Controlling Odors is More Than Being a Good Neighbor1

The Professional Animal Scientist 10:11B-123

Controlling Odors is More Than Being a Good Neighbor1 J. RONALD MINER Bioresource Engineering Department, Oregon State University, Corvallis, OR 97331

taken legal action against them based on the odor nuisance in many of the traditionally agricultural states. These actions may seek damages in the millions of dollars and injunctions to cause the operations to cease. Odors have both a physical and an emotional component. The production, escape, transport, and perception of livestock production odors are biochemical and physical processes. The environment in which these processes proceed can be designed, managed, and predicted. By changing the environment, the designer can change or prevent those processes that are causing the problems. The response of an individual and the intensity of that response is an emotional issue and may depend upon the previous relationship between the odor receptor and the enterprise owner or manager. Odor complaints affect only a small fraction of producers. Most livestock producers will operate throughout their careers without major problems related to odor complaints. Odor complaints tend to become serious under very particular situations. 1) When larger than normal livestock housing facilities are constructed in an area that was previously used by smaller enterprises; 2) When confinement facilities are placed sufficiently close to a community, rural home, or other incompatible land use so as to cause odors to be detectible on a regular or frequent basis; 3) When the producer has made other design or management decisions so that the odors become a reminder of other reasons why the community may be unhappy with the producer. There is no magic to the contiOl of odor. Research has provided a useful background on how odors are produced, where odors are most likely to be formed, and how those odors might be prevented from forming or how they might be cap-

Abstract

Odor control continues to be a major challenge to livestock and poultry producers across the country. Research and testing have devised systems that are capable of achieving reduced odor frequency and intensity; however, these systems are typically more expensive to build and operate than the standard lagoon or holding basin. This places those producers close to sensitive odor perception sites at a clear disadvantage to those located in more remote locations. In addition to the cost factor is the uncertainty associated with odor control. Some operators are able to co-exist with their neighbors in spite of frequent odor detections; others find that their neighbors demonstrate much less tolerance. Odor control additives, either fed or applied to the manure, have generally been less than fully successful. Careful site selection, appropriate facility design, flawless management, and a generous amount of positive local relations have proven to be the most effective means of avoiding costly odor confrontations. (Key Words: Manure Management, Odor, Lagoons, Feed Additives, Odor Control Chemicals, Legal Considerations.) Introduction

Livestock and poultry producers are accustomed to risk. Prices change. Some animals thrive, others perform poorly. Among the worrisome risks is that they wi.1I enco~nter an enterprise-threatening odor complaint. Neighbors of livestock producers have

1Jo~rnal Paper No. 10,501. Oregon Agricultural Experiment Station Corvallis, OR 97331. ' Reviewed by S. Neal and R. Simms. Sponsored by J. E. Oldfield.

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tured rather than allowed to escape. Techniques are also available that allow us to predict the distances that odors will be transported in identifiable concentrations under various climatic conditions. Low velocity constant wind movement favors odor transport because it minimizes dilution. Engineering solutions have been demonstrated that will solve most of the odor control issues. The challenge is that those housing and manure management features that have the lowest odor production potential are generally more expensive to construct or operate than are those technologies known to have greater odor release. Typical manure management system design is to balance the construction and operating cost of the system with the degree of odor control. Mannebeck (4) indicated that installing a cover on an outside manure storage pit, tank, or lagoon is an effective means of odor control because it effectively reduced the ventilation rate and hence the rate of odor emission. A packed bed dry scrubber filled with zeolite (clinoptilolite) reduced ammonia emissions from a poultry house by 45% initially, but efficiency dropped to only 15% in 18 d (5). The soil is an excellent odor-scrubbing medium because of chemical absorption, oxidation, and aerobic degradation of organic gasses. Lindvall et al. (3) determined that soil injection reduced odor emissions from liquid swine manure by over 90% as compared with surface spreading. Odor from soil-injected manure was about equal to that from a nonmanured soil surface. Disk harrowing, or plowing of surface-spread manure, reduced the odor threshold level by 67 to 95%. Soil filters with perforated pipe in a shallow soil bed have proved effective for scrubbing odors from a process or building exhaust air. Kowalewsky et al. (2) removed 52 to 78% of the ammonia and 46% of the organic constituents from the ventilation air from a swine confinement building using a soil filter system. Bohn (1) reported 99.9% odor reduction from a soil filter used to treat high density odors from rendering plant cookers. Soil filters required a moderately fine textured soil, sufficient moisture, and pH control of 7 to 8.5. A typical land area requirement is 2500 to 4600 ft2/1000 cfm. Sweeten et al. (8) measured 95 to 99% reduction in ammonia emissions and 30 to 82% reductions in odor intensity (matching butanol concentrations) using a .25

