On-farm Composting of Livestock and Poultry Mortalities

Agdex#:	725/400
Publication Date:	November 2003
Order#:	03-083
Last Reviewed:	November 2003
History:	Original Factsheet
Written by:	Gary Koebel - Livestock Mortality Specialist/OMAFRA; Andrew Rafail - Program Assistant/OMAFRA; Jim Morris - Contract Lecturer/Researcher/Ridgetown College, University of Guelph

Table of Contents

1. Introduction
2. The Composting Process
   1. What is Composting?
   2. The Case for Composting
3. Planning Your Composting Unit
   1. Siting the Composting Unit
   2. Sizing the Composting Unit
   3. Constructing the Composting Unit
4. Getting Ready to Compost
   1. Choosing Your Substrate
   2. Equipment and Supplies
5. The Mechanics of Composting
   1. Managing the Process
   2. Monitoring the Compost
   3. Finished Compost
6. Summary
7. References
8. Appendix 1
9. Appendix 2
10. Appendix 3

Introduction

Livestock and poultry producers in Ontario are recognized worldwide for their progressive approaches to animal husbandry. However, on-farm mortalities due to disease, accidental death and acts of nature are inevitable in the livestock production business.

The proper disposal of livestock mortalities is critical in preventing environmental contamination and the spread of disease. In Ontario, the Dead Animal Disposal Act (DADA) regulates the disposal of dead farm animals, specifically cattle, swine, sheep, goats and horses.

Under DADA, producers are required to properly dispose of on-farm mortalities in a safe and environmentally friendly manner within 48 hours of death. The Act permits the following 3 disposal methods:

• pick-up by a provincially licenced deadstock collector
• burial under 0.6 m (2 ft.) of soil on the farm
• composting on the farm

This factsheet provides an overview of composting on-farm mortalities and how you can apply composting to your own livestock operation. Although there are a number of composting system options, the information here is based on the popular bin composting unit, such as the one illustrated in Figure 1, which could even be constructed of straw or hay. Included are the basics of construction and guidelines for starting, managing and monitoring your composting unit.

Figure 1. A bin composting unit. (Photo courtesy of Minnesota Department of Agriculture)

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The Composting Process

What is Composting?

Composting is a natural process by which micro-organisms, such as bacteria and fungi, break down organic material into a product called called compost. Compost is a stable, dark brown, soil-like material (humus) that can be applied to land.

The composting process cannot be successful without a balanced integration of the following five elements:

• carbon
• nitrogen
• oxygen
• moisture
• temperature.

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The Case for Composting

There are a number of advantages to adopting composting for disposal of on-farm mortalities, not the least of which are its practicality and environmental soundness. Here are some of the better known benefits of this disposal method:

Biosecurity

• Improves biosecurity and reduces health risks by eliminating the need for deadstock personnel and vehicles to visit the farm
• Significantly reduces the number of pathogens through the natural heating process

Cost Effectiveness

• Requires minimal to moderate start-up costs, depending on design and materials chosen
• Requires minimal operating costs, especially when using on-farm materials
• Provides a value-added soil amendment as an end product
• Eliminates processing and service fees associated with mortality collection

Practicality

• Offers an option for immediate disposal of livestock mortalities
• Accommodates animals of all sizes, as well as afterbirth
• Provides an alternative for disposing of mortalities that are not accepted for rendering
• Offers a disposal strategy to deal with an unexpectedly high number of mortalities
• Can generally be done year round

Environmental Soundness

• Provides a stable form of nitrogen and other nutrients
• Eliminates offensive odours and flies when units are well-managed
• Recycles on-farm materials

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Planning Your Composting Unit

Consider the following factors in the planning and design of your on-farm composting unit:

• site selection
• size of unit
• construction.

Siting the Composting Unit

Select a location that is out of view of neighbours and the travelling public. Also make sure you know about and can comply with the environmental guidelines and regulations for your area by checking with the chief building official and by-law officer in your municipality.

