Livestock farming: how to contain the problem of odor emissions

Odor emissions mitigation techniques in animal husbandry with osmogenic barriers

The annoying smells of the farms

The problem of odorous emissions generated by livestock farms is often the cause of disputes brought by those who live near this type of establishment. The criticality has particularly intensified with the increase in livestock farming and the extension of residential areas towards rural areas with an agricultural and livestock tradition.

Although unpleasant odor emissions are not necessarily associated with toxicological risks, the problem of the low social acceptability of olfactory nuisance remains, which negatively affects the "quality of life" of the populations involved.

In reality, the odors produced by farms do not constitute a toxicological problem, as the compounds responsible are metabolites of the microbial degradation of manure, present in very low concentrations (with the exception of ammonia).

The emission of malodorous volatile compounds common to a multiplicity of industrial processes and the problems of social acceptability of some categories of plants have led the legislator to lay the regulatory foundations for a more rational policy of regulation of "odorigenic" activities also through the setting of rigorous air quality indices, as well as precise methods for measuring and evaluating odors.

Where odors on farms originate from

The odorous compounds identified on farms are numerous and derive from various factors such as feed and skin of the animals, but mainly from their excrement which originates from nutritional elements.

The main groups of odorous compounds are:

  • sulfur compounds (among which hydrogen sulphide is particularly offensive);
  • indoles and phenols;
  • volatile fatty acids;
  • ammonia;
  • volatile amines.

There are numerous studies aimed at identifying and quantifying odorous compounds in farms, but it is not, essentially, possible to univocally identify the chemical compounds that indicate the olfactory impact.

The main sources of emissions in livestock farming

In livestock farms, odors can derive from all phases in which there is the presence and movement of effluents: from the shelter of animals, to the storage, treatment and agronomic use of the effluents themselves.

Zootechnical wastewater, or zootechnical effluents, is the set of waste produced by an animal farm and composed of solid and liquid excrement (feces and urine), any solid materials of vegetal origin used as bedding, drinking water and washing, from unused food remains.

Odor emissions are highly dependent on climatic conditions and are therefore extremely variable not only over the course of the seasons, but also during individual days.

In the case of hospitalizations, for example, they depend on the variation in ventilation regimes, which in the summer period can be up to 10 times higher than those in the winter period. The presence of animal shelter and excrement storage facilities is permanent and it is therefore possible that the persistent and prolonged olfactory discomfort attributable to these phases has a significant impact on residents.

The type of diet adopted also has an influence on the odor component.

Odor emissions mitigation techniques

The most effective strategies for odor control in the livestock sector are preventive and management ones, but downstream abatement techniques, with specific treatment devices, can also be a valid aid in solving the critical issues of odor emissions.

1. Techniques for mitigating emissions in shelters

In this analysis we leave aside the aspects related to animal welfare and underline that management interventions can allow an effective containment of the olfactory impact of the breeding premises. These mainly concern the maintenance of a good level of hygiene and cleanliness of the stable, associated with systems for rapid removal of excrement and effective ventilation.

  • Rapid removal systems
    Rapid removal systems avoid the establishment, within the collection pits, of anaerobic degradation processes of the excrement, which are certainly responsible for the production of unpleasant odors.

  • Use of litter boxes
    Even the use of litter, where the production system allows it, generally proves effective in reducing odor emissions.

  • Reduction of the emissive surface
    Finally, the reduction of the emissive surface of the manure collection pits (the partially fissured floor compared to the totally fissured floor) can be an effective measure for limiting emissions. This is provided that excessive animal density or high temperatures do not cause the animals to not respect the functional areas (feeding, resting, defecation). In fact, to combat the heat, pigs can choose the cracked part of the pen as a rest area, dirtying the solid part.

Abatement with osmogenic barriers

Where all this is not enough, the reduction of unpleasant odors can take place with specific abatement techniques that take into consideration the treatment of the air leaving the factories and exploit the technology of osmogenic barriers.

This technology is an excellent solution when it is necessary to intervene on a non-dangerous but annoying emission.
In the sector in question we always find ourselves in this condition and this is why more sophisticated technologies must be carefully evaluated from an economic point of view.

The osmogenic barrier involves the use of a nebulization system consisting of:

  • a high pressure pump
  •  and a high pressure distribution line.

Both systems are designed to feed a network of nozzles of suitable flow rate, capable of distributing the neutralizing properties of specific products.

The intervention strategy must take into account various aspects, such as:

  • micronization / vaporization / evaporation;
  • strategic diffusion;
  • uptime and timing.

These characteristics may vary depending on the source, whether diffused or conveyed.

For this type of system, deodorizing products are used to control and reduce odors.

Labiotest products are tested and guaranteed for use even in work environments. For a "green" choice we have decided not to propose them for use in the internal areas of the farms where the animals are present in order to always guarantee their well-being.


Osmogenic barrier technology can be used to treat both diffuse and conveyed emissions:

  • in exit routes to the outside (domes, windows and doors);
  •  in conveyed emissions;
  • in sewage storage areas;
  • in the storage yards of organic animal waste.

The technology for reducing diffuse emissions using water or emulsion spray systems with/without additives is indicated as BAT in the documents on the best available techniques (BAT Conclusion).

2. Techniques for mitigating emissions from sewage storage

The reduction of odorous emissions from effluent storage tanks can be effectively achieved by reducing air circulation on the exposed surface, using various forms of covering.
The possible solutions range from the simplest (promoting the formation of natural surface crusts, floating covers) to the more "engineered" such as fixed covers.

In the case of existing storage structures, especially in the case of lagoons, these interventions are technically and economically problematic.

Instead, for newly built storage tanks, covering the structure is a practicable and effective option not only for mitigating odor emissions, but also those of ammonia, which constitutes another important pollutant.

However, in order to guarantee the mitigation of odorous emissions that can be generated during the loading and unloading phases of sewage or, where coverage is not possible, it is possible to treat the area with mobile misting systems that are positioned where there is both necessity.

The legislation on odors

The requirements that an industrial company must have to obtain the Integrated Environmental Authorization are indicated in Legislative Decree 59/2005. One of these is attention to the environment as a whole.

In fact all activities must know their olfactory impact, in order to reduce it. In particular, farms which, as we have underlined, undoubtedly present impacts linked to the odors emitted.

The specific regulatory references can be found on the LOD website, the dynamic olfactometry laboratory of Gruppo Luci with which we collaborate on a permanent basis.


Farming activities are an undeniable source of olfactory nuisance. To address the problem, both sustainable mitigation techniques and standardized methods of evaluating the odor impact are needed, which allow the effectiveness of the techniques to be established and the management strategies to be identified.

The regulations impose specific measures on farmers to be able to coexist without too many conflicts with the inhabitants of the nearest settlements, and they are induced to pay ever greater attention to reducing the olfactory impact of their activity.

Osmogenic barriers are therefore an excellent solution in the treatment of odors on farms which guarantee good abatement efficiencies for both conveyed and diffuse emissions.

The "social responsibility" of a company requires increasingly more attention to environmental issues, responding to the demand for quality of life coming from the territory in which it operates; responsibility that makes it essential to address the issue of odor linked to one's production activities, introducing knowledge and technologies available today.