Options for disposing of carcases
There are several means of carcase disposal for losses of farm animals following fire, flood or drought:
- leave in situ: this is a choice for isolated small animals, but is not recommended
- burial on-farm: this has been the traditional method of carcase disposal following emergency incidents (fire, flood, drought)
- composting on-farm: this is suitable for small animals but experience or technical expertise in composting is desirable
- off-farm disposal: may be suitable where the farm size or conditions do not favour on-farm disposal; contact your local government for advice.
- If burying livestock carcases on your farm, there is no limit to the weight or volume of carcases that can be buried.
- 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.
- must not be within 10 kilometres (km) of a town water supply intake or within 300 metres (m) of a borehole used for drinking water
- must be more than 2km from a town and 1km from any dwelling
- should be on soils of low permeability; clay is ideal
- should have groundwater at the site more than 10m below the base of the burial pits at all times
- should be more than 100m from any watercourse
- should be more than 400m from any lake and 100m from any wetland
- will be more than 2km from the coast
- will not be within 1km of a World Heritage Area
- will not be within 250m of a national park or conservation area
- should be accessible to large trucks and earthmoving equipment, allowing them to enter easily and be effectively disinfected
- should not be on a slope greater than 6% and allow digging of 5m deep pits with heavy equipment.
It is advisable to record the GPS coordinates of the site for future land-use planning.
Battered pit dimensions
Carcases 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 carcases from surfacing.
Figure 1 Example of the dimensions of a battered burial pit (ignore the lining)
- 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 carcases is 2m.
A pit 3m wide at the base, 5m wide at the top of the carcases, and 5m deep, filled with carcases 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 or 40 sheep can be buried.
Composting is the natural aerobic decomposition of carcases. This disposal method will require expertise with composting animal carcases or the input of a composting contractor.
- it is a low-technology disposal method
- it can be used where a high watertable 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 carcases and results in a saleable product (subject to acceptable use)
- it does not require long-term monitoring or remediation.
- 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.