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Appendixes

Archive: 1999 Session - Appendix 23

1999 Session of the Research Group of the Standing Technical Committee of EuFMD

 

 

Deciding how to dispose of large numbers of Animal Carcasses in an Environmentally-Friendly Manner

 

John Ryan, EuFMD Secretariat

 

Introduction

National Veterinary Services face increasingly difficult tasks and a greater workload than ever before as the volumes and complexity of world trade in animals and animal products increases. Compounding these difficulties, the National Veterinary Services are increasingly having to serve the interests of not only the agricultural industry but consumers, animal welfarists and environmentalists also.

There has never been an objection within the veterinary profession to serving any of these constituencies. However, as public and scientific awareness of welfare and environmental issues rises, more constraints than ever before are placed on the actions and interventions of the national veterinary services. No longer can an intervention such as emergency slaughter be justified on epidemiological and economic grounds to the agricultural industry, it must also be justified on welfare and environmental grounds to an increasingly sceptical general public too.

Recent massive epidemics of contagious diseases such as BSE in the UK, Classical Swine Fever in the Netherlands, Avian Influenza in Hong Kong and FMD in Taiwan and the realisation that National Veterinary Services are working more and more under the spotlight of media and interest group attention has provoked concern among Chief Veterinary Officers world-wide.

Halting the spread of highly contagious animal diseases is always a difficult task and the available tools are limited. "Stamping-out" with its associated measures such as movement controls, disinfection routines and destruction of infected and potentially infected carcasses is a highly effective tool for controlling and eradicating contagious animal diseases. However, it does not appeal to the general public nor the animal welfare activists and often not even to the agricultural industry itself. Furthermore, when stamping out is contemplated on a large scale it poses a threat to the environment also.

These concerns were voiced by the Chief Veterinary Officers of member countries at the 33rd General Session of EuFMD in Rome on 4-5th April 1999, where they formally requested the Research Group to examine the problem of the environmental impact of disposing of large numbers of animal carcasses in an environmentally friendly manner. This paper is intended to introduce the topic and hopefully stimulate some further interest and research.

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The Options

 

The options for disposal of animal carcasses on a routine basis e.g. casualty animals, pets etc. are generally prescribed by law in most countries. Directive 90/667/EC on animal disposal confirms the acceptable disposal routes as a treatment or processing plant; or burning; or burial.
For small scale disposal problems these regulations are generally acceptable, but it is not always possible or safe for the environment for these methods to be used on a large scale such as large scale animal disease epizootics like those mentioned in the introduction. While many countries have guidelines on what to do with carcasses slaughtered in contagious disease emergencies, it is not clear if there are any scientific studies demonstrating the safety of these protocols for the environment.
The only literature that comes close to approaching this problem is that of agricultural engineering, where the engineers have contemplated the environmental safety of disposing of the regular and often large numbers of mortalities associated with intensive poultry and pig production. However, this literature generally prescribes measures that appear to be insufficient in dealing with highly contagious animal disease and would have huge difficulties in scaling up from 5% of a herd capacity to full herd capacity. (I have listed some of these methods in the Other Potential Options section below) This leaves us with the three generally prescribed methods of carcass disposal, rendering, burning and burying, and the advantages and disadvantages of these methods are discussed below. In order to stimulate discussion and some lateral thinking, I have also listed some non-standard solutions to this problem in the section titled Other Potential Options below.

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Rendering
National and European Union regulations tightly control and regulate the rendering process particularly since the BSE crisis. National Environmental Agencies will ensure that these plants operate in a manner that poses negligible threats to the environment. A critical area for environmentalists and veterinarians is the method for treating waste water and effluent from these plants.

 

Advantages

  • Efficient elimination of virus.
  • Recovery of Meat and Bone Meal (may help offset costs and is less wasteful).
  • Negligible risk to the environment if the plant complies with the relevant licensing laws and environmental agency provisions
  • More acceptable to the general public.

 

Disadvantages

  • Limited short term capacity in any given area for dealing with outbreaks.
  • Possibly limited long term capacity in all of Europe as the economics of the rendering business become unfavourable.
  • Requires transport of infected material often over long distances and through clean areas.
  • May require cold-storage of carcasses on site for prolonged periods to deal with large volumes.

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Incineration
There are two methods of incinerating carcasses, on-farm funeral pyres and specially built or adapted commercial incinerators. Specially built incinerators may offer the potential to use the calorific value of the incinerated carcasses and are therefore less wasteful.

 

Funeral Pyres
There are many guidelines available on how to practically construct effective Funeral Pyres, the environmental impact of these pyres has rarely been studied.

