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Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention
Engineering in Agriculture, Environment and Food xxx (2016) 1e7
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Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention Gopi Krishna Kafle a, *, Lide Chen b, **, Benton Glaze c, Terry Tindall d, Sai Krishna Reddy Yadanaparthi e a
Biological Systems Engineering, Washington State University, Pullman, WA 99164, USA Department of Biological and Agricultural Engineering, University of Idaho, Moscow, ID 83844, USA Department of Animal and Veterinary Science, University of Idaho, Moscow, ID 83844, USA d J.R. Simplot Company, Boise, ID 83702, USA e Environmental Science Program, University of Idaho, Moscow, ID 83844, USA b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 March 2015 Received in revised form 27 June 2015 Accepted 23 January 2016 Available online xxx
In the present study, the effectiveness of polymer (maleic-itaconic acid) on ammonia (NH3) emissions reduction and in retaining nitrogen (N) in fresh liquid swine manure (SM) was evaluated. The relationship between pH and NH3 emission was also determined. Different doses of polymer (namely Treatment 1 ¼ T1 ¼ 0.8 L polymer/ton of manure, Treatment 2 ¼ T2 ¼ 1.6 L polymer/ton of manure, Treatment 3 ¼ T3 ¼ 2.4 L polymer/ton of manure, and Treatment 4 ¼ T4 ¼ 3.2 L polymer/ton of manure) were added to the SM and its effects were observed for 30 d. The tests results showed significant reduction in pH for T1, T2, T3 and T4 compared to control (C). For the short term (up to 3d) T2, T3, and T4 showed significantly lower NH3 gas concentrations than C, however, for the long term (up to 10e20 d) only T4 continued to indicate significantly lower NH3 gas concentrations. Although numeric observations were reported for other treatments (T1, T2 and T3), no significant differences in NH3 gas concentrations were found. The NH3 emissions reductions were calculated in the range of 81e92%, 31e88%, 39e61%, 6 e41%, 106% to 6% for the treatment period of 1, 3, 10, 20 and 30 d, respectively. The addition of polymer resulted in no significant difference in total ammonia nitrogen (TAN) and NO 3 eN concentration. However, the addition of polymer had a significant influence on total Kjehldahl nitrogen (TKN) and soluble chemical oxygen demand (SCOD) concentration. The NH3 gas emissions strongly correlated with the manure pH (R2 ¼ 0.911e0.999). © 2016 Asian Agricultural and Biological Engineering Association. Published by Elsevier B.V. All rights reserved.
Keywords: Aerobic treatment Ammonia emissions Lagoon Nitrogen retention Polymer Swine manure
1. Introduction Swine is the most widely consumed meat product in several countries of the world, and its production is predicted to rise in the next few decades (FAO, 2012; Kafle et al., 2015; Philippe and Nicks, 2015). Livestock slurry, including swine manure (SM), is an important nutrient source for crops but its nutrient value decreases over time by significant losses of nitrogen (N), attributed greatly to the volatilization of ammonia (NH3) (Pain et al., 1987; Hartung and Phillips, 1994). The largest emitters of NH3 are China, the European
* Corresponding author. ** Corresponding author. E-mail addresses: gopikafl[email protected], (G.K. Kafle), [email protected] (L. Chen).
