The Buffer Zone
By Treena Hein
Natural emission control for particulate matter and odour
By Treena Hein
Getting along with our neighbours is always a good idea, but that can be easier said than done if you’re a poultry farmer.
| Planting trees makes an ‘environmental statement’ to neighbours that the farmer is making every effort to resolve odour, noise and dust problems. Photo credit: Todd Leuty, OMAFRA Agroforestry Specialist|
Getting along with our neighbours is always a good idea, but that can be easier said than done if you’re a poultry farmer. The good news is that there is an easy and inexpensive way to mitigate odour, dust, noise and more all at the same time – with lots of brand new research findings on which to base best practices. The method? Planting trees.
“Tree buffer strips accomplish many goals at once,” says OMAFRA Agroforestry Specialist Todd Leuty. “They reduce odour by diluting and dispersing gas concentrations. Odorous dust can land on trees rather than dispersing through the air, and trees also collect and store the chemical constituents of odour pollution in their wood as they grow.”
Trees also dramatically improve the look of a farm, shielding neighbours from continual exposure to delivery truck traffic. “Planting trees makes an ‘environmental statement’ to neighbours that the farmer is making every effort to resolve odour, noise and dust problems,” observes Leuty. “It goes a long way to foster good relations.”
There are still more benefits. “Shrubs and trees can also help reduce energy costs,” says Dr. Paul Patterson, a professor at Penn State University’s Department of Poultry Science who has studied buffer strips around farms for many years. “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. Trees can also shade buildings from summer sun and cool the air entering inlets or curtains.”
Patterson’s research team has found the presence of trees around poultry barns has a significant mitigating effect on particulate matter (PM), odour and other emissions. For example, PM was reduced by 67 per cent downwind from a five-row vegetative buffer around an Iowa hen farm in comparison to one with no buffer. “We found that willow captured more of the fine PM and juniper captured more of the intermediate-sized PM,” says Patterson. Associated research showed that spruce and hybrid willow are also effective ‘dust traps.’
With regard to odour, the researchers found a vegetative buffer comprising 50 fir, juniper, willow, ornamental pear and birch trees cut odour roughly in half compared to the same site without trees (the team used removable potted trees). Odour measurements were made using St. Croix Sensory’s AC’SENT® olfactometry software. Patterson suspects there are differences between plant species in their capacity to trap odour, but hasn’t tested that yet.
Patterson has also tackled the question of whether vegetation can trap ammonia emissions, and found the amount of foliage needed to ‘scrub’ emissions depends on the size and type of facility. Among honey locust, hybrid poplar vegetation, Reed canary grass, and Norway spruce, poplar and honey locust took up more nitrogen in their leaf material than the other species in his studies. The honey locust also increased the most in total plant and root biomass.
The team also completed some exciting preliminary studies showing that “vegetative buffers interrupted downwind transmission of Infectious Bronchitis significantly,” says Patterson, via wind between birds on the same or different farms.
OTHER RESEARCH FINDINGS
The B.C. Sustainable Poultry Farming Group (B.C. SPFG) based in Abbotsford, B.C., has also found trees to be effective in controlling dust. “Dust emissions from poultry farms in the Fraser Valley are resulting in environmental issues and neighbour complaints,” says B.C. SPFG Manager Kevin Chipperfield. “For three seasons, we’ve used excelsior cedar and red maple trees in pots and in planted forms at one broiler and one layer farm. “We don’t have definitive results yet,” says Chipperfield, “but we are sure that significant amounts of larger particulates are being trapped by the trees. Measurement of dust movement and filtration in and around trees is a new and evolving science. At this time, measurement technology is in its infancy and understanding the best way to measure the dust is at least as important as the results indicating the amount of dust that is being captured by the trees.”
University of Guelph (Ontario) Environmental Engineering Associate Professor Bill Van Heyst also researches air quality issues arising from agricultural operations. He’s found that, overall, the emission factor used by Environment Canada in predicting the emissions of PM from the Canadian poultry sector (part of the Criteria Air Contaminant emission inventory that Environment Canada updates annually) was lower than what he has observed in broiler barns. “By having an unrealistically small emission factor,” says Van Heyst, “the potential effect this may have is that Environment Canada (in conjunction with provincial environmental ministries) may adopt unattainable PM emissions limits for the poultry sector.”
In addition, Van Heyst has recently found that emissions of small PM increase from broiler barns as the flock ages. He says, “Reasons for this include greater bird masses stirring up more material from the litter bedding, increased feed consumption (and hence spillage), greater amount of shedding of material from the bird (more skin area and feathers as the bird ages), and accumulation of fecal matter in the bedding material (in Ontario, the litter bedding is typically cleaned out after every flock).” Future research will focus on verifying the PM emission reduction of various management or control technologies, such as barn misters, litter additives and feed additives.
