Slaughter plants: solutions to reduce odour emissions

Odorous emissions are a major problem in slaughter plants. 
In addition to the environmental impact, these emissions can negatively affect the quality of life of surrounding communities. 

Unpleasant odours can result from different stages of the production process, such as: 

• Receipt and housing of animals 
• Slaughtering and meat processing 
• Treatment of animal by-products 
• Waste water treatment systems 
• Solid waste storage and disposal 
• Surface cleaning and washing 
• Grease and oil treatment 

In fact, odour emissions in slaughterhouses are mainly related to the handling of animals, organic by-products and cleaning operations, with an emphasis on the decomposition of organic matter. 

However, there are solutions and technologies to contain and reduce these emissions, making the process more sustainable. 

In this article, we analyse the critical areas of a slaughterhouse that are most responsible for the production of bad odours, present a practical example of a chicken slaughterhouse and indicate the most effective technological solutions to reduce these emissions. 

In slaughterhouses, certain areas are particularly prone to the production of bad odours. These problems affect most slaughterhouses, although there may be differences depending on the type of animal being slaughtered. 

These include: 

• Live storage and sorting area 
  The handling of live animals, their stationing and sorting represent one of the first stages of the process that can cause odorous emissions. In particular, the critical points may be the entrances to the plants and the area of the exhaust fans. Ventilation, necessary to control the internal temperature, involves recirculation of air that may carry unpleasant odours to the outside.   
  
  
• Process water collection tanks 
  Open tanks that collect waste water produced during the process are another source of odour emissions, especially during filling and emptying. The turbulence created during these operations can disperse odours into the environment. 
  
  
• Screening, feather separator and collection bin area 
  This area, connected to the chemical and physical treatment of waste water, is characterised by the use of open containers for the collection of solid residues (such as feathers and other waste). Exposure to open air and the raw nature of the treated materials make this phase one of the most critical from the point of view of odour emissions. 
  
  
•  Blood tank and floating sludge tank 
  Tanks containing blood and floating sludge are equipped with vent pipes. During filling, these pipes release intense odours into the environment due to the organic nature of the stored liquids.
  
  
• Blood loading in tanker trucks 
  When the stored blood is picked up by the trucks, the exhaust air from the pumping system, coming directly from the tanker, is released with a particularly high odour impact.  

Let us look at a chicken slaughtering plant, which our technicians analysed in detail, to understand the process and the main sources of odour emissions.

Critical areas of the plant

• Storage and sorting of animals 
  In the plant we analysed, chickens are transported in cages that are unloaded, sorted and washed in a tunnel. Vacuum cleaners used to maintain a healthy environment during the process can favour the spread of odours externally, especially at the openings. 
  
  
• Waste water collection tanks 
  The plant uses open tanks to collect waste water, which is then sent to a chemical-physical treatment system. Filling the tanks causes turbulence that increases the spread of odours, which are particularly unpleasant in the vicinity.  
  
  
• Tanks and tank trucks 
  Floated blood and sludge are collected in tanks, with constant emissions from the vents. In addition, the loading of blood onto tank trucks is done through a depressurisation system that emits intense odours

Plant solutions for abatement of poultry slaughterhouse odours 

In the case under consideration, two distinct plant solutions were identified for the different and not very heterogeneous situations present: 

•  dry filtration technology for ducted air; 
• osmogenic barrier for diffuse emissions.   

Dry filtration technology

For the treatment of the conveyed emissions (consisting of processing water collection tanks, blood and float tank and blood loading vehicle), we planned to use dry scrubber technology, which involves the following abatement process  

• capture and conveyance of aeriform  
• condensate separation;  
• physical and chemical absorption with neutralisation and oxidation of pollutants in the emission;  
• extraction by centrifugal fan;  
• release of the mitigated aeriform into the atmosphere via a stack.   

Osmogenic barrier

In this case, the following emission points were planned to be treated:  

•   windows in the live storage area;  
• shed portal where the cages exit from the carousel;  
• gratings
• front of the collection box (extraction side);   

After the construction of a cover, to confine the upper part of the box and prevent malolent diffusion from the area, a pressurisation system sized to feed all the spray nozzles provided at the correct pressure was installed.  

A control panel then allows the plant to be started up with cycles of pause times within predetermined working hours. 

The plant is equipped with a neutralising product dosing system suited to the actual odour abatement requirements.    

Effectiveness tests

In order to correctly assess the environmental controls to be installed, olfactometric sampling is carried out upstream and downstream of them so that we can objectively understand their contribution in terms of odour reduction.  

The olfactometric sampling (which we perform with the support of the LOD Laboratory, also part of the Luci Group) is the only internationally accepted method for measuring odour concentration. It is based on UNI EN 13725:2004, the purpose of which is to provide a standard for odour measurement.  

 This type of investigation is also fundamental in the case of slaughter plants, both to obtain a complete picture of the type and intensity of emissions and therefore for the subsequent design and construction phase of abatement plants.  

Managing odour emissions in slaughter plants is a crucial aspect of minimising environmental impact and preserving the quality of life in the surrounding areas. Identifying critical areas and implementing appropriate technological solutions can contribute to a more sustainable management of the production process.  

As we also described in the case of the poultry slaughterhouse examined, abatement systems can be different depending on the areas and the odour criticalities to be treated. 

The use of air filtration systems, the closure of risk areas and the treatment of emissions are among the most effective strategies to minimise odour problems.