Concentrated animal feeding operations (CAFOs) on industrial animal factories can stink up an entire county, due to ammonia, and a smorgasbord of volatile organic compounds (VOCs). Jeppe Lund Nielsen of Aalborg University, Aalborg, Denmark, et al. report that biofiltration with microbial filters can remove most of the butyric acid, dimethyl disulphide, and ammonia from the exhaust air, along with other smelly compounds. The research is published in the December 2011 issue of the journal, Applied and Environmental Microbiology, according to American Society for Microbiology.

The investigators mounted trickle biofilters directly on livestock facilities. These filters are stuffed with porous corrugated cellulose pads that serve the bacteria as soil does plants, and irrigated with water to support the active biofilm and wash away toxic waste.

"We hypothesised that the bacteria in these air filters would be highly specialised, with individual microbes targeting specific organic compounds in the smell, which consists of 200 to 300 compounds in total," said Dr Nielsen.

The study's main aim was to identify microorganisms involved in breaking down butyric acid and dimethyl disulphide, as well as to measure their performance. The filters removed 99.9 per cent, 94 per cent, and 90 per cent of the butyric acid, dimethyl disulphide and ammonia in the exhaust air, respectively, as well as reducing carboxylic acid concentrations by more than 70 per cent, organic sulphur compounds by up to 50 per cent, and various aromatic compounds by anywhere from 48 to 89 per cent. The main community members breaking down dimethyl disulphide were Actinobacteria, followed by the beta-proteobacterial ammonia-oxidising bacteria and bacteroidetes, as well as some fungi.

Nielsen added that humans can smell some of these compounds at concentrations of less than a part per billion, and thus, that "only very specialised microbes [would] thrive at such low concentrations. This aspect of the filter environment was expected to select for a uniquely tolerant group of specialised microbes."

Reference

Kristiansen A., S. Lindholst, A. Feilberg, P.H. Nielsen, J.D. Neufeld and J.L. Nielsen. 2011. Butyric acid- and dimethyl disulfide-assimilating microorganisms in a biofilter treating air emissions from a livestock facility. Appl. Environ. Microbiol. 77:8595-8604. doi: 10.1128/AEM.06175-11

Further Reading

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