Research that really reeks

ON CAMPUS

CAN YOU ENGINEER THE STINK OUT OF PIGS? IT'S A QUESTION THAT PORK producers, pig farm neighbors, environmentalists, and chemical manufacturers would like to answer. To find out, the agricultural engineering department at Purdue University in Lafayette, Indiana, has put its nose to the grindstone.

It's actually not the pigs that stink, but their manure almost a ton per pig each year. Pig farms are getting bigger-- tens of thousands of pigs can be on one farm site alone. State and federal regulations about air and odor standards are getting stricter. Combine those factors with the encroachment of suburbia on previously isolated farms, and you can smell trouble. A Missouri hog farm recently got slapped with a $5 million penalty for failing to contain its aroma. The National Pork Board has launched an Odor Solutions Initiative, with $2.3 million slated for odor management exploration.

In an effort to clear the air, the pork industry is enlisting the help of engineers like Al Heber at the Purdue Agricultural Air Quality Laboratory, who has worked on the science and research of odors since 1994.

"We develop methodology to measure odor and emissions," says Heber. That includes terms like "hedonic tone," measuring the pleasantness or unpleasantness of an odor, and trained research panelists who follow strict rules (no spicy foods, gum, coffee, tea, or deodorant) to keep their noses in top form while sniffing.

On farms, pig manure is routinely deposited into pits beneath barn floors, transferred to outside lagoons, and finally sprayed on farmland or sold to other farmers as organic fertilizer. Because the manure is often stored for up to a year before being sprayed, the smell is overpowering. Chemical additives-dismissed by hog farmers as "foo-foo dust" because they doubt their effectiveness-have long been touted as a method to control the offensive ammonia and hydrogen sulfide emissions, but are used with widely varying results. To give farmers a scientific yardstick for these products, the National Pork Board funded a project to analyze samples of 35 commercially available additives in a controlled laboratory environment.

Heber designed a custom-built lab incorporating 40 four-foot tall PVC pipes capped at top and bottom. Swine manure was brought in to fill each column half full, with more manure added daily for a period of five weeks, simulating manure accumulation and storage on farms. The commercial additives were then added, and resulting gas concentrations, temperatures, and pressures were monitored continuously. Bag samples were collected and evaluated first by an electronic nose-that is, equipment with sensors to measure smell-and then by the ultimate smell device: the human nose.

Although the results of the study weren't available when Prism went to press, varied farm use of these additives, combined with minimal impact reported by farmers, suggests that they are not the "silver bullet" in odor management.

Innovative approaches often produce better results, says Heber, citing the example of a Minnesota farmer who reduced his 650-sow barn smell by 90 percent by designing and building his own barn ventilation system.

Some of the research indicates that the solution may be more old-fashioned good sense than scientific breakthroughs. Phil Aulis, the farm manager for a 1200-sow operation 40 miles southwest of Chicago, says the seven employees of the 100-year-old farm work hard with one goal: Cleanliness. "Lots of farmers have the mentality that it's a farm, so it smells bad," says Aulis. " We don't use any additives at all. We just keep everything as clean as possible." That includes pressure washing and disinfecting every inch of the operation every few weeks.

Still, when the manure is sprayed onto the farmland, it's not perfume, says Aulis. "They're trying to do something unnatural in taking the odor away entirely. For that, you do need something scientific. And if we can do it without costing too much, and it makes the neighbors happy, that's what we'll do."

Linda Creighton is a freelance writer living in Arlington, Va.

Copyright American Society for Engineering Education Feb 2001
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