Since it is difficult to quantify odor originating from animal agriculture, there has been a push to regulate the emission of specific compounds that can be measured, including ammonia and hydrogen sulfide.

Emissions of ammonia and hydrogen sulfide above certain thresholds are subject to U.S. Environmental Protection Agency reporting requirements under the Comprehensive Environmental Response, Compensation and Liability Act.

A commercial polymer bio-cover on a swine lagoon with a total surface area of 7,800 square meters was measured in east central Missouri. Researchers continuously monitored the flux rate of ammonia, hydrogen sulfide and methane from two adjacent, circular controls and treatment plots during three sampling periods that ranged between 52 and 149 hours.

Development of a stable anaerobic bio-film on the bottom surface of the bio-cover, helped ammonia abatement efficiency improve from 17 percent to 54 percent over a three-month period. During the same time, hydrogen sulfide abatement efficiency improved from 23 percent to 58 percent.

In addition to biological effects, the bio-film reduced mass transfer of ammonia and hydrogen sulfide across the surface of the bio-cover. Analysis of methane production activity showed the bio-cover enhanced the rate of anaerobic digestion occurring in the lagoon by 25 percent when compared to the control. This was shown to represent an effective mechanism to counteract accumulation of methanogenic substrates in bio-covered lagoons.

The bio-cover costs about 15 cents to 30 cents per pig, and could be an important community relations tool for some producers, says James Zahn of the National Swine Research and Information Center in Ames, Iowa.