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Writing Objective: Design and carry out a major research project on an aspect of our 1999 Seminar Topic: “Hog Lots in Iowa”

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Over the past few years in Iowa, farming has become more than just a family owned and run business; it has become a corporate affair. These livestock intensive corporate operations have the potential for high concentrations of animal waste, which has led to more complaints about odor, greater challenges of animal odor management, and growing public concern that more environmental protections are needed to combat these problems. At present, the major source of odor concern from these intensive corporate farming operations is the swine industry. The topic of odor sources and causes and odor control is a logical subset of “Hog Lots in Iowa” because of the public apprehension that has been raised and the scientific efforts that have been employed to remedy the problem at hand. Specific areas focused upon in this paper are: what are the primary sources and causes of odor from swine operations, and how can those odors be reduced and made less offensive.

In researching the topic of odor sources and causes and odor control on hog lots in Iowa, many sources were utilized. Journal articles obtained from the Gcisler Library were examined, websites were visited, and some personal contacts were made. The strategy employed first focused on background information on the topic of hog lots in Iowa. Then, the determination of which subtopics were relevant to this issue led to the topic of odor sources and causes and odor control. An exhaustive search through library materials turned-up several journal articles and other print references. Searches on the Internet were used to find related information, as well as to make contacts.

“When the wind is coming from the wrong direction, the smell is just terrible,” explained Blaine Nickles, a lifelong farmer who lives in close proximity to one of Iowa’s largest hog operations. Mr. Nickles continued to state that no longer are hog farms simply family operations; they have become more like factories. “Everyone is entitled to raise livestock, but when you interfere with the quality of life and the environment…that should not happen,” expressed Mr. Xickles in relation to large hog farming operations (“Corporate Hogs at the Public Trough: DeCoster Farms, Iowa”, 1999). One such interference to the quality of life that Mr. Nickles referred to is the subject of odors relating to hog farms. Odor, odor control, in particular, has raised a lot of public controversies recently. Offensive odors stemming from hog farms and manure-handling systems pose real costs to those who are exposed to them. Numerous rural residents who are neighbors to large hog operations have complained that odor has adversely affected their lives and demanded that some precautions should be taken to reduce the amount of odor these operations produce (Palmquist 1997). Since Iowa is the United States’ number one hog producer, many of the concerns about hog odor and its control have been expressed and addressed. To be better informed on the problems associated with odor and hog operations, it is important to understand the problem of swine odor, the complexities of swine odor, and the solutions and practical options used to combat the swine odor nuisance.

In 1995, hog production nationwide reached 103 million. Over the last 15 years, hog farm numbers nationwide fell from 600,000 to 157,000, yet this smaller number of farms still manages to the same number of hogs (“Animal Waste Pollution in America,” 1997). Iowa has a human population of approximately 2.9 million; its hog population is almost five times that at approximately 14.1 million (“America is Wasting Away: Iowa,” 1999). With these large numbers of hogs come enormous amounts of waste. Nationwide, hogs produce 116,652,300 tons of manure annually, which is 11 times that of human waste (“Animal Waste Pollution in America,” 1997). Every day, a nursery pig with an average weight of 25 pounds produces 0.04 cubic feet of manure. A 150-pound finishing pig produces 0.16 cubic feet of manure a day. A 275-pound gestation-sow and a 350-pound boar produce 0.15 and 0.19 cubic feet of manure a day, respectively (“Design and Management of Anaerobic Lagoons in Iowa for Animal Manure Storage and Treatment,” 1995). In a single day, a 10.000-head hog operation produces as much waste as a city of 25,000 people (“What Are the Health Impacts of Livestock Factories,” 1999).

Odor problems from swine operations are connected to manure handling and management techniques. Hog odors come from the release of organic compounds during the microbial fermentative (anaerobic) decomposition of protein waste material including, feces, urine, skin cells, hair, feed, and bedding. Resulting from this anaerobic decomposition is the “rotten egg” odor of hydrogen sulfide gas and the familiar odor of ammonia. The amount and type of microbial activity influences die amount and type of odor emissions. Microbes are very sensitive to environmental parameters, such as moisture content, temperature, pH, and oxygen concentration, and any change to these parameters will alter odor emissions. For example, in the winter months, temperatures decrease by significant levels; hence, microbial activity also lessens causing few odors to be emitted.

