Preparing an odor management plan

In Minnesota (US) an odor management plan for feedlots with 1,000 animal units or more must include: methods and practices that will be used to minimize air emissions resulting from animal feedlot or manure storage area operations including manure storage area start-up practices, loading, and manure removal; measures to be used to mitigate air emission in the event of exceedance of the state ambient hydrogen sulfide standard; and a complaint response protocol describing the procedures the owner will use to respond to complaints directed at the facility including a list of each potential odor source at the facility, a determination of the odor sources most likely to generate significant amounts of odors, and a list of anticipated odor control strategies for addressing each of the significant odor sources. A summary of University of Minnesota extension publication: FO-07637 2001

Introduction

Minnesota Rules Relating to Animal Feedlots and Storage, Transportation, and Utilization of Animal Manure, Chapter 7020.0505 Subpart 4 B, requires feedlots with 1,000 animal units or more to submit an air emission plan. This plan must include:

  • methods and practices that will be used to minimize air emissions resulting from animal feedlot or manure storage area operations including manure storage area start-up practices, loading, and manure removal;
  • measures to be used to mitigate air emission in the event of exceedance of the state ambient hydrogen sulfide standard; and
  • a complaint response protocol describing the procedures the owner will use to respond to complaints directed at the facility including a list of each potential odor source at the facility, a determination of the odor sources most likely to generate significant amounts of odors, and a list of anticipated odor control strategies for addressing each of the significant odor sources.

The air emissions plan must specifically address odor but may also include dust and individual gases such as hydrogen sulfide and ammonia. Although an air emission plan is only required for sites with 1,000 animal units or more, all feedlots should consider writing such a plan to help avoid nuisance odor conflicts and demonstrate the intent to be a good neighbor. Odor management plans for farms of any size can be developed using the information in this publication.

Odor management plans

Manure management plans have become a standard practice for most animal production systems. These plans document the proper handling and application of manure onto cropland. Likewise, odor management plans systematically identify potential odor sources, determine control strategies to reduce these odors, and establish criteria for implementing these strategies.

The development of an odor management plan consists of the following four steps:

  1. Create a list of the potential odor sources on the farm.
  2. Determine which of the odor sources are the most likely to bring about odor complaints.
  3. List one or two odor control strategies for each of the significant odor sources.
  4. Develop a protocol to respond to odor complaints.

Inventory of odor sources

Nuisance odors can be a single odor source, a single odor event, or the combination of several sources and events. Therefore, it is important to conduct a thorough inventory of all odor sources on the farm. This inventory should be conducted on-site in a systematic way to ensure that all odor sources are included.

Animal production site odors originate from three primary sources: manure storage structures, animal housing (including open lots), and land application of manure. However, other sources including dead animal disposal sites, silage piles, feed centers, and any other areas where organic matter is present may also contribute to odor emissions. These other odor sources are often overlooked in discussions about nuisance complaints. For instance, improperly managed dead animal disposal sites can generate significant amounts of odor. Intermittent odor events (e.g., manure agitation) should also be listed in the odor inventory because these events, though infrequent, can often be the source of significant odor emissions and odor complaints.

A brief description of each odor source should be included in the inventory. This description should include the size of the odor source (physical area) and its distance and direction from roadways, neighbors, property boundaries, etc.

Table 1. Odor emission reference rate for animal and poultry housing*

Species
Animal Type Housing Type Odor Emission Number (Rate)
Cattle
Beef Dirt/concrete lot, Free stall, scrape; 4

Dairy Free stall, deep pit, Loose housing, scrape; 6
    Tie stall, scrape;
2
Swine
Gestation Deep pit, natural or mechanical 50

  Pull plug, natural or mechanical 30
  Farrowing Pull plug, natural or mechanical
14
  Nursery
Deep pit, natural or mechanical; Pull plug, natural or mechanical; 42
  Finishing
Deep pit, natural or mechanical 34
    Pull plug, natural or mechanical
20
    Hoop bar, deep bedded, scrape; Cargill (open front), scrape;
4
    Loose housing, scrape; Open concrete lot, scrape;
11
Poultry Broiler
Litter 1

Turkey Litter 2

*Taken from Livestock and Poultry Odor Workshop Manual II, Department of Biosystems and Agricultural Engineering, University of Minnesota, 2000

Table 2. Odor emission reference rate for manure storage*

Storage Type
Odor Emission Number (Rate)
Earthen basin, single or multiple cells
13
Steel or concrete tank, above or below ground
28
Crusted stockpile
2

Earthen basins are designed for manure storage only. A properly designed treatment lagoon may have far less odor.
*Taken from Livestock and Poultry Odor Workshop Manual II, Department of Biosystems and Agricultural Engineering, University of Minnesota, 2000

Determination of high odor sources

A good odor management plan must identify which of the many on-farm odor sources have the highest potential to create nuisance odors.
Research has shown that some odor sources emit more odor per unit area than other sources (Tables 1 and 2). Therefore, both relative odor emissions and the size of the odor source must be considered in determining the high odor sources. Intermittent sources, such as liquid manure agitation and pumping or land application, also cause relatively high odor emissions and should be considered in any list of high odor sources.