 

Advantages

  • Effectively eliminates virus.
  • Can be carried out on most farms even on those farms where burial is not feasible.
  • No transport of infected material off-farm
  • No long term significant environmental damage is believed to result.

 

Disadvantages

  • Smoke is a significant short term pollutant and may be totally unacceptable if human dwellings are downwind or in certain weather conditions.
  • CO, VOC’s, NOX, dioxins, particulates, SO2, HCL and heavy metals are significant pollutants that may be released by incineration.
  • These pollutants pose particular difficulties in the context of large numbers of pyres located close together as in a cluster of outbreaks.
  • Negative emotional reaction is to be expected from the general public and it may fuel significant animal welfare resistance to the slaughter policy.
  • Odours from the pyre are a significant public nuisance
  • Pyres can be very long with 3 feet required per adult cow.
  • Ground water may be affected by the hydrocarbons used as initiators and accelerators.
  • Ashes must still be disposed of in a suitable licensed landfill site.

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Incinerators
Construction and operation of incinerators must meet strict environmental regulations as laid down by the national environmental agency.

 

Advantages

  • Effectively eliminates virus.
  • Risk assessments have demonstrated that the risks to the environment are negligible if licensed and operated according to the guidelines of the relevant Environmental Agency.
  • Carcasses, like meat and bone meal, are a good grade fuel and it is environmentally preferable to recover the energy from the carcass whenever possible.
  • Easy to monitor compliance with emission levels.
  • Air scrubbing or filtering processes can be added if necessary.
  • No odour should be detectable at the boundary of the premises

 

Disadvantages

  • Limited short term capacity in any given area.
  • Requires transport of infected material often over long distances and through clean areas.
  • May require cold-storage of carcasses on site for prolonged periods to meet large volumes.
  • CO, VOC’s, NOX, dioxins, particulates, SO2, HCL and heavy metals are significant pollutants that may be released by incineration.

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Burial
Regulations on the burial of carcasses can also be widely found in national legislation, and while these ensure that the risk of FMD virus resurfacing from the burial pits is negligible, no scientific proof of the safety of this measure for the environment was found. Most legislation will describe in detail the selection of suitable sites based on soil type and depth to the watertable. Some countries have already zoned their country in advance to identify areas that are suitable and not suitable for burial, particularly in relation to groundwater used for human consumption. Most regulations specify the following or close variants of it:

  1. The trench (the most suitable shape for filling and burial) must be deep enough to allow sufficient topsoil coverage to prevent carnivorous animals or vermin access to the carcasses.
  2. Suitable soil type and depth to prevent contamination of groundwater is usually pre-determined from zoned groundwater maps.
  3. Usually on level ground, slopes are not suitable.
  4. At least 250-300m from a well, 10m from a field drain and 30m from a spring or watercourse 5. Minimum of 1m subsoil below the pit, base of pit free of standing water, and 1m soil cover over carcasses. Carcasses at least 1m above watertable (carcasses take approx. 1m). As carcasses take up 1m depth, 3m is the minimum depth required but usually 4m depth is used.
  5. A Quicklime lining and covering on the carcasses is used to inactivate virus in the leechate.
  6. Beware of private water sources using local groundwater that may not be included in geological maps of ground water uses.
  7. Protocols for fencing off the site and for when animals can subsequently have access to the site.

Regulatory authorities when examining the burial site subsequently would look for indicators such as faecal coliforms, faecal streptococcus, chloride, and various nitrogenous breakdown products in the groundwater at various depths and distances from the burial site.

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On Farm

 

Advantages

  • Negligible risk of virus resurfacing.
  • No risky transport required.
  • Very inexpensive.
  • Bacteria (and possibly viruses) seem not to move very far in soil. Faecal coliforms and faecal streptococcus were found to be very low when measured around dead bird disposal pits (Ritter and Chirnside, 1995).
  • Possibly more acceptable and discrete than burning to the general public.

Disadvantages

  • Availability of suitable sites may be limited or non-existent in certain geological areas.
  • No proof that large scale burials do not have long term detrimental effects on the environment.
  • Acceptable carcass load for any given area or volume of groundwater catchment has not been determined.
  • Greatest impact may be caused by toxic breakdown products such as ammonia, nitrites and chloride. There is evidence that this occurs around dead bird disposal pits (Ritter and Chirnside, 1995), which it must be remembered are on a much smaller scale than would be the case in the event of a large epidemic of FMD

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Landfills
Usually stringently controlled by the licensing authority and will have very large plastic lined pits to prevent the escape of leechate to the ground water. The leechate is subsequently drained off and treated (chemically, biologically or by heat).