Although the principal odorous gases generated from pig production include ammonia, hydrogen sulfide, and methane, hog odor consists of over 160 identified odorous compounds (Church, 1998). Odorous compounds associated with odor are interactive, not additive, and each individual compound contributes to the overall character of the odor by either making the odor more offensive, easier to detect, or harder to measure. These odorous compounds, which include organic acids, alcohols, aldehydes, ammonia, fixed gases, carbonyls, esters, amines, sulfides, disulfides, mercaptans, phenols, ketones, indole, skatole, and nitrogen heterocycles, are a result of natural biological reactions, including the anaerobic decomposition of swine wastes (Donham and Thu, 1995). “Odorous mixtures vary with location, the size, and type of swine operation, production practices, season, temperature, humidity, time of day, and wind speed and direction. With so many compounds and environmental variables, it is often difficult to determine which compound, or combination of compounds, is giving offense” (North Carolina Agricultural Research Service, North Carolina State University, 1995).

An odor episode created from a hog operation is composed of three mechanistic components: emission, transport, and detection. Emission is simply the source of the odorous gas related to the hog facilities. Transport of the odorous gas is determined by weather conditions, in particular, wind speed and direction, along with the terrain of the countryside. Other weather conditions, like relative humidity and atmospheric stability, affect the concentration, frequency, and duration of odorous gases at the receptor. Detection is a subjective component that is quite variable in respect to the ability of people to smell the odorous gas and the odor threshold they possess.

To be able to successfully and effectively control odor, it is imperative to identify its source and take appropriate action in that area. Typically, odor sources from swine production systems originate and are divided into four primary sources: hog buildings and facilities, manure storage and treatment systems, land application of manure, and carcass disposal. Odors released from swine buildings and facilities are relatively constant throughout the year, while odor production from manure storage units, the spreading of manure onto the land, and carcass disposal is seasonal to quite sporadic depending upon weather conditions, manure addition rate, and manure spreading time patterns.

Swine buildings and facilities are often overlooked as sources of odor. The ability to control gas generation and capture gases before they are emitted into the atmosphere is the most significant problem with reducing odors from buildings and facilities (Schmidt, 1998). Odorous gases arc generated in and around swine buildings from the following: manure covered floors, manure covered hogs, spilled moldy feed, improper disposal of dead pigs, manure pits under building floors, incinerators with incomplete combustion, and dust from feeders and hog surfaces. Every part of the facility’s waste-handling system produces odor if it is not kept clean. Also, many of the volatile compounds associated with odor attach themselves to dust particles. When this odor-rich dust is allowed to coat animals, walls, and ventilation systems, practically every surface releases odor; hence, reducing the amount of dust in and around the building will reduce odor levels. In a poorly ventilated building these odors can build up and may escape in concentrated levels, li the building contains an underfloor manure storage unit, odor control can be a simple as removing the manure and cleaning the pit if it is shallow, or reducing pit ventilation if the pit is deep below the facility’s floor (1998).

