The odor control research arsenal is getting better, according to Purdue University agricultural engineer Al Heber. He says researchers are now becoming better equipped with more highly sophisticated analytical equipment. Consequently, the war on odor will be more strategically fought.

"We're beginning to take the guesswork out of this research and starting to scientifically quantify odor and emissions," says Heber. As federal, state and local governments come up with various air quality standards or setback requirements, having a scientifically grounded set of data on what is actually being emitted is essential, he says.

The research effort at Purdue was moved substantially forward with the assistance of private industry. Monsanto's EnviroChem division had developed a manure pit additive, Alliance, and wanted to test it and document its effects.

When the company explained the type of comprehensive test they were considering, Heber's eyes lit up.

Since it's impossible to simulate a 1,000-pig unit with an 8 ft. pit and varying weather conditions and ventilation rates, Monsanto wanted a field test. They found two, 4,000-head finishing sites, one with natural ventilation, another with power ventilation.

Specially modified trailers were fully equipped with a complex set of tubes and pipes to pump air from above the pit, within the buildings and near the fansat each site. Data-collecting equipment in the trailers recorded the information. Heber estimates each trailer cost about $150,000 equipped.

The Alliance solution was sprayed into the top of the pit via a gate-mounted pipe and nozzle that extends 6 in. through the slats. An aerial mist in the pit covers most of the manure slurry surface. One nozzle was installed in each pen and spraying cycles were prescribed using programmable logic controllers. Alliance was delivered for a total of 24 minutes/day. Target amounts were 300-660 parts of the product per million parts of fresh manure.

Air was pumped continuously through two gas-sampling tubes from inside each building into the trailer.

A personal computer at each site controlled sequential switching of three gas analyzers (ammonia, hydrogen sulfide and carbon dioxide) on 15-minute sampling intervals.

Ammonia was measured with chemiluminescence-based ammonia analyzers after conversion to nitric oxide. The analyzers detect small light emissions triggered by a controlled chemical reaction within a chamber. These state-of-the-art analyzers run about $18,000 each. Hydrogen sulfide was converted to sulfur dioxide and measured with pulsed-fluorescence, sulfur dioxide analyzers ($11,000 each).

These analyzers can measure specific fluorescent wavelengths given off by sulfur dioxide when it's exposed to pulses of ultraviolet light in a chamber.

Carbon dioxide was measured with an infrared sensor ($2,000). Gas instruments were normally calibrated weekly, another important but expensive process, says Heber.

A PC-based data acquisition system ($5,000) also continuously recorded air temperatures, building static pressure, outside relative humidity and temperature, inside wet bulb temperatures and wind speed and direction.

Dust samples were taken periodically and weighed with sensitive scales in the laboratory. Manure samples were obtained from the pit biweekly, and analyzed for total nitrogen, dry matter, phosphorus and potassium.

This full-scale data collection continued through three groups of pigs at one barn and two groups at the other. All told, Monsanto put in close to a million dollars, says Heber.

Although significant reductions in ammonia could be documented, the overall impact on odor was not statistically significant, he says. The product is in reformulation and may be tested again this year.

But in the process, the pork industry has gained substantial data and equipment (as Monsanto donated much of the lab equipment to Purdue) to pursue further research. Eight technical papers have been published already; Heber says there's data enough for at least another eight.

Heber says they were able to nail down ammonia, hydrogen sulfide and carbon dioxide emission levels in the study. These levels are important in establishing air quality standards and scientifically grounded setback limits. See the odor link on Heber's Web site ( for an interactive program to calculate setbacks for your own site. The program factors in animal units, building type, manure storage method, prevailing wind and weather conditions, among other things.

Another side benefit was establishing that there's 30% more heat production from pigs than older data had suggested, says Heber. "We think the more modern genetics create an animal with a higher metabolism," says Heber.

The biggest benefit of the project is the quantifying of emissions, says Heber. "There's a big mistake of people going around sniffing and saying whether they smell something or not. That leads to a lot of confusion.

"Remember, concentration is different than emission. You can burn your finger with a match but you can't heat your house with it," says Heber. He makes an analogy with a farm site with a finisher and a nursery. On the farm, being next to the high concentration from the 8-in. fan of the nursery, "you just about fall over." Meanwhile, the air from the 48-in. fans of the finishers doesn't seem as bad. But, the high emissions from the finishing barn's 48-in. fans will take longer to dilute than the low-emission nursery. These high emissions may catch the neighbor's attention 1/2 mile away.