ISU Scientists Study Ways to Improve Poultry Production Air Quality

July 11th, 2005

In Iowa, hogs get most of the attention during discussions of air quality and livestock production. And while numerous research projects are underway at Iowa State University to improve air quality in and around hog production units, scientists at Iowa's land-grant institution also spend time and resources studying poultry production air quality. After all, Iowa leads the nation in egg production.

Hongwei Xin, professor of agricultural and biosystems engineering, is a national leader in the search for answers to questions about poultry production air quality. He chairs a 14-member national scientific panel for the United Egg Producers that provides research-based information, technical advice and recommendations to the U.S. egg industry regarding air emissions. The panel consists of representatives from the egg industry, the U.S. Department of Agriculture and leading researchers from other land-grant universities.

"The poultry industry realizes the importance of air quality and emission issues and the need to proactively address them," Xin said.

There are three types of commercial poultry buildings. Egg-laying hens are housed in either high-rise or manure-belt buildings. In a high-rise, manure drops or is scraped to a storage area in the lower level of the building and is removed once a year. In manure-belt houses, manure drops onto a belt and is removed anywhere from daily to weekly to a nearby storage facility. Broilers and turkeys are raised on bedded floors. Manure mixes with the bedding, forming litter, which is removed to storage or land applied after one or more flocks have been produced.

Xin is involved in projects that take into consideration the unique features of each of the three types of production units. One of the first steps has been to develop baseline information on ammonia emissions as influenced by housing type, manure management techniques, dietary manipulation and time of year.

A recently completed three-state study funded by the USDA grant involved air quality monitoring at 10 commercial laying hen houses and 12 commercial broiler houses. It was done in collaboration with the University of Kentucky and Pennsylvania State University, with monitoring done at layer houses in Iowa and Pennsylvania and broiler houses in Kentucky and Pennsylvania. The study helped establish house-level ammonia emissions for both species under different housing and management plans.

Based on the data collected, the number of birds that can be expected to emit 100 pounds of ammonia daily has been estimated for each type of housing system at different production stages. "This information should help poultry producers assess how much ammonia is being released from their facility," Xin said.

"Our results show that some manure management systems do emit less ammonia than others," Xin said. "Ammonia levels are much lower in belt houses than in high-rise houses because manure moves out of the belt building. Manure removal frequency also has an impact. Daily removal is better than biweekly."

The study also showed ammonia emissions from commercial high-rise layer houses can be reduced by about 10 percent with a one-percent reduction in crude protein fed. Study findings have been shared with producers, industry professionals and the academic community.

Xin said the national scientific panel he chairs has identified two important areas concerning practical, feasible mitigation of air emissions where further research is needed - diet manipulation (pre-excretion) and treatment of manure with amendment agents (post-excretion).

To that end, efforts are ongoing at Iowa State to evaluate the effects of more dietary manipulation and surface application of some manure amendments. Project funding has come from the U.S. Poultry and Egg Association, the Iowa Egg Council and the ISU College of Agriculture.

"We've had some promising preliminary results in both aspects which have been shared with industry stakeholders," Xin said.

Ammonia emissions from poultry manure storage units are another piece of the puzzle. Controlled experiments have been ongoing that quantify emissions from stored poultry manure based on stacking configuration, time of storage, manure properties and environmental conditions.

"For example, moisture content of poultry manure can range from 20 to 70 percent, depending on the manure handling scheme," Xin said. "Because moisture content greatly affects gaseous emissions, emission levels will be quite different under different operating systems."

Based on the experimental data, Xin said manure should be stacked to reduce the exposed surface area, thereby reducing ammonia emission.

Research findings so far have been shared with the egg industry and academic community. This project is funded by the Iowa Egg Council, Iowa State's Institute for Physical Research and Technology and the Midwest Poultry Consortium.

A new 18-month project to extensively monitor two commercial broiler houses in Kentucky also is underway. The project involves continuous monitoring of ammonia for one year using mobile labs and state-of-the-art monitoring instruments. Funded by Tyson Foods, researchers will collect more baseline data on ammonia emission rates from broiler houses. Robert Burns, associate professor of agricultural and biosystems engineering, is leading this project with Xin as co-investigator.


Hongwei Xin, Agricultural and Biosystems Engineering, (515) 294-4240,
Robert Burns, Agricultural and Biosystems Engineering, (515) 294-9806,
Susan Thompson, Communications Service, (515) 294-0705,