An ASAE Meeting Presentation Paper Number: SD05-801
Hydrogen Sulfide Reduction of Swine Manure using Potassium Permanganate and Hydrogen Peroxide
Sara Smith, Graduate Research Assistant South Dakota State University, PO Box 2120, Brookings, SD 57007,
[email protected].
Dr. Dick Nicolai, Associate Professor South Dakota State University, PO Box 2120, Brookings, SD 57007,
[email protected].
Written for presentation at the 2005 ASAE Midwest Regional Meeting Sponsored by ASAE South Dakota State University Brookings, SD Sept 2005- Oct 2005 Abstract. When swine manure is agitated, high levels of hydrogen sulfide (H2S) are released into the air, which has the potential to cause fatalities. Hydrogen peroxide (H2O2) and potassium permanganate (KMnO4) have been proven to reduce hydrogen sulfide production in swine manure at a laboratory scale. The objective of this study was to determine the amounts of H2O2 and KMnO4 that reduce the amount of H2S released at a life-size scale. Two trials of H2O2 and two trials of KMnO4 were performed. In each trial, H2S was reduced by at least 91%. With the second trial of H2O2, H2S concentration in the head space was reduced from 50 ppm to 0.38 ppm in 6 minutes. Additional research is needed to prove the amount of chemicals to add to ensure safe entry of the pit. Keywords. Manure, hydrogen sulfide, confined space, safety. The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
[email protected] or 269-429-0300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
Introduction As manure decomposes anaerobically, its organic sulfur portion decreases as the proteins and amino acids containing sulfur breakdown. Sulfur is contained in numerous compounds at various stages of reduction and oxidation. In the process of degrading these organic compounds containing sulfur, new compounds are formed that can volatilize and create odor. The primary route of H2S formation is the mineralization transformation of organic compounds containing sulfur. The amino acid methionine hydrolizes into methyl mercaptan and then to methyl alcohol, generating hydrogen sulfide (ASCE, 1989): CH3SCH2CHNH2COOH + H2O → CH3SH + NH3 + CH3CH2COCOOH methionine
methyl mercaptan CH3SH + H2O → CH3OH + H2S
methyl mercaptan
(1)
ketobutyrate
(2)
methyl alcohol
Spoelstra (1980) indicated that H2S and methyl mercaptan (MM) are the most frequently reported sulfur compounds in swine manure. The primary origin of H2S in manure is the reduction of sulfate, which is the primary form of sulfur excreted in urine. The reduction of sulfate to sulfide was characterized by Sawyer and McCarty (1978): SO4= + organic matter → S= + H2O + CO2
(3)
The recommended maximum of H2S in air for human health is 5 parts per million (ppm) and 10 ppm causes eye irritation (Doss, 2002). At 600 ppm, H2S causes unconsciousness, respiratory failure, and death within minutes (Doss, 2002 and Millar, 1990). In addition, H2S may be explosive at a wide range of concentrations in air--4.3% to 46% by volume (Millar, 1990). In many swine and dairy barns manure is scraped into a small collection pit and then pumped to an outside storage. The equipment in these collection pits requires periodic maintenance and occasionally is done in the pit. The H2S concentration in the pit head space may exceed safe human limits. Also, part of the problem in a swine barn is that the sulfide is created in the air and it stays within the confined space of the barn. OSHA does have a confined space standard that industries must follow; however, the standard does not currently apply to agriculture (OSHA, 2005). In 1990, the National Institute for Occupational Safety and Health (NIOSH) published a paper stating a “need existed to inform farm owners and workers about the dangers of entering [swine manure] pits, where oxygen-deficient, toxic and/or explosive atmospheres often result from fermentation of the wastes in confined areas,” (Millar, 1990). There was an effort to widely distribute this document for the
prevention of asphyxiation fatalities. Doss et al (1993) suggested that if one must enter a manure pit, a self-contained breathing apparatus (SCBA) and a safety harness must be worn with two people available to help remove the body from the pit. The SCBA equipment cost ranges from $1290.00 to $4264.00 (Fisher Scientific, 2005). There is also an emergency air unit that costs only $435.00, but the air only lasts for 10 minutes (AFCINTL, 2005). Even with warning publications and availability of SCBA’s, there continues to be a number of deaths due to entering manure collection pits. Previous Research Research performed at the University of Minnesota in 1999 shows the percent reduction of hydrogen sulfide with the addition of hydrogen peroxide and also with potassium permanganate. This research was performed in a laboratory in small dishes. The objective of this research was to evaluate the effectiveness of chemical additions in reducing H2S gas emissions from waste in a bench-top study. The goal was to identify a specific chemical and dosage rate. Seven chemicals were tested: Calcium hydroxide, Ferric chloride, Ferrous chloride, Ferrous sulfate, Hydrogen peroxide, Potassium permanganate, and Sodium chlorite. Hydrogen Sulfide Percent Reduction
120.0% 100.0% 80.0% 60.0% 40.0% 20.0% 0.0% 0.000 0.020 0.040 0.060
0.080 0.100 0.120 0.140
Hydrogen Peroxide g/g dry manure
Figure 1. Percent reduction of hydrogen sulfide with the additions of H2O2 (Clanton,1999).
