Growing number of swine operations have turned to natural buffers (also called shelterbelts or vegetative buffers) as part of their odor mitigation strategy. However, there is little to no data on the effectiveness of these buffers and little to no guidance on metrics that should be used to determine the performance of a buffer. This study was designed to measure the effectiveness of buffers in lowering odor from a swine facility by measuring odor indicators. These indicators included particulate concentrations and odorous compound concentrations emitted from a swine facility. The facility monitored was a finishing unit with a tree buffer system on the north and west sides of the operation. Samplers were positioned to measure particulates and odorous compounds when the winds were from the south, blowing over the buildings and samplers.
For particulates, there was a 44% reduction in concentration load when comparing samplers before the buffer and samplers placed behind the buffers. In terms of particulate sizes, 94% of the particles on the north side of the buffer were in the range of 0.3-0.5 mm compared to only 88% on the south side of the buffer (i.e., building side). For 0.5-1.0 mm size particles, the building side contained 10% compared to 4% on the north side of the buffer. The tree buffer appeared to consistently filter out the larger particles with a greater proportion of 0.3-0.5mm particles detected at the sampler outside the buffer.
For odorous compounds, the effectiveness of the buffer is a little more complicated. The results show that shelterbelt removed compounds from the air stream just not the most odorous compounds (phenols and indoles) as effectively as less odorous compounds (volatile fatty acids, VFAs). There was a 50% reduction in the VFA concentrations comparing samplers before and after the buffer. Leaves taken from 8 ft had significantly higher amounts of the odorous VFAs, phenolic, and indole compounds sorbed as compared with samples taken from either 2 or 4 ft. This may indicate that as the shelterbelt grows in height their effectiveness for lowering odor increases; however, more research is needed to confirm these findings.
A random sample of existing hog confinements throughout Iowa was used to design buffer systems for each production site. The full costs of establishing and managing these shelterbelt systems were calculated. The effects of a cost share program were then examined. Individual farm level costs were averaged regionally and aggregated by county to estimate the total investment needed by the Iowa hog industry to utilize shelterbelt systems for air quality purposes and to get a baseline understanding of potential cost share program outlays. Across all of Iowa the total costs for the buffer per pig produced (over 20 years) came to $0.036 per pig. Overall, cost sharing reduces total 20 year costs by 18% and upfront costs by just under 50%. Per pig costs are lowered by almost a penny per animal.
The presence of a vegetative buffer at the study site reduced the amount of particulates and some odor compounds by approximately one half. The estimated cost for establishing and maintaining a vegetative buffer was $0.036 per pig produced over 20 years. Although more research is needed, the effectiveness and cost of this practice should encourage wider adoption.
