Strategy for Addressing Livestock Odor Issues

FOREWORD

The Livestock Odor Task Force considered it important that any livestock odor policy be fair to farms of all sizes, protect the public from undue odors, and not place an excessive burden on regulators or producers. Although it would be far easier to say that there is not enough information available to develop such a policy, this was not the choice made by the Task Force. Instead, the Task Force has made recommendations that it hopes will move the state forward in resolving some of the controversy surrounding livestock odors.

TASK FORCE MEMBERSHIP

INTRODUCTION

What is the Livestock Odor Task Force?

The Feedlot and Manure Management Advisory Committee (FMMAC) was created during the 1994 legislative session (Minnesota Statutes 17.136) to, among other tasks, "identify needs, goals, and suggest policies for research, monitoring, and regulatory activities regarding feedlot and manure management." Odor is an issue that in recent years has become a source of contention in many areas of Minnesota as well as across the country. In some instances, the issue has created conflict between neighbors. Because the conflict adversely affects farms, their neighbors (both farm and non-farm), and local communities, the FMMAC created the Livestock Odor Task Force (LOTF) to advise FMMAC on odor control issues. FMMAC's charge to the LOTF was to "develop workable solutions to address the odor issue."

LOTF consists of 12 members (see Task Force Membership on page 3) representing the following constituencies involved in the odor issue: FMMAC, research, environmental, producer, local government, industry/consultant, rural non-farm, Association of Minnesota Counties, MN Department of Health, MN Pollution Control Agency, MN Department of Agriculture, and an at-large position. LOTF was co-chaired by Steve Olson of the Minnesota Department of Agriculture (MDA) and Dave Nelson of the Minnesota Pollution Control Agency (MPCA). LOTF members were selected jointly by FMMAC, MPCA and MDA.

In its recommendations, the LOTF has tried to meet the legislature's goals for FMMAC and FMMAC's goal for the LOTF. The LOTF believes that it may be tempting to mandate policy of zero odor, but this is impractical, as livestock production, or any other industry, could not exist with such a policy. Likewise, having no regulation of odors will only result in increased conflict in rural areas. In its odor policy recommendation the LOTF strived for middle ground of protecting the public interest along with the livestock industry. To do this there will be a need for reductions in odor emissions from some facilities and a tolerance of some odors from the public.

What is the Odor Issue?

In livestock production, odor is a product of microbial degradation of organic matter. The major source of odor on livestock farms is manure. As biological activity occurs gases are released. Over 168 compounds such as hydrogen sulfide and ammonia have been identified which contribute to odor from livestock manure.

Odors have always been associated with livestock. The question is "why is livestock odor an issue now compared with 20 to 30 years ago?" In the past two decades farms have increased in size. The frequency and intensity of odors from the small farms of the past were possibly different and more than likely less intense and less frequent than the odors generated by current facilities. Two factors might help explain the controversy: the increase in density of livestock (more animals per site); and in some areas an increase in numbers of people -- both farm and non-farm living near livestock farms. Odor has been a contentious issue in areas where human populations are stable or decreasing.

Hydrogen Sulfide
Most of the odorous compounds are created during anaerobic decomposition of organic matter. Of these compounds, hydrogen sulfide (H₂S) has received the most attention and has been the center of recent monitoring efforts in Renville County, Minnesota.

In addition to contributing to odor, H₂S can be a health concern. H₂S is a compound that, at certain levels, can affect human health. Portions of the following discussion are segments taken from a Minnesota Department of Health (MDH) analysis of ambient air monitoring done by citizens in Renville County. The concerns regard the potential level of hydrogen sulfide from livestock operations.

The LOTF discussed these findings at several of its meetings. It considered linking odor control policy to existing hydrogen sulfide regulations, i.e. if the MPCA is planning to reduce hydrogen sulfide emissions would odor be reduced as well? However, the correlation between hydrogen sulfide and odor is not sufficient to warrant only one standard. There can often be high odorous emissions and low hydrogen sulfide emissions from the same facility. Therefore, odor emissions must be considered a separate problem. The LOTF reached consensus early in its discussions that regardless of how the livestock odor issue is resolved, the health of all citizens must be equally protected. Therefore, the health and air quality standards related to hydrogen sulfide should be enforced. While the evidence of direct health effects related to odor is still open to debate, this is not the case for hydrogen sulfide. The discussion with respect to differing standards based on different zoning or population density which the LOTF considered with respect to odor do not apply with regard to hydrogen sulfide.

