As concerns escalate, farmers are looking for ways to reduce agricultural odors cheaply and effectively. Many products on the market claim to reduce or eliminate odors, by altering the microbial makeup in either hog digestive systems or manure storage tanks. However, these products have met with limited success. “There are probably hundreds of magic powders that people claim will eliminate odors in manure storage structures,” Graves says. “But I don’t know of any that have demonstrated any efficacy or consistency.”

Penn State researchers are searching for both technical and social solutions that will reduce conflicts over agricultural odors. They are focusing primarily on swine and mushrooms, two of the biggest farming enterprises in Pennsylvania.
Through tests conducted at the University and on Pennsylvania farms, researchers have identified several odor-reducing techniques that could work for large animal operations:

Soil Injection. Graves says injecting manure into the soil on crop fields, a technique that has been used for decades, is a reliable solution. Instead of spraying manure directly on fields, a special tillage device injects it underground and covers it, so it never sits on top of the soil, dispersing odors. However, this method is not suitable for all soil types, and may add to the cost and complexity of applying manure.

Composting. Controlled aerobic digestion, or composting, is another alternative to spreading manure on fields. “Microorganisms break down the manure, and the finished product does not emit strong odors,” Graves says. “The process of composting is often time-consuming, though. It may require additional dry materials and it becomes complicated if the farmer wants to sell the compost commercially.”

Biogas Production. Controlled anaerobic digestion, or biogas production, effectively decreases agricultural odors, although it requires machinery and technical knowledge. In biogas production, manure is placed in a closed tank under manipulated environmental conditions. The organisms living in these conditions break down manure, making it smell less offensive. This reduced-odor manure can be stored for long periods before being spread on fields. Biogas also can be used as a fuel, which helps to offset the cost of the equipment. Only a handful of biogas units have been installed on farms in Pennsylvania, Graves says, because of the expense and daily maintenance. Biogas units are usually better suited for large farms, where employee specialization is possible.

Reducing Odors at Mushroom Facilities

Mushroom farmers often hear complaints about the odors associated with the compost, or substrate, that is used to grow mushrooms. When anaerobic organisms break down the substrate, strong odors are emitted. At Penn State’s Mushroom Test Demonstration Facility, researchers are testing ways to prevent the anaerobic breakdown.

“Aerated floor bunkers may be a good solution for large mushroom producers who make their own substrate,” Heinemann says. “These bunkers have pipes running through concrete floors. The nozzles on top force air through the substrate to distribute it uniformly. The presence of oxygen throughout the substrate may prevent the anaerobic conditions, reducing the negative odors.”

Only a small percentage of mushroom farmers have implemented these bunkers, Heinemann says, because most buy the substrate instead of producing it themselves. In addition, changing the air composition with bunkers may affect the mushroom growth. “At this point, the technology and implementation is outpacing science in the mushroom industry,” Heinemann says. “The bunkers are built, and then producers guess how it will affect mushroom growth.”