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Ten (10) Steps to Manage Odor – Pig farming
The questions commonly associated with odor control are basic:
 What are the realistic expectations for odor in the building, at the site of production?
 Where does the odor originate?
 How difficult will it be to manage the odor?
 What is the cost of controlling the odor and where will I get the most bang for my buck?
1: Siting decisions — The proposed siting of hog production facilities is all about location. The
distance to nearby dwellings, the size of the pork production facility and the exposure angles — from
the facility to a residence — must be taken into account.
Before siting, study the historical prevailing winds for direction and frequency during various times
of the year. Understand the percentage of time (hours) that a dwelling will experience the
“downwind” direction of prevailing winds. The exposure angle — the angle when neighbors are
directly downwind — should be documented. The terrain will affect the intensity of the odor. As
winds die down, wind flows down through valleys.
Acceptable distances are not equal in all directions. In Iowa, predominant summer winds are from the
south and south-southeast. A facility to the south of a neighbor at a given distance has a greater odor
impact than one to the north at the same distance.
Selecting the proper site for a new hog production unit is one of the cheapest odor-control options
available.
2: Manure handling — Injecting manure can reduce odor 50-75% compared to broadcasting. The
cost is roughly $0.003/gal. Umbilical systems can be less visible than tankers because of the
difference in road traffic. “This may make handling manure more ‘invisible,’” he says.
3: Dietary manipulation —This is one of the easiest options to implement for reducing odors.
Cutting crude protein levels and bumping crystalline amino acids can reduce odors 20%.
4: Cover manure storage — Whether permeable (straw, cornstalks, geotextiles) or impermeable
(high-density polyethylene or HDPE), covers help prevent gases from escaping.
Permeable covers can reduce odors by 40-50% at a cost of 10-25¢/sq. ft.,
Impermeable covers are more costly at $1.00-1.40/sq. ft., but they also improve odor reduction by
70-85%. Snow and rain accumulation on the impermeable covers must be managed, he adds.
5: Visual barriers and eye appeal — Well-kept sites get fewer complaints,” Harmon relates. “It
serves as a reflection on the overall management of the site.
The fact of the matter is, people complain less when the hog operation is out of sight. Although it is
very difficult to quantify the impact or costs, the adage ‘out-of-sight, out-of-mind’ is real.
6: Pit ventilation — The more odorous air comes from the pit, contributing more than half of the
total odor during critical periods. Pit ventilation accelerates volatilization and offers limited benefits
to indoor air quality. “Inlet management is more critical with pit ventilation, and remember, a full pit
essentially eliminates pit ventilation.
7: Biofilters — Drawing exhaust air through a biofilter bed can reduce odor, ammonia, hydrogen
sulfide and dust. Like any odor-curbing technology, the biofilters must be managed properly,
particularly the moisture content. Odor levels can be reduced 65-80% at an estimated cost of about
42¢/finished pig.
Precautions must be taken to ensure the biofilter design is compatible with the ventilation system.
Whole-house ventilation through a biofilter is not practical, he explains.
8: Vegetative environmental buffers — A properly designed vegetative filter helps lift and mix
odorous gases. A wedge-shaped design, with shorter shrubs/trees planted in the outside rows and
progressively taller trees in the rows closer to the buildings, will help with this lifting and mixing
action.
Naturally, these barriers take years to establish, with the cost ranging from 6-10¢/pig over 20 years,
he estimates. A side benefit is the vegetation provides a visual barrier, but be aware of the impact
these trees and shrubs can have on a naturally ventilated facility.
9: Chimneys — These relatively low-cost design features promote air mixing and reduce the noise
of the ventilation system. Height of the chimney is important for effectiveness, as is the crosssectional area.
10: Other odor deterrents:

Additives — Most effective in dilute systems; effectiveness varies from zero to about 20%.

Aeration — 40 to 80% effective in dilute systems with costs averaging about $4/pig.

Barriers — They force exhaust air up and reduce dust at ground level; Harmon estimates this
relatively low-cost option is about 20% effective.

Biocurtains — Remove dust.

Digestion — Requires a large investment, but considered 50-80% effective in reducing odors;
nutrient neutral.

Oil sprinkling — Considered 40-50% effective; can create slippery conditions; commonly not
automated.
Focus on the simple solutions first. Consider management as well as cost. If you are building new
facilities, spend time focused on proper siting. Consider covering or protecting outside manure
storage. And be careful with manure application. Remember, you are hauling odor to your neighbor's
doorstep.