LOTF Discussion and Methodology

The LOTF started a twelve month process of facilitated discussions with the identification of four issue areas :

1. How should government policy motivate development and use of design and management techniques to prevent or control odor?
2. What is the relationship of land use policies to odor control? Parts of this question are:
   • What could each level of government do to reduce conflict?
   • Can the odor problem be reduced through land use planning?
   • If the odor problem were solved would land use conflict evaporate?
3. How do we measure odor to achieve the goals of policy regarding community/industry exposure to odors?
4. What should the government policy be on how much odor a community or individual should have to tolerate?

Assumptions
The LOTF discussion was guided by the following assumptions:

1. Both animal agriculture and the public good are important to the state of Minnesota; therefore, the state should invest time and resources toward resolving the odor issue.
2. The state is responsible for establishing health-based criteria for specific components of emissions and developing appropriate standards.
3. Government policy should not inhibit the creation of effective and economical odor control technologies.
4. The state should promote low emission and low energy use systems.

Methodology
The LOTF divided into working teams to develop through a brainstorming process options/alternatives to address each of the problem statements. Afterward, as a whole, the LOTF reviewed, commented on and revised the options and alternatives. They then developed pros and cons for each of the alternatives. Next, each group was responsible for drafting a discussion on the options. The intent was to present a balanced discussion on the issue that would assist the LOTF in developing recommendations. The options/alternatives are described in Appendix A. Finally the LOTF as a whole evaluated elements of recommendations. These were subsequently written up in draft, revised and adopted by consensus.

Overview of Recommendations

The most effective odor policy is one that is based on total odor emissions from a farm site. An odor policy based on total emissions allows farms of any size and manure handling system to be compared and regulated on a uniform basis. However, since actual monitoring of odor emissions from individual farm sites is both difficult and expensive, odor emissions from an individual farm site must be estimated. To be reliable, these estimates must be based on on-farm odor measurements of typical odor sources. On-farm odor sources include livestock housing and manure storage. (Note: odors from land application are intermittent and are not currently included in the discussion of on-farm odors; however, different land application methods could also be evaluated similarly). Once total emissions from an individual farm site are estimated, acceptable and standardized separation distances can be determined.

The recommended odor policy is based on two key elements: the development of an odor rating system; and a method to relate odor emissions to separation distances. Recommendations also address implementation and interim issues.

The Livestock Odor Task Force is recommending that the State of Minnesota take the following actions:

I. Recommendation for Odor Policy

• Total Odor Emissions Rating System. Research, development, and implementation of a system for rating the total odor emissions from livestock facilities based upon evaluation of new and existing manure management odor control technologies, practices and size of facility.
• Emission/Separation Curves. Development of a line graph for use by county governments in determining separation distances between livestock facilities and other land uses, based on the total odor emissions rating system.
• Best Management Practices for Peak Odor Events. Development of best management practices (BMPs) to address seasonal or periodic peak levels of odor that are not adequately addressed by the total odor emissions rating system, emission/separation curves, and resulting separation distances

II. Recommendations for Implementation

• Funding. Identification of funding mechanisms for rating emissions from both common, and patentable production practices.
• Users Manual. Development of a users manual to assist county government and producers in use of the total odor emissions ratings system and emission/separation curves.
• County Implementation. Facilitation and encouragement of local implementation of the total odor emissions rating system, emission/separation curves, and best management practices for peak odor events, through funding and technical assistance.
• Mediation Services. Development and provision of mediation services to local governments to assist in resolving conflicts of livestock odor.
• Evaluation. Assessing the effectiveness of the rating system, emission/separation distance curves, and best management practices for peak odor events; and the level of implementation by county governments.

III. Recommendations for the Interim

• Promotion of Best Management Practices (BMPs) Develop fact sheets on current odor control practices to assist producers in reducing odors and county government in addressing complaints.
• Hydrogen Sulfide (H₂S) Support MPCA's efforts in determining extent of H₂S emissions from livestock operations.

RECOMMENDATIONS OF THE LIVESTOCK ODOR TASK FORCE

I. Recommendations for Odor Policy

Total Odor Emission Rating System
Several types of livestock farming systems are currently in use throughout the state of Minnesota. These farming systems range from low density pasture systems to high density confinement systems. The number of animals raised on individual farms also ranges from a few animals to several thousand animals. Because of these variations each individual farm will generate a different amount of odor. Trying to monitor or measure the amount of odors being emitted from each farm would be a nearly impossible task. Some system therefore must be developed to estimate the amount of odors generated on these farms. Having a reliable estimate of the total odors generated allows farms to be compared based on odors emitted rather than on the number of animals.