Manure storage can be the most significant source of odor creation on swine production facilities. Storage of manure is taken care of by lagoons, concrete or metal tanks, and in earthen storage and treatment basins. All of these systems generate odor without careful design and management. Usually, if storage facilities arc mature, large enough, and well managed, offensive odor production will be reduced. Unfortunately, mature storage limits can emit odors if raw wastes are added too rapidly or if spring warming creates thermal inversion, thereby lifting material from the deepest level up towards the surface. have been proven to reduce odors from manure storage. Covers on manure storage facilities act to reduce odors in three ways. First, a gas impermeable cover captures gases as they are released and funnels them into a biofilter, where they are treated and released with less odor content. A gas permeable cover serves as a boundary between the manure and the air, decreasing the release of gases. Lastly, an organic crust, which is a combination of a gas permeable membrane and a treatment system, increase the area between the manure and air forcing the released gases through an aerobic environment with microorganisms that oxidize the gases. Anaerobic digestion also aids in the reduction of odor. When placed in a manure storage unit, an anaerobic digester controls the microbial activity in the degradation process, resulting in the creation of biogas, which can be used to generate heat or produce electricity and a stable waste matter (North Carolina Agricultural Research Service, North Carolina State University, 1995). Another very effective means of controlling odor is via the process of aeration. Production of odorless gases results when manure is aerated appropriately. Land application of manure is considered to release the largest percentage of odor from a swine production facility, and typically it brings about the most complaints. Usually, land application is performed during warm weather when manure can be used to fertilize pastures or crop fields. This warm weather also brings heat and humidity that promotes the production of odor. Therefore, if manure is treated adequately in storage units, odor should not be a problem when manure is transferred from storage facilities to the land. Also, odor produced during land application can be virtually eliminated by injection, “knifing” or immediate incorporation techniques. Often, equipment like a slurry tanker or an umbilical system is used during land application process to inject the manure into the soil. These techniques directly incorporate the manure into the soil below the actual substrate surface where odorous gases are not in contact with the air, thereby reducing the volatilization of these odorous compounds.

Another odor-causing concern related to hog production operations is the disposal of swine carcasses. Most carcasses are disposed of by landfill, on-farm burial, rendering, or incineration. If the decaying carcasses arc stored too long before disposal or pickup, they can emit offensive odors. All of the above disposal options are problematic. Landfill fees are high, and restrictions on animal disposal have increased. Incineration is quite costly in the effort to prevent air pollution and odor production. On-farm burial techniques risk the outbreak of disease and water contamination. Rendering presents the most feasible options for disposal, but new options need to be developed to meet the needs of the swine industry.

It is almost impossible and impractical to eliminate all odors from hog farming operations. This makes odor control drat much more difficult because how much odor is too much? Compounding the issue of acceptable levels of odor is the fact that at present no standardized measurement protocol exists for swine odor. Further, variability of sources, causes, environmental factors, and subjective human detection makes it complicated to measure hog odors or determine some acceptable limit for odor emissions. Another problem with measuring hog odor and finding an acceptable odor level is the fact that an odor’s offensiveness does not always correspond to its intensity. For example, at low intensities, the agitation of manure has been judged to be very offensive in nature. On the other hand, high intensities of odors ventilated from swine facilities have been ruled less offensive.

Since odor detection is subjective, the primary indicator that odors are a problem is complaints. It is difficult to check for the validity of these complaints because odor perception varies from person to person with no clear explanation of why someone feels a particular odor is worse than another person. Four conditions are thought to control the human perception of odor. First, people are more readily able to tolerate an odor if they feel they can do something about it (North Carolina Research Service, North Carolina State University, 1995). But, if the source of the odor is thought to come from an uncontrollable situation, it is more likely to be conceived as offensive. Second, if the source of the odor is understood, it may be easy to cope with the problem (1995). Thirdly, the perceived context of the odor may cause a greater reaction than the odor itself (1995). Lastly, exposure time to the odor affects the perception of the odor (1995). For example, if constant exposure to the odor occurs, awareness may become lessened, and ability to detect the odor may be lost.

At present, odor is not directly measurable; however, methods have been constructed to determine the threshold value of odor emission using dilution processes in an instrument called an olfactometer. Because the human nose is the best available odor-detector, these techniques utilize a human panel. These methods are quite expensive and time-consuming, but they are the best present measurement of odor levels. Olfactometry measures odor concentration by first collecting odorous air from buildings or pits in odorless PVC bags (Lorimor, 1996). During analysis in the lab the olfactometer dilutes pungent air with odor-free air, and the odor panel evaluates the different dilutions. The panel simply slates whether he or she can detect the odor, not whether the odor is strong or weak. The concentration of odorants that can be detected by observers is called the detection threshold or the dilution level at which die odor can just be detected (1996). The greater the threshold level the greater the raw odor level in die air. Olfactometry is still a subjective analysis and does not account for all of the variables affecting human response to odor. Moreover, an objective measurement technique would be useful in helping the swine industry respond to odor standards, design better facilities, and improve management practices (North Carolina Agricultural Research Service, North Carolina State University, 1995).