As you plan your buffer strips, there are a few basics to understand. First of all, to maximize deposition of odorous dust on planted trees, Leuty says tree rows should be located upwind and downwind of the building. “Upwind shelterbelts reduce the quantity of dust and odour that is picked up by wind,” he notes, “and shelterbelts located downwind of the facilities are essential to reduce wind speeds to allow settling of odorous dusts that have become airborne.”
It’s also important to avoid planting trees that attract wild birds and increase the risk of possible disease transmission. “Keeping trees back from the building also helps with this, says Leuty. “Species to avoid include those producing berries or fruit that birds are known to eat, such as highbush cranberry, ornamental crab apples, service berry and black cherry.”
Selecting several species of trees and shrubs is also wise because it will help prevent loss or destruction of the entire shelterbelt if insect or disease attack occurs. “Having diversity also offers a better chance for tree survival during alternating seasons of drought and wet soil conditions,” observes Leuty.
When asked what he would advise a poultry farmer in planning a tree buffer to best mitigate odour, noise, dust, and provide esthetics, Patterson offers these very general guidelines, cautioning that site specifics are important.
With a 15,000-bird broiler house of 35 by 320 feet, he says, “you might need three rows of plants on two sides to block wind, snow and to obscure the building itself. We might do a row of willows 30 feet from the building with plants every 3 feet.” That adds up to 138 trees, stretching about 350 feet on the longer side of the barn and 65 feet on the shorter end. “Behind that, a row of poplar at 10-foot spacing 15 feet back from the willows (42 trees),” says Patterson. “And a final row of evergreens about another 15 feet back from the poplars at 15-foot spacing (28 trees).”
Leuty says, however, that farmers may want to plant a mix of conifers only because they provide foliage in all seasons. He adds, “Conifers such as Colorado blue spruce and Austrian pine may also be a good option if your facility is near a highway. Road salt applied in winter can mist onto and kill shelterbelt trees, and these species have some tolerance to that.”
Once producers have decided to move forward with buffer strips, they can either plant seedlings or larger trees. “Transplanted trees such as eight- to ten-foot conifers create an instant visual barrier and quick odour management advantages,” says Leuty. “Then, producers will sometimes also plant smaller bulk-ordered trees to top up the shelterbelt over the following five to 10 years.” To save money, he advises producers to look into what organizations such as the Christmas Tree Farmers of Ontario offer – purchasing from them may be substantially less costly than from landscape nurseries.
Leuty has also heard of producers renting, borrowing or buying a tree spade and moving trees from another part of their farms. “A London, Ont.-area poultry producer transplanted 10-foot spruce trees from his own overcrowded windbreak and established a good solid shelterbelt around his barns over a two- to three-week period,” he says, “which was very effective in terms of time and money.”
Another method of dust control
The B.C. Sustainable Poultry Farming Group (B.C. SPFG) has also been testing a Baumgartner Environics Inc. ionization system that traps barn dust. The system, composed of a power supply of 30,000 volts x 2 mAmps and an ionization discharge line, negatively charges the dust in the air, which then is deposited on the grounded surfaces of the barn, such as the walls, floor and ceiling. The cost for an installed system in a broiler barn is about $0.85 per square foot, says B.C. SPFG manager Kevin Chipperfield.
The technology is new to the market and there has not been much testing of it in poultry production barns,” he adds. “We started in a chicken barn about two years ago and now have a project assessing its utility in a turkey barn.” The local distributor for the technology, UAS of Abbotsford, B.C., helped fund the initial study, which found that the system cut all size ranges of particulate matter by about half. “[This is] a substantial environmental benefit to poultry farm workers, poultry flocks, and the surrounding exterior environment,” Chipperfield observes.
“In addition, we have found a positive return-on-investment of about $0.045/bird/production cycle over 10 cycles of sampling and monitoring,” he notes. “Other valuable but limited results suggest that the system can potentially be effective in reducing disease-producing microbial populations.” At this time, the B.C. SPFG is applying for funding for an expanded study. “At this time, it appears that the additive effect of both the vegetative filters and the in-barn ionization system may be a powerful tool for a poultry producer to address air quality issues and reduce neighbour complaints,” says Chipperfield.
Dr. Karen Bartlett from the University of British Columbia and Dr. Shabtai Bittman from AAFC are research partners with both this ionization system and B.C. SPFG’s research into using trees to control dust. The B.C. SPFG gratefully recognizes its funding partners, which include: B.C. Investment Agriculture Foundation, the B.C. poultry industry, Agriculture Environment Initiatives, provincial and federal departments of agriculture, and the B.C. Agriculture Council.