An odor rating system needs to be developed as a means to predict and compare odor emissions from farms. By taking odor measurements from a variety of odor sources, a rating of these sources can be established. Odors can be measured using an olfactometer (see Appendix A). Olfactometery is a method that uses the human nose to evaluate the strength of an odor. It is a systematic method that records the amount of clean dilution air needed to make a sample of odorous air undetectable. This number is recorded as odor units (ou). Although the olfactometer does not give an actual measure of odor emissions (mass per time), it does indicate a relative rating of the strength of an odor from a particular source. Once a system is given an odor rating it can be compared to other systems. Although a particular protocol has not been established, it is thought that the sample of odorous air from a particular source would be measured directly from the source, e.g., directly off the surface of a manure storage basin, rather than somewhere downwind from the source.

An odor rating for any particular type of system could be generated by taking actual air samples from several existing systems, evaluating the sample using an olfactometer, and averaging the results. (Note, these odor ratings would be based on average odor measurements from these systems. Considerations would not be made for the multitude of variables that impact gas emissions. The rating system would be based on a standard testing protocol and would only indicate average odor emissions). These odor ratings would be published in a table. As new technologies become available they would be evaluated and given an odor rating.

The development of an odor rating system makes it possible to compare relative odor emissions from different types of systems, or to evaluate the percent odor reduction that could be anticipated by implementing an odor control technology. However, an odor rating can only compare the relative odor emissions from different types of systems. What is also needed is a method to compare the total emissions from different types of systems that are in use on various farm sizes. Therefore, a method to relate the odor rating to the estimated total odor emissions from a farm is needed. Although no such method currently exists, it is anticipated that such a method can be developed. This method would factor in variables such as the surface area of the odor source or the amount of odorous air being ventilated from a building. With this type of information the total odor emissions from a farm site could be estimated.

Example
A farm is looking at some expansions and modifications. Currently they are finishing 1000 pigs per year in cargill units (open front barns). Manure is currently being scraped from these units into an earthen basin. The farmers are proposing a new facility on the same site which will finish 2500 pigs per year in a deep pitted, mechanically ventilated barn. The existing facilities, including the earthen basin, will be abandoned. Does the potential for off-site odors increase or decrease with this change?

Currently this question can not be answered. With the proposed system the cargill units, the earthen storage, and the deep pitted barns will have an odor rating; some number that indicates the average amount of odors generated. Using the odor rating number for each system and the sizes of the facilities estimated odor impact from the existing and proposed could be compared.

Will the system promote or stifle innovation?
The proposed recommendations will most likely stimulate the creation of economical odor control technologies. Currently any odor control technology is seen as suspect. One key factor in stimulating the creation of new technology is the ability for new products and technologies to be evaluated. It is the hope of this task force that the rating of new technologies will be very economical and timely. Provisions may also be made to accept test results from other testing facilities.

What will the odor rating include?
The evaluation of systems will be primarily based on average odor generation from a given system or technology. However, other information could be attained at the same time with little additional effort. Other information may include the emissions of hydrogen sulfide or ammonia or the cost of implementing the technology.

Challenges
Although the Task Force has agreed that the proposed system would be the best policy option, some difficulties still exist.

Rating manure handling systems based on odor emissions can be a simple process once the protocol has been determined. However, there are a multitude of manure handling systems and system variations that need to be evaluated. For instance, there are three or four different methods for storing liquid manure. These few systems could easily be given a rating, given the same type of manure was in the storage. However, odors from these storage may vary by type of livestock manure, solids concentration, initial sulfate content in the water, animal diet, management practices, odor reducing additives, etc.. Preliminary investigations indicate that some of these factors may contribute significantly to odor while others may not. Therefore, the sheer number of options or variations to evaluate may make the rating system very difficult to create and maintain.

Another potential problem with the rating system is the lack of methodology for estimating total emissions from a system based on individual odor measurements. An odor measurement from the surface of a manure storage will give a ratio of dilution to threshold or odor unit. This odor must then be related to the total emissions from that storage. It is logical that the total emissions is related to the total area of the odor emitting surface or the amount of odorous air exhausted from a building, however, these relationships have not fully been established.