The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
[email protected] or 269-4290300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
Hydrogen Sulfide Percent Reduction
120.0% 100.0% 80.0% 60.0% 40.0% 20.0% 0.0% 0.000
0.020
0.040
0.060
0.080
0.100
Potassium Permanganate g/g dry manure
Figure 2. Percent reduction of hydrogen sulfide with the additions of KMnO4 (Clanton, 1999). Hydrogen peroxide and potassium permanganate appeared to be the most cost effective (Clanton, 1999). The results of Clanton’s (1999) research are shown here in Figures 1 and 2. These data were used to determine the amount of chemical to add to the pit to potentially reduce hydrogen sulfide. As shown in Figure 1, H2O2 gives an 80% reduction at 0.05 g/g dry manure. Potassium Permanganate KmnO4 reacts with H2S as shown in Equations 4 and 5. 3H2S + 2KMnO4 → 3S + 2H2O + 2KOH + 2MnO2 (Acidic pH)
(4)
3H2S + 8KMnO4 → 3K2SO4 + 2H2O + 2KOH + 8MnO2 (Basic pH)
(5)
KMnO4 is available in dry crystal, granule, or pellet form and must be mixed with water to approximately a 6% solution (1.04 kg/L). Hydrogen Peroxide H2O2 oxidizes H2S into elemental sulfur or sulfate depending upon the pH of the manure, as shown in Equations 6 and 7. The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
[email protected] or 269-4290300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
H2S + H2O2 → S + 2H2O (pH < 8.5)
(6)
H2S + 4H2O2 → SO4= + 2H2O (pH > 8.5)
(7)
These reactions of H2O2 with sulfide are rapid. One to three parts H2O2 are usually needed per one part sulfide. One of the advantages of H2O2 is that the byproducts are harmless. Objective The objective of this research will compare H2O2 and KMnO4 as sulfur precipitators in reducing H2S formation from swine manure on a farm-size scale manure collection pit.
Materials and Methods The experiments were conducted at the South Dakota State University Swine Unit. Manure from a pull plug system in a gestation barn was emptied into the lift station collection pit. The lift station is 3 meters by 3 meters by 2 meters in height and sits just southwest of the swine unit, as shown in Figure 3. The lift station contains a pump and a valve going out to the storage tank and a valve returning from the storage tank. To agitate the manure, the pump was run and both valves were open so that no manure was leaving or entering the lift station pit. After agitating the manure for 10 minutes, three profile samples were taken using the PVC pipe sampler and mixed in a 5 gallon pail. This swine manure was then stirred vigorously and poured into a 500mL bottle. The total solids content was determined following the procedure outlined in Recommended Methods of Manure Analysis (Peters et al., 2003). The swine manure was shook in the bottle with the lid tight and 50 mL were measured out. Three dry crucibles were weighed and 50 mL of swine manure were poured into each of the crucibles. The crucibles containing the wet manure were weighed again and then placed in the drying oven under the fume hood. The manure samples were dried at 70oCelcius for 24 hours. Dry manure content = (Wet manure (gr) – Dry manure (gr))/Wet manure (mL)
(8)
The dry manure content from this first manure sample was found using Equation 8 and then used to determine the amount of chemical to add for each of the trials. The actual dry manure content was found for the manure used in each chemical addition in Table 1. The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
[email protected] or 269-4290300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
Therefore, the actual amount of chemical added per dry manure content is different than the predicted amount from the preliminary sample. Jerome Meter
Sampling Tube
Float for Supporting Sampling Tube 8 cm
Valve 2m Manure Pump
To Manure Storage 3m
Not to Scale
Figure 3. Lift station showing Jerome® meter sampling location used to measure hydrogen sulfide. H2S was measured with a Jerome® meter just above the agitated manure before the chemical was added. As shown in Figure 3, there was a hose mounted on a float, so that the end of the hose was always 8 cm above the swine manure. The other end of the hose went into the Jerome® meter to measure H2S. The chemical addition occurred during a 2-3 minute time period, due to multiple bottles and pouring procedures. Then H2S was measured for an hour after the addition on 1-2 minute intervals, the lid was closed, and then opened 2 hours after the addition for more measurements. The H2S measurements were graphed and analyzed.
