Biofiltration of exhaust air from animal houses: Evaluation of removal efficiencies and practical experiences with biobeds at three field sites. (July 2017)

• Record Type: Journal Article
• Authors: Melse, Roland W.; Hol, Johanna M.G.
• Is Part Of: Biosystems engineering. Volume 159(2017)
• Page Start: 59
• Page End: 69
• Publication Date: 2017-07
• Subjects: Biofilter -- Biofiltration -- NH3 -- Odour -- N2O -- Livestock; Bioengineering -- Periodicals; Agricultural engineering -- Periodicals; Biological systems -- Periodicals; Génie rural -- Périodiques; Systèmes biologiques -- Périodiques; 631
• DOI: 10.1016/j.biosystemseng.2017.04.007
• Languages: English
• ISSNs: 1537-5110

Abstract

Abstract : Three wood-chip based biofilters ('biobeds') with media depth of 0.25 m were monitored during 6–12 months (capacity and surface area for biofilter #1: 75, 000 m 3 h −1 from poultry manure dryer, 68 m 2 ; biofilter #2: 100, 000 m 3 h −1 from pig house, 188 m 2 ; biofilter #3: 300, 000 m 3 h −1 from pig house, 440 m 2 ). Average empty bed residence times (EBRT) were 1.4, 2.6, and 3.3 s; average pressure drops were 287, 22, and 91 Pa, respectively. Average ammonia (NH3 ) and odour removal efficiencies per site were 38–74% and 43–62%, respectively; a large variation was found between measurements. Poor moisture control of the packing material decreased these efficiencies (breakthrough). Average fine dust (PM10 ) removal was mostly 90% or higher. It was found that a significant part of the NH3 may be converted to nitrous oxide (N2 O), a potent greenhouse gas. At one site even 21% of all NH3 -N was converted to N2 O-N. It is the first time that such high average N2 O production rates have been reported for long-term monitoring of biofilters. It is concluded that biofilters have potential for emission reduction at animal houses, but especially high pressure drop (clogging/fouling) and homogeneous moistening of the biobed need attention. To prevent breakthrough of air at dry spots, it is recommended to increase the media depth. Further research is necessary to explore the conditions and parameters that influence N2 O production in this type of systems, as currently no control strategy is available for preventing N2 O generation. Highlights: Three biofilters for treating air from pig and poultry houses were investigated. Emissions were significantly reduced for NH3 (40–70%), odour (40–60%), and PM10 (>90%). At two biofilters high N2 O production was found: currently no control strategy is available. Proper moisture control of wood chip packing material is essential for operation. A too thin layer of packing may result in poor humidification and breakthrough of air.