gopikrishna.kafl[email protected]
Union and the United States with 15.2, 3.8 and 3.7 Tg NH3 per year, respectively (Philippe et al., 2011). Worldwide, swine farming is responsible for approximately 15% of NH3 emissions related to livestock (Olivier et al., 1998). Emissions from housings are the major source, accounting for approximately 50% of swine NH3 (Philippe et al., 2011). Loss of NH3 via volatilization from animal houses, hardstandings, and manure stores decreases the nutrient value of manure (Sørensen and Amato, 2002). The variation of NH3 emissions from manure causes variability in fertilizer efficiency which results in a decline in crop growers' reliance on manure as a source of N for plants. This may result in excess N supply to crops, risking a declination in crop quality and inclination in losses of N to the environment by leaching of nitrate (NO 3 ) and emission of nitrous oxide (N2O) and dinitrogen (N2) (Sommer et al., 2006). In addition to the monetary loss, NH3 volatilization and subsequent
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Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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deposition can cause soil acidification and ground and surface waters pollution (McCrory and Hobbs, 2001). In the livestock housing, NH3 emissions can adversely affect the performance, health, and welfare of both animals and workers (Donham and Gustafson, 1982; McCrory and Hobbs, 2001). Similarly, atmospheric NH3 emissions contribute to ecosystem fertilization, acidification, and eutrophication (NRC, 2003). The livestock manure N transformation process includes (1) mineralization of organic N into NH3, (2) assimilation of N into organic matter, (3) nitrification of N into nitrite (NO 2 ) and into NO 3 , and (4) finally, denitrification of N into dinitrogen (N2) with nitrous oxide (N2O) as a potential by-product (Philippe et al., 2011). Reduction of N losses from livestock farms should be started with proper animal feeding and management to decrease N excretion. Even with better management, a huge amount of N ends up in manure (Rotz, 2004). A major portion of this excreted N can rapidly change into NH3, which may promptly volatilize and escape into the atmosphere. Volatile loss starts soon after excretion and continues through all manure handling processes until the manure nutrients are incorporated into soil (Rotz, 2004). Ammonia volatilization is directly related to the proportion of aqueous NH3 in the total ammonia nitrogen (TAN). Generally, at a steady temperature, pH determines the equilibrium between ammonium NHþ 4 and NH3 with a lower pH favoring the NHþ 4 form and hence lower potential of NH3 volatilization (Ndegwa et al., 2008). The transformation and loss of ammonia are very sensitive to manure pH; there is almost no measurable free ammonia at pH of 4.5, relatively low loss occurs below a pH of 6.0 and very high loss occurs when the pH exceeds 8.0 (Muck and Steenhuis, 1982; Hartung and Phillips, 1994). Storage of livestock manure has been regarded as a major source of NH3 emissions (Hartung and Phillips, 1994), with reported N losses ranging from 3 to 60% of initial total N (Muck and Steenhuis, 1982; Dewes et al., 1990). Van Horne et al. (1998) reported that major part of the N entering the lagoon is lost to the atmosphere. Commonly, a series of lagoons are used where the effluents from the first become the influent of the next and there could be 70% or more of the N entering a series of lagoons lost to the atmosphere (Van Horne et al., 1998). Similarly, Harper et al. (2000) found that less than 1% of the initial N entering the first lagoon was recovered from the final lagoon and applied to cropland. Given its adverse economic and environmental impacts, reducing NH3 emissions from manure has been of great interest to academics, regulators, livestock farmers, environmentalists, and the public. Different methods have been recommended and tested for mitigating NH3 volatilization from excreted manure which include decreasing N excretion through manipulating feeding rations, decreasing volatile NH3 in the manure, and separating urine from feces to lower contact between urease and urine (Ndegwa et al., 2008). Methods for lowering volatile NH3 in manure include lowering manure pH, which shifts the equilibrium in favor of NHþ 4 over NH3; using chemical additives that bind