To select an ideal site for your composting unit:

• Choose a high, level, well-drained area away from wells, watercourses and tile drains.
• Choose a southern exposure where possible.
• Stay away from animal feed and housing units, and wildlife habitat.
• Note any biosecurity risks (e.g., traffic patterns or vermin access) and make changes needed to reduce the risk of spreading disease.
• Allow space for handling mortalities, substrate and finished compost.
• Ensure easy access to manage and monitor the unit.
• Ensure convenient access to a water supply so that you can add water to composting bins as needed.

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Sizing the Composting Unit

The size of the composting unit will depend on the size and nature of your livestock operation and the projected annual number of mortalities.

Determining Composting Unit Area
The total area needed for composting units on your farm will depend on the following:

• number and size of bins needed for composting
• number and size of bins, if needed, for storing carbon sources such as sawdust or straw (called substrate) and the finished compost
• space needed for traffic flow and the operation of equipment

Determining Number and Size of Bins

For each composting unit, plan for three composting bins. Two bins are needed for the primary stage of composting (first heat stage), and a third one is needed for the secondary stage of composting (second heat stage). Some larger livestock and poultry operations will require more than one composting unit. One or more bins may also be needed for storing substrate or finished compost, depending on your operation.

The size of bins required will depend on the weight of mortalities and the substrate used, so this must be calculated for each individual operation. Consider the following when sizing bins:

Composting Bins

• Each primary composting bin needs at least 1.25 m³ for every kilogram (20 ft.³/lb.) of average daily mortality that will be composted if you use sawdust as a substrate. However, your composting bins should be one-and-a-half times this size to allow for an unexpected increase in mortality rate or expanded production. If you plan to use less dense substrates, such as straw and corn silage, you will need more bin space per kilogram (pound) of mortality.
  
  
• Each secondary composting bin should be at least two-thirds the size of a primary bin (i.e., at least .83 m³ for every kilogram (13 ft.³/lb.) of average daily mortality that will be composted). It may be practical to make the secondary bin the same size as a primary bin.

Storage Bins

• A storage bin for substrate should equal the volume of two primary bins, depending on your operation and supply of substrate.
  
  
• A storage bin for finished compost may be desirable. A bin equal in volume to one primary bin should be adequate for most operations.

Refer to Appendix 1 for a worksheet to help you determine the number and size of composting bins needed for your operation.

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Constructing the Composting Unit

A number of structures lend themselves to efficient on-farm composting, including newly built, stand-alone units and add-ons to existing buildings. Even cattle and machine sheds may be adapted for composting. Composting units may be subject to municipal by-laws or other government standards. Check with the by-law officer and chief building official in your municipality, and ensure you can comply with all laws and guidelines before beginning construction.

Base

Build the base of the unit to prevent leachate (liquid from the pile) and run-off from affecting the environment ( Figure 2). A well-constructed concrete pad effectively reduces environmental impact and provides a solid base for operating loaders and equipment without disturbing sub-soils. A clay soil (at least 1 m (3.3 ft.) of soil containing 20% clay) is also an acceptable base.

Figure 2. A composting unit with a reinforced floor. (Photo courtesy of Minnesota Department of Agriculture

Walls
Walls should be 1.4-1.8 m (4-6 ft.) high and be constructed to reduce leachate permeation. They should also be designed to keep out all animals, including vermin, and to withstand the demands of turning the composting piles with large equipment and loaders. Recommended wall materials include concrete, untreated wood and large tightly packed bales of hay or straw. Pressure treated wood is not recommended because of the possibility of heavy metal contamination of the compost. Figure 3 shows a compost unit built of large square bales.

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Wall Height

Recommended wall height for a composting bin is 1.8 m (6 ft.). As a general rule, bins deeper than 1.8 m (6 ft.) may need a forced aeration system. The potential for spontaneous combustion increases with greater depth due to the reduced air space caused by compaction of the pile.

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Figure 3. A simple large bale composting unit.

Text Equivalent of Graphic

Build three-sided bins that allow accessibility for the type of operating equipment you will use. The opening should be at least 0.6 m (2 ft.) wider than the loader or turning equipment being used. Bins should be at least 1.8 m (6 ft.) wide. Installing a gate at the open end of each bin helps discourage animals from scavenging.

