Frequently asked questions about livestock odor

PDF icon Livestock odor facts (wq-f2-04)

What is livestock odor?
Livestock odor is caused when organic matter such as manure decomposes and releases gases containing chemicals such as ammonia and hydrogen sulfide, which smells like rotten eggs.

How overpowering is the smell of hydrogen sulfide?
Hydrogen sulfide is detectable at a very tiny amount (1 part per billion), but the nose desensitizes quickly to the odor. That's a concern, since more than 50 parts per billion of hydrogen sulfide can cause headaches, nausea, vomiting and diarrhea.

What is Minnesota's air pollution standard for hydrogen sulfide?
Minnesota's standard is a 30-minute average of 30 parts per billion twice in five days, or a 30-minute average of 50 parts per billion twice per year.

What's a part per billion?
A part per billion is the equivalent of one silver dollar in a roll of silver dollars stretching from Detroit to Salt Lake City.

Why is livestock odor an issue now?
Two changes have occurred over the past two decades that are aggravating the problem of odor:

  1. Livestock operations have more animals, and
  2. More people are living near livestock farms.

Why is odor worse at some feedlots?
Livestock odor can be affected by:

  • how manure is stored,
  • what food is fed to the animals,
  • how well the farm is maintained,
  • what methods farmers use to reduce odors, and
  • what the weather conditions are.

What about when feedlots are close to each other?
 In the spring of 1998, the MPCA conducted a study that showed when feedlots are located within a few miles of each other, hydrogen sulfide from each of them may combine and raise the air's hydrogen sulfide concentration downwind.

What is the MPCA doing about livestock odor?
In 1997, the MPCA started to monitor the amount of hydrogen sulfide emissions from feedlots. Agency staff primarily use a hand-held meter than instantly read hydrogen sulfide levels. When a monitor reading is above the state standard, MPCA staff send a letter to the feedlot owner, who can then begin to solve the problem on his or her own.

What if the hydrogen sulfide emissions continue after high readings?
The MPCA continues to monitor feedlots that initially exceed the hydrogen sulfide standard. If the feedlot owner can reduce emissions before the MPCA conducts formal monitoring, the agency won't take action. However, if the hydrogen sulfide emissions aren't reduced, the MPCA will start enforcement actions.

How much monitoring has the MPCA done this year?
As of August 1, 1998, feedlot air monitoring staff have monitored 49 feedlots with hand-held meters. Twelve have exceeded or potentially exceeded the hydrogen sulfide standard.

Who can I call for more information?
Call the MPCA at 651-296-6300 or 800-657-3864

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