NH4eN; and applying biological nitrification-denitrification to convert NHþ 4 into non volatile N-species such as NO 2 , NO3 , or gaseous N (Ndegwa et al., 2008). Other methods for mitigating NH3 emissions target emitting surfaces, and include capturing air using physical covers and treating the captured air using bio-filters or/and scrubbers (Ndegwa et al., 2008; Kafle and Chen, 2014; Kafle et al., 2015), and manure subsurface injection during land application. Manure collection facility designs and appropriate facility management are also essential for abating NH3 emissions (Ndegwa et al., 2008). Earlier studies have clearly demonstrated the effectiveness of pH reduction in the mitigation of NH3 volatilization from different livestock manures (Ndegwa et al., 2008). Acidification of swine and cattle slurries from a pH of 8 to a pH of 1.6 using H2SO4 reduced NH3 emissions progressively and completely stopped NH3 volatilization
at a pH of 5.0 in pig slurries and at a pH of 4.0 in cattle slurries (Molloy and Tunney, 1983). Jensen (2002) maintained a pH of 5.5 using H2SO4 in swine slurry in full-scale sow-confinement housings with slatted floors and manure pits under-the-floor. In a similar study, Stevens et al. (1989) used H2SO4 to acidify cow and swine slurries to pHs of 5.5 and 6.0, respectively. Ammonia volatilization was reported to be effectively reduced by 95% in the lab and by 82% in the field under such pH conditions. In another study, NH3 loss reductions of 14e57% were reported by Pain et al. (1990) when the pH of cattle slurry was lowered to 5.5. More Than Manure (MTM), a maleic-itaconic copolymer product, was developed by Specialty Fertilizer Products (Verdesian Life Sciences, Cary, NC 27513) for improving manure fertilizer use and reducing NH3 emission from manure. The objectives of this study were to: (1) evaluate the effect of the polymer (MTM) on mitigating NH3 gas emissions from fresh liquid SM, (2) evaluate the effect of the polymer on retaining N in liquid SM, and (3) to derive the relationship between pH and NH3 gas emissions. 2. Materials and methods 2.1. Swine manure and polymer Fresh SM was collected from a commercial swine farm (swine nursery barn) in Kimberly, Idaho on March 14, 2014. A shallow pit with depth of 0.6 m was constructed below the slatted floor to collect manure and washing water. Around 60e70% of total volume in the shallow pit was drained to the lagoons every 5 d. The manure was sampled from a drained pipe connected to a lagoon. The collected manure was then transported back to the University of Idaho Twin Falls Research and Extension Center. The characteristics of SM are shown in Table 1. The polymer was prepared from the mixture of maleic-itaconic copolymer partial calcium salt and maleic-itaconic copolymer partial ammonium salt, 30e60% w/w total solids solution in water. The pH, specific gravity and freezing range of the polymer was 3.0, 1.2 and 5 C, respectively. 2.2. Experimental setup and design The experimental setup for the tests is shown in Fig.1. The collected manure was mixed before being randomly distributed into 16 twenty-liter buckets. Five liters of manure were placed in each bucket without any pretreatments. Three of the 16 buckets were randomly chosen to be controls and treatments with four different doses (namely Treatment 1 ¼ T1 ¼ 0.8 L polymer/ton of manure, Treatment 2 ¼ T2 ¼ 1.6 L polymer/ton of manure, Treatment 3 ¼ T3 ¼ 2.4 L polymer/ton of manure, Treatment Table 1 Characteristics of swine manure used for the tests. The manure was stored in a shallow pit below slatted floor for around five days in pig nursery barn. Parameter
Units
Mean ± SD
Total solids (TS) Volatile solids (VS) VS/TS pH Total volatile fatty acids (TVFA) Alkalinity (mg/L) Crude protein (CP)a Crude fiber (CF)a Ether extract (EE)a C/N ratioa
% %
5.5 4.7 0.86 6.18 7956 1952 26.88 20.40 9.40 12:1
mg/L mg/L % TS % TS % TS
± ± ± ± ± ± ± ± ±
0.2 0.1 0.02 0.05 346 246 0.88 0.29 0.06
SD: Standard deviations. a Adapted from Kafle and Chen, 2014.
Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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Fig. 1. Experiment setup and ammonia measurement apparatus (a) numbered empty bucket, (b) bucket with 5 L of liquid swine manure, (c) bucket lid with two two-inch diameter holes, (d) closed buckets in lab (e) Ogwa passive sampler; (f) gas detection pump and tubes.
