VEGETATIVE ENVIRONMENTAL BUFFERS AND EXHAUST FAN DEFLECTORS FOR REDUCING DOWNWIND ODOR AND VOCS FROM TUNNEL-VENTILATED SWINE BARNS
Scientists have investigated methods for reducing odor emissions from livestock buildings for decades, yet few technologies have proven effective. Vegetative environmental buffers (VEB), which are specially designed combinations of trees, shrubs, and grasses, have shown promise in recent years for reducing odors at poultry operations, but they have seen less testing at swine farms. A field research project was conducted at two similar 8-barn swine finisher sites in Missouri to assess the effectiveness of VEBs in combination with fan deflectors for reducing downwind odor impacts from tunnel-ventilated swine barns. A VEB and fan plume deflectors were installed in spring 2009 at one 8-barn site, while the other site, with neither VEB nor fan plume deflectors, served as the control. Odor was monitored from July to November 2009, with trained human panelists at eight locations, upwind and downwind of the VEB, barns, and lagoons. Five aromatic volatile organic compounds (VOCs: phenol, 4-methylphenol, 4-ethylphenol, indole, skatole) were sampled from ambient air using sorbent tubes and gas chromatography/mass spectrometry. Compared to the control site, the VEB reduced odor concentrations (dilutions to threshold, D/T) by 49.1% in the VEB and by 66.3% at distance 15 m downwind of the VEB (p < 0.001). There was a larger percentage of non-detect odor concentrations (D/T < 2) at 15 m downwind for the VEB site (57.6%) as compared to the control site (16.4%). Mean upwind odor concentrations ranged from 1.4 to 2.4 D/T. Mean odor concentrations at the 150 m downwind location were not significantly different for the control (mean DT = 3.0) and the VEB site (mean DT = 3.5) (p = 0.42). Mean odor concentrations at 300 m downwind were not significantly different for the control (mean DT = 2.3) and the VEB site (mean DT = 2.5) (p = 0.47). In late 2010, a laboratory wind tunnel was used to compare VOC flux from VEB vegetation samples before and after rinsing. Wind tunnel VOC fluxes from vegetation were 78% to 98% lower after rinsing, qualitatively showing that particulate matter (PM) captured on the vegetation reduces VOC emissions. The results of these field and laboratory experiments confirm that VEBs reduce downwind odor within 30 m of the barn or 15 m from the VEB by increasing dilution and capturing odorous PM in the vegetation.