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acre sand filter field to scrub air from a poultry manure composting operation. Under current social and regulatory constraints, there is no easily identifiable level of odor control that can be assured to be acceptable. Sites that are close to developed areas, along major highways, and near an adequate feed and labor supply may have more demanding odor control constraints, making them more expensive to develop. Anaerobic lagoons are generally regarded as the least cost means of manure storage and treatment. Lagoons also have a high level of odor production during certain times of the year. An important issue is whether the savings from using an anaerobic lagoon at a specific site is sufficient compensation for the risk that might be associated with odor complaints. Numerous additives and several devices have been made available to reduce odors. Warburton et al. (9) conducted odor control studies using an extensive array of odor control additives, including biological supplements, masking agents, and odor suppressants. Their studies indicated that none of the products tested was effective in reducing odor. Miner and Stroh (6) reported similar results based on a cattle feedlot study. More recently, Patni and Jui (7) tested a number of odor control additives with the same results except for the addition of peat moss, which formed an intact scum layer on top of the manure storage tank. Based on these repeated investigations, the most reasonable conclusion is that only those additives that are logically capable of changing the odorant production process, stopping the escape of odorous gases, or preventing the transport of those gases to downwind receptors have proven to have value as farmer-applied odor remedies. There is no easy or magical solution; however there are some very reasonable steps that a responsible livestock producer can take to minimize the frequency and intensity with which odors from his/her operation will be detected by sensitive neighbors. Products to Control Odors: Pit Additives, Feed Additives, and Lagoon Amendments

Livestock and poultry manure is a rich mixture of organic materials and organisms being shed from the intestine of the animals. Without any further

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addition of nutrients, enzymes, or microbial additives, degradation will begin almost immediately. The nature of the decomposition process, whether aerobic or anaerobic, whether rapid or slow, will depend upon the environment in which that decomposition occurs. Throughout the decomposition process, various components of the fresh manure as well as materials formed in the decomposition process will tend to escape due to their volatility. Compounds with smaller molecular weight tend to escape most rapidly. The volatility of many of these components is dependent upon the environment in which they exist. For example, hydrogen sulfide, the "rotten egg smelling" compound, is more volatile under acidic conditions. Ammonia is just the opposite, It is more volatile under alkaline or basic conditions (high pH values). Thus, one of the early proposals to control odors was by adjusting the pH of the manure storage or treatment. By adjusting the pH, the nature of the odor can be changed; however, most people agree that little progress is made on overcoming the odor problem. Manure decomposition begins even before the material is excreted. The proteins are being broken down into amino acids and the carbohydrates are being shortened to energy-producing sugars. Within the animal intestine, that process was underway in a warm anaerobic environment with little temperature variability. Immediately upon excretion, the volatile materials present will vaporize and the odor of fresh manure will be produced. Depending upon the environment in which the manure is maintained, further biodecomposition will occur. If plenty of oxygen is present, an aerobic process will proceed with relatively nonodorous products evolved. If there is an inadequate supply of oxygen available to the bacterial population, more odorous end-products will be formed. In a liquid slurry, the water will become saturated with these materials and whenever the liquid is agitated, an abundant release of odor is noted. There are ways to stop these decompositions; however under most housing systems, none of these is operationally or economically attractive. Anaerobic bacterial decomposition can be stopped by creating an environment that is not suitable for the survival of anaerobes. That is the role traditionally served by bedding. By mixing a small amount of manure with a large volume of

