Malodor and Air Pollution Technologies
Wet scrubbers are used on ventilation air as it exits livestock housing. They use liquid to collect dust or particulate matter (PM) and absorb gases from air by using a wet surface, spray system, or wet material bed. Some scrubbers use water, which is then partially recirculated, while others use an acid or base to shift the pH for absorption of specific gases in the air. The liquid effluent is then treated as a waste product.
Poultry scrubber operations were found to be more efficient in ammonia recovery. Preliminary economic analysis showed that scrubbers for a swine finishing facility and a poultry manure composting facility would need one year (5) and five years (1) of continuous operation, respectively to break even with total fixed costs and operational and maintenance costs.
The use of biogas or methane digesters with CAFOs not only serves as a source of energy for the farm, thereby decreasing the amount of fossil fuels, but also allows a reduction in methane, CH4, and nitrous oxide, N2O, and a decrease in the use of synthetic fertilizers (Hermansen et al., 2011). When manure is stored in a digester, it is covered, which prevents much of the odor from escaping into the air.