4 ¼ T4 ¼ 3.2 L polymer/ton of manure) of the polymer, respectively. The polymer doses were chosen based on the polymer manufacturer's recommendation. The remaining bucket was used for a time series test. The time series test was utilized to determine if the passive samplers reached their saturation capacities within a period of 24 h, therefore, no polymer was applied to the time series test bucket. 2.3. Analytical methods The NH3 gas concentrations for the duration of 24 h were measured using Ogawa passive samplers (Ogawa & Co. USA Inc., Pompano Beach, FL) (Fig.1e). The NH3 gas absorbed in the filter of the passive sampler was analyzed using a Quickchem 8500 system (QuickChem 8500, Lachat Instruments, Milwaukee, WI). The QuickChem 8500 system reported NH4eN concentrations as mg/l. The NH3 gas concentrations for day 1 to 30 was measured using detection tubes and a gas pump (Gastec Co. Ltd.) (Fig.1f). The detection ranges of the NH3 gas tubes were 0.5e75.0 ppm. The CO2, CH4 and N2 concentrations in the headspace of each bucket were measured using a Gas Chromatography (Agilent 7980A, Agilent Technologies, CA) following the method described by Kafle and Chen (2016). TAN, total Kjehldahl nitrogen (TKN), NO 2 eN, NO 3 eN, and soluble chemical oxygen demand (SCOD) were analyzed using a spectrophotometer (DR 5000, Hach, USA). The total volatile fatty acids (TVFA) and alkalinities were determined using a Hach titrator (Kim and Kafle, 2010; Kafle and Kim, 2011). 2.4. Test procedure and conditions After pouring manure into the buckets and applying the
treatments, all of the 16 buckets were covered with lids. Two twoinch holes were made on each lid for placing passive samplers into and pulling passive samplers out of the headspace of each bucket. These holes also allowed for the measurement of pH in each bucket. Five passive samplers were placed in the headspace of each control and treatment bucket. Seven passive samplers were placed in the headspace of the time series test bucket. After passive samplers were placed in the headspace of each bucket, all the buckets were sealed by sticky tape and were kept at the University of Idaho Twin Falls Research and Extension Center during the test periods. The temperatures in the lab were maintained between 20 and 22 C during the test. During the first 24 h test period, at 2, 4, 8, 12, and 24 h, a passive sampler was pulled out from the control and treatment test buckets, respectively; at 2, 4, 6, 8, 10, 12, and 24 h, a passive sampler was pulled out from the time series test bucket, respectively. Immediately after removing the passive samplers, sampler filters (part No. 3 in the passive sampler- Fig. 1e) were transferred using clean forceps into 15-ml centrifuge tubes and were stored in a refrigerator for later analysis. Manure pH was measured after a passive sampler was pulled out from a bucket. Manure was mixed for 1 min using a stick after measuring manure pH and before sampling 30e40 ml of manure which was used for chemical analysis. After all the passive sampler samples were collected, the 15 ml centrifuge tubes were brought to the United States Department of AgricultureeAgriculture Research Service (USDA-ARS) Northwest Irrigation and Soils Research Center located in Kimberly, Idaho for analysis on the following day. The CO2 concentrations in the bucket head spaces were found in the range of 3.6e13.0% during the test period of 1e30 d. The N2 gas concentrations in the bucket head spaces were in the range of
Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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alkalinity, and NH3 gas in the bucket head spaces was determined by using single factor ANOVA (Analysis of Variance) in Excel software 2007. If the calculated F value is higher than the tabulated F value, Least Significant Difference (LSD) was calculated to judge whether two or more averages were significantly different at levels of a ¼ 0.05 and a ¼ 0.01 (Kafle and Kim, 2013; Kafle et al., 2013, 2014). 3. Results and discussion 3.1. Effect of polymer on manure pH and COD concentration The pH values after 2 h of polymer addition were measured to be 6.14, 6.03, 5.86, 5.71, and 5.48 for C, T1, T2, T3 and T4, respectively. Statistically, no significant difference (p > 0.05) was found in pH between the C and T1 but pH was significantly lower (p < 0.01) for all other treatments compared to the C (Table 2). pH values remained constant for up to 3 d and increased thereafter (Fig. 2a). Significant differences in manure pH among the treatments T2, T3, T4 and C were observed up to 10 d, but not for times longer than 10 d. Thus, it can be concluded that polymer addition showed a positive effect on pH reduction for up to 10 d only for doses up to 3.2 L/ton manure. Fig. 2b and c shows the TVFA and alkalinity concentration of manure during treatment period of 3e30 d. Polymer addition increased the TVFA and decreased the alkalinity concentration of the manure. Statistically, T3 and T4 showed significantly higher TVFA and T2, T3, and T4 showed significantly lower alkalinity concentrations compared to the control (Fig.2 and Table 2). During 3e10 d there was a slight increase in alkalinity for all the treatments and a decrease in TVFA (except for T4) and thereafter the trend was rapid for both TVFA (decrease) and alkalinity (increase). The regular increase in manure pH after d 3e10 can be supported by the increase in the alkalinity and decrease in TVFA (Rani et al., 2012; Rani et al., 2013; Kafle et al., 2014). Similar to TVFA, the SCOD concentration of SM increased with the addition of the polymer. The SCOD concentration measured after 2 h duration increased 2.3e36.1% for all treatments (Fig. 2d). Statistically, no significant difference (p > 0.05) in SCOD concentration was found for T1 and T2 but the SCOD concentration for T3 and T4 was significantly higher than the control. For the first 10 d (except for the time period of 12 h), concentration was almost constant for all the treatments. The C and T1 showed significantly lower SCOD concentrations between 20 and 30 d of the treatment period.
