regulatory agencies and the state veterinarian. The end of this document contains a series of questions that can be utilized as you formulate an emergency mortality disposal plan specific for your facility.
Examples of the types of questions that should be addressed within the emergency mortality management plans provided at the end of this document.
Burial can occur either on site or via transport of carcasses to approved landfills. Typically, on-farm burial of routine mortalities is performed using a trench method, which involves excavating a narrow and shallow trench, placing a single layer of carcasses in the trench and then covering with soil. Pigs slowly decompose until they are unrecognizable, generally after a few years. One concern is that burial can have negative environmental impacts if the sites aren’t selected carefully. In particular, depth to groundwater or sandy/gravely soils where leachate transport to groundwater is more likely. This method is not available when the ground is frozen and predators can uncover carcasses not buried deep enough. Using burial requires the trench or burial pit be covered within a few days to help discourage scavenging and reduce odors.
In terms of catastrophic mortality disposal burial is more common. With emergency disposal burial, the number of carcasses placed in a location is typically greater, increasing the potential for leachate, making location selection critical. The use of modern engineered landfilled equipped with leachate collection and treatment significantly reduces the risk of leachate concerns. But utilization of the landfill relies on cooperation of owners and transport of dead carcasses and often they won’t be accepted in large volumes, especially if mortality is due to disease. Transport of carcasses requires vehicles that must retain all liquids from the carcasses, vehicles must be tarped, and route selection should be performed to minimize exposure to other operations where possible. If you plan to rely on land filling for emergency disposal contact local landfills to determine if they are willing to accept carcasses, under what conditions, and what the disposal cost will be.
If mass burial is required on site, the combination of topographic, geologic, soil, and water resource data should be used to identify and map burials sites. Important factors include locating burial pits on soils which do not flood and have a separation of at least two-feet from the bottom of the burial pit to the water table. Before digging locate any buried utilities on the proposed site and ensure that there is no field drainage tile located in the area (states often have specific tile separation requirements of approximately 200 feet). Surface water should drain around the site; diversion berms can be used to direct water away from burial locations. Other state regulations may apply. Farms should work to identify locations for on-farm burial as part of emergency preparedness plans. Some states have complied maps to help identify appropriate, for example, the IDNR Iowa Livestock Burial zone map found at https://programs.iowadnr.gov/maps/afo/burial.html
or similar web pages published by environmental agencies in livestock intensive states or for Illinois at https://www2.illinois.gov/sites/agr/Animals/AnimalHealth/Pages/Emergency-Livestock-Mortality-Management.aspx.
Incineration is the burning of material to turn it into gaseous emissions and residual ash. Three types of carcass incineration are: (1) fixed-facility incineration, (2) air-curtain incineration, and (3) open-air burning.
Fixed-facility units are typically diesel or propane units and are used for routine mortality disposal. These units are sized for a farm’s typical weekly mortality capacity. Dead stock is loaded into the incinerator, the controls are set, the unit is run, and then periodic clean-out of ash are required. In many states on-farm incinerators for livestock require an air permit from the appropriate state regulatory agency. Incineration is believed to significantly reduce or eliminate pathogens, but has higher operational costs due to fuel and can contribute to air pollution.
Neither air-curtain incineration nor open-air burning are typically used to routine mortality disposal on individual farms, but instead receive focus for mass mortality disposal. Air-curtain incineration uses a high-velocity “curtain” of air driven through a manifold system over the burn chamber to contain smoke and particulate matter in the burn zone, increasing temperature and encouraging more complete combustion, and has been used after FMD outbreaks in Europe and AI outbreaks in Virginia. However, it requires adequate equipment, trained operators, and fuel be available at the time of outbreak. Burning carcasses in air curtain destructors frequently results in smoke and odor complaints from adjacent property owners
If incineration of mass mortality is being considered look to find an emergency service provider that can provide an air-curtain incineration unit that can provide high capacity, high temperature incineration. If the incineration service is mobile, establishing a standing contract for their services should an emergency happen is encouraged.
