Disposal of fallen livestock

Composting and other techniques for carcase disposal

The Animal By-Products (Enforcement) (England) Regulations 2011 allow the composting of pig carcases, but only after a number of rendering treatments have taken place and the appropriate authorisations obtained. The resulting compost cannot be spread on agricultural land. These treatments make the process unviable in most situations because incineration or rendering are more cost-effective.

What is anaerobic bioreduction?

The use of microbes without air (anaerobic) to digest carcases. This process works similarly to septic tanks and anaerobic digesters. The use of pig carcases as part of anaerobic digestion (AD) was optimised in a trial at Harper Adams University and showed some reduction in pathogenic bacteria.

A trial was designed to produce a report for the European Food Standards Authority (EFSA) to find out whether AD can be accepted as a safe means of disposal of fallen pigs under EU legislation as well as to determine the optimum conditions for AD of porcine carcase material (PCM). 

Findings 

• Significant levels of biogas can be produced from AD of PCM
• AD of PCM was more efficient and stable at 35ºC than at 55ºC
• Pathogen destruction was greater at 55ºC than at 35ºC and reduction of spore-forming bacteria such as perfringens was minimal at 35ºC
• Small-scale on-farm systems may be a cost-effective alternative to incineration or collection 
• Some form of pre-treatment by sterilisation is required to ensure adequate levels of pathogen destruction, and pig slurry can be effectively used as a co-substrate

Research details

On-farm storage and bioreduction of pig carcase material by anaerobic digestion

Pig carcase bioreduction using anaerobic digestion (AD) stage 2

What is bioreduction?

Bioreduction uses bacteria that break down animal carcases using oxygen. This is different from AD in that oxygen has to be supplied to the tank rather than excluded.

In this system, a septic tank-style system is buried in the ground, which contains a heating element, thermostat and air delivery system. Any fallen stock added to the system must be covered by water. The tank is kept at a constant temperature using a thermostat and air, provided that oxygen is bubbled through the system. The gut is split before the carcase is added, allowing natural cultures of bacteria to break down the carcases.

An aim of research completed at Bangor University was to strengthen the case for EC legislation of bioreduction as a means of managing fallen stock.

Findings

• The trial found negligible numbers of human pathogens in the waste generated from bioreduction
• No pathogens were detected in gaseous emissions from the system
• The system was relatively costly to install, but running costs were relatively low
• On a weight basis, cost of waste disposal was considerably less than costs of disposing of fallen stock via the conventional method
• The findings indicate that in-vessel bioreduction could potentially offer livestock farmers a sustainable, practical, cost-effective and biosecure method of containing fallen stock prior to disposal by an approved collector
• Further work is needed before making any formal application to the EC for its legislative approval 

Research details

Bioreduction of fallen stock – final report

The Houston Report (published by the Royal Agricultural College 100 club in June 2012) identified carcase cooling as a possible means of adding value to fallen stock and recommended that ‘the Danish system of cooling for storage of porcine carcases on farm merits consideration’. 

It recommended there should be ‘enhanced collaboration between farmers and fallen stock collectors in pursuit of optimum practical storage arrangements on farm’. However, there has previously been little independent evidence to verify the effectiveness of on-farm carcase cooling. 

Since the Houston Report, a feasibility study on the desirability of the UK pig industry adopting carcase cooling as an on-farm method for the storage of fallen pigs prior to disposal, was conducted on behalf of AHDB Pork by Research partners: the Foodchain and Biomass Renewables Association (FABRA) and Harper Adams University.

Evaluation of a carcase cooling container

Carcase cooling containers have were installed on two farms as part of a series of field trials. Results from both trial farms indicated that the containers kept the contents of the dead bin at a steady temperature of between 2°C and 7°C, even when external temperatures reached 30°C. This was the case even when the bin was opened to add carcases or to empty it.

Electricity use was in the region of 500 kwh for the quarter, which equates to approximately £20 per month to run.

Comments from farm staff

“The container is easy to use and has reduced the odour and number of flies over that side of the farm.”

“Don’t take it away – even if it takes £20 a month to run, it is worth it.”

“We think the cooling container is fantastic. As far as creating the best possible environment for the village, it is a winner because the smell is virtually nothing and it looks neat, tidy and professional.”

Comment from the collector: “An absolutely marvellous idea – there was no smell and no flies – let’s hope everyone gets one!”

Background

On-farm cooling of fallen stock prior to collection and rendering may provide significant economic, environmental and biosecurity benefits to the UK pig industry, according to the report ‘Feasibility of Carcase Cooling in the UK’ (Harper Adams University, September 2014).

The aim of the 14-month trial was to evaluate the operation and performance of cooling containers for the on-farm storage of dead pigs (fallen stock) in England. This was for the purposes of potentially achieving improved biosecurity, on-farm management and carcase quality for improved marketable yield of products derived from rendered material following storage.

Key messages

• Fewer pick-ups may be required, which would reduce the biosecurity risk
• The coolers maintain a stable temperature (largely between 2°C and 7°C) even when outside temperatures exceed 30°C
• The running cost (in terms of electricity consumption) is approximately 80p/day during warmer months and less during cooler periods
• Anecdotally, the coolers reduced odour and flies around the dead stock bin
• Staff and fallen stock collectors think they are a good idea and that they make the job of handling fallen stock less unpleasant

Pig keepers may incinerate fallen stock on the holding of origin using equipment with a capacity of less than 50 kg/hour.  

These are referred to as ‘low capacity incinerators’. These incinerators must be of a type approved under the Animal By-Products (Enforcement) (England) Regulations 2011. These are exempt from the more onerous controls of the Waste Incineration Directive.

However, plants that burn other animal by-products (ABPs), (e.g. former foodstuffs, catering waste, manure), processed products (meat and bone meal, tallow), or other waste not of animal origin, must be authorised under the Waste Incineration Directive. The regulations covering low-capacity incinerators apply to most incinerators found on pig farms, as pig carcases are classified as non-Specified Risk Material (SRM).

Defra guidance: Animal by-products – how to burn them at an incinerator site