Table 2 Results of ANOVA and least significant difference (LSD) analysis. Parameter Fig. 2. (a) pH; (b) total volatile fatty acids (TVFA); (c) alkalinity; (d) soluble chemical oxygen demand (SCOD) for different doses of polymer at different duration of time. C, T1, T2, T3, and T4 represents 0, 0.8, 1.6, 2.4, 3.2 L polymer/ton of manure, respectively. The values are means ± standard deviations (vertical bars, n ¼ 3rd deviations).
75.4e82.7% during the test period of 1e30 d. The methane gas concentrations were less than 1% and not detected in the most of the cases. This represents aerobic condition in all the buckets. 2.5. Statistical analysis The statistical significance of differences in the manure average pH, TAN, NO 3 eN and NO2 eN, TKN, TN, SCOD, VFA, and
pH TAN NO 3 N TKN SCOD NH3 gasa NH3 gasb TVFA Alkalinity
Units
mg/L mg/L mg/L mg/L mg/L (NH4eN) ppm 0e10d 10e30d mg/L mg/L
LSD
p-value
a ¼ 0.05
a ¼ 0.01
0.17 84 1.2 120 1547 0.83 0.6 2.65 456 251
0.23 111 1.7 161 2043 1.11 0.79 3.57 606 333
2.65E-44 3.06E-14 0.008397289 3.5442E-05 0.004559 5.80E-19 0.006766 0.000484 4.3421E-18 1.88E-27
TAN: total ammonia nitrogen; TKN: total Kjeldahl nitrogen; SCOD: soluble chemical oxygen demand; TVFA: total volatile fatty acids. a Measured using Ogwa passive sampler. b Measured using Gastec detection tubes.
Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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found. For the treatment period of 2e20 d, only T4 showed significantly higher (p < 0.01) TKN concentration than the control, but for the treatment period of 30 d, three treatments (T2, T3 and T4) showed significantly higher (p < 0.01) TKN concentration than the control. Among the three treatments (T2, T3 and T4), T3 showed significantly higher (p < 0.01) TKN concentration compared to other two treatments for the treatment period of 30 d. Similar to TAN and TKN, the manure NO 3 eN concentration increased after adding the polymer. For the treatment period of 1e10 d, T3 and T4 showed significantly higher NO 3 eN concentrations compared to the control. For the treatment period of 20e30 d only T4 showed higher (p < 0.05) NO 3 eN concentration than the control. 3.3. Effect of polymer on NH3 gas emissions from liquid SM The NH3 gas concentrations (measured as NH4eN concentrations) measured over a 24 h period using passive samplers are shown in Fig. 4. The linear relationship between the NH4-N concentration and the treatment period indicated that the passive samplers did not reach their saturation points during the 24 h passive sampler test period (Fig. 4a). For treatment period of up to 8 h, no significant difference in NH3 gas concentration was observed. For the 12 h test period, only T4 showed significantly
Fig. 3. (a) Total ammonia nitrogen (TAN); (b) nitrate-N (NO 3 N); (c) total Kjeldahl nitrogen (TKN) for different doses of polymer at different duration of time. C, T1, T2, T3, and T4 represents 0, 0.8, 1.6, 2.4, and 3.2 L polymer/ton of manure, respectively. The values are means ± standard deviations (vertical bars, n ¼ 3rd deviations).