 

Advantages

  • Properly licensed and operated sites pose little risk to the environment.
  • The risk of virus disseminating or resurfacing can be negated by veterinary specific protocols.
  • High capacity with the necessary machinery usually readily available or already in place.

Disadvantages

  • Licensing is difficult to obtain.
  • Pits used for carcass disposal must be closed soon after filling and thus the capacity of the pits designed for domestic waste can be greatly reduced
  • Availability is limited and owners and planning authorities may not want to sacrifice precious available landfill sites
  • Transport to the sites is dangerous for the dissemination of virus
  • Expensive
  • Vermin and birds may present problems while filling

Other Potential Options
These are presented as extreme examples of possibilities for disposal of carcasses in general. Their environmental impact and suitability for FMD infected carcasses is not known but these or other novel ideas may lead us new approaches to this problem. These are also ideas that may be worth exploring for other diseases not as contagious as FMD.

 

On-Farm Processing
Composting
Fermentation
Sterilisation
Dumping at Sea?
Deep Mines?

 

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The Decision

 

The following sections outline the factors one needs to take into consideration in deciding how to dispose of large numbers of carcasses.

 

Don't ever get into a position to need it!
Preventing this problem from ever arising is by far the best strategy. National Veterinary Services should concentrate their efforts on preventing the introduction of FMD and having sufficient awareness and an effective contingency plan to ensure that the disease is rapidly stamped out before the number of carcasses to be disposed of reaches levels where the environmental impact is significant. A CVO will never have to justify slaughtering only one herd in controlling an outbreak to animal welfare groups or environmentalists!
This is advice that is easily given, but in the real world it is extremely difficult to implement and cases will arise where there will be large numbers of animal carcasses to be disposed of and some framework should guide the decision on how they will be disposed of. As with every other aspect of dealing with FMD outbreaks, advance preparation is critical for timely and successful decision making and disposal of the carcasses in an environmentally friendly manner. Detailed plans and advance contracts for the equipment, personnel and services required for disposal of carcasses should be an integral part of any FMD Contingency Plan.

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Advance Preparation
Groundwater maps and consultation with a specialist from the national environmental agency will identify areas of the country that are suitable for burial and funeral pyres.
Other essential maps and data that need to be collected in advance of an outbreak and updated regularly are the location of Rendering plants, Slaughter Houses, Incinerators licensed and equipped to handle animal carcasses and Landfill sites that are licensed and equipped to handle animal carcasses. If no incinerators or land-fill sites are licensed to accept animal carcasses or if they are of limited capacity or of limited geographical distribution, then it may be useful to encourage existing facilities to upgrade and become licensed for this purpose.

Other useful information to have would be the locations and dates of previous large scale burials and maps locating human settlements. Meteorological data on wind speeds and directions will of course also be necessary for siting funeral pyres, but as it is necessary for modelling airborne spread of virus from infected farms, it should be available by prior arrangement already.

Advance arrangements for the supply of necessary equipment or services are highly recommended. For example, sealed trucks with functioning and disinfectable waste tanks for the transport of carcasses to landfills, rendering plants or incinerators. Excavators, quick lime, fencing contractors will be required for burials.

For funeral pyres the list of requirements is significant and may not be readily available in crisis times: Sleepers; Straw; Kindlewood; IsoKal or tyres; Coal; Plastic bags; fork lifts/trucks/tractors with bucket loaders for moving fire ingredients and carcasses; diesel for singeing and initiating the fire; lamps to keep vermin away from stored carcasses and to allow night working; hand forks; rakes; eyegoggles; heavy gloves; and firetenders for two nights are all listed as requirements for an effective pyre.

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Deciding by Setting Priorities
At all times the number one priority is ensuring the complete destruction of all FMD virus and ensuring that in no way will any process or action that takes place during the disposal of the carcasses result in further spread of the virus.

Due to the lack of data on the long term environmental damage from the disposal of carcasses by the most popular on-farm options, the next priority should be to limit the environmental damage from the disposal activities. The simplest method of doing this for a particularly large environmental load (e.g. in a high density intensive production area) is to share the load across as many disposal routes as possible. For example, exhausting local rendering capacity then exhausting local incinerators capacity, then a combination of burying where feasible and creating funeral pyres for the balance of the load may be a good strategy for certain areas. For other areas where the farms are remote from human settlements, funeral pyres may be the best method. In areas with a deep watertable and a large catchment area where the ground water is not used for human consumption then burial may be the best option.