Rendering is disposal of mortalities by processing into fat and protein products through physical and chemical transformation. Rendering processes involves the application of heat and the separation of fat. The number of rendering plants in the US has been on the decline and access to rendering is based on location to the nearest plant and its capacity.
In terms of managing catastrophic mortalities rendering, while generally regarded as environmentally safe, capacity limitations would be an issue or at least a limiting logistical concern. If swine producers plan to use rendering during a mass mortality event, they should contact the rendering company to discuss its policies regarding mass mortality events. Do they have excess capacity that could be used or are they running at full capacity handling routine mortality customers. Will they accept diseased carcasses? Will they be able to supply transport to the plant or is it the farmer’s responsibility to locate suitable transportation? When addressing these questions, bear in mind that if mortalities are due to regional disease outbreaks, processing capacity limitations, or weather conditions (example being extreme weather such as flooding, blizzards, heat stress) other farms may be hoping to utilize rendering as well.
Composting is a natural biological process for aerobic decomposition of organic materials. Bacteria, fungi, and other microorganisms break down products such as dead pigs, straw, or sawdust and converts them into an odorless, inoffensive, generally pathogen-free product that can be used as a soil amendment. Four variables are considered crucial to composting success: (1) moisture content (aim for 40-60%), (2) temperature (aiming for 45-60°C), (3) oxygen content (10%), and (4) C:N ratio (aim for 20 to 30 to 1). If pathogen kill is required, temperatures of at least 55°C will be required and sufficient time-temperature measurements may be required to ensure biosecurity.
Most farm mortality composting operations use a static-pile technique. Mortalities are placed in a mound of carbonaceous biomass and time for decomposition is allowed. These swine mortalities are high moisture areas in the pile that decompose anaerobically with the carbonaceous material soaking up the liquid generated and maintaining an environment where generated odors are oxidized. Success of this pile is generally based on pile construction and using appropriate amounts of plant-biomass between layers. Piles will be turned generally once or twice during composting to aerate the pile, but may not be required if material has sufficient oxygen permeability.
Characteristics of effective biomass include sufficient water-holding capacity, maintaining gas permeability and porosity, biodegradability, wet mechanical strength and adequate available carbon. These properties combine to ensure that the cover materials absorb excess liquids, maintain temperature and heat, permit oxygen flow, and encourage microbial activity. Typical biomass materials include sawdust, wood shavings, wood chips, ground cornstalks, ground straw or hay, poultry liter, used livestock bedding.
Composting can be done in bins (A three-sided enclosure with a compacted clay soil or concrete floor, figure 1. A typical arrangement would consist of at least four bins, with one bin being filled, another in the primary stage of composting, and a third in the secondary stages of composing. Overall compost facility capacity must be adequate to hold all material between land application events and is often sized for annual mortality. Minimum bin width is recommended as two-times the width of the loader bucket being used for turning with a front to back dimension of one to two times the bin width within a designated building or in windrows. In both cases structures should have low-permeability bases to prevent leachate contamination of the underlying soil and encourage trafficability. In-vessel composting bins are also available.
Composting is also used in mass mortality management, typically using windrow composting methods. Utilizing composting in these situations requires obtaining and processing sizable amounts of carbonaceous materials (a base of 18-24 inches of depth of carbon material should be constructed where the pile, an additional three to five cubic yards of co-composting material is needed for every 1,000 pounds of animal carcass, and then a 18-inch layer of carbon material is placed over the windrow to help with odor control and discourage scavengers. Overall this amounts to generally 8-12 cubic yards of co-compost material for every 1000 pounds of carcass) and may require composting in areas that don’t have compacted soil bases due to capacity issues. In cases where the mortality was disease-related, there are potential biosecurity risks. In cases where that is the concern, construction and operating procedures that maximize the likelihood of pathogen retention and inactivation are needed. These include the use of highly biodegradable cover materials that produce large amounts of pathogen-killing heat, and delaying and decreasing compost turning until after pathogen deactivation.
Figure 1. Composting bin structure.
Mortalities, both regular and catastrophic can happen. Having a plan of the resources required and how your operation should proceed facilitates sound decision making during stressful times. Understanding the basics of the different potential disposal methods helps you make the best decision for your operation.