The primary goal of the rating system is to determine the total emissions from a farm site. Most farms will have a combination of odor sources, some emitting surfaces and some ventilation fans. These two very different types of emissions must be combined in determining a total odor emissions for the farm. No current method exists that can compare or combine these two odor sources.

Emission/Separation Distances
Another key to the odor impact on a community is separation distance, the distance between an odor source and the property line, nearest neighbor, or residential area. Once an odor rating system is developed it is possible to develop separation distances that are based specifically on odor. Current separation distances are based on the assumption that larger facilities generate more odor and therefore require greater separations. This theory would hold true if all operations were identical. However, with the diversity of manure handling systems and facility designs and the new odor control technologies currently being developed, farm size is not the only variable in odor emissions. With the odor ratings system, it will be possible to develop separation distances based on the actual odor impact from a facility. Therefore, the second key element of the recommendations is a method to compare the odor impact of various existing and proposed farm sites on a community. One method to determine this impact is with a dispersion model. A dispersion model is a mathematical method of estimating how a gas, emitted into the atmosphere, is dispersed in the ambient air. Although many factors exist in determining how a gas is dispersed, the model could be used with a standard set of input variables. In this way, the only variable would be the odor emissions as estimated by the odor rating. The separation distances generated by a dispersion model could be verified by reviewing existing livestock and poultry operations that are acceptable to the community.

A line graph would be developed showing several curves, with each curve representing a different frequency or intensity of odor. The line graph would allow the user to determine a separation distance between a livestock site and a receiving site, based on the odor sensitivity of the receiving site and the odor rating of the livestock site.

Figure 1. Odor emission vs. separation distance curves (theoretical).

A set of separation distance curves might look similar to what is shown in figure 1. In figure 1 the different categories represent some indication of the acceptable limits of odor impact. These categories could represent various odor intensities and frequencies. For instance category 1 may be a land use classification where more intense or more frequent odors could be expected. Category 4 may represent a land use classification with a fairly low tolerance to intense or frequent odors. The total odor emission represented on the horizontal axis would be the total odor emissions as estimated by the odor rating system. The separation distances would be calculated values based on odor dispersion modeling and verified by field measurements or experience with existing facilities.

Best Management Practices for Peak Odor Events
An odor rating system would most likely rate systems at average odor emissions. Outdoor manure storage facilities may emit more odor during periods of transition between cold and warm weather (spring and fall turnover). Also, odor emissions are much greater when manure storage facilities are being agitated during emptying. Because the recommended odor policy is based on average odor emissions, these periods of high odors will impact surrounding neighbors and communities. The actual impact of these periods of high odor is dependent on wind speed and direction during those periods.

The proposed odor rating system deals with typical odor in a quantitative way. Because of the transitory nature of peaks, it would be impractical to address them in the same manner. Peaks need to be addressed in a prescriptive fashion (BMPs). There are some management practices and technologies that are currently available to address these periods of high intermittent odors. Technologies currently being developed will also be available to address those periods.

II. Recommendations for Implementation

Implementation of Odor Rating System and Emission/Separation Distance Curves Current rules and regulations involving the operation and construction of livestock facilities differ across the state. This inconsistency is especially obvious in the regulation of livestock odors. Counties throughout Minnesota are developing methods of regulating livestock facility with regard to odor. These systems typically do little to control odor problems or put an excessive burden on producers. In counties where no odor regulations are implemented the public may not be protected from undue or excessive odors. One method to standardize these odor regulations would be for the state to set minimum separation distance based on odor rating and emission/separation curves. The LOTF determined that implementation of such statewide standard would not be appropriate because such a standard may be too permissive for some counties and too restrictive for other counties. Therefore, it was determined that the use of the total odor emissions ratings and emission/separation curves should be at the option and discretion of local government. However, it is important to both producers and the public that most or all counties in Minnesota adopt this system. Therefore the adoption of this system should be strongly supported and encouraged by the state.

Setting up and maintaining an efficient method to rate systems will cost money. Most elements of a manure handling systems are very common. However some elements of manure handling systems are specific technologies that are patented by the manufacturer. This difference in systems must be accounted for when funding the odor rating test. LOTF recommends that odor ratings for standard systems be funded by public funding sources while ratings for patentable systems be funded through the private firm developing the odor control technology.