straw, an environment is created in which the bulk is sufficiently dry that air permeates the mass. As a result, anaerobic bacteria are inhibited and aerobic bacteria, fungi, and more complex organisms thrive. This creates what we typically note as a compost odor. Some ammonia escapes but in general the gases released are not overly offensive. By adding oxygen in sufficient quantities to a liquid, a similar process can be promoted. Extended aeration sewage treatment plants and oxidation ditches for swine manure both utilize this process. Although both of these have proven effective in reducing odors, the operating costs have made them unattractive to livestock producers except under those conditions in which odor control is at a premium and when lack of odor control might spell doom. Another technique to prevent anaerobic decomposition is to maintain the temperature sufficiently low that biological activity is inhibited. This technique has little application to the control of odors, but it does explain the unusually severe odors encountered from lagoons during the spring when the water warms after a winter of limited biological activity. Several people have sought additives that could be fed to animals, added to the manure storage pit, or could be sprayed over the manure to eliminate odors. Among these have been products containing concentrations of specialized bacteria or enzymes that were selected to alter the pathway of decomposition. Thus far, objective evaluation has confirmed what science would predict; namely, that there is a large concentration of bacteria and a plentiful supply of enzymes in manure already. The likelihood of having a small volume of an additive change the pathway of decomposition is very small. Similarly, the ability to add an alternate odorant that is strong enough to mask the manure odor but yet be socially acceptable is most unlikely. Controlling Manure-Spreading Odors

Each year livestock producers are pummelled by their friends and neighbors with regard to the odors associated with the distribution of manure to cropland. Alternatives exist to the conventional spreading. Equipment is available to inject manure into cover crops or to knife liquid manure into the

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soil. Each of these technologies requires more time and requires the use of more equipment that does distribution on the land surface of either solid manure from a manure spreader or liquid from an irrigation system. The critical question for the hog farmer is, "How important is controlling the odor associated with spreading manure?" The answer to this question may be that it is more important than you would think. Most state laws provide a degree of protection to well-conducted agricultural practices, but that protection may not be adequate considering that there are alternatives that greatly reduce odor escape and make more complete use of the nutrients available. In final analysis, it is a matter of balance. There is an additional cost to injecting manure. Not all soils are suitable for injection. Injecting manure takes longer than surface application, and if the wind blows from the residences toward the farm, no odor travels to the residences. No single rule exists that serves every farm or farmer. The answer depends upon the environmental sensitivity to which each owner or manager must respond. Not all fields are equivalent for the application of manure. However, there are situations in which manure injection is the most reasonable answer. Planning a Farmstead to Control Odors

It is important to remember that just as there is no magical cure for odors there is no magic in the formation of odors. With proper planning any desired level of odor can be achieved. More elaborate systems for odor control are obviously more expensive than are the less sophisticated techniques. For many operations, site selection is the only odor control technology that will be required. Good judgement is critical. Clearly, it will be more difficult and probably more expensive to achieve an acceptable degree of odor control if the facility is located adjacent to a suburban housing development, a school, or a shopping center where urban folks gather. Areas that people have identified as being appropriate for upscale retirement living have also proven difficult. Having adequate land for manure disposal and having that land where it will be accessible from an odor control perspective are both critical. Facility design is the second opportunity to achieve odor control. Depending upon the degree

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of odor control sought, there are several alternatives that can be selected. Systems that facilitate frequent manure removal lead to less in-house odor generation. The extent to which the floors, walls, and animals can be maintained clean and free of manure will be important in determining the amount of odor that will be discharged in the exhaust air. Pulling exhaust air from beneath slatted floors but above the liquid manure level will minimize building odors but that exhaust air discharged towards a sensitive neighbor may well become a problem. The choice of the manure storage is the next odor control opportunity. Storages may range from a carefully covered above-ground manure storage tank to an open earthen basin into which liquid manure flows prior to application to crop land. Just as these options differ in cost, so too do they differ in the amount of odor released. Anaerobic lagoons have been among the most popular manure storage-treatment devices during the past 30 yr. They typically provide long-term storage and considerable conversion of manure solids into liquid that can be pumped with conventional centrifugal pumping equipment. Groundwater concerns dictate that anaerobic lagoons be constructed so that downward movement of water is restricted to a very small amount. In addition to storage, these lagoons facilitate anaerobic breakdown of the manure converting the nitrogen to ammonia, the sulfur to hydrogen sulfide, and the carbohydrates to carbon dioxide and water. Intermediates are also released. As herds have grown so have lagoon sizes. Large anaerobic lagoon surfaces, 20 acres and larger, have been smelled several miles away. An option to anaerobic lagoons is the use of aerated or aerobic lagoons. Aeration is typically accomplished by placing a floating mechanical surface aerator in the lagoon. Aerator requirements are typically 1 hp for each 50 finishing pigs. Power costs are high and initial investment for aerators may be in the order of $200lhp. Although aerated lagoons were popular in the 1970s, their use has been restricted to emergency situations during the past decade. Another option to capture the treatment benefits of anaerobic lagoons but to avoid the odor problems has been to cover them. Gas-tight rubber covers have received some use but for the larger