Square bins with a floor area larger than 6 m² (64 ft.²) may require a forced aeration system to reduce the potential for spontaneous combustion due to lack of airflow in the middle of the pile. If the floor area needed for your operation exceeds that, consider building rectangular bins no wider than 2.45 m (8 ft.) or build more than one unit.

Roof
Having a roof or cover, as shown in Figure 4, will help to control moisture levels by protecting the composting pile from rain and snow. Excessive moisture increases the risk of leachate and run-off, and interferes with the composting process, thereby increasing the risk of odour.

Figure 4. A covered compost unit. (Photo courtesy of Minnesota Department of Agriculture)

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Getting Ready to Compost

To make composting work, you need to create and maintain the ideal environment for the micro-organisms to function in your pile. There are four essential components you must provide to accomplish this.

1. Carbon and Nitrogen

   The carbon to nitrogen ratio (C:N ratio) in composting is critical for providing the required environment for the micro-organisms. To facilitate the composting process, you will need to add a substrate that is high in carbon to balance the high levels of nitrogen contained in the mortalities. Too low a C:N ratio may cause odours. Too high a C:N ratio may limit microbial activity, resulting in lowered temperatures and slowed decomposition. A C:N ratio ranging from 25:1 to 35:1 is recommended.

2. Oxygen
   

   Oxygen must be available in the pile to support necessary microbial activity. The substrate you use in the pile must create the space that traps air. The type and size of the substrate particles will affect air space. The substrate also provides insulation for the pile and absorbs liquid produced by decomposing mortalities.

3. Moisture
   

   An adequate moisture level is also needed to ensure proper microbial activity in the compost pile. The ideal moisture content is 45%, but levels from 40%-60% are acceptable. Low moisture levels can reduce microbial action while high moisture levels inhibit the flow of oxygen and can lead to odour. The presence or absence of a roof, weather conditions, substrate type, animal species, and the number and size of the mortalities in the composting bin can each influence moisture levels.

4. Temperature
   

   Heat is the result of the composting process and is necessary for composting to work. To a certain extent, the more heat there is, the more heat is produced, and the faster composting proceeds. For proper composting, the temperature must reach at least 55°C (131°F) and remain there for several days or weeks, depending on the size of the mortalities. Lower temperatures will slow the micro-organisms, resulting in slower decomposition and less effective reduction of pathogen numbers. Temperatures higher than 71°C (160°F) will destroy the micro-organisms needed for composting.

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Choosing Your Substrate

You can source substrate material on-farm or off-farm. Cost, availability, and physical characteristics are important factors to consider. Clean sawdust has proven to be an excellent substrate for composting mortalities, although other materials with high carbon content such as wood mulch, straw, corn cobs and corn silage may be used. Table 1 shows the C:N ratio of some common organic materials found on farms.

• Consider your options for on-farm or low cost substrates, such as straw, sawdust or wood shavings. If using an off-farm substrate, care must be taken to ensure that it does not contain foreign material such as metal or glass or chemical contamination. When ordering substrate for pick up or delivery, verify the origin and quality of the material and any related environmental regulations that may apply.
  
  
• Estimate the annual amount of substrate you will likely need, based on your annual mortality rate and the substrate available, and make sure you can access adequate quantities of substrate throughout the year.
  
  
• Ensure substrate particles are large enough to ensure adequate airflow but small enough to decompose or work effectively in the composting process. If necessary, chop substrate so particle length ranges from 3-13 mm (1/8-1/2 in.).
  
  
• Use finished compost as a "starter" for up to half of the weight of needed substrate, as an option.

(On-Farm Composting Handbook, 1992)

How Much Substrate?

The size, number and species of mortalities will determine the amount of substrate needed for the process. Generally, a weight to weight ratio of 1.5 sawdust to 1 of mortality (i.e., 1.5 kg:1 kg or 1.5 lb.:1 lb.) is needed to balance the nitrogen in mortalities. This is approximately 1:1 on a volume to volume basis. More substrate relative to mortalities will be required if you use a substrate with a lower C:N ratio.