Is odor more than just a nuisance? The answer is, quite simply, yes; odor can cause many negative health effects for individuals who live near or work in an odorous hog facility. “Reports indicate that odors may elicit nausea, vomiting, and headache, cause shallow breathing, and coughing; upset sleep, stomach, and appetite; irritate eyes, nose, and throat, and disturb, annoy, and depress” (Donham and Thu, 1995). Some gases associated with hog odors, ammonia, and hydrogen sulfide, can cause adverse physiological responses when present at high enough concentrations.

Psychological and emotional responses can also be adverse in relation to swine operations. For example, a study at Duke University “shows that people living near intensive hog operations report significantly more anger, confusion, tension, depression, fatigue, and less vigor than people not living near intensive swine operations” (1995). Furthermore, these studies have also shown dial people frequently exposed to intense hog odors experience more mood disturbances than those not living in close proximity to intensive swine operations (1995). Odors can also cause more than health effects. Declines in property values have been seen in areas near intensive swine operations, and the increased nuisance of insects and rodents has been experienced (North Carolina Agricultural Research Service, North Carolina State University, 1995).

At present, there is a perception that odors emitted from hog confinement facilities are inevitable and nothing can be done to avoid their escape into the surrounding community. This is simply not the case. Great progress has been achieved in technology and management techniques exist that allow for production of hogs in a confinement operation at any level of odor production. There are also many incentives to help reduce odor emissions levels. Because of die health risks associated with swine odor, no operation can afford to ignore the problems at hand. Also, new regulations have been put into place, which has catalyzed the development and research of odor control techniques.

Even with regulations in place, the odor problem is one to be dealt with on a technical level rather than a regulative level (1995). Odor control techniques are implemented via an odor control strategy. Understanding the nature and sources of odors released is key to developing a sound odor control strategy (Baumgartner, 1998). Choosing a proper strategy for odor management depends on numerous factors. For example, degree of odor control required, whether odor control is desired for the long or short term, whether total odor control is desired or only selected gaseous emissions need to be controlled, and cost considerations all play a part in the selection how an odor control strategy is chosen and employed. These strategies can be best classified into three groups: controlling odor through nutrition to change manure composition; reducing odor emissions by the direct treatment of manure or other manure management plans; and controlling odorous emissions from buildings and land application (Jacobson, 1998). The right plans, projects, construction, and management of a hog confinement facility can definitely reduce the occurrence and intensity of odors.

Since nitrogen is a key component to odorous compounds, especially ammonia, it is generally true that the higher the nitrogen content of hog manure the greater the potential odor (Donham and Thu, 1995). With this information, it is easy to see that by regulating a hog’s diet odor can be directly controlled. When pigs ingest more protein than they can efficiently use, they excrete excess nitrogen. Therefore, changing a pig’s diet so that protein is more efficiently used will result in lower excretion of urea and uric acid, lowing ammonia emissions (Jacobson, 1998).

Presently, much research is being done on feed conversion via feed additives to reduce odor. In some diets, amino acids are not in balance with a pig’s requirements; hence, studies have devoted to this problem involve the use of synthetic amino acid in the place of traditional protein sources (North Carolina Agricultural Research Service, North Carolina State University, 1995). This approach is still young, and considerable research is still necessary. Studies are also addressing the topic of how protein sources can be better processed. This technique uses proteolytic enzymes as supplements to increase protein digestibility (1995). Dietary supplements such as calcium bentonite, zeolite, sagebrush, and charcoal, which all absorb odor-causing compounds, have been researched, but the levels of these compounds needed to be added to a pig’s diet to reduce odor may reduce growth or the efficiency of feed conversion (1995). Plant extracts, enzymes, and direct-fed microbes are some of the most promising feed additives. All of these compounds have been shown to reduce odor and improve growth performance. “Research indicates that sarsaponin, a natural extract from the yucca plant, can reduce ammonia and promote beneficial microbial action in pits and lagoons. In some studies, mixing sarasponin with pig feed has also increased weight gain and improved feed conversion” (1995). At present, it is not understood exactly how sarasponin works, but it is known that sarasponin passes unabsorbed through the pig, providing a simple, indirect means of treating waste and the contents of lagoons. Further research is necessary for all areas of feed additives, but they show promise in improving feed conversion and reducing odor.