What about existing facilities?
The odor rating system is intended primarily for use in evaluating and regulating proposed livestock facilities. However, the system could also be applied to existing facilities. In enforcement of any new zoning provision, a local government must decide how to address "nonconforming lots, buildings, or uses"; land, structures, or uses of the land that complied with local laws before adoption of new zoning provisions, but that are in violation of the provisions after adoption. A lawfully-existing livestock facility that does not comply with new odor-related separation distance provisions could be considered a nonconforming building or structure. Possible options to address nonconformities range from allowing their continued existence, to requiring termination after a specified period of time (a concept known as "amortization"), to immediate termination. A number of legal issues are associated with addressing nonconformities in zoning regulations, and local governments should obtain sound legal advice before developing and implementing such regulations.

The following two recommendations are critical to the success of the odor rating system and emission/separation curves.

County Implementation
Both state and local governments have an interest in solving the issues related to odors from livestock facilities. Odor policy recommendations include the state and county governments in policy implementation. Under the recommendation, state government would be responsible for developing and maintaining an odor rating system along with setting guidelines for determining separation distances. County governments would be responsible for implementing the odor rating system through their zoning authority. County governments could make separation distances more or less restrictive than the state guidelines.

Mediation Process
The LOTF envisions county governments handling odor complaints by first inspecting the livestock facility, followed by referral of mediation services, where appropriate. Upon a livestock odor complaint, inspection would be conducted by trained local personnel to determine whether the facility meets odor rating criteria, and whether odor levels being generated are above those that would be expected from the plan. Inspection personnel would also provide complainants information on what odors would be expected from proper implementation of the odor management plan. Results of the inspection would be provided to both the complainant and the producer. Subsequent to the inspection, if the facility was found to be in noncompliance, then the local government would require the facility to be brought into compliance.

If the facility was found to be in compliance with the local provisions, and an odor issue still exists between the parties, mediation between the complainant and producer would be offered to resolve the odor issues. Initiating mediation would be at the option of the complainant and the producer.

Evaluation
This use of an odor rating system and separation distance curves is a new approach to addressing this issue. As a new approach the effectiveness and implementation will need to be evaluated and adjusted as necessary. After development of odor ratings, implementation by counties will probably occur over a couple of years. The LOTF realizes that after a period of time the rating system will need to be evaluated for its effectiveness in addressing the odor issue. The effectiveness should examine the level of implementation by counties, and the usefulness to counties and livestock producers.

If the odor rating system is found to be practical and effective, and two years after the system is developed and available for local use, the State should evaluate the rate at which local agencies are adopting and using the odor rating system. The State should also evaluate the how the system fits in with feedlot regulation by the State.

III. Recommendation for Interim

The projected timeline for developing the odor rating system, separation curves, and BMPs for peak odor events is estimated to be 2-3 years. The LOTF recognizes that in the interim efforts will need to be made to address the issue. The LOTF recommends promotion of current odor control BMPs, and continued analysis by MPCA and Minnesota Department of Health of the prevalence of hydrogen sulfide emissions from livestock operations.

The Minnesota Pollution Control Agency currently has regulations governing the concentrations of hydrogen sulfide in the ambient air. Hydrogen sulfide is one of the odorous gases emitted from livestock and poultry operations. The MPCA's control of hydrogen sulfide emissions will most likely reduce the amount of odor generated at many livestock facilities. However, reductions in hydrogen sulfide may not lead to sufficient reductions in odor. Therefore, the livestock odor task force recommends that an odor policy be implemented regardless of the MPCA's efforts on hydrogen sulfide. The recommended odor policy should not interfere with any hydrogen sulfide regulations.

CONCLUSION

The LOTF recognizes that development and implementation of an odor rating system and its other recommendations will be no simple task. However, the LOTF believes that development and implementation of such a system is the right course and direction for Minnesota.

Steps to Implement an Odor Rating System

The following are areas identified by the Livestock Odor Task Force for future work to further address the issue of odor from livestock. These areas include implementation of odor emissions based standards as well as other necessary research and education.

1. Develop a protocol for rating systems on odor emissions.
2. Designate an appropriate body to rate the systems.
3. Determine the relationship between relative odor measurements from systems and total odor emissions.
4. Determine an acceptable relationship between separation distances and total odor emissions.
5. Develop dispersion modeling.
6. Request funding from legislature for determining odor ratings for standard, non-patentable systems and dispersion modeling.