Figure 4. The Jerome meter was used to measure hydrogen sulfide. Figure 5. This float was used to keep the hose 8 cm above the manure surface.
The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
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Results From Table 1 column 2, there was less dry manure content in both trials of the KMnO4 than for the trials of H2O2. In column 4, the KMnO4 amounts ended up being much higher at 0.05613 g/g and 0.0617 g/g than the predicted of 0.03 g/g and 0.04 g/g. More KMnO4 was added per gram of dry manure than predicted. The KMnO4 additions also gave the lowest values of H2S, as shown in Figures 6 and 7.
Table 1. Percent dry manure for the preliminary sample and amount of predicted and actual chemical for each of the four trials. Percent Dry Matter Preliminary manure sample 5 kg KMnO4 Addition 7 kg KMnO4 Addition 7.5 L H2O2 Addition 12.5 L H2O2 Addition
1.14% 0.79% 0.95% 1.33% 1.02%
Predicted Chemical Amount g/g dry manure
Actual Chemical Amount g/g dry manure
0.03 0.04 0.04 0.07
The H2S readings from the first trial of KMnO4 added to swine manure is displayed in Figure 6. The temperature ranged from 42oF to 45oF during this trial. The H2S readings were very low and then jumped up abruptly while agitating and adding the chemical. After 6 minutes, the H2S level was lower and stayed low for 10 minutes, until making a small jump to 5.9 ppm, then decreasing again for 25 minutes. Then there is a linear rise over the next two hours up to 8.9 ppm.
The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
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0.0513 0.0617 0.045 0.102
Hydrogen Sulfide (ppm)
5 kg KMnO4 18 16 14 12 10 8 6 4 2 0 0:00:00
0:28:48
0:57:36
1:26:24
1:55:12
2:24:00
2:52:48
3:21:36
Tim e
Figure 6. Hydrogen sulfide levels after the addition of 0.0513 gram of KMnO4 per gram of dry manure. For the 7 kg addition of potassium permanganate, the data are shown in Figure 7. The initial sampling of H2S was very scattered, and did not even reach 20 ppm. It seemed as if the pump was not completely agitating the manure, and stirring the manure with a stick caused the H2S to jump. However, once the chemical was added, the H2S levels were much lower than for any other trial, the lowest was 0.011 ppm or 11 ppb.
Hydrogen Sulfide (ppm)
7 kg KMnO4 5 4 3 2 1 0 0:00:00
0:28:48
0:57:36
1:26:24
1:55:12
2:24:00
Time
Figure 7. Hydrogen sulfide levels after the addition of 0.0617 gram KMnO4 per gram of dry manure.
The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
[email protected] or 269-4290300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
The addition of H2O2 created large bubbles on the surface that turned into a foamy substance. The temperature during this first trial of H2O2 ranged from 48oF to 52oF. As shown in Table 1, there was more dry manure content in the swine manure for the H2O2 trials. This may explain the high levels of H2S upon agitation. The H2S level dropped quickly after the addition of H2O2, down to 2.6 ppm in 3 minutes and to 0.40 ppm within 6 minutes. When the H2S level was checked after two hours, the manure level had dropped. There may have been untreated manure entering and leaving the pit during those two hours. This is a possible explanation of the high H2S levels. However, they could also be due to the 0.045 mL/g dry manure ratio. More research is needed.
Hydrogen Sulfide (ppm)
7.5 L H2O2
60 50 40 30 20 10 0 0:14:24 0:43:12 1:12:00 1:40:48 2:09:36 2:38:24 3:07:12 Time
Figure 8. Hydrgen sulfide levels after the addition of 0.045 mL of H2O2 per gram of dry manure. For the second addition of H2S, the level stayed steady. The temperature ranged from 49oF to 52oF. Figure 9 shows that the H2S level dropped off with the addition of H2O2, from 39 ppm to 0.38 ppm, and then slowly rose over time, up to 19 ppm two hours later.
The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
[email protected] or 269-4290300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
Hydrogen Sulfide (ppm)
12.5 L H2O2 45 40 35 30 25 20 15 10 5 0 0:00:00
0:28:48
0:57:36
1:26:24
1:55:12
2:24:00
2:52:48
3:21:36
Time
Figure 9. Hydrogen sulfide levels after the addition of 0.102 mL of H2O2 per gram of dry manure.
All Trials 30 Hydrogen Sulfide (ppm)
25 20 15 10 5 0 0:00:00
1:12:00
2:24:00
3:36:00
Time 5 kg KMnO4
7 kg KMnO4
7.5 L H2O2
12.5 L H2O2
Figure 10. Hydrogen sulfide levels over time of two trials of hydrogen peroxide and two trials of potassium permanganate added to swine manure. As shown in Figure 10, all trials dropped below 5 ppm initially, and then rose over the next two hours.
