Semi-continuous air sampling versus 24-hour bag samples to evaluate biofilters on a swine nursery in warm weather

Kevin A Janni, L. D. Jacobson, Brian Hetchler, J. P. Oliver, L. J. Johnston

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Economical and effective methods are needed to assess practices that reduce gas emissions. This project compared gas concentrations measured using semi-continuous sampling with dedicated gas analyzers versus concentrations obtained using 50 L FlexFoil bags filled over 24 h. Sampling was done over four months in summer and early fall of 2010 and 2011 from four biofilters (flat-bed with old media, A-frame, and two flat beds with either 10 cm or 5 cm screen birch mulch) treating air from deep manure pits below swine nurseries. Concentration ratios and percent reductions were calculated and compared using both sampling methods. The NH3, H2S, CO2, CH4, and N2O concentration data indicated that the 24 h bag sampling concentrations and percent reductions tracked the semi-continuous sampling concentrations and percent reductions well. Most (77%) of the NH3 concentrations differences (24 h bag sample minus semi-continuous) were within ±2 ppm of the semi-continuous concentrations, 78% of the H2S concentration differences were within ±200 ppb, 87% of the CH4 concentration differences were within ±10 ppm, and 88% of the N2O concentration differences were within ±75 ppb. Ratio means for NH3, CO2, and N2O were close to one (between 0.95 and 1.09). H2S ratio means varied from 0.61 in 2010 to 1.68 in 2011. Semi-continuous percent reduction results indicated that the four biofilters reduced NH3, H2S, and CH4 emissions. For three of the four biofilters, mean percent NH3 reductions ranged from 53% to 86%, mean percent H2S reductions ranged from 41% to 74%, and mean percent CH4 reductions ranged from 8% to 39%. One biofilter reduced N2O concentrations by 17% to 22%, while three biofilters generated N2O by 8% to 81%. The 24 h bag sampling system tested was an effective method for measuring gas concentrations and percent reductions of an air treatment system in the field based on NH3, CH4, and N2O.

Original languageEnglish (US)
Pages (from-to)1501-1515
Number of pages15
JournalTransactions of the ASABE
Issue number5
StatePublished - 2014

Bibliographical note

Publisher Copyright:
© 2014 American Society of Agricultural and Biological Engineers.


  • 24 h sampling
  • Ammonia
  • Biofilters
  • Hydrogen sulfide
  • Nitrous oxide
  • Reduction efficiency
  • Semi-continuous sampling


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