Burial of On-Farm Deadstock
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Table of Contents
This Factsheet describes some of the requirements for on-farm burial of deadstock as specified in Ontario Regulation 106/09 under the Nutrient Management Act, 2002 (NMA). The Factsheet does not cover all burial requirements contained in the regulation nor deadstock burial under emergency situations such as after a fire or other catastrophe. For this information, refer to the regulation.
For generations, farmers have buried deadstock by digging a pit or trench, placing carcasses in it and covering them with excavated soil material (Figure 1). Burying deadstock must be done properly to:
Decomposition of buried deadstock is like a slow, composting process. Composting deadstock works best if they are mixed well with a good carbon substrate, such as sawdust, under favourable moist, warm, aerobic conditions. Similarly, burying deadstock works best if they are:
Under favourable conditions, decomposition can occur in a few months, especially in the biologically active upper layers of the soil. However, under poorer conditions, decomposition can take years, especially if deadstock are packed together in wet soil, and buried deep, where soil temperatures are cool.
Figure 1. Burial is a traditional deadstock disposal method, but it must be done properly.
The regulation permits farmers to keep deadstock in cold storage for up to 14 days following death, or in frozen storage for up to 240 days. Freezers can work well in conjunction with burial for smaller deadstock, since a freezer can be filled over time, then emptied in a burial pit when digging conditions are suitable. Because freezers have fixed volumes, it is easy to match their frozen contents to a predetermined burial pit size.
Locating the burial site in the right place is critical for good carcass decomposition and protection of the environment. Generally, soil materials ranging from sandy loams to clays that are well-drained to imperfectly drained are suitable for burial. However, the regulation does not permit burial of deadstock in soils where there is a higher risk of polluting groundwater. These soils include:
The regulation does not permit the burial of deadstock in areas subject to flooding once or more every 100 yr. To find out if you are in such an area, contact your local conservation authority or municipality. The regulation requires the lowest point of a burial pit to be at least 0.9 m (3 ft) above the top of the uppermost identified bedrock layer or aquifer. Table 1, above, shows several setbacks for burial pits. For more specific information, see the regulation itself.
1 Maximum allowable total: 2,500 kg
The regulation specifies a maximum of 2,500 kg total deadstock per burial pit, so the weight of each dead animal determines the number of deadstock per pit (Table 2, above). Due to the 2,500 kg/pit limitation, very large or deep pits are not necessary; generally, digging deeper than about 1.2 m (4 ft) makes little sense. Limiting the depth of burial pits to 1.2 m places deadstock in the biologically active part of the soil, protects groundwater and avoids the dangers of deep trenches.
The Construction Safety Association (CSA) defines trenches (pits) as excavations where the depth exceeds the width of the pit. The CSA cautions anyone digging trenches to be aware of factors such as soil type, moisture content, weather or excessive weight that might cause cave-ins, such as heavy equipment beside a trench.
Never climb into any pit deeper than 1.2 m (4 ft) unless it is properly sloped, shored or protected by a trench box. This is impractical for burying deadstock. Figure 2 shows different pits 1.2 m (4 ft) deep that will hold about 2,500 kg of deadstock. Closing these pits would require a minimum of 0.6 m (2 ft) of soil, to form a mound higher than the level of the ground at the perimeters of the pit.
Figure 2. Each of these pits will hold about 2,500 kg of deadstock. Bury smaller deadstock in narrow pits, to maximize soil-to -carcass contact, and larger deadstock in wider pits, to accommodate their awkward body dimensions.
Type of pits
The type of soil determines the strength and stability of pit walls; this is especially important for pits that will remain open for up to 120 days. Suitable soils that will allow pit walls to be stable for an extended period include:
Suitability: Death of one or more animals at the same time (due to sickness, heat stress) or for deadstock stored over time so burial is done all at once (e.g., a freezer full of dead chicken broilers). Single-use pits are usually open only a few hours.
Suitability: Operations with daily to weekly deadstock (weaner pigs, poultry). Since all deadstock placed must be covered at all times with 0.6 m (2 ft) of soil, dig these pits oversized, since soil is being constantly added as deadstock are placed, which takes a lot of room. Flag pits as open or fence them off. Frozen soil may make covering a pit difficult in winter.
Suitability: Smaller deadstock on smaller farms with a few periodic death losses.
Unsuitable soils that might have unstable pit walls over an extended period include:
Figure 3. Pits can be dug quickly using a tractor auger. Augers over 0.6 m (24 in.) in diameter and augers that dig more than 1.2 m (48 in.) deep are costly and require a lot of tractor power. Auger pits will only hold a few smaller deadstock.
Once a pit is dug, its sides are exposed to drying. The longer the exposure, the greater the risk of a cave-in. Rain, melting snow, thawing earth and surface water all produce changes in soil conditions that can severely affect pit stability. Heavy equipment beside a pit can affect its stability, so stay as far away as possible. Place the soil excavated from the pit at least 1 m (3.3 ft) from the edge of the excavation.
The regulation specifies a burial pit must be immediately closed when 120 days have elapsed since the day the pit was first opened, or when 2,500 kg of deadstock have been buried in the pit, whichever comes first.
How big should the pit be?
Deadstock have odd shapes, making them difficult to bury, especially if they have begun to bloat or rigor. The effective burial bulk density (EBBD) of deadstock is the weight of a deadstock carcass at death, divided by the effective volume it takes up in a burial pit.
