Livestock carcass disposal after fire, flood or drought

Options for disposing of carcasses

There are several means of carcass disposal for losses of farm animals following fire, flood or drought:

1. leave in situ: this is a choice for isolated small animals, but is not recommended
2. burial on-farm: this has been the traditional method of carcass disposal following emergency incidents (fire, flood, drought)
3. composting on-farm: this is suitable for small animals but experience or technical expertise in composting is desirable
4. off-farm disposal: may be suitable where the farm size or conditions do not favour on-farm disposal; contact your local government for advice.

Burying carcasses in trench pits

Environmental compliance

• The burial must avoid any environmental emissions. Any smell (gases) will be minimised if pit construction guidelines (as below) are followed. Liquid leaking into the environment will be avoided by selecting a site with impermeable soils.

Checklist of criteria when selecting a site for carcass burial

Soil characteristics and topography

• Soil of low permeability (avoid highly permeable sands, gravels, substrata, Karst geology).
• Not located on land with a moderate to high risk of acid sulphate soils.
• Area free of exposed granitic rocks (shallow depth, waterlogging, recharge).
• Elevated locations on erosional lateritic surfaces (deep soils of low permeability).
• Convex landforms, no drainage lines (prevention of erosion and waterlogging).
• Land with a moderate slope (no greater than 6%).
• Not located in areas subject to landslip, excessive erosion, or geological fault.
• Not located in a flood prone area i.e. > 1 in 100 years flood level.
• Near remnant vegetation (dry soils, erosion protection, soil biologic activity).

Exclusions, including minimum distances from features, such as surface water and dwellings

• At least 500m from surface waters, groundwater supply bores and drainage channels that may lead to waterways.
• At least 500 metres from stock watering points.
• At least 1 km from dwellings and private drinking water supplies including bores and dams.
• Located away from public view (e.g. major roads).
• Not located in a gazetted drinking water catchment, or a Sensitive Water Resource Area, including catchments of sensitive water resources, Conservation Category wetlands, groundwater dependent ecosystems, coastal inlets, and estuarine systems.
• At least 1 km from World heritage sites, conservation areas and sites of cultural significance.
• At least 2 Km from significant wetlands, tidal areas, estuaries, marine coast, wildlife habitats.
• Not located on contaminated land as defined under the Contaminated Sites Act.

Features relating to the construction of the pit

• Avoid underground infrastructure (power, telephone, gas, water, sewerage).
• At least 3m separation between bottom of proposed pit and groundwater level, considering the seasonal maximum depth of ground water.
• Site is accessible to trucks and earthmoving equipment, allowing for entry and disinfection.
• Site is big enough to accommodate the burial activity without affecting neighbours.
• Need a permit under the Environmental Protection Act if clearing native vegetation.
• Compliance with any other regulatory requirements e.g. Soil and land Conservation Act 1945.

It is advisable to record the GPS coordinates of the site for future land-use planning.

Battered pit dimensions

Carcasses are most conveniently and safely buried in a trench or long pit. To minimise safety risks, use a pit with outwardly sloping (battered) sides to prevent collapse. There must also be enough cover to prevent carcasses from surfacing.

Figure 1 Example dimensions of a battered carcase-burial pit

Figure 1 Example of the dimensions of a battered burial pit (ignore the lining)

Dimensions required:

• 1.5 cubic metres (m³) per cow
• 0.3m³ per pig or sheep
• minimum depth of pit is 5m 
• required depth of soil to cover carcasses is 2m.

A pit 3m wide at the base, 5m wide at the top of the carcasses, and 5m deep, filled with carcasses to within 2m of ground level (Figure 1) has an effective available volume of 12m³ for every linear metre.

Using these dimensions, for each linear metre of trench, 8 cattle, 40 sheep and 2,400 birds can be buried in a battered trench and then covered with 2m of soil.

Composting carcasses on-farm

Composting is the natural aerobic decomposition of carcasses. This disposal method will require expertise with composting animal carcasses or the input of a composting contractor.

Advantages of composting:

• it is a low-technology disposal method
• it can be used where a high water table or unsuitable soil types preclude other disposal methods
• commercial operators are available in some areas
• it can be initiated immediately if adequate co-composting material is available
• it recycles carcasses and results in a soil impover for farm use or a saleable product (subject to DWER requirements)
• it does not require long-term monitoring or remediation.

Disadvantages of composting:

• it may require a large area
• it may require a large supply of co-composting material (sawdust, straw or similar organic material)
• localised odour and soil contamination is possible if poorly managed
• daily control and monitoring is required during initial stages
• possible biosecurity risk if required temperatures are not achieved
• it may take longer than other disposal methods
• efficiency may be affected by adverse climatic conditions
• there is limited experience with large numbers of large carcasses
• there is no data for composting of livestock with heavy fleece
• potential local community resistance
• access to commercial composters may require pre-planning or additional time to arrange
• it may require final product testing to release compost.

Contact information

For further information, please contact Bruce Twentyman, Principal Veterinary Officer (Policy) at the department on 08 9363 4127 or bruce.twentyman@dpird.wa.gov.au