Manure/Odor Management

Pit Additive May Reduce Odor, Hydrogen Sulfide Research trials conducted at the University of Minnesota found the soybean-based pit additive, Barrier, may reduce odor and hydrogen sulfide (H2S). Barrier is marketed by Agriliance. In the test, a 400-head, partially slotted, positive-pressure, mechanically ventilated barn was used. The barn and deep pit are unevenly divided into two sides with 22 pens

Pit Additive May Reduce Odor, Hydrogen Sulfide

Research trials conducted at the University of Minnesota found the soybean-based pit additive, Barrier, may reduce odor and hydrogen sulfide (H2S). Barrier is marketed by Agriliance.

In the test, a 400-head, partially slotted, positive-pressure, mechanically ventilated barn was used. The barn and deep pit are unevenly divided into two sides with 22 pens on one side and 18 on the other. Test and control groups were alternated. Two replications of approximately 350 pigs were used.

Barrier was applied in the test half of the barn each month, at the suggested application rate (27 fl. oz./pen).

Air samples were collected monthly at pig level, about 18 in. above the slats. A Jerome Meter was used to test for H2S and boric acid trapping/sulfuric acid titration was used for ammonia testing.

Feed intake, growth rate and feed conversion were not affected by the addition of Barrier. H2S and ammonia readings in the rooms and at the pit fans were not affected by the product.

Odor detection level was lower at the pit fans from the Barrier-treated pits, but was not statistically significant.

The researchers will continue testing the product using the same barn. The research will also examine the effect of volatile organic compounds on odor.

Researcher: Mark Whitney, University of Minnesota. Phone Whitney at (612) 624-1793 or e-mail

Hydrogen Sulfide Emissions Reduced by Pit Additive

Iowa State University researchers included laboratory odor testing on Agriliance's Barrier pit additive. The tests used 4-ft. by 15-in. diameter PVC columns.

At the base of each column, there was a 2-in. diameter valve for manure disposal and mixing. The air intake and exhaust valves were 4-in. PVC pipes and the intake pipe was connected to a pressurized charcoal filtering system. Each column had a flowmeter set to 0.5 cu. ft./min. (cfm) of filtered air in the headspace above the manure. The exhausted air was released outside of the laboratory building.

Manure was collected from a typical swine confinement barn where pigs were fed a typical corn/soybean meal diet. The manure was agitated for 30 min. before loading into the columns.

A total of 27.6 gal. of manure was pumped into the columns and Barrier was added, based on company specifications, to the test columns. The manure was mixed once a week to break the crust.

Every seven days, H2S was measured with a Jerome Meter and if found to be above 4 ppm, a Gastec/Sensidyne Hydrogen Sulfide Detection Tube and a Gastec Pump Set Model GV-100S were used. Gas concentration was determined by pulling either 50 or 100 ml. of air through the tube. The concentration was determined by reading the colormetric scale on the tube. Ammonia was tested with the same technique.

H2S concentrations were 1,163 ppm for the control column and 173 ppm for the Barrier-treated column, a reduction of 85%.

Ammonia concentrations were 24 ppm for the control and 49 ppm for the test column, an increase of 100%.

Researcher: Amy Beatty, Iowa State University. Phone Beatty at (515) 294-9174 or e-mail

Lower Crude Protein May Reduce Odors

Reducing the crude protein in swine diets reduces ammonia (NH3) emissions, but further study is needed on its impact on odors from manure, according to research from Michigan State University.

Previous research found that reducing the crude protein in finishing diets from 15% to 12% reduced the NH3 emissions by 63% without impacting growth performance.

To test the impact on odor emissions, as measured by olfactometry, six 110-lb. barrows were fed one of six diets. The diets consisted of 15, 12, 9 and 6% crude protein from corn-soybean meal, a casein-based diet with 15% protein and a protein-free diet. Synthetic amino acids were included in the 12, 9 and 6% diets. The diets were formulated to meet amino acid requirements based on an ideal amino acid profile and digestible basis.

The pigs were housed in metabolism crates and all feces and urine were collected and pooled for each pig. The feces and urine were tested for volatile fatty acids (VFA) and phenolic metabolic concentrations and then mixed, stored and fermented in containers at room temperature for 31 days.

For NH3 testing, air from the head space of the containers was sampled from the slurries at 24, 48 and 72 hours after fermentation. Slurry samples were evaluated by an odor panel.