Odor-control additives added to manure storage tanks or lagoons, also known as pit additives, are considered a feasible, inexpensive way to reduce odor emissions. Many different pit additives exist including: masking agents, counteractants, digestive deodorants, adsorbents, and chemical deodorants (Lorimor, 1998). Masking agents, mixtures of aromatic oils, cover up objectionable odor with a more desirable one. Counteractants are aromatic oils that cancel or neutralize odor. Digestive deodorants contain bacteria or enzymes that eliminate odor through biochemical digestive processes. Adsorbents are used to absorb the odor before it is released into the environment. Chemical deodorants fall under two classes, strong oxidizing agents or germicides. Hydrogen peroxide, potassium permanganate, and ozone are examples of oxidizing agents that oxidize odor-causing compounds. Orthodichlorobenzene chloride, formaldehyde, and paraformaldehyde are germicides that alter or eliminate bacterial action responsible for producing odor. Each of these products has its limitations, and most of them are organic compounds that are susceptible to being broken down by bacteria, losing their effectiveness in lagoons or tanks. While some of these additives are effective in the short-term, it is unlikely that any single product or procedure will solve the odor problem (Zhu, 1997).

Odor control strategies that involve manure, management techniques via direct treatment or lagoon covers are numerous and quite effective. The most effective way of lessening odorous emissions from a lagoon is to reduce die organic load on the lagoon (Miner, 1999). Pretreatment with an anaerobic digester, separating solids from waste before entry to the lagoon, and aeration of the lagoon are viable options used to reduce the organic load on a lagoon. The addition of either a permeable cover to oxidize the escaping gases or an impermeable cover to capture the gases are additional options used to reduce the organic load.

Anaerobic digestion is a proven method of controlling odors, as shown by its previous use, in industries and municipalities. This technique controls odors by stabilizing waste solids and generating methane gas. In a lagoon that contains an anaerobic digestion system, anaerobic bacteria break down manure, releasing anaerobic gases such as, methane, ammonia, hydrogen sulfide, and carbon dioxide. The size of the digester in this system is dependant upon the amount of volatile or biodegradable waste produced by the hogs each day and the detention tune of the solids. To allow the bacteria to work and the waste to be efficiently stabilized, solids must be detained in the digester for at least 10 to 15 days (Lorimor, 1998).

Iowa State University has developed a new type of anaerobic digester called the sequencing batch reactor, SBR, which separates solid and liquid detention time, whereas traditional digesters held both liquids and solids together. Designed to hold solids as long as needed, the SBR allows liquids to move through the digestion process quickly, resulting in a smaller, more efficient digester. However, an additional storage tank to hold the treated liquid until it is disposed of further must accompany each digester. Anaerobic digesters can almost eliminate odors from manure storage facilities because odors remain sealed during biodegradation in the digester. Also, very little odor is created when the stabilized solids and liquids are transferred from the digester to additional storage facilities.

Another odor-reducing technique that has been recently researched is solids separation. In this process, solids are separated and removed from the hog slurry via settling tanks. By removing solid waste from the slurry, less waste is added to the lagoon, resulting in reduced odor. Lagoons that have less surface area or are more lightly loaded have less odor production potential than overloaded lagoons or ones that have larger surface area (Lorimor, 1998). Simply removing die solids from hog slurry can reduce odor by a fair amount because the surface area of the lagoon is reduced, but the separated solids must also be reduced so that they do not become an odor problem (1998). Methods like composting and immediate land application are recommended to prevent separated solids from becoming an odor source.