Another factor to consider in determining high odor sources is the proximity of the sources to public areas or neighbors. Dilution of odors is caused through the mixing of odors with ambient air. Dilution is a function of distance, topography, and meteorological conditions. Greater distances between odor sources and the public will result in fewer nuisance complaints. Topographical features can either enhance or reduce dilution. Wind breaks or tree lines will encourage mixing of the odorous air with clean air, whereas valleys or low areas may reduce odor dilution. Meteorological conditions also affect dilution. Maximum dilution occurs when the cool air near the ground is heating and rising. Conversely, during the late evenings when it is calm and the atmosphere is cooling, the odorous air is trapped near the ground and there is little dilution.

Of these three factors (distance, topography, and meteorology) separation distance generally has the biggest impact on nuisance complaints.

Possible odor control technologies

Odor control technologies fit into three different categories; reducing odor generation, decreasing emissions, and increasing odor dilution. Several of these technologies are listed in Table 3. Since little is known about many of these technologies, the odor management plan should list one, two, or possibly three control technologies for each of the high odor sources. If the first odor control strategy proves ineffective, then the second or third strategy can be implemented.

biofilter on exhaust fans for odor control

Figure 1. Biofilter on exhaust fans for odor control.

Reduce odor generation

Production of odorous gases can be decreased by manure treatment technologies such as anaerobic digesters or aeration systems, diet manipulation to reduce the amount of manure produced or the amount of nutrients in the manure, or chemical or biological additives. Manure treatment technologies can be very effective at odor control but are typically expensive. Chemical additions can also be effective, with cost depending on the specific chemical and the frequency of addition. Biological additives are typically less expensive than manure treatment or chemical additives, but their effectiveness often varies by farm site and additive.

Manure storage cover for odor control

Figure 2. Manure storage cover for odor control.

Reduce odor emissions

Capturing and treating odorous gases before they leave the site reduce emissions. In most situations these gases are converted through biological, physical, or chemical processes to other non-odorous gases. Biofilters are a good example of a technology that reduces odor emissions. Microorganisms in the biofilter media oxidize complex odorous chemicals into simple odorless compounds. The air emitted from the biofilter is nearly odor free.

Increase odor dispersion

Odors can be dispersed and/of diluted by; shelterbelts, windbreak walls, and setback distances. Setback distances are the most effective. New information on shelterbelts suggests that some odor reduction is due to increased turbulence caused by the windbreak as well as some capture of the odorous gases on the tree foliage.

Table 3. Odor control technologies.

SYSTEM
DESCRIPTION
Biofilters
Odorous gases are passed through a bed of compost and wood chips; bacteria and fungal activity help oxidize organic volatile compounds.
Biological and chemical wet scrubbers
Odorous gasses are passed through a column packed with different media types; water (and/or chemical) is sprayed over the top of the column to help optimize biological and chemical reactions.
Diet manipulation*
Enzymes added to diet to improve nutrient utilization; diets formulated to reduce crude protein content; or other changes in diets to enhance digestion.
Fat added to feed
Dust reduction and subsequent odor reduction by adding fat to the feed.
Manure additives*
Chemical or biological products are added to the manure.
More frequent manure removal*
Fresh manure (fewer than 5 days old) produces less odor than stored manure.
Nonthermal plasma
Odorous gases are oxidized when passed through plasma.
Oil sprinkling
Vegetable oil is sprinkled daily at low levels in the animal pens.
Ozone*
Ozone is added to the ventilation air to oxidize the odors.
Shelterbelts*
Rows of trees and other vegetation are planted around a building, thus creating a barrier for both dust and odorous compounds emitted from the building exhaust.
Windbreak walls*
A solid or porous wall constructed 10 to 15 feet from the exhaust fans will cause dust to settle out and will also help disperse the odor plume.

