Odor emission is of great concern to the general public. An odor management plan is required in the permit application for livestock operations with more than 1,000 animal units. Producers need to understand odor emission from animal housing, manure storage and handling, and land application and available management options.
Site Selection and Management
Odor problems can be minimized through site selection. Find a site that is located the proper distance from neighborhoods and public places. Take into account prevailing winds in the summer when many people spend significant time outdoors. Don't locate where slope gradient will let odors 'flow' to neighbors. Try and keep housing and storage out of sight and surrounded by crops and windbreaks.
With open lots, the influence of pen moisture on odorous emissions is well documented. Poor drainage and/or improper diversion structures in holding pens or feedlots favor anaerobic microbial activity. Adequate drainage is critical to avoid odors. A pen slope of three to four percent will help ensure that the surface sheds water rapidly. Research has shown that open lot moisture levels between 20 and 40 percent moisture content are best for controlling odor and dust. Lots that have below 20 percent moisture become too dry and generate dust; lots that have above 40 percent moisture produce odors that dominate emissions. Frequent manure collection is also critical, especially in feedlots. When scraping the surface of a feedlot, it is best to use equipment that leaves a smooth surface (box scrapers are excellent) to prevent standing water and the resulting odors.
The Nebraska Odor Footprint Tool is available for your use in deciding where to site an operation and to determine the effect of potential odor control technologies.
When designing housing and the management of housing, consider cleanliness to be a significant factor in reducing odors. Odors cling to dust, holding the odors near ground level. All management practices that reduce dust will help with reducing odors. More fat in the feed, covers for feed equipment, and cleaning fans and areas where dust can accumulate are all management techniques that help reduce dust and odor. Windbreaks near the housing will help push odorous air up into the atmosphere and avoid movement along the ground surface.
Management of the housing area to keep areas clean minimizes odors. Outdoor lots need similar housekeeping. Design and maintain open lots to encourage good drainage and rapid drying. Keep lots clean and remove manure and unused or spoiled feed. Design feed bunks to drain. Keep grass cut around feedlots, provide good drainage from feedlots, keep dust down on access and feeding roads, and use windbreaks to hide line of sight to pens.
Livestock Waste Control Facility (LWCF)
The LWCF can be a source of odor. Anaerobic lagoons, manure storage (including underbarn pits), or a sediment basin are types of LWCFs. An anaerobic lagoon is designed to treat and store manure. A properly designed and operated lagoon should not produce the odors that a manure storage often emits and should not require agitation. A lagoon should never be completely emptied except for sludge removal, and then it should only be pumped down to the permanent pool marker. A manure storage structure is designed to store manure from a production facility for a period of time and is routinely emptied. Covering a manure storage is an option that will help minimize odors. Sediment basins collect runoff from feedlots and should be allowed to drain completely and be cleaned regularly to minimize odors.
Land Application Considerations for Reducing Odor
Discuss manure application with your neighbors. Plan applications to coordinate with their outdoor events and minimize impact from odors. If neighbors know about the manure application ahead of time, they may be less likely to be offended.
When emptying a pit or manure storage facility, agitation is necessary to have a uniform material. Agitate and land-apply between 8 a.m. and 4 p.m. on warm, sunny days when wind direction does not impact neighbors. The optimum time to apply manure is in mid- to late-morning when the air is warming and rising; avoid evening applications. When applying manure, management processes that minimize mixing of air and manure are helpful. Immediate incorporation with injectors, knives, or tillage implements will reduce odors. Drop hoses are better than broadcast sprayers.
Effluent can be applied by irrigation equipment and the same principles apply. Large guns that direct water and effluent into the air with high pressure will produce more odor than low pressure drop nozzles under the crop canopy. Use only the effluent from lagoons and apply when the lagoon is functioning well (summer and fall). Lagoons 'turn' in the early spring as biological processes restart. At this point, odors may be worse and the effluent should not be irrigated onto fields.
Emerging technologies should be monitored since this area is being researched and new management tools may prove very useful. In addition, public education and communications need to be practiced continually. The goal is to use all available technology to minimize odors, or if odors are unavoidable that they are produced at a time when their effect on neighbors will be minimized.
Having a specific plan and recording its implementation will be very useful if anyone ever questions the intent and procedures of a specific operation.