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lagoons, they too have proven sufficiently expensive to be unacceptable to most swine producers. Several years ago it was noted that dairy waste lagoons that developed floating scum covers were generally less odorous than were those with a free water surface. Research has indicated that other permeable covers may also offer similar benefits. Research currently underway at Oregon State University is attempting to develop a low-cost floating permeable cover that will capture this benefit. The Importance of Perception in Avoiding Nuisance Suits

Lawsuits generally result when people perceive situations differently. In the case of odor complaints this means that the offended neighbor perceives the odor situation as much more severe than does the owner. Part of these differences on perception has to do with the subjective nature of odor. Each of us has individual responses to odors. Part of this is training, part of it has to do with our previous experience and the extent to which we can or should be inconvenienced for the benefit of our neighbors. Livestock producers can draw one important insight from the subjective nature of odorant responses. Odors from the operations of respected neighbors, trusted friends, and valued community supporters is dramatically less objectionable than that from the invasive, irresponsible, and assaultive foreigner. Seldom is a nuisance suit filed between friends or people who value one another's friendship. There is clearly a reward for the responsible community member who is appreciated by his neighbors. Criminal and Civil Legal Concerns

Odors are an established feature of livestock production systems. To date, odor sources have been subject to nuisance suits based on the unreasonable interference with their neighbors use of their property. Under most conditions, the damages awarded in odor-based suits have been those associated with actual property damages and decreased property values. The costs of neighbors' responses to the odors have also been reimbursable. In exceptional cases, punitive damages have been awarded in association with odors. Punitive

damages have to do with behavior that is perceived as deliberately irresponsible or a belligerent disregard for other people's property. It is important that livestock producers take seriously any legal steps that are taken or being proposed by their neighbors relative to odor nuisance. Attorneys having experience with such actions have learned how to more effectively assemble the data necessary for a successful defense of an operation. Having high quality objective data that document that the complaint is unreasonable is the single most effective defense against a law suit. Even better, however, is the avoidance of the suit. Producers can avoid many of the potential law suits that threaten them by being worthy of retention in their local communities. Communities support enterprises that contribute to the overall wellbeing of the area. When the benefits of having an operation in the community outweigh the total cost, that operation becomes a valued and desirable member of the community. Odor Control and Nutrient Conservation

There is a relationship between manure treatment and the extent to which nutrients, particularly nitrogen, are conserved. Anaerobic decomposition involves the conversion of nitrogen compounds to ammonia. When these anaerobic units are open to the atmosphere, there is a great tendency to have ammonia escape. Mechanically aerated manure storage units are similarly prone to nitrogen volatilization. This tendency to lose nitrogen is related to the establishment of alternate aerobic-anaerobic conditions. When aerobic conditions are maintained, ammonia is converted to nitrates. Those nitrates are subject to further conversion to nitrogen gas if the slurry becomes anaerobic at a later time. Maximum manure nutrient conservation is achieved when manure is collected and incorporated into the soil with minimum handling and delay. This is an ideal that is seldom possible but establishes the standard. Retention of manure in a storage tank with minimum dilution and handling followed by frequent soil incorporation is a second best technique for nutrient retention. More extensive handling, treatment, or spraying operations increase nitrogen volatilization and loss as a soil