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Equipment and Supplies

Loading and Moving Equipment
Equipment will be needed to move substrate and mortalities, and to move composting material from a primary to a secondary bin. No specialized equipment is required, although a tractor-mounted, front-end loader is commonly used. To determine what is appropriate for your situation, consider the equipment available on-farm, frequency of usage, amount of material being handled, size and location of the composting system and available labour.

Thermometer
Use a thermometer to measure the temperature of composting piles. A thermometer constructed of stainless steel with a shaft of 6 mm (1/4 in.) diameter and measuring at least 1 m (3 ft.) in length is recommended. Thermometers may be available at farm supply stores.

Moisture Meter
A moisture meter (e.g., a hay moisture probe) is needed to measure the moisture level of composting piles. Use a meter that can accurately measure moisture levels from 30%-70%. Moisture meters may be available at farm supply stores.

Screen
If you will be composting mortalities that weigh more than 200 kg (440 lb.), a screen 13-25 mm (½-1 in.) will be needed to remove bone fragments prior to applying the compost to land. Screens may be available at farm supply stores.

Recording System
A record-keeping system is critical to your composting success. A simple system would allow you to record dates, details about mortalities added to a pile, substrate used, pile temperature, pile moisture and general observations (e.g., condition of top substrate layer, amount of leachate, odours, evidence of scavenging, and actions taken to correct problems). Create one that best suits your needs. Refer to Appendix 2 for an example of a simple record-keeping system.

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The Mechanics of Composting

A complete composting cycle has three main stages: bin filling, the primary heating stage and the secondary heating stage. Successful composting requires management and monitoring throughout this cycle.

Primary Bins--Filling and First Heat Stage

• Fill one of the primary bins over a period of 45-90 days, depending on the average weight of the mortalities.
  
  
• Leave the material in this primary bin to compost for an additional 45-90 days. The pile should heat to temperatures ranging from 55°C-65°C (131°F-149°F). In general, the pile temperature should remain within this range for at least 7 days to ensure that composting at this stage is effective. While one primary bin is composting, you would be filling another primary bin.
  
  
• Move the pile from the primary bin to the secondary bin after the first heat stage has occurred. By now, the temperature should have dropped to below 48°C (120°F).
  

Secondary Bin--Second Heat Stage

• Ensure mortalities protruding from the newly made pile are covered with at least 0.6 m (2 ft.) of substrate.
  
  
• Leave the partially composted material in the secondary bin for the second heat stage. The pile again needs to heat to temperatures ranging from 55°C-65°C (131°F-149°F) and remain within this range for at least 7 days to ensure the composting is effective. In this heat cycle, the pile will reach the same high temperature observed during the first heat stage, but it may not remain high for as long. The main composting process is complete after the second heat stage has occurred and the temperature has dropped to below 48°C (120°F).
  
  
• Screen the composted material if visible bones remain in the material, e.g., from mortalities weighing more than 200 kg (440 lb.). Return any larger remaining bones back to a primary bin for further decomposition.

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Managing the Process

Timing and Flow
Each of the filling, primary heating and secondary heating stages takes about the same length of time. While the principles of composting are the same for both small and large animals, the size of mortalities and the substrate used will influence the time needed for decomposition. Typically, mortalities under 25 kg (55 lb.) take 45 days for each stage, for a total of 135 days for the complete cycle. For mortalities 25 kg and over (55 lb. and over) each stage takes 90 days, for a total of 270 days. However, it may take a year to completely compost mortalities over 200 kg (440 lb.).

Once the first primary bin in your composting unit is filled and left to sit, the second primary bin can be filled while the first is heating. When the first primary bin is ready to turn into the secondary bin, the other primary bin is ready to sit. Figure 5 shows the movement of material between bins during the compost cycle.

Figure 5. A schematic of the composting process.

Text Equivalent of Graphic

1. Make a Base

• Spread 0.6 (2 ft.) of substrate on the floor of a primary bin in your composting unit.
  
  
• Moisten as needed for substrate moisture level to reach 40%-45%. (Additional moisture will come from the mortalities so it is important to start with less moisture in the base layer of substrate than in upper layers.)

2. Add a Mortality Layer

• Ensure that your veterinarian has examined animals that were euthanized or died on-farm of an unknown cause, to ensure they did not have a serious disease.
  
