Vegetative buffers, like good fences, make for good neighbors

While there has been a lot of talk about planting vegetative buffers around poultry farms, what can they really do for some of these issues? There are five positive effects of planting vegetation on these modern commercial farms.

Vegetative buffers, like this one on a layer farm comprised of willow, poplar and arborvitae, can remove significant amounts of ammonia, dust and odor from exhaust fan emissions.
Vegetative buffers, like this one on a layer farm comprised of willow, poplar and arborvitae, can remove significant amounts of ammonia, dust and odor from exhaust fan emissions.

Commercial poultry and livestock farms today -- considered “factory” farms by some at the urban-rural interface -- are still the ones that supply 95 percent of the meat, eggs and milk the people of this nation consume. However, they are at the threshold of a sustainability crisis, because of the real or perceived emissions and runoff from these farms, and because the animal facilities and farms do not match the idyllic red-barn picture of yesteryear. Rather they are large, strategically engineered structures for hens, chicks or pigs to best manage the environment, feed and manure.

While there has been a lot of talk about planting vegetative buffers around poultry farms, what can they really do for some of these issues? Vegetative buffers are single or multiple rows of trees, shrubs or grasses that are established for multiple environmental reasons.

There are five positive effects of planting vegetation on these modern commercial farms. Vegetative buffers can scrub exhaust fan emissions of odor, ammonia and particulate matter (PM), which is comprised of fine particle dust, endotoxins, and microorganisms. Vegetative buffers can reduce the impact of these emissions on those working or living near the farm.

Riparian buffers can filter sediment, nutrients and bacteria associated with runoff events from roofs, access roads, barnyards and load-out areas. Shade trees, windbreaks and snow fences can reduce the solar load and winter winds drawing heat from the poultry barns for energy conservation and snow piling and drifting on roofs, near feed bins and load-out doors. Biomass crops such as switch and Miscanthus grass, willows and poplar can be grown for bedding materials and the spent litter can be burned replacing fossil fuels like propane utilized for brooding birds and heating animal facilities. And lastly, the screened and landscaped appearance of farms with visually pleasing trees and shrubs can improve the image of these modern high-density animal farms at the urban-rural interface.

The environmental impacts of these conservation practices are highly transferable to most regions in the country because there are many native plant species to draw upon in your area. Our environmental assessment indicates that, for water and air quality, there is the potential to reduce emissions and filter contaminants by 28 to 50 percent with vegetative and riparian buffers.

There is the potential negative impact of buffers encouraging unwanted animals near the buildings that might be biosecurity/health risks to your birds. However, these risks can usually be managed. In short, the innovative application of vegetation buffers on poultry and livestock farms would result in multiple environmental and social benefits enhancing the sustainability of farms and the enterprise of producing meat, eggs and milk for U.S. consumers.   

Visual screen & farm beautification

Trees and shrubs can provide a visual barrier for some of your buildings and operations from neighbors’ view. Routine activities such as feed deliveries, placing and loading out birds, and litter handling can be negatively perceived next door, because of noise, lights and the activity at odd hours of the day. Vegetation strategically placed can block or mute from view these practices, lessening neighbors' awareness of what is going on and giving the farm a landscaped or groomed appearance. Many beautiful tree, shrub, and ornamental grass species can be utilized with diverse heights, colors, foliage, and architecture for this purpose. 

Catching dust

Dust is something we have coped with in poultry production for years as bird dander, feed, and litter all contribute, but recently, dust has a new name and meaning with implications for farm worker health. However, few studies have reported the potential of plant foliage to trap farm dust or particulate matter (PM), which is an EPA regulated emission (PM2.5 and PM10 with aerodynamic diameters of 2.5 and 10 microns, respectively). At our Penn State hen farm, we measured a 67 percent reduction in total PM levels at a distance of 20 feet downwind of a five-row vegetative buffer.

Interesting species differences were measured, as well, with willow capturing more of the fine PM2.5 and less of the intermediate-sized PM10 than juniper vegetation. We also measured plant species differences on commercial broiler, turkey and hen farms in Pennsylvania.  In this work, Norway spruce and hybrid willow trapped more PM2.5 and total PM than poplar or Streamco willow. Spruce also trapped more PM10 and PM>10 microns than the poplar, hybrid, or Streamco willow. These studies indicated that spruce and hybrid willow are effective traps for dust and its associated odors.

We have also witnessed that arborvitae, while an effective dust-trapping species, can trap so much as to reduce respiration, photosynthesis, or other metabolic processes, resulting in plant death. These plants were effectively choked with dust. Therefore, there are limits that plants can tolerate that must be managed by the right species at the proper distance from fans. 

