A12 Use of biological air scrubbers in pig housing

Biological air scrubbers have been found to reduce ammonia emissions by 70%, whilst also removing fine dust and odour (Ogink and Bosma, 2007). To deal with the high dust loads, multistage air-scrubbers with pre-filtering of coarse particles have been developed (Melse and Ogink, 2005; Ogink and Bosma, 2007). In a study on pig and poultry houses in the Netherlands, Melse and Ogink, (2005) found the ammonia elimination achieved by Biological air scrubbers displayed ammonia removal ranging from -8% to +100%, averaging at 70%. Conversely, acid scrubbers ranged from 40% to 100%, with a mean of 96%. Notably, odour removal through acid scrubbers ranged between 3% and 51%, with an average of 27%, whereas biological air scrubbers exhibited odour removal ranging from -29% to +87%, averaging at 51%.  

In a review of ammonia emission mitigation techniques for concentrated animal feeding operations, Ndegwa et al., (2008) provide the following summaries of studies on air filtration to remove ammonia emissions. Sun et al., (2000) assessed a 200 mm deep biofilter composed of a blend of compost and wood chips to ascertain its efficiency in ammonia removal from pig housing ventilation air. At a biofilter moisture content of 50% and a retention time of 20 seconds, this system demonstrated an average ammonia removal rate of 83% from the carrier air. Tanaka et al., (2003) documented a notable ammonia reduction of 94% within the initial 72 hours of treatment using a biofilter comprising finished compost (comprising cattle manure and sawdust) for composting air. Hong and Park, (2005) achieved a 100% ammonia removal efficiency using a biofilter composed of a 500 mm deep mixture of 50:50 manure compost and coconut peel, treating air emanating from a composting pile involving dairy manure and crop residues.  

In pilot-scale investigations, Sheridan et al., (2002) evaluated a wood chip biofilter with a depth of 500 mm for diminishing ammonia in exhaust air from a pig finishing building. Depending on the volumetric loading rate, this biofilter, utilising 20 mm screen size wood chips, effectively eliminated between 54% and 93% of ammonia. To uphold biofilter efficiency, a filter bed moisture level of 63% or higher was recommended. A biofilter employing a mix of pine and perlite achieved a substantial ammonia removal rate of 96% from ventilation air originating from a pig rearing facility in a pilot-scale setup (Chang et al., 2004). In the context of a contemporary 2400-sow farrow-to-wean unit, Kastner et al., (2004) demonstrated that a biofilter constructed with pre-screened yard waste compost achieved ammonia reduction rates ranging from 25% to 95%, contingent upon the residence time and inlet ammonia concentration. Lastly, Martinec et al., (2001) conducted an evaluation encompassing diverse biofilter materials (biochips, coconut peels, bark-wood, pellets and bark, and compost) for ammonia reduction in pig operations, resulting in ammonia reduction percentages ranging from 9% to 26%.