Odor offensiveness was rated: 1 = non-offensive; 2 = mildly offensive; 3 = moderately offensive; 4 = strongly offensive; and 5 = extremely offensive.

Testing revealed that reducing the crude protein increased the fecal VFA concentrations and did not reduce the phenolic concentrations in urine. Manure NH3 emission was reduced as dietary protein concentration decreased from 15% to 0% and was minimized at a dietary protein concentration of 9%.

The 15% diet had the least offensive manure slurry, with a 2.58 rating (mild to moderately offensive). The 12%, protein-free and casein-based diets had similar results to the 15% diet. The 9 and 6% diets, had odor ratings of 2.92 and 3.10, respectively.

The researchers concluded that reducing the dietary protein lowers ammonia emissions, but does not diminish odor offensiveness or fecal VFA concentrations. Further research is needed to determine the potential use of alternative feed ingredients and their impact on manure odor quality.

Researcher: Nathalie Trottier, Michigan State University. Phone Trottier at (517) 432-5140 or e-mail

Feeding Paylean Offers Environmental Advantages

Research conducted at Purdue University shows feeding Paylean in swine diets can reduce the total phosphorus in manure by up to 12% and odorous compounds by 48%.

The data also indicated feeding Paylean with a 16.1% crude protein (CP) diet reduces pH, total nitrogen and phosphorus, when compared to a 13.8% CP diet without Paylean.

Table 1. Slurry Total Nitrogen (N)
Crude Protein
20 ppm
Total N, ppm
Day 01
Day 17 Day 35 Day 64
13.8 - 7,360a 6,352a 5,826a 5,501a
16.1 - 8,330b 8,123b 6,618b 6,080b
16.1 + 5,976c 5,938a 5,051c 4,908c
13.8 + 4,498d 4,604c 4,069d 2,034d
CV* 8.21 7.02 6.69 6.69
abcdDiffering superscrips within a column indicate significance at P<.05
1Day on trial
*Coefficient of Variation - a measure of the variability of this data set

Table 2. Slurry Total Phosphorus (P)
Crude Protein
20 ppm
Total P, ppm
Day 01
Day 17 Day 35 Day 64
13.8 - 2,717ab 2,817ab 2,797a 2,894ac
16.1 - 2,880a 2,852a 2,685ab 2,973a
16.1 + 2,633b 2,599c 2,558b 2,705bc
13.8 + 2,394c 2,654bc 2,686ab 2,686b
CV* 6.03 5.04 4.24 5.76
abcdDiffering superscrips within a column indicate significance at P<.05
1Day on trial
*Coefficient of Variation - a measure of the variability of this data set

In the experiment, 24 Dekalb crossbred barrows (initial weight 185 lb.) were adapted to metabolism crates for eight days after a 10-day acclimation to one of four diets. Diets studied were: 13.8% CP and 0.80% lysine; 13.8% CP, 1.10% lysine and 18 g. of Paylean/ton; 16.1% CP and 1.10% lysine; and a diet with 16.1% CP, 1.10% lysine and 18 g. of Paylean/ton.

Pigs were fed and watered four times a day and total feces and urine were collected for a three-day period. The collections were refrigerated and then blended for a mixture with 7.5% dry matter.

Simulated anaerobic manure pits were set up in 4-liter glass jars. The last day's manure collection was used as the initial inoculum. Additional slurry allotments were frozen and added to the jars three times a week. The jars were capped and air pumped across the headspace at 200 cc./min.

The simulated pits were maintained for 64 days. Olfactometry air samples, total volatile fatty acids (VFA), gas chromatography fibers and mixed slurry samples were taken from the jars at days 0, 17, 35 and 64. Air samples were collected in Tedlar bags and evaluated by an eight-person olfactometry panel.

The slurry from the pigs fed the 16.1% CP diet with Paylean had 9, 6 and 10% more dry matter on days 17, 35 and 64. This may have been due to decreased bacterial populations or activity from limited nutrient additions or decreased pH of manure from Paylean-fed hogs.

The addition of Paylean to the 16.1% CP diet resulted in a 5% decrease in pH, when compared to the 13.8% diet. The lower pH is a result of less urea nitrogen excreted in urine from more efficient retention of nitrogen.

The total nitrogen was reduced 24% to 28% and 28% to 39% from pigs fed Paylean at 16% CP and 13.8% CP, respectively, when compared to similar CP diets without Paylean. See Table 1.

