Source: Questline

Manure and feed spoilage are the major sources of building odor in swine facilities. One solution to controlling odor is to process the manure right after removal from a building using anaerobic digesters. However, they are expensive and require a large herd size to be economically viable. A more commonly used solution is to mitigate the odor within the building. Biofiltration and oxidation are two potential approaches.

Biofiltration

Air is exhausted through a biofilter media made from organic material. Biofilters are large beds of peat, loam, compost or wood chips through which air is passed. A microbial population in the bed converts the odorous gases to carbon dioxide, water and mineral salts that remain in the media. Biotrickling, a continuous cleaning of the filter by adding water flow, can help continuously rejuvenate the biofilter.

Researchers at South Dakota State University have shown that biofilters reduce odor emissions by 96%.

Oxidation

Another approach is to destroy the odorous gases as they are exhausted from a building or rising from a lagoon using super-reactive oxidizing agents, such as ozone or hydroxyl (OH) radicals. The oxidizing agents can be pumped into the building prior to being exhausted or pumped into the surface of a lagoon using a float aerator.

Ozone is generated onsite using a high-voltage corona discharge or ultraviolet (UV) irradiation to convert oxygen to ozone. While ozone dissipates quickly, it can irritate the throat and eyes of animals and people. A common practice is to remove swine from the space before ozone treatment.

A cold plasma discharge can also be used to create OH radicals from the ionization of hydrogen peroxide using a catalyst material. Highly reactive OH radicals are even more reactive than ozone. However, OH radicals are much safer for living creatures than direct ozone and have a relatively short residence time.

Odor mitigation can dramatically reduce the need for ventilation in cold weather, which saves energy. It also has the potential to reduce dust particulate levels.