Disposing of carcasses after bushfire, flood or drought

On-farm burial is the traditional method of carcass disposal during bushfire, flood and drought. Whilst it is quick, effective and relatively cheap, other options need to be considered before initiating a major burial program.

Rendering

Rendering is an effective method of converting animal carcases into saleable products such as meat and bone meal and tallow. Rendering plants are located throughout Victoria and some have the capacity to process large volumes of animal material.

The practicality of using rendering as a disposal method may be limited by the rendering companies willingness to receive product, suitability of product (such as degree of burns, decomposition, emaciated stock, amount of wool), plant capacity and cost of transport.

Knackeries

Knackeries provide an efficient means of disposing of dead, unsaleable or suffering livestock. Carcases can be processed for their fresh meat, saleable hide, or offal.

For commercial reasons, knackeries prefer to process larger animals such as cattle and horses. Knackeries may pick up sheep carcases, but this is usually as a service and generally only in small numbers. It is unlikely that knackeries will accept moderate to severely burnt livestock.

Licensed landfill

Disposing of carcases to licensed landfill is an acceptable and effective option for agricultural emergencies.

The advantage of landfill is that it may already be licensed to accept animal materials (putrescible waste) and generally has the existing infrastructure to manage long-term containment issues (such as leachate, gas, security).

Another advantage of landfill is that many sites are owned by local government and may already be identified as potential disposal sites under Municipal Emergency Management Plans.

On-farm burial

When planning for on-farm burial there are many factors that need to be considered. These issues include the environment, statutory controls, logistics and safety.

As a guide a burial site should be located:

• on heavier soil of low permeability and good stability
• on elevated land but with a slope of less than 5% (preferably less than 2%)
• above the one in 100-year flood level
• at least 200 metres from any surface water (creek, river, lake, spring)
• at least 200 metres from any ground water supply (stock and domestic bore)
• at least two metres from the bottom of pit to the water table level
• at least 300 metres from any sensitive use (such as a neighboring house)
• a safe distance from underground and above-ground infrastructure (such as a powerline, telephone line, gas line, waterpipes, sewerage)
• well away from the view of the general public

Operators should also:

• cover carcases with at least two metres of soil
• slightly mound pits after backfilling to allow for subsidence and promote runoff rather than infiltration
• where necessary, excavate cut-off drains upslope of the burial pits to direct surface run-off away from the pits
• where possible, plan destruction activities close to burial site
• have good, safe access to site for machinery

Other important factors that need to be considered are:

• monitoring programs (if required by EPA)
• leachate and gas management (if required by EPA)
• use of synthetic liners in pits (if required by EPA)
• native flora and fauna planning controls, heritage overlays, native title and covenants

Final site selection usually involves the agreed best outcome after consultation with relevant agencies and a risk assessment of all factors.

Site assessments

A potential burial site should be physically assessed for suitability by an EPA representative. In a bushfire response where there are many on-farm sites this may not be practical and decision making may be delegated to an experienced representative from another agency. The location of each disposal site should be recorded for future reference using a Global Positioning System (GPS).

Pit construction

The typical method of digging a pit is to construct a deep, narrow, vertically sided pit (trench burial), but this will be dictated by the soil stability.

Where soil stability is of concern, a battered design should be used to enhance operator safety. Worksafe Victoria can provide information on safety precautions for emergency trenching operations – https://www.worksafe.vic.gov.au/

The preferred equipment for constructing this type of pit is an excavator. During construction, topsoil should be separated from subsoil for later return to the top during pit closure. Excavated material should be stored along one side or at the ends of the pit, depending on the operation. Surplus soil should be heaped as overfill.

Pit dimensions

Figure 1: Example of on-farm trench burial.

In designing dimensions of a pit, consideration should be given to the method used to fill the pit with carcases. Typically, carcases will be unloaded (out of tip trucks) and then pushed into the pit (loader, bulldozer or excavator) from one of the long sides.

It is critical that a safe operating zone is established as part of a documented work procedure. Excavators can be a good option to fill pits with carcases, especially where soil stability is a potential issue.

When using on-farm trench burial the following dimensions can be used as a guide:

• Depth: Four to five metres (depending on reach of machinery, soil stability and depth to water table). Base of pit to be at least two metres above water table level.

• Width: Not greater than three metres wide (to allow for even spread of carcases in pit)

• Length: Depends on number and size and of carcases to be buried (volume).

• Backfill: Two metres of backfill to be placed over carcases.

• Volume: Carcass volume will vary according to number and size of animals:

  Previous drought experience has shown that approximately 10 adult sheep in poor condition and with limited wool will take up one cubic metre of pit space. (North-East Region Flock Reduction Scheme)

  As a guide, allow 1.5 cubic metres of pit space for one adult beast or five adult sheep in good condition. (AUSVETPLAN Disposal Manual, 2015)

The slashing of the abdomens of carcases prior to burial (to reduce the buildup of gas) is not recommended for sheep or other small animals, or badly decomposed cattle.

For freshly dead cattle a risk assessment should be conducted to determine if the benefits of slashing outweigh the safety risks to the operator. Machinery may be used to puncture the abdomens of cattle to reduce manual handling risks.

Example diagrams of burial pits

Click on the diagrams to view larger versions.