Slaughter plants: solutions to reduce odour emissions

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

Unpleasant odours may result from various 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 in fact mainly due 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. We present the practical example of a poultry slaughterhouse and indicate the most effective technological solutions to reduce such emissions. 

In slaughterhouses, some 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 may cause odorous emissions. In particular, the critical points may be the entrances to the plants and the area of the exhaust fans area. Ventilation, necessary to control the inside temperature, involves recirculation of air that may convey unpleasant odours outside.   
  
  
• Process water collection tanks 
  Open tanks that collect wastewater produced during the process are another source of odour emissions, especially during filling and emptying. The turbulence created during these operations could 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 characterized 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, there is a release of exhaust air from the pumping system, coming directly from the tanker, which causes a particularly high odour impact. 

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

Critical areas of the permises

• 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 could favour the spreading of odours outside, especially where there are openings. 
  
  
• Waste water collection tanks 
  The plant uses open tanks to collect wastewaters that must be then sent to a chemical-physical treatment system. Filling the tanks causes turbulence that increases the spread of odours, particularly unpleasant in the surroundings.  
  
  
• 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 performed through a depressurization 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 conveyed air; 
• osmogenic barrier for diffuse emissions.   

Dry filtration technology

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

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

Osmogenic barrier

In this case, we considered a treatment for the following emission points:  

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

After having set up a cover, to enclose the upper part of the box and prevent odours diffusion from the area, we set up a pressurization system sized to feed all the spray nozzles provided at the correct pressure.

 A control panel then allows starting the plant based on cycles of work intervals within predetermined working hours. 

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

Effectiveness tests

order to get a correct assessment of the environmental controls to be set up, olfactometric sampling is performed upstream and downstream of the equipment, so that we can objectively understand their contribution in terms of odour reduction.  

The olfactometric sampling (which we perform with the support of LOD Laboratory, also part of the Luci Group) is the only internationally accepted method for measuring odour concentration. Based on UNI EN 13725:2004, its 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 of abatement plants.  

Managing odour emissions in slaughter plants is a crucial matter to minimize environmental impact and preserve the quality of life in surrounding areas. Identifying critical areas and implementing appropriate technological solutions may 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 critical odours 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 minimize odour problems.