A good philosophy when siting livestock buildings is to always prevent odor problems rather than cover them up, according to Iowa State University engineers.
Selecting appropriate building sites can go a long way toward minimizing odor problems. Some people may consider this to only be important when purchasing land or building a farmstead from scratch. But in reality, it is important to evaluate a building site before investing much in improvements or expansion. Such an investment in a site that may have potential odor problems probably would not be wise.
Topography around a building site is very important since it affects air movement. Relatively flat sites that have good air movement and mixing are good places to build livestock facilities. It is best to avoid hilltops above residences in a valley, as odors may travel down hills. On calm nights cool air drains from higher to lower elevations. Any odors from livestock facilities will travel with the cooler air, thus creating potential odor problems. If there are no residences at lower elevations, hilltops are a good location for livestock buildings, especially naturally ventilated ones.
Wind direction has a major impact on how odors travel. Check the direction of prevailing winds and compare them with the direction toward neighboring residences, public use areas, highways, population centers and also any areas to be developed in the future. If the summer prevailing wind is toward any such places, it would probably be best to choose another site. In Iowa, winds typically come from the northwest in winter and south to southwest in summer. Therefore, preferred locations for facilities are straight north or straight east of housing to minimize potential problems.
In addition to wind direction, distance is important. Odor intensity decreases as distance from the source increases. Distance allows fresh air to mix with the odors, resulting in decreased odor intensity.
Many states have regulations that set forth required distances for certain types of livestock buildings and facilities.
Building orientation also has an impact on the odor emitted. Buildings or outdoor manure storages that are exposed broad side to neighbors are more likely to cause odor problems a greater percentage of the time due to the fact that there is a much larger building surface area exposed toward the direction of the neighbors. Therefore, it is advisable to orient buildings with the narrow side toward neighbors. An exception to this is naturally ventilated buildings, in which the wind direction needed for proper ventilation is of more concern than exposure to neighbors. However, if neighbors or a public use area is not far away, it may be best to consider relocation of a naturally ventilated building. If potential odor problems are a concern, it may be better to construct a mechanically ventilated building and orient it to reduce exposure or find a different site.
The importance a person's perception has on their judgment has already been discussed. This is also true with regard to the appearance of livestock facilities. Well-maintained production units usually are not perceived to smell as bad as units that look run-down. Nice landscaping and a regularly mowed lawn will also encourage workers to do a better job of cleaning up spilled feed and disposing of livestock carcasses. A production site that is overgrown with weeds and has junk accumulated throughout the site certainly wouldn't encourage workers to keep everything tidy. Properly planted and maintained windbreaks can serve a number of functions. Windbreaks that shield the production site from the view of passers-by may decrease the chance of odor complaints. When people cannot see the source of an odor, they are less likely to notice an odor or complain about it. Windbreaks also cause air to be lifted up, which causes more mixing of fresh air with the odorous air, thus diluting the odor effect. However, windbreaks need to be used with caution around naturally ventilated buildings because they can reduce the air-flow through buildings and create ventilation problems. £