Odor Control Technologies for Manure Storages

SYSTEM
DESCRIPTION
Aerobic treatment
Biological process where organic matter is oxidized by aerobic bacteria; mechanical aeration is required in order to supply oxygen to the bacterial population.
Anaerobic digestion
Biological process where organic carbon is converted to methane by anaerobic bacteria under controlled conditions of temperature and pH.
Floating clay balls
Floating clay balls cover the manure surface.
Geotextile cover
Geotextile membranes are placed over the surface of the manure.
Manure additives*
Chemical or biological products are added to the manure to reduce gas formation.
Natural crust
Dairy and sometimes swine storage basins can form a natural crust. This crust will reduce odor emissions.
Solid cover
Non-porous cover floated on, or suspended over, the liquid surface. Covers trap gases before they escape. Gases must be drawn off and treated.
Solid composting
Biological process in which aerobic bacteria convert organic material into a soil-like manure called compost; itÕs the same process that decays leaves and other organic debris in nature.
Solid separation*
Solids are separated from liquid slurry through sedimentation basins or mechanical separators.
Straw cover
An 8-12 inch blanket of dry wheat, barley, or other good quality straw floated on the manure surface reduces emissions.

Odor Control Options for Land Application of Manure

SYSTEM
DESCRIPTION
Manure incorporation or injection Manure is incorporated immediately after land application or manure is injected under the soil surface.
Chemical addition
Chemicals added during agitation to reduce hydrogen sulfide or ammonia emissions.

Odor Control Options for Other Odor Sources

SYSTEM
DESCRIPTION
Mortality composting
Method to dispose of dead animals. Carcasses are buried in sawdust or some other organic composting material. Decomposition takes place very rapidly.

*Effectiveness of these technologies has not been verified.

New facilities

New or proposed facilities should be designed to minimize odor emissions; however, there are currently no standard design criteria. Nevertheless, design elements that reduce the surface area of exposed manure, control dust, capture and treat gaseous emissions, increase dilution of emissions, or treat manure could be considered as odor reducing. This may be as simple as building a deep pit manure storage versus having an outdoor manure storage structure, using a pull plug system with manure stored in an outside covered storage structure, or using a wet/dry feeder system to reduce dust. A new or proposed facility might also include plans for future odor control technologies should problem arise. The design might include designated space for a biofilter, liquid solid separation equipment, or plans for a windbreak. Solid manure systems also produce less odor per unit area than liquid systems and should also be noted on the odor management plan.

Odor complaint response

The protocol to address odor complaints is the most important piece of the management plan. This is a critical issue from three perspectives. First, it is sometimes difficult to separate serious odor complaints from complaints registered by disgruntled neighbors. Second, it is difficult to determine how many valid complaints are needed to trigger the implementation of an odor control technology. And third, there must be some method for monitoring effectiveness of the technology. The complaint response protocol sets up an odor monitoring plan and guidelines for an acceptable number of odor events as well as an evaluation of odor control effectiveness. For this, fostering and maintaining good relationship with neighbors and other community members is critical.

Item 1. Avoid Odor Complaints

Avoid odor complaints by making an effort to control odor emissions, including peak odor events such as manure agitation or land application of manure. Document efforts and their perceived effect on odors.

Item 2. Establish a Relationship with Neighbors and Community Members

An effective complaint response protocol requires the input of neighbors and other community members such as environmental service specialists, county feedlot officers, and county and township officials. These individuals provide an honest evaluation of farm odor impacts. They could be listed on the odor management plan and help in the development of the complaint response protocol. A team approach fosters communication and flow of information which is critical to responding to complaints.

Item 3. Monitor Odor Events

Monitoring odor events will help verify odor complaints and identify odor sources. Monitoring might include scheduled drives around the farm perimeter with a notebook recording the date, time, and location and strength of any detected odors. Other monitoring might include recording of odor events by neighbors or community members. Strength of odors can be recorded on a three point odor intensity scale where 1=detectable odors, 2=recognizable odors, and 3=very distinct and annoying odors.

Item 4. Set Acceptable Intensity and Frequency Standards

It is impossible to expect 100% odor free air around the farm. However, frequent, high intensity odor events are unacceptable. Therefore, some reasonable frequency of odor events should be established on either a yearly or monthly basis. Above this frequency, the odor management plan would be implemented. Establishing the acceptable frequency and intensity (how often and how strong) of odor events should be done with input from neighbors and community members so everyone is familiar with the goals of the farm.

Item 5. Evaluate the Odor Control Technology

After an odor control technology has been implemented, an honest evaluation of its effectiveness is needed. A complaint response protocol will outline evaluation methods and techniques. This evaluation will most likely be similar to Item 3 (Monitoring Odor Events).

Maintaining odor management plans

An outline for an odor management plan is given below. This plan should be reviewed and adjusted annually. Changes in farm operation and management; additions or modifications to buildings or manure storages; changes in ownership of surrounding property; or changes in local, state, or federal regulations may all be reasons for altering the odor management plan. The success of any farm operation can be measured by the avoidance of community conflicts and nuisance complaints. This requires a planned approach to odor management and good communication between farm management and the community.

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