EBBD = weight of deadstock carcass at death ÷ effective volume it takes up in burial pit
The effective volume is difficult to establish, because different animals have different profiles and awkward shapes when buried, and there are unavoidable air pockets. The EBBD of deadstock is estimated in the broad range of 175-1,000 kg/m3 (10.962.4 lb/ft3), but for planning, use 400 kg/m3 (25 lb/ft3). When soil is placed on deadstock, it fills some air pockets, and as deadstock decomposes, soil settles into body cavities.
Use Table 4 as a guide for burial pit dimensions dug by backhoe. Modify dimensions as necessary based on the shape of your deadstock. It is better to over-dig than under-dig. Once deadstock are in the pit, do not move them again. Because deadstock must be covered with at least 0.6 m (2 ft) of soil, multiple-use pits may have to be longer than shown in Table 4.
The dimensions in Table 4 are based on:
Example: 40 dead feeder lambs weighing a total of 1,000 kg require a burial pit at least 1.2 m wide x 1.2 m deep x 1.8 m long (4ft x 4 ft x 6 ft)
Formula for calculating length of pit in metres:
L = Total kg of carcasses ÷ EBBD (kg/m3) ÷ width of pit (m) ÷ depth of pit (m)
Use Table 5 as a guide for tractor auger burial pit dimensions, knowing the total weight of deadstock to bury and the type of animal. Modify dimensions as necessary, based on the shape of your deadstock. Unless an auger pit has a large diameter and is augered deep, it will not hold many deadstock, but it may be an option for some operators.
Example: 8 dead feeder lambs weighing 200 kg in total require an auger burial pit at least 1.2 m deep x 0.75 m diameter (4 ft x 2.5 ft).
Digging near field drainage tiles
Field drainage tiles are prevalent on Ontario farms. To prevent leachate reaching them, avoid burying deadstock near tiles. The regulation specifies that every part of a burial pit must be at least 6 m (20 ft) from a field drainage tile. Further, if any part of the burial pit is less than 15 m (50 ft) from a field drainage tile, deadstock must be placed so that the highest point of the uppermost deadstock is lower than the lowest point of the nearest field drainage tile. This way, any leachate from the burial pit would be below the level of the tile and would not be able to reach it (Figure 4).
Figure 4. The regulation specifies that deadstock cannot be buried within 6 m (20 ft) of a tile drain. If there is a tile drain within 615 m (2049 ft) of the burial pit, the highest point of the uppermost deadstock must be below the level of the lowest point of the tile drain. If tiles are more than 15 m (49 ft) from the burial pit, no tile-related restrictions apply.
Within about 48 hr of death, some carcasses begin to bloat due to retained gases; lancing (puncturing or venting) carcasses larger than 100 kg is sometimes necessary. Use a bale spear to cut a deep stab wound posterior to the ribs to vent the thoracic and abdominal cavities. Lance deadstock just before placing it in the pit. Noxious gases and bodily juices are likely to escape.
Plan carefully how to place carcasses in the pit. Do not drop them in from a tractor front-end loader bucket unless your front wheels are well back from the pit. Push large, heavy carcasses, such as cows, into the pit from the side. Always stay as far away as possible from the pit with the tractor (Figure 5).
Adding lime on top of carcasses is not recommended. In the past, lime was added to discourage scavengers, prevent odours and slow decomposition. Correctly buried deadstock will not attract scavengers or produce odours.
Figure 5. Pushing large deadstock, such as cows, into a burial pit is safer than getting too close to the pit with a tractor and loader and dropping it in.
Covering deadstock with soil
Place as much soil as possible in the spaces between deadstock to encourage quicker decomposition. Reduce the chance of a cave-in by pushing in soil rather than dumping it in. The regulation specifies a burial pit must be closed by filling it with enough soil that the top of the fill soil forms a mound higher than the level of the ground at the perimeter of the pit by the greater of half the depth of the pit measured with reference to its lowest point or 0.6 m (2 ft).
This ensures enough soil on top of the deadstock to reduce the chance of scavenging, but also allows for settling as the deadstock decomposes and soil falls into the voids between them (Figure 6). The minimum amount of soil required above ground after closing the pit varies depending on pit depth (Table 6).
Figure 6. Mounded soil on top of the deadstock reduces the chance of scavenging and allows for settling as the deadstock decomposes and soil falls into the voids.
Lightly compact the soil using a front-end loader or backhoe bucket. Do not drive over the pit. Mark the area with a flag for a period of time so you can find the location again and monitor it for scavenger problems, uneven settling or leaching. See O. Reg. 106/09 for the recordkeeping required for the deadstock, including the location. Include GPS coordinates of the site if possible.
Joe grows 25,000 chicken broilers per crop on a 9-week cycle and produces 6 crops per year. His death loss is 4%, and the average carcass weight is 0.76 kg. Joe wants to use chest freezers holding 0.71 m3 each (25 ft3) to collect and freeze dead birds as they occur. He proposes burying all the birds from the freezers once every 6 months, or about every 180 days, in May and November, when the freezers are full.
The burial pit costs per year are:
$800 for freezers
$800 for hired backhoe labour
$1,600 total yearly cost
The cost to bury (not including labour to transport and empty freezers of deadstock to the burial pit) is: $1,600/4,560 kg = $0.35/kg ($0.16/lb)
Nutrient Management Disclaimer 2018
The information in this factsheet is provided for informational purposes only and should not be relied upon to determine legal obligations. To determine your legal obligations, consult the relevant law, www.e-laws.gov.on.ca. If legal advice is required, consult a lawyer. In the event of a conflict between the information in this factsheet and any applicable law, the law prevails.
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