3.2. Effect of polymer on manure nitrogen composition TKN accounted for more than 98% of the manure total N and the rest was in the forms of NO 3 eN and NO2 eN. The NO2 eN concentration in the manure was less than 5% of NO3 eN (data not shown). Fig. 3 shows the TAN, TKN and NO 3 eN concentrations for the control and treatments at different durations of time. The TAN concentration was recorded higher for the treatments than the control for entire test periods. Statistically, for the duration of 24 h all the treatments (except T1) showed significantly higher TAN than the control. For the treatment period up to 10 d, T2, T3, and T4 maintained significantly higher TAN concentrations than the control, however, there was no significant difference among T2, T3 and T4. For the treatment period of 20e30 d, only T4 showed significantly higher TAN than the control. Addition of polymer increased the TKN concentration in the manure. For the treatment period of 24 h, no significant difference in TKN concentration was
Fig. 4. Results of 24 h ammonia emissions experiment using Ogwa passive sampler (a) time series test; (b) ammonia gas concentration for different doses of polymer for treatment period of 24 h. Ammonia gas concentration was expressed as NH4eN (mg/L). C, T1, T2, T3, and T4 represents 0, 0.8, 1.6, 2.4, and 3.2 L polymer/ton of manure, respectively. The values are means ± standard deviations (vertical bars, n ¼ 3rd deviations).
Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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Table 3 NH3 gas concentrations (ppm) and NH3 gas emissions reduction (%) for different treatments measured using gas detection tubes during treatment period of 1e30 days. The values are expressed as mean (standard deviation, n ¼ 3). Treatment period
1d
3d
10 d
NH3 gas emissions concentration (ppm) C 2.6(0.1) 1.6(0.3) 1.8(0.2) T1 0.5(0.0) 1.1(0.5) 2.5(0.8) T2 0.3(0.0) 0.5(0.1) 1.9(0.2) T3 0.2(0.0) 0.3(0.2) 1.5(0.5) T4 0.2(0.0) 0.2(0.1) 0.7(0.1) NH3 gas emissions reduction compared to control (%) T1 81 31 39 T2 88 69 6 T3 92 81 17 T4 92 88 61
20 d
30 d
8.2(2.0) 5.8(2.0) 7.7(2.3) 7.1(2.4) 4.8(1.6)
9.0(1.4) 18.5(4.9) 12.0(7.1) 11.8(6.7) 9.5(4.2)
29 6 13 41
106 33 31 6
C: 0.0 L polymer/ton of manure; T1: 0.8 L polymer/ton of manure; T2: 1.6 L polymer/ ton of manure; T3: 2.4 L polymer/ton of manure; T4: 3.2 L polymer/ton of manure.
lower (p < 0.01) NH3 gas concentrations than the control. For the 24 h test period T2, T3 and T4 showed significantly lower (p < 0.01) NH3 concentration than the control. The NH3 emissions were reduced by 38.8e69.5% corresponding to polymer dose of 1.6e3.2 L/
ton of manure. For the 24 h treatment period no significant difference (p > 0.05) was found between the ammonia concentrations of T2 and T3, however, T4 was significantly lower than both T2 and T3 (p < 0.01). T1 showed significantly higher NH3 gas concentration than control for treatment period of 4, 6 and 12 h. This result was not expected and the reason needs to be investigated. The NH3 gas concentrations measured using gas detection tubes for duration of 1e30 d are shown in Table 3. Table 3 also shows the calculated NH3 gas emissions reduction percentages for different treatments and for different treatment periods. Data from day 1e3 showed significantly lower ammonia gas concentration (p < 0.05) for the treatments T2, T3 and T4 compared to the control (Tables 2 and 3). Data from day 10 to day 20 showed that only the treatment T4 had significant lower NH3 gas concentrations than the control. The treatments showed no effect on NH3 emissions based on the samples collected on day 30. Thus, test results showed that NH3 gas emissions reduction increased with increase in polymer dose but decreased with increase in treatment period length. The ammonia gas emissions reductions were calculated in the range of 81e92%, 31e88%, 39e61%, 6e41%, 106% to 6% for the treatment period of 1, 3, 10, 20 and
Fig. 5. Relationship between pH and NH3 gas emissions using data of (a) C; (b) T1; (c) T2; (d) T3; (e) T4; (f) C, T1, T2, T3 & T4. C, T1, T2, T3, and T4 represents 0, 0.8, 1.6, 2.4, and 3.2 L polymer/ton of manure, respectively.
Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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30 d, respectively (Table 3). 3.4. Relationship between pH and NH3 emissions Fig. 5 shows the relationship between pH and NH3 gas emissions. The NH3 gas emissions increased as manure pH increased. The relationship between NH3 gas emissions and pH followed a secondary order polynomial line. The correlation coefficients (R2) were found in a range of 0.911e0.999 when deriving the relationship using each individual treatment data (Fig. 5aee) and to be 0.917 (Fig. 5f) when the relationship was derived using all treatments data together. Although it is well known that pH is one of the major parameters influencing NH3 volatilization, this study, in addition to those by Avnimelech and Laher (1977) and Vlek and Stumpe (1978) indicate that the potential NH3 loss from an NH4eN solution is proportional to its total alkalinity. Similarly, Husted et al. (1991) also derived a close relationship between reduction in total alkalinity and a decrease in ammonia loss when various pH depressing additives were employed for cattle slurry. This study results also supports the relationship between alkalinity and NH3 gas emissions. After the treatment period of 10 d the alkalinity concentration was increased rapidly for all the cases and there was found similar rapid increase in NH3 emissions for all the cases (Fig. 2c). 4. Conclusions The addition of the polymer showed positive effects in reducing NH3 emissions and retaining N contents in the liquid SM. For the test period of 30 d, the polymer treatments (T1, T2, and T3, 0.8e2.4 L polymer/ton of manure) showed no significant difference in TAN and NO 3 eN concentration and showed significant increase (p < 0.01) in the TKN concentration of the liquid SM. Polymer doses in the range of 1.6e3.2 L/ton of manure showed significant effect on NH3 emissions reduction for the treatment period less than 10 d. The NH3 gas emissions reduction increased with increase in polymer dose and maximum reductions were calculated in the range of 61e92% for treatment period up 10 d for the highest tested dose of 3.2 L/ton manure. The SM pH was decreased with increasing the polymer dose and the relationship between NH3 emissions and manure pH followed a secondary order polynomial line with R2 ¼ 0.911e0.999. This study showed feasibility for using polymer for the short term (<10 d) treatment of the liquid SM at polymer doses in the range of 1.6e3.2 L/ton of manure. For the long term treatment of liquid SM, polymer can be added to SM at an interval of 3e10 d depending on the polymer dose. The tests performed in this study served as a preliminary investigation. However, the data obtained from this study could be the basis for the long term evaluation of the polymer and can also be useful in designing field scale treatment of the liquid SM stored in lagoons using the polymer. Acknowledgments This research was supported by the College of Agricultural and Life Sciences, University of Idaho and the J.R. Simplot Agribusiness Company. References Avnimelech, Y., Laher, M., 1977. Ammonia volatilization from soils: equilibrium considerations. Soil Sci. Am. J. 41 (6), 1080e1084. Dewes, T., Schmitt, L., Valentin, U., Ahrens, E., 1990. Nitrogen losses during the storage of liquid livestock manures. Biol. Wastes 31 (4), 241e250. Donham, K.J., Gustafson, K.E., 1982. Human occupational hazards from swine confinement. In: Annals of the American Conference of Governmental Industrial Hygienists, pp. 137e142.
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FAO, 2012. Animal Production and Health. Citted at: http://www.fao.org/ag/againfo/ home/en/index.htm (accessed 25.03.15.). Harper, L.A., Sharpe, R.R., Parkin, T.B., 2000. Gaseous nitrogen emissions from anaerobic swine lagoons: ammonia, nitrous oxide, and dinitrogen gas. J. Environ. Qual. 29 (4), 1356e1365. Hartung, J., Phillips, V., 1994. Control of gaseous emissions from livestock buildings and manure stores. J. Agric. Eng. Res. 57 (3), 173e189. Husted, S., Jensen, L.S., Jørgensen, S.S., 1991. Reducing ammonia loss from cattle slurry by the use of acidifying additives: the role of the buffer system. J. Sci. Food Agric. 