Total phosphorus was reduced 8% when the 13.8% CP diet was compared to the 16.1% CP plus Paylean diet. The researchers note the reduced excretions may be due to increased lean deposition and therefore more demand for phosphorus when pigs are fed Paylean. See Table 2.

The initial odor detection and recognition values by the olfactometry panel, were not different among the treatments, but the Paylean diets were numerically lower. The detection threshold was 49% and 48% lower for the 13.8% CP and 16.1% CP diets with Paylean, when compared to the 16.1% CP diet without Paylean.

The researchers conclude that Paylean reduced the total nitrogen and ammonia, plus lowered the pH and VFA production. The data indicates that feeding Paylean at the 16.1% CP level would reduce pH, total nitrogen and phosphorus, when compared to the 13.8% industry standard diet.

They note that Paylean's enhancement of protein accretion may also be beneficial in reducing environmentally detrimental nutrient levels in stored manure and in reducing odors from storage.

Researchers: Alan Sutton, D.B. Anderson, Brian Richert, S. A. DeCamp and S. L. Hankins, Purdue University. Phone Sutton at (765) 494-8012 or e-mail

Liquid-Solid Separation Does Not Control Odor

Research at the University of Minnesota Southern Research and Outreach Center shows that liquid-solid separation of manure to control odor may not be feasible at this time.

The researchers sieved fresh hog manure into seven different particle size categories (<0.075 mm., <0.15 mm., <0.25 mm., <0.5 mm., <1.0 mm., <1.4 mm. and <2.0 mm.). The manure was stored in seven PVC columns and sampled every five days for 30 days.

Samples were analyzed for total volatile fatty acids (VFA), biochemical oxygen demand (BOD), total solids (TS), total suspended solids (TSS) and total volatile solids (TVS). VFA and BOD were used to determine the odor generation potential of the manure. The levels of TSS explained 40% of the BOD and 46% of the VFA, both of which increased with storage time, regardless of solid particle size.

The data inferred that most of the odorous compounds were in manure particle sizes of less than 0.075 mm. These small particles cannot be removed by a commercial mechanical separators with screen sizes ranging from 0.5 to 3.0 mm.

The researchers also point out that with average separation efficiency of 25% for most commercially available mechanical separators, the removal of BOD and VFA are as low as 10% and 12%, respectively.

The researchers note the findings cannot justify the use of liquid-solid separation for odor control.

The data also showed that separation should be done within 10 days for particle size equal or greater than 0.5 mm. and within five days for particle sizes less than 0.5 mm. After the first 10 days of storage, the TSS tended to decompose faster, thus reducing separation efficiency, they explain.

Researcher: Jun Zhu, University of Minnesota. Phone Zhu at (507) 835-3620 ext. 125 or e-mail

Struvite Formation Reduces Phosphorus in Manure

The forced precipitation of struvite in swine manure before land application can reduce the soluble phosphorus by as much 90%, according to research conducted at the University of Tennessee.

Field and laboratory tests were conducted using magnesium chloride (MgCl2) to force precipitation of struvite, which converts the phosphorus in manure to a crystalline mineral. It is believed that this mineral could be less prone to pollution by runoff and useful as a slow-release inorganic fertilizer.

Swine manure slurry samples were taken from primary and secondary storage ponds from a farm in Tennessee. Testing indicated the primary samples had 3.5% total solids and secondary samples had 11.7% solids.

Samples were analyzed for soluble phosphorus (SP), total phosphorus (TP), pH and x-ray diffraction (to confirm the presence of struvites).

In experiment one, MgCl2 was added to the samples in the laboratory.

In the sample from the primary and secondary pond, the MgCl2 lowered the SP by 76% and 60%, respectively.

Researchers continued their work with a field experiment to assess the practicality of adding MgCl2 to swine slurries.

About 520 gal. of MgCl2 were added to 36,400 gal. of liquid manure. The storage pond was agitated during the chemical addition and for 50 min. after with a Houle pumping agitator. The manure was then land applied with a Nelson SR-200 irrigation gun at a rate of 728 gal./min.

Samples were taken from the pond, irrigation pump and field before, during and after the treatment.

The SP in the manure after land application was 90% less than before the chemical was added to the manure slurry. X-ray diffraction analysis confirmed the formation of crystalline struvite in the treated manure.

The researchers conclude that this technology may be a means for swine producers to continue to apply manure based on nitrogen rates.

Researchers: Forbes Walker, Robert Burns, Lara Moody and D. Raj Raman, University of Tennessee. Phone Burns at (865) 974-7237 or e-mail