The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
[email protected] or 269-4290300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
Cost H2O2 and KMnO4 can be purchased in a 500 lb drum as a liquid and a 330 lb drum as a dry granular, respectively. The cost for 35% H2O2 is $.65/lb and for the granular is $2.15/lb (Hawkins, Inc., 2005). For calculations, an entire swine barn with dimensions 61m x 12m x 1.5m (200 ft x 40 ft x 5 ft) and for a lift station pit with dimensions 3m x 3mx 2m (10 ft x 10 ft x 6.5 ft). The costs are shown in Table 2. Table 2. Cost of chemical to add to an entire pit or to the lift station pit only (Hawkins, Inc. Sioux Falls, SD September, 2005). Chemical KMnO4 KMnO4 H2O2 H2O2
Actual Chemical Amount 0.0513 g/gdry manure 0.0617 g/gdry manure 0.045 mL/g dry manure 0.102 mL/g dry manure
Entire Pit $2,104.53 $3,085.70 $3,185.24 $5,365.61
Lift Station Pit $31.06 $45.52 $46.95 $79.15
Conclusion H2O2 and KMnO4 at either concentration used reduced H2S to below the 5 ppm maximum for human health suggested by the National Ag Safety Database. After the 5 kg of KMnO4 addition, H2S level was reduced 91.2% from 17 ppm to 1.5 ppm within 5 minutes. After 25 minutes, the H2S level dropped to 1.2 ppm for a 93% reduction. For the 7 kg of KMnO4 , H2S dropped 96.7% from 48 ppm to 0.15 ppm within five minutes and then dropped 99.76% to 0.011 ppm within 21 minutes. H2S dropped from 48 ppm to 0.4 ppm, a 99.2% reduction, within 6 minutes after the 7.5 Liters of H2O2. After 24 minutes, however, the level rose to 2.4 ppm, a 95% reduction. After 12 Liters of H2O2 were added, the H2S was reduced 99.1%, from 39 ppm to 0.38 ppm within 6 minutes. After 20 minutes the H2S rose slightly to 1.4 ppm, a 96.4% reduction. These four trials have shown that chemical additions work in swine manure at the lifesize scale. Further research will find the exact amounts of H2O2 or KMnO4 needed. Two trials are not enough to know what amount of chemical is needed to create a safe pit to enter.
Acknowledgements The South Dakota State University Swine Unit was cooperative in using their lift station pit. Ryan Lefers and Lowell Blankers helped with collecting data. The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
[email protected] or 269-4290300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
References AFCINTL. 2005. Quick Air Emergency Escape Breathing Apparatus from Draeger Safety: Available at: www.afcintl.com/resp7a.htm Accessed June 2, 2005. ASCE 1995. Odor Control in Wastewater Treatment Plants. Published by American Society of Civil Engineers and Water Environment Federation. Alexandria, VA. Clanton, C.J., R.E. Nicolai, and D.R. Schmidt. 1999. Chemical additions to swine manure to reduce hydrogen sulfide losses: a laboratory study. ASAE paper No. 994007. St. Joseph, MI.:ASAE. Clanton, C.J., and D.R. Schmidt. 2000. Sulfur Compounds in Gases Emitted From Stored Manure. Transactions of the ASAE. VOL. 43(5): 1229-1239. Doss, H. J., H. L. Person, and W. McLeod. 1993. Beware of Manure Pit Hazards. Center of Michigan Agriculture Safety & Health. Michigan State University. East Lansing, MI. Fisher Scientific. 2005. SCBA Respirators. Available at: www.fisherscientific.com Accessed: April 14, 2005 Millar, J. D. 1990. Preventing Deaths of Farm Workers in Manure Pits. NIOSH NO. 90103. OSHA. 2005. Permit-required confined spaces – 1910.146. Occupational Safety and Health Administration. U.S. Department of Labor. Available at: www.osha.gov. Accessed April 14, 2005. Peters, J., S. M. Combs, B. Hoskins, J. Jarman, J. L. Kovar, M. E. Watson, A. M. Wolf, N. Wolf. 2003. Recommended Methods of Manure Analysis (A3769). University of Wisconsin, Madison, WI.
The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural Engineers (ASAE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASAE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASAE meeting paper. EXAMPLE: Author's Last Name, Initials. 2005. Title of Presentation. ASAE Paper No. 05xxxx. St. Joseph, Mich.: ASAE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASAE at
[email protected] or 269-4290300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).