Utilizing ammonia

Ammonia is an issue for grower health and the well-being of the birds. Environmental losses from poultry farms can also be an issue for water and air quality. For example, based on some work we did in the 1990s, layer, turkey, and broiler farms can lose as much as 40, 26, and 18 percent of the feed nitrogen as ammonia emissions. Many things have changed in the past 20 years with poultry feeding, management, and equipment that have reduced these losses, although they still can be significant.

Ammonia is probably not an issue for neighbors, because concentrations downwind are very low, and it readily mixes with surrounding air and is diluted to levels way below normal thresholds of detection at the fence line. However, the U.S. EPA cares about ammonia, because it is a component of PM2.5 that has been linked to respiratory illness. PM2.5 includes small molecules such as sulfur oxides and nitrogen oxides that can combine with agriculture-related ammonia to make ammonium nitrate and ammonium sulfate. There are many counties in the U.S. that are in non-attainment for meeting the EPA PM2.5 standards.

In multiple studies at Penn State, we have documented the capacity of plants to trap ammonia emissions emanating from poultry houses. In one study, 240 plants (honey locust, red cedar, hybrid poplar, and reed canary grass) were divided equally into four environmentally controlled chambers. Two chambers received a continuous flow of ammonia at 5 ppm, while plants in the other chambers were controls with fresh air. For 12 weeks, the plants remained in the chambers, and measures of plant growth and tissue nutrients were taken. From this study, we learned that plants can absorb aerial ammonia via the leaf's stomata (pores) and metabolize it by incorporating it into the structural and vegetative proteins in the plants. Foliage nitrogen levels of the honey locust, reed canary grass, and poplar in the ammonia chambers increased 1.8, 2.6 and 6.0 times that of plants in the control chambers.

The red cedar in this study, and white spruce, arborvitae, and Streamco willow in another chamber study, all deposited almost two-fold greater nitrogen in their leaves or needles when exposed to continuous ammonia. The same kinds of observations were made on eight commercial poultry farms (broiler, layer and turkey) among vegetation downwind of exhaust fans versus plants planted a control distance away.

Reducing odor

While we know that odorous molecules coming from poultry and livestock farms often travel with dust, it has not previously been shown that vegetation on farms can reduce odor; albeit intuitive that vegetation would have that potential for trapping dust. At both our facilities at Penn State and on a 6-house, 2.5 million-hen complex in central Pennsylvania, we had the chance to demonstrate this opportunity. Downwind of our farm, we established a five-row vegetative buffer using a pot-in-pot system with the trees and media in male pots and female pots sunk in the ground downwind of the exhaust fans in a grid to receive the male pots. This pot-in-pot system allowed us to remove all the trees and shrubs from the exhaust field to measure odor under experimental conditions with no vegetation and bring them back to see their merits. This buffer was comprised of fir, juniper, willow, an ornamental pear, and birch (n=50 trees). In the fall, odor detectable threshold measures using the AC’SENT olfactometry software averaged 21.2 with trees and 39.2 with them removed. Additional measures using the Nasal Ranger detectable threshold averaged 4.3 with trees and 9.4 without. These measures represent between a 46 and 54 percent reduction in odor levels as a result of the vegetation compared to when it was removed. Additional AC’SENT odor measures were gathered at the hen complex behind four-row vegetative buffers vs. measures in the open at the same 90 feet distance from hen house tunnel fans. Odor reductions averaged 34 percent behind the vegetation compared to houses with no vegetative buffer.

Wind break

Other ancillary benefits of vegetative buffers that are well documented include reducing wind speed and damage to buildings, crops and livestock in open fields. The same benefits for poultry buildings can be realized by blocking the heat-sapping effect of winter winds that create drafts, chill birds, and drive up fuel consumption. Strategically placed, these buffers can act as snow fences, dropping snow in front of the buildings instead of on the roof or around access roads, feed bins, or fans. Other vegetation can be planted to shade the radiant load of summer sun on the buildings and cool the air entering the inlets or curtains.

Current studies at Penn State include using the same vegetative buffer plant materials such as poplar, willow, and Miscanthus grass as bedding for broilers and turkeys. These plants, in turn, can be harvested using modified forage choppers and shaving equipment to generate your own shavings on-site. The litter from these projects is also being evaluated in on-farm furnaces as a “green, carbon-neutral” fuel to replace propane.

Vegetative buffers can do a great job of landscaping your farm and buildings. The screening of birds and activities one can achieve with the vegetation can be the “out of sight, out of mind” you may need with some neighbors. Other tangible benefits can include scrubbing ammonia emissions, reducing odors downwind, trapping dust leaving the farm, improving water quality, and muting severe winter and summer weather with some energy savings. 

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