A three-year livestock odor study involving more than 1,700 measurements from around Iowa has been completed by the Department of Natural Resources (DNR).

Odors associated with livestock operations have been a concern in rural areas of Iowa and those concerns have intensified in recent years as livestock operations have grown in size and as more non-farmers have moved to rural areas. In addition to measuring odor levels, the study also looked at trends associated with various livestock species, sizes of operations, types of operations, conditions and manure application methods.

"We wanted this to be an unbiased, straightforward study to assess odors using the technology available to do so and I believe we've succeeded in producing such a study," said Wayne Gieselman, division administrator for the Environmental Services Division of the DNR.

Iowa does not currently have any odor standards or regulations. For the purpose of the study, the current standard used by the state of Wyoming that uses a 7:1 dilution level recorded on a device known as a scentometer was utilized to determine "exceedances."

Study Shows Odor Exceedances are Minimal

Overall, the study recorded odor exceedances in seven percent of the measurements taken, including 11 percent of the time when the measurement was associated with manure application and seven percent of the time when associated with livestock facilities. Only four percent of the measurements taken at public use areas, educational institutions, religious institutions, residences and commercial enterprises had exceedances recorded.

Other key findings of the study included:

• Liquid animal manure that was stored under the barns in deep pits had a lower exceedance rate than manure stored outside the barns in lagoons or tanks.
  
• The exceedance rate was not directly correlated to the size of an animal feeding operation; the way that the manure was managed played a significant role in determining the odor exceedance rate measured.
  
• Injection of liquid manure resulted in a lower exceedance rate than surface application with subsequent incorporation.

The study, overall, did not indicate wide-spread odor problems at locations afforded special setback considerations under law such as the public use areas, educational institutions, religious institutions, residences and commercial enterprises, according to Gieselman.

"The study also indicates that at least some of the odor problems we may have out there could be taken care of with better management practices, application methods or different storage systems," Gieselman said.

Odor Study a Learning Process

"This was an opportunity for us to begin measuring odors and to gain a better understanding of the issue," Gieselman said. He said the DNR not only learned from the information collected, but from the actual collection of the data as well.

"For us, it was a chance to learn about and gain experience using the equipment that measures odors. This is not a case of someone simply being able to grab the equipment, go out and take measurements. Our people had to receive a great deal of training and their noses actually had to be 'calibrated,' to do the study," said Gieselman.

The odor study, which was required as part of legislation passed in 2002, will be presented at the next meeting of the Environmental Protection Commission on March 20.

"The study was discontinued because there was no additional money appropriated to continue it," said Gieselman. "What is done with these results is now up to the Legislature."

You can access the study results at http://www.iowadnr.com/air/afo/files/Odor.pdf.