The exact number of carcasses disposed of by each method should be determined on the spot by examining the local possibilities and constraints. In very constrained circumstances methods to regulate the flow of carcasses for disposal should be considered (e.g. cold storage until there is rendering or incineration capacity). It may also be preferable to store carcasses on the farm of origin under supervision until capacity is available for their safe disposal.

The other very important factors to consider are time and cost. The need for rapid decision-making and disposal makes this decision very difficult on the ground as the decision-maker will never know what his future disposal load will be.

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Theory of Constraints
This problem is a classic Theory of Constraints problem. The solver function in Microsoft Excel allows the creation of a spreadsheet which can aid the decision on how to distribute the carcasses over the different disposal methods available in the location with given capacity constraints for burying, local incineration or rendering. It can also be used to help minimise the costs of the disposal operation.

 

 

Conclusions

 

Give the environment a break....ensure that the decision on how to dispose of large numbers of animal carcasses has never to be taken, by preventing the introduction of FMD and having a ruthlessly efficient contingency plan in place to eradicate the disease in a short period of time with the minimum number of animals destroyed.

Prepare as much information in advance on the options for disposal, in case it is needed.

Slaughter the animals that need to slaughtered first and then worry about disposal. It may be beneficial for there to be a division of responsibilities in this matter so that the person deciding what farms to slaughter is not influenced unduly by the disposal problem. Another expert may have the sole responsibility for disposal of the carcasses subsequently. Holding slaughtered animals on-farm for a long period may not be particularly risky for the dissemination of the virus while the decision is made on finding a safe method for their disposal.

Make the decision on the spot on how to dispose of the carcasses based on local factors and use a variety of methods to reduce the environmental "load".

Prioritise the least environmentally damaging options such as rendering, incineration and land filling in licensed and approved facilities. When transporting the carcasses ensure that they are in totally sealed and disinfected trucks and that all other measures are taken to prevent distribution of the virus.

If feasible, cold-storage of slaughtered carcasses can be a means to continue using environmentally-friendly methods when their daily capacities are exceeded.

Funeral pyres and local burial of carcasses should be used whenever the capacity of environmentally sound techniques are exhausted and when a suitable local site can be found.

An on-farm disposal method should always be used if the absolute security of transport to a disposal plant cannot be guaranteed.

Always follow the prescribed guidelines on how to select a site for burial and funeral pyres. Always follow the prescribed procedure for burning and burial.

Document the location, amount of carcasses and disposal procedure used in each site for burial. Fence off the site for the prescribed period and monitor the safety of nearby groundwater subsequently.

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The Future

 

There are many unknown factors in trying to approach this problem. Limited knowledge of the real or imaginary risks from current disposal methods; of the likely reactions of the different interest groups; of the usefulness and safety of new techniques etc. With so many unknowns, it is difficult to see where the attention of researchers should be directed in order to find the solution to this problem.

For the moment, avenues should be pursued to make existing methods more environmentally friendly. For example:

Licensing rendering and incineration plants;
Mapping the country for the availability of safe burial sites;
Improving on-farm incineration to reduce pollutants (air curtain accelerators);
Investigating the use of land-fill technologies on farm (esp. for very large units);
Investigating the possibility of designing mobile rendering or incineration units;
Investigating the dangers of storage of carcasses on farm until suitable disposals methods are available.

The solution is never going to be a simple one but with awareness of the options available; a consideration of the real concerns of the various interest groups and the use of combinations of methods to reduce the environmental "load", an optimal solution may be found for each unique circumstance.

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References

  • Crane, N (1997) "Animal Disposal and the Environment" State Veterinary Journal Vol. 7, No. 3 October 1997, MAFF(UK).
  • FAO (1990) "FAO seminar on emergency action against FMD (Mediterranean)" FAO reports.
  • Ritter, W.F. & Chirnside (1995) "Impact of Dead Bird Disposal Pits on Ground-Water Quality on the Delmarva Peninsula" Bioresource Technology 53 105-111.
  • Moutou, F.(1995) "Destruction des cadavres. La dçmarche francaise" personal communication.
  • AUSVETPLAN (1996) "Disposal Procedures" Agriculture and Resource Management Council of Australia and New Zealand.
  • The Environment Agency (UK), Technical Guidance Notes: IPC S2 5.01 Amplification Note on Animal Remains Incineration (1997) and IPC S21.05 Amplification Note on Combustion of Meat & Bone Meal (1998) from http://www.environment-agency.gov.uk/epns/ipchome.html.
  • Richardson, H., UK Environment Agency, personal communications.
  • Morton, T., veterinary advisor to MAFF (UK), personal communications

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