After solids separation, solids need to be further treated to prevent odorous emissions. Composting is just such a technique. A relatively new method, about ten years old, composting is an exothermic biological oxidation process of organic matter by aerobic microorganisms (1998). The first stage of composting involves the transferring and spreading the solid waste over the fermentation substrate, such as a lignocellulose litter, at the composting area, preferably a concrete surface because it provides for adequate drainage and the piles can be turned in any weather (Abbozzo, 1996). Next, the compost pile must be provided with adequate amounts of oxygen to keep it aerobic. This is done through aeration of the pile by periodic mixing and turning or by forced air from fans. Keeping the composting process aerobic is the key to effective, composting and odor management. The final product of composting is low in moisture, odorless, easy to transport, and can be used as a soil conditioner (1996). Research at Iowa State University shows that well managed composting sites can be virtually odor free (Lorimor, 1998).

Like anaerobic digestion systems, aeration is a proven technique that has been used in industries and municipalities to stabilize waste odors for years. Aeration utilizes a mechanical device that forces air into the lagoon waste liquid. With this added oxygen to the manure, aerobic bacteria can be effectively used to transform the manure into chemically stable compounds with reduced odor by rapidly degrading phenol, p-cresol, volatile fatty acids, and other compounds (North Carolina Agricultural Research Service, North Carolina State University, 1995). The bacteria work in numerous ways on the waste material and do not create malodorous compounds as a byproduct of their activity. Some oxidize carbohydrates to carbon dioxide and water; others convert nitrogen to ammonium, while still other oxidize ammonium salts into nitrites then nitrates in the process of nitrification. The main advantage of aeration and aerobic treatment of wastes is that they do not produce the volatile fatty acid or odor compounds commonly associated with offensive odors. Resulting gaseous products from an aeration system include: carbon dioxide, water, and sulfates, rather than methane, hydrogen sulfide, ammonia, and volatile fatty acids. Thus, if the aerobic aeration system is designed and operated in a proper and effective manner, the product emissions are odor-free (Lorimor, 1998).

Odor control of swine manure storage facilities can be employed in a passive manner also instead of the active techniques of anaerobic digestion, solids separation, composting, and aeration. Pit or lagoon covers are an effective management method used to reduce odor emissions. Covers reduce the odors released at the manure storage surface. Synthetic covers are placed on the top of the waste storage unit and create a physical barrier between the manure and air. which is essential in the reduction of odor emissions. These covers must cover as much of the storage unit as possible to be an effective odor reducing method, and they must be fixed to prevent and air and manure interaction (1998). Synthetic covers are also suspended above the manure surface by cables in a floating fashion, to create the air-manure boundary that is so crucial for odor prevention. Synthetic and floating synthetic covers keep most of the odorous gas from being emitted into the atmosphere. Instead, it is collected and weakened by passage through a biofilter (Baumgartner, 1998). Bioiihcrs, which contain microorganisms, absorb odors and gases from polluted ah”, converting odorous compounds to carbon dioxide, mineral salts, water, and other harmless products, and ammonia is oxidized to nitrite or nitrate (Jacobson, 1998). Generally, the filtering material may be peat, compost, soil, or some other low-cost, biologically active medium. Evaluations performed at Iowa State University show that a cover significantly reduces the odor liberated by the pit.

Another feasible way to cover a pit and reduce odor is with the addition of a biocovcr. A biocover is made of fibrous biological materials such as have, chopped cornstalks, and wheat and barley straw. The fibrous material is generally blown on the top of the manure storage unit to provide the same physical aerobic barrier between the manure and the air as in a synthetic cover. Biocovers can greatly reduce odor production from manure storage units if they are used and managed properly. “The success of biocovers depends on season-long flotation and continuous one-hundred percent coverage of the storage structure. Getting an adequate depth of cover is important to accomplishing both of these criteria. Biocovers must be eight inches deep” (Lorimor, 1998). Biocovers tend to be most effective for slurry pits instead of anaerobic lagoons because of the larger surface that needs to be covered on the lagoons. In an evaluation performed at Iowa State University the addition of a biocover resulted in odor emissions being drastically reduced (1998).

