Ten states use direct regulations; 34 states have indirect odor rules on the books. As farms grow larger and environmental awareness increases, many states are adding new regulations.



Think the disputes and lawsuits about odors between pork producers and their neighbors are a new phenomenon? Think again.

Back in 1610, an English court ruled that a hog farmer had to remove his pigs because their presence infringed on his neighbor's right to wholesome air. The court found that four elements were necessary in a home: habitation by man, pleasure of the inhabitants, necessary light and wholesome air.

“Interestingly, the Clean Air Act mimics the four things that the law sought to protect, even back then,” says Jarah Redwine.

Redwine, a graduate research assistant at Texas A&M University, has researched agricultural odor regulations and has found a wide range of standards and rules across the country.

In the U.S., 44 of the 50 states have regulations that deal directly or indirectly with odors from concentrated animal feeding operations (CAFO).

Ten states have direct odor regulations, which means they have specific rules that prohibit odor emissions greater than their standard. See Table 1 for rules for top pork-producing states.

Another 34 states have indirect regulations — such as setbacks, permits, public comment periods and manure handling training — as methods to reduce odor from feedlots.

Redwine identifies five common methods for states to indirectly regulate odor:

  1. Setbacks. Twenty states have setback rules, ranging from 50 ft. to 16,000 ft. Rules are based on source type (lagoon, confinement building, etc.) or type of receptor (home, school, park or community). Size of CAFO also is used in setback rules.

  2. Permits. Registration of feedlots is the most common method. Forty-one states have some type of permit system. There are three types of permits. Individual permits are specific to that operation. General permits are issued based on criteria set up by state agencies. Permit by rule includes criteria set up in state regulations. Operations that meet the regulations automatically receive the permit.

  3. Public comment/involvement. Twenty-one states allow public involvement, and several states have set public comment periods.

  4. Operator training. Fifteen states have requirements that owners and operators applying manure have to have training.

  5. Land application training. Twenty states use this method, which focuses on when, where and how to apply manure to the land.



States also are using other methods of indirect regulation. Arkansas has a good neighbor policy, for example.

“People who have permits for facilities are encouraged to increase relations with their neighbors so they might avoid some of the problems that may arise from odors,” Redwine says.

States with direct rules use scentometers or butanol olfactometers to measure odors. A scentometer measures how many times an odorous air sample must be diluted with clean air before the odor is no longer detectable, or dilutions to threshold (DT).

For example, in Colorado, if two scentometer measurements taken at least 15 minutes apart but within one hour are greater than 7 DT at the property line, the producer is in violation.

Because odor is a subjective sensation that varies from one person to another, states are looking for ways to quantify odors with science, Redwine says.

There are two trends in state odor regulations. Older laws and measurement methods are based on perception of odor.

“The newer methods are trying to make more objective measurement of the odor and set some method to quantify it,” Redwine says.

States, pushed by lawsuits and public perception of odors from larger animal operations, have implemented many rule changes.

In the past five years, 32 states have changed, amended or proposed new odor regulations, Redwine says. In 1998 and 1999, 17 states changed their regulations.

Table 1. Summary of State Odor Regulations for Top 10 Pork-Producing States
State Odor Rules Setbacks Permits Required Public Hearings Training Required Land Application Restriction Other Governing Agency
IA no yes, 750-2,500 ft yes, construction yes to land apply wastes yes MMPa required. Dept.of Natural Resources
IL no yes, 0.25 to 1 mile New lagoons must be registered. yes yes yes Specific OCPb for lagoons are outlined. Environmental Protection Agency
IN no no Must gain approval to construct or expand. no no no MMPa required. New rules have been drafted. Dept. of Environmental Management
KS no yes 1,320 to 16,000 ft yes, permit or registration yes yes, (swine only) yes MMPa, NMPc, OCPb may be required. Dept. of Health and Environment
MN no no yes, certificate or permit no no no hydrogen sulfide ambient air standard Pollution Control Agency
MO Yes, CAFO odor rule starts Jan. 2002. yes, 1,000 to 3,000 ft yes yes yes no 7,000 AU or over must file extensive OCPb. Dept. of Natural Resources
NC no yes, 75 to 5,000 ft yes no no yes May have to file BMP that includes OCPb, use liquid waste system; permit includes MMPa. Dept. of Environmental and Natural Resources
NE no yes, 1,000 ft yes yes no yes Permit requires BMP for odor; all feedlots 300 AU and over without permit must be inspected. Dept. of Environmental Quality
OH no no yes no no no MMPa required. Environmental Protection Agency
OK no yes, swine 0.25-3 miles construction permit yes odor control education no OCPb required for permit; odor is indirectly defined as air pollution. Dept. of Environmental Quality; Dept. of Agriculture, Water Quality Division
aMMP = manure management plan bNMP = nutrient management plan cOCP = odor control plan


Redwine points to the concentration of livestock on larger farms and society's emphasis on the environment.

“Especially with the hog operations and broiler operations, there has been an exponential increase in the number of animals per operation,” she says. “During the same time period, we've seen an increase in environmental awareness in our society. When those two things come together, it results in a more focused attention on odor from animal feeding operations.”

Currently, no state is using odor modeling in their regulations, but Redwine suggests that such changes are coming.

“This is not a new problem. This is a conflict that we've been dealing with legally for over 400 years,” she says. “Because of changes in society and changes in the livestock industry, we have seen more attention focused on odor. States are responding with changes in their regulations.”