Comparing semi-continuous air sampling versus 24-hour bag samples to monitor gas emissions and treatment from a swine nursery with biofilters

摘要

There is a need for economical and effective methods to assess practices that reduce gas emissions. The purpose of this project was to compare gas concentrations measured using semi-continuous sampling with dedicated gas analyzers versus concentrations obtained using 50 L bags filled over 24-h. Sampling was done in 2010 and 2011 from four biofilters (flat-bed with old media, A-frame, two flat beds with either 10 cm or 5 cm birch mulch) treating air from swine nurseries. Concentration ratios and percent reductions were calculated and compared using both sampling methods. The NH_3, H_2S, CO_2, CH_4 and N_2Oconcentration data indicated that the 24-h bag sampling concentrations and percent reductions tracked semi-continuous sampling concentrations and percent reductions well. Most NH_3 concentrations differences (24-h bag sample minus semi-continuous) were within ±2 ppm of the semi-continuous concentrations, H_2S concentration differences within ±200 ppb, CH_4 concentration differences within ±10 ppm and N_2Oconcentration differences within ± 75 ppb. Ratio medians for NH_3, CO_2 and N_2Owere close to one, between 0.95 and 1.09. H_2S ratio medians varied from 0.61 in 2010 to 1.68 in 2011. Semi-continuous percent reduction results indicate that thefour biofilters were able to reduce NH_3, H_2S and CH_4 emissions. Mean percent NH_3 reductions of three out of four biofilters ranged from 53 to 86%, percent H_2S reductions ranged from 41 to 74%,, percent CH_4 reductions of three out of four biofiltersranged from 8 to 39%. One biofilter reduced N_2Oconcentrations 17 to 22% while three biofilters generated N_2Oby 8 to 81%.