  
• Place the mortalities on the substrate at least 0.3 m (1 ft.) from the exterior edge of the bin.
  
  
• Space the mortalities evenly on the substrate, ensuring they do not touch each other.
  
  
• Place a larger mortality on its side to maintain the recommended pile height of less than 1.8 m (6 ft.). If needed cut the ligaments and tendons in the legs and fold them down. Cutting open the body cavity will reduce bloating and promote increased microbial activity.

3. Cover with Substrate

• Moisten substrate as needed for substrate moisture level to measure from 40%-60%.
  
  
• Immediately cover the mortalities with at least 0.6 m (2 ft.) of substrate.
  
  
• Ensure all parts of the mortalities are covered with substrate and the pile shape is appropriate for your situation (see below for information about pile shape).

4. Add More Mortalities

• Skim off a portion of the top layer of substrate leaving 0.2-0.3 m (8-12 in.) of substrate on top of the old mortalities.
  
  
• Add new mortalities to the pile following steps 2 to 3 above.

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Winter Composting Issues

As the temperature drops, it is more difficult to establish microbial activity in a composting pile. Avoid initiating a new pile from December to February. If a new pile must be started during the winter, be sure to use finished compost for up to half of the substrate. If a mortality is frozen, it should be thawed before being added to the pile.

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Size and Shape of the Pile
Ensure the composting pile is 1.2-1.8 m (4-6 ft.) high. Piles less than 1.2 m (4 ft.) high generate insufficient heat, especially in colder weather, and there may not be sufficient substrate to maintain microbial activity for adequate decomposition. Piles higher than 1.8 m (6 ft.) may become compacted and not permit enough airflow for proper composting, possibly resulting in spontaneous combustion.

The shape of a pile will affect how moisture will filter into the pile. For a pile with a roof or cover, the top layer of substrate may be left flat or concave so that any added moisture will be easily absorbed. However, a convex or peaked shape may be appropriate for an uncovered pile to limit the amount of rain or snow that will filter into the pile. Note that although a peak may be desirable during a wet period, the pile may need to be flattened or dipped to hold moisture during a dry period.

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Monitoring the Compost

If you're not monitoring, you're not managing your composting unit! Check the pile daily to monitor the substrate cover, temperature and moisture, and record the information. Throughout the composting cycle, watch for and take steps to prevent:

• scavenging by animals
• excessive leachate
• odour.
  

Substrate Cover
Make sure all mortalities are completely covered with 0.6 m (2 ft.) of substrate. Factors such as settling of the pile or wind may reduce the depth of substrate covering the mortalities.

Temperature
Take the internal temperature of the pile at several locations, including close to the last mortality added. Temperatures should increase and need to remain between 55°C (131°F) and 65°C (149°F) for at least 7 consecutive days in the primary and secondary bins. If temperatures fall below 48°C (120°F), the composting process is becoming non-active; temperatures higher than 71°C (160°F) will destroy the composting micro-organisms and may lead to a fire in the pile. Refer to troubleshooting guide in Appendix 3 to address temperature problems.

Moisture
Check the moisture content of the pile frequently to ensure it ranges from 40%-60%. You may need to change the shape of the pile and adjust moisture content. Refer to troubleshooting guide in Appendix 3 if problems with moisture levels occur.

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Moisture Control in Uncovered Composting Unit

In the absence of a roof or cover, the shape of the compost pile will greatly influence its moisture level. A concave or dipped shape pile will retain moisture from rain and snow. By creating a peaked shaped pile, moisture will generally run off the sides, with less absorbed into the pile.

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Record Activity and Results
Set up a system to record the following:

• temperature
• moisture
• mortalities (date added, number, species and weight)
• substrate (amount and type used)
• general observations about the composting process, as well as problems and corrective actions taken.

Refer to Appendix 2 for an example of a simple system for recording composting information.

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Finished Compost

Properly finished compost has a slight earthy odour and resembles humus, or potting soil, in colour and texture, as shown in Figure 6. Ensure that visible bones remaining after the secondary heating are screened out and returned to the primary bin being filled. Once you ensure larger bones are removed, the compost is ready for on-farm land application.

