VOC emissions from beef feedlot pen surfaces as affected by within-pen location, moisture and temperature

A laboratory study was conducted to evaluate the effects of pen location, moisture, and temperature on emissions of volatile organic compounds (VOC) from surface materials obtained from feedlot pens where beef cattle were fed a diet containing 30% wet distillers grain plus solubles. Surface materials were collected from the feed trough (bunk), drainage, and raised areas (mounds) within three feedlot pens. The surface materials were mixed with water to represent dry, wet, or saturated conditions and then incubated at temperatures of 5, 15, 25 and 35 °C. A wind tunnel and gas chromatograph-mass spectrometer were used to collect and quantify emissions of eight volatile fatty acids (VFAs), five aromatics and two sulfur-containing compounds. Pen location significantly (P < 0.05) affected measurements of 10 of the VOC with the largest values occurring for materials collected near the mound area. The largest VFA and aromatic emissions resulted for the dry moisture condition while wet and saturated conditions produced the largest sulfide emissions. Temperature affected emission of each VOC except indole, with values generally increasing as temperature increased. Odour activity value (OAV), which was the ratio of measured concentration of a single compound normalised to the odour threshold for that compound, was calculated for each compound. Four VFAs contributed 7.5% of the total OAV but only one aromatic, 4-methylphenol, was a major contributor to total OAV at 2.5%. In comparison, sulfide compounds contributed 87.3% of the total OAV. This research shows VOC emissions are affected by pen location, moisture condition, and temperature.