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nutrient. Long-term storage in which anaerobic degradation is nearly complete represents the greatest possible nutrient loss. Long-term anaerobic lagoon treatment followed by high pressure spray irrigation can achieve nitrogen losses well in excess of 75%. Whether this is good or bad depends upon the cost of alternative nitrogen sources, the availability of cropland on which to utilize the manure, and the more personal attitude toward the virtue of energy conservation. The other major plant nutrients, phosphorus and potassium, are much more durable than is nitrogen. As a result, much smaller fractions of these nutrients are lost during manure handling and storage. Odor Control for Your Farm

Research over the past 25 yr has shown that it is possible to control the odors evolved around a livestock enterprise. Most of the odors to which people complain are those related to manure decomposition. How manure is handled is vitally important in controlling odors. Even more important, however, are some preliminary decisions. Site Selection. Site selection is the single most important decision relative to avoiding odor complaints. Careful consideration of all aspects of a site will avoid numerous future conflicts. Sites that are close to nearby residences require more expensive odor control technology and increase the risk of devastating conflicts over odors. Although the direction of the prevailing wind is important, it is not absolute protection because of the tendency of the wind to blow from all directions. Building and Equipment Design. Building and equipment designs that facilitate clean animals and manure free surfaces are essential. Modern facility designs include features that quickly separate manure and animals. Whether slotted floors or flushed gutters, it is important that manure covered surfaces be minimized. Manure Management Technology. Manure management technologies are available to provide any necessary degree of odor control. Covered

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manure storage units, aerobic storage and treatment devices, and soil injection equipment are available and can be designed to serve those systems in which their additional costs are justified. It is important that designers continue to carefully identify sites that are appropriate for more elaborate odor control technologies and those for which conventional manure management is sufficient. The Livestock Management System. Effective odor control includes the housing facility, the manure storage and treatment plan, and the application of the manure to cropland. Each of these three components of a livestock management system deserves and demands consideration if odor control is to be achieved. Inadequacies in anyone of the three can be sufficient to cause the system to fail. Literature Cited 1. Bohn, H. 1972. Soil absorption of air pollutants. J. Environ. Quality 1: 372. 2. Kowalewsky, H. H., R. Scheu, and H. Vetter. 1979. Measurement of odour emissions and imissions. In: J.K.R. Gasser (Ed.), Effluents from Livestock. p 609. Elsevier Applied Science Publishers, London. 3. Lindvall, T., O. Noren, and L. Thyselius. 1974. Odor reductions for liquid manure systems. Trans. ASAE 17(3):508. 4. Mannebeck, H. 1985. Covering manure storage tanks to control odour. In: V. C. Nielsen, J. H. Voorburg, and P. L'Hermite (Ed.). Odour Prevention and Control of Organic Sludge and Livestock Farming. Proceedings of a Seminar Held in Silsoe, United Kingdom, April 15-19, 1985. p 188. Elsevier Applied Science Publishers, London. 5. Miner, J. R. 1981. Controlling odors from livestock production facilities: State of the art. In: Livestock Wastes: A Renewable Resource. p 297. ASAE, St. Joseph, MI. 6. Miner, J. R., and R. C. Stroh. 1976. ContrOlling feedlot surface odor emission rates by application of commercial products. Trans. ASAE 19:533. 7. Patni, N. K., and P. Y. Jui. 1993. Effectiveness of manure additives. Paper No. 93-4021, Summer Meeting. American Society of Agricultural Engineers, Spokane, WA. June 20--23, 1993. 8. Sweeten, J. M., R. E. Childers, and S. J. Cochran. 1988. Odor control from a poultry manure composting plant using a soil filter. ASAE Paper No. 88-4050. International Summer Meeting, American Society of Agricultural Engineers, Rapid City, SO. June 26-29, 1988. 9. Warburton, D. J., J. N. Scarbrough, and D. L. Day. 1981. Evaluation of commercial products for odor control and solids reduction of liquid swine manure. In: Livestock Wastes: A Renewable Resource, Proceedings of the Fourth International Symposium on Livestock Wastes. p 309. ASAE, St. Joseph, MI.