Since swine building and facilities contribute to odor problems, various management practices have been geared toward the prevention of odor sources from these facilities. Odorous gases arc generated all throughout swine facilities from the waste management system, to the floors, and even to the hogs themselves. Therefore, the best management practice for reducing these odor sources is the common sense solution of keeping these facilities clean. Adequate ventilation can control gases, dust, and vapors, the three major carriers of odors. Ventilation systems help to prevent the buildup of noxious gases formed by the decomposition of stored hog manure. By greatly affecting the movement of particles in a hog confinement building, ventilation can move large volumes of air to dilute the concentration of odor-causing particles inside the building as well as the air exhausted outside the building (North Carolina Research Service, North Carolina State University, 1995).

Landscaping is another way in which odors arc controlled around swine buildings and facilities. Trees, shrubs, and other vegetation are used to form a boundary around the hog facilities affecting the airflow near and around the site, along with visual isolation and/or aesthetic improvement. “Windbreaks are thought to reduce odor emissions in two ways. If they are upwind, they help deflect the air currents up and over the odor source so fewer odors are collected and earned offsite. If they are downwind, they promote mixing and cause the air currents to rise, resulting in increased odor dilution” (Lorimor, 1998). Vegetation used in landscaping as a barrier should include a combination of slow and fast-growing trees and shrubs. Trees should not be planted too close to ventilated buildings to avoid interference with the building’s ventilation system (1998). Since landscape options are considered a relatively new odor control technique and are in the initial phases of research, odor control effectiveness has not yet been evaluated. But, preliminary results have considered landscaping to be somewhat effective in the reduction of odor emissions (1998).

Odor from hog operations is most noticed during or after surface spreading to the land. High odor emissions are produced when manure is spread on the top of the soil via tankers or irrigation. For maximum odor control during land application manure should not be released at the soil surface, instead it should be injected into the soil (Nicolai, 1996). This management practice calls for immediate injection or incorporation of the liquid manure slurries or sludges in which soil immediately cover the manure, isolating it from the above air. All of the manure must be buried below the soil surface for maximum reduction of odor. Cultivation practices can also help to lessen odor production during land application, but it does not provide as much reduction as injection because some manure will always remain on the surface. Studies in Iowa conducted by Iowa State University illustrate a drastic reduction in odor production during land application with the use of soil injection techniques (Lorimor, 1998).

Some of the above odor control techniques are in the early stages of development and are not proven tactics. Current options employed on hog farming operations include some of the above-mentioned methods, often in combination. Cleanliness of the hog facility is a major option used to prevent odor, and management option pays much attention to detail. Floors are kept clean to prevent die buildup and decay of mine, manure, and dust. Cleaner floors will allow for cleaner hogs, and they will emit less intense odors. Ventilation in die buildings maintained at adequate levels to prevent the factors that intensify odors, dust, gases, moisture, and heat. Some feed additives are utilized to reduce the amount of nitrogen emitted by the hog and increase the conversion from feed to weight gain. Manure collection pits arc often scraped and flushed to prevent anaerobic decomposition from occurring and the release of gases that ensues. Lagoons are designed and built large enough to handle the manure load that will be placed in them. Covers are often used on lagoons to capture odorous gases and allow biofilters to stabilize them. Aeration also is utilized to take advantage of the odorless products of aerobic digestion. Land application procedures have made drastic changes to accommodate less odor production regulations. Sprayers and spreaders are adjusted so that manure is spread at low pressure with little agitation. Liquid wastes arc usually spread on dry days with little or no wind and early in the morning so drat the odors are not bothersome to neighbors. Most manure slurries and sludges arc injected or incorporated in the soil so that the odor-causing compounds are not exposed to air.