Figure 6. Finished compost.

Be sure to get a nutrient analysis of the finished compost to accurately determine nutrient content, and include it in your nutrient management plan or strategy. Table 2 shows the nutrient content of finished compost from a research project on composting swine mortalities.

* ppm - parts per million

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Summary

With good planning and management, on-farm composting can be an effective and environmentally friendly way to dispose of livestock and poultry mortalities. On-farm composting is a legal option for producers bound by Ontario's Dead Animal Disposal Act. Existing farm resources such as buildings or straw can be used to construct a bin composting unit. You must provide a high source of carbon (e.g., straw, sawdust or wood mulch) for your compost pile to balance the nitrogen contained in mortalities. You must also make sure the pile has enough oxygen from trapped air and the right amount of moisture, so it can reach the high temperatures that are needed for composting. A composting unit can be used year round, although you should avoid starting a new pile during the winter. Monitoring the unit regularly will help you ensure the composting process is working. With a well-managed unit, you should have properly finished compost for on-farm application in less than a year.

References

Manitoba Pork Council. 2000. Composting Deadstock: A Producer's Guide to Effective Mortality Composting. Manitoba Pork Council, Winnipeg, Manitoba.

Dougherty, M. (ed.). 1998. Composting for Municipalities: Planning and Design Considerations. Publication NRAES-94. Natural Resource, Agriculture and Engineering Service, Ithaca, New York.

Dougherty, M. (ed.). 1999. Field Guide to On-Farm Composting. Publication NRAES-114. Natural Resource, Agriculture and Engineering Service, Ithaca, New York.

Fulhage, Charles D., R. Wright, J. Feistner and J. Igert. 1993. Composting Poultry Carcasses in Missouri. Publication WQ205. University Extension, University of Missouri-Columbia, Missouri.

McGuire, K. (ed.). 1997. Composting Module, Environmentally Assured. National Pork Producers Council (NPPC), Urbandale, Iowa.

Morse, D.E. 2001.Composting Animal Mortalities. Minnesota Department of Agriculture, St. Paul, Minnesota.

Morris, J.R., T. O'Connor, F. Kains and H. Fraser. 1997. Composting Livestock Mortalities. Factsheet 97-001. Ontario Ministry of Agriculture, Food and Rural Affairs, Guelph.

Rynk, R. (ed.) 1992. On-Farm Composting Handbook. Publication NRAES-54. Natural Resource, Agriculture and Engineering Service, Ithaca, New York.

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Do you know about Ontario's new Nutrient Management Act?

The provincial Nutrient Management Act (NMA) and the Regulation 267/03 as amended regulates the storage, handling and application of nutrients that could be applied to agricultural crop land. The objective is to protect Ontario's surface and groundwater resources.

Please consult the regulation and protocols for the specific legal details. This Factsheet is not meant to provide legal advice. Consult your lawyer if you have questions about your legal obligations.

For more information on the NMA call the Nutrient Management Information Line at 1-866-242-4460 or visit www.omafra.gov.on.ca.

Factsheets are continually being updated so please ensure that you have the most recent version.

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Appendix 1: Worksheet for Sizing Mortality Composting Units

A. Determine the annual weight of mortalities on your farm

B. Determine the volume needed for the composting unit consisting of two primary bins and one secondary bin, and the number of units required

C. Determine the approximate volume of a storage bin needed for an annual supply of substrate

^*The volume of the secondary bin should be at least 2/3 the volume of one primary bin.

^**Generally, the volume of substrate required for one year of composting will equal the combined volume of the primary bins. A larger bin may be necessary if a very coarse and low density substrate is used.

"Purple" colour indicates a standard number used in a calculation.

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Text Equivalent of Graphic

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Appendix 2: Composting Record Sheet

(use one sheet per bin)

Temperatures must reach 55°C (131°F) and remain between 55°C (131°F) and 65°C (149°F) during both heating cycles.
Moisture levels will range from 40%-60%. Substrate cover be at least 0.6 m (2 ft.).
If measured values are outside of expected ranges, refer to Appendix 3, Troubleshooting Guide, for possible solutions.

Appendix 3. Troubleshooting Guide

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