With current knowledge of odor sources and odor behavior, many new technologies are being developed. Most importantly odor characterization and measurement systems are being developed to allow successful quantification of odor components and how to correlate these with the subjective responses of human panel (North Carolina Agricultural Research Service, North Carolina State University, 1995). Pit additives are gaining popularity and research is directed to developing a more effective and safer odor-reducing additive. Odor removal from buildings and lagoons are being improved with more sophisticated biofilters and chemical scrubbers that will deodorize the air and reduce dust. Composting practices are gaining support from research not only because of the odor-reducing potential but also because of the useful products they convert wastes into. An option for gas disposal called biogas generation is a very promising technique at the forefront of current research. In this method biogas such as methane arc harvested and used as fuel for gas-fired generators, boilers, refrigerators, turbines, space heaters, and crop dryers (1995).

With continuing urban sprawl and the importance of farming in general, it is essential for communities to find workable solutions to the odor problem. For this reason, the swine odor problem cannot be viewed in isolation; a solution requires communication from all parties involved. Also, the future growth and development of the swine industry will be dependant on how well environmental problems, like swine odor, associated with hog production facilities are resolved. Even though numerous odor control strategies exist, more research and development will be needed in this area to ensure proper odor management. Also, better odor measuring techniques will need to be developed so that a definitive odor emission level can be set and regulated. “The debate will continue on how much odor control is enough. However, one fact remains, odors from livestock production must be reduced significantly in order for livestock production to remain in harmony with die environment” (Schmidt, 1998). In summation, the best and most obvious remedy for swine odors will be a clean, efficient operation, die sort of operation the most producers are already striving to achieve.

Critical Reviews

Understanding the Impacts of Large-Scale Swine Production: Proceedings from an Interdisciplinary Workshop edited by Kelly Donham and Kendall Thu breaks down the concerns associated witii intensive hog farming issue by issue. Issues, such as air quality, water quality, etc., are discussed and summarized as presented at this workshop held in Des Moines, Iowa, in June 1995. Under the issue of air quality, questions pertaining to odor sources and odor control are extensively answered. Acceptable odor levels, primary odor sources, health risks, physiological and psychological, associated with swine-related gases, and concerns related to odor emissions are all topics included under the issue of air quality. Since this conference was held in Iowa and many of the head researchers are from Iowa State University, this source directly ties into the topic of “Hog Lots in Iowa”.

Jeffery Lorimor’s publication “Iowa Odor Control: Demonstration Project” summarizes many of the current odor control technologies being researched at Iowa State University. Nine different techniques are discussed complete with an in-depth description of the technique, test results via effectiveness of method, and the costs associated with each process. What makes this source so useful for the topic of “Hog Lots in Iowa” is that all of the techniques discussed are being tested on hog operations throughout Iowa to control swine odor production. Also, relatively new methods that are still in the initial stages of development are tested and evaluated by Lorimor and Iowa State University.

North Carolina State University Agricultural Research Service’s “Options for Managing Odor: A Report from the Swine Odor Task Force” dives directly into the swine odor problem facing Americans, not only Iowans, today. Odor sources, options for control, and future developmental needs for odor control are the main topic of this report. The report is quite in-depth, and each topic at hand is discussed at length. Even though this source primarily dealt with research conducted in North Carolina, the second largest hog producing state next to Iowa, most of the information contained can be applied to Iowa because odor sources and control techniques are comparable throughout the U.S. This source was also quite useful to compare research from Iowa State University from other resources to this research information from North Carolina State University. The research from both institutions is consistent for each topic.

Works Cited

Abbozzo, Paolo, Antonio Boggia, and Mauro Brunetti. “Environmental Quality and Hog Production.” Environmental Monitoring and Assessment. June 1996: 171-182.

“America is Wasting Away: Iowa.” Sierra Club Online, 1999. http://www.sierraclub.org/cafos/rn ap/iowa.asp.

“Animal Waste Pollution in America: An Emerging National Problem. Environmental Risks of Livestock and Poultry Production.” Report Compiled by the Minority Staff of the. United States Senate Committee on Agriculture, Nutrition, and Forestry for Senator Tom Harkin (D-IA), Ranking Member. December 1997. United States Senate Online. http://www.senate.gov/~agriculture/animalw.htm.

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