57 (3), 335e349. Jensen, A., 2002. Changing the environment in swine buildings using sulfuric acid. Trans. ASABE 45 (1), 223e238. Kafle, G.K., Chen, L., 2016. Comparison on batch anaerobic digestion of five different livestock manures and prediction of biochemical methane potential (BMP) using different statistical models. Waste Manage. 48, 492e502. Kafle, G.K., Chen, L., 2014. Emissions of odor, ammonia, hydrogen sulfide, and volatile organic compounds from shallow-pit pig nursery rooms. J. Biosyst. Eng. 39 (2), 76e86. Kafle, G.K., Kim, S.H., 2011. Sludge exchange process on two serial CSTRs anaerobic digestions: process failure and recovery. Bioresour. Technol. 102 (13), 6815e6822. Kafle, G.K., Kim, S.H., 2013. Anaerobic treatment of apple waste with swine manure for biogas production: batch and continuous operation. Appl. Energy 103, 61e72. Kafle, G.K., Kim, S.H., Sung, K.I., 2013. Ensiling of fish industry waste for biogas production: a lab scale evaluation of biochemical methane potential (BMP) and kinetics. Bioresour. Technol. 127, 326e336. Kafle, G.K., Bhattarai, S., Kim, S.H., Chen, L., 2014. Anaerobic digestion of Chinese cabbage waste silage with swine manure for biogas production: batch and continuous study. Environ. Technol. 35 (21), 2708e2717. Kafle, G.K., Chen, L., Neibling, H., He, B.B., 2015. Field evaluation of wood bark-based down-flow biofilters for mitigation of odor, ammonia, and hydrogen sulfide emissions from confined swine nursery barns. J. Environ. Manage. 147, 164e174. Kim, S., Kafle, G.K., 2010. Effective treatment of swine manure with Chinese cabbage silage through two serial anaerobic digestion. J. Biosyst. Eng. 35 (1), 53e63. McCrory, D., Hobbs, P., 2001. Additives to reduce ammonia and odor emissions from livestock wastes. J. Environ. Qual. 30 (2), 345e355. Molloy, S., Tunney, H., 1983. A laboratory study of ammonia volatilization from cattle and pig slurry. Ir. J. Agric. Res. 22 (1), 37e45. Muck, R., Steenhuis, T., 1982. Nitrogen losses from manure storages. Agric. Wastes 4 (1), 41e54. Ndegwa, P., Hristov, A., Arogo, J., Sheffield, R., 2008. A review of ammonia emission mitigation techniques for concentrated animal feeding operations. Biosyst. Eng. 100 (4), 453e469. NRC, 2003. Air Emissions from Animal Feeding Operations: Current Knowledge, Future Needs. National Academy Science, Washington, DC. Olivier, J., Bouwman, A., Van der Hoek, K., Berdowski, J., 1998. Global air emission inventories for anthropogenic sources of NOx, NH3 and N2O in 1990. Environ. Pollut. 102, 135e148. Pain, B., Thompson, R., Cremer, L.D.L.L., Ten Holte, L., 1987. The use of additives in livestock slurries to improve their flow properties, conserve nitrogen and reduce odours. In: Animal Manure on Grassland and Fodder Crops. Fertilizer or Waste? Springer, pp. 229e246. Pain, B.F., Thompson, R.B., Rees, Y.J., Skinner, J.H., 1990. Reducing gaseous losses of nitrogen from cattle slurry applied to grassland by the use of additives. J. Sci. Food Agric. 50 (2), 141e153. Philippe, F.X., Nicks, B., 2015. Review on greenhouse gas emissions from pig houses: production of carbon dioxide, methane and nitrous oxide by animals and manure. Agric. Ecosyst. Environ. 199, 10e25. Philippe, F.X., Cabaraux, J.F., Nicks, B., 2011. Ammonia emissions from pig houses: influencing factors and mitigation techniques. Agric. Ecosyst. Environ. 141 (3), 245e260. Rani, R.U., Kumar, S.A., Kaliappan, S., Yeom, I.T., Banu, J.R., 2012. Low temperature thermo-chemical pretreatment of dairy waste activated sludge for anaerobic digestion process. Bioresour. Technol. 103 (1), 415e424. Rani, R.U., Kumar, S.A., Kaliappan, S., Yeom, I.T., Banu, J.R., 2013. Impacts of microwave pretreatments on the semi-continuous anaerobic digestion of dairy waste activated sludge. Waste Manage. 33 (5), 1119e1127. Rotz, C., 2004. Management to reduce nitrogen losses in animal production. J. Anim. Sci. 82 (13), 119e137. Sommer, S.G., Zhan, G.Q., Bannink, A., Chadwick, D., Misselbrook, T., Harrison, R., Hutchings, N., Menzi, H., Monteny, G., Ni, J., 2006. Algorithms determining ammonia emission from buildings housing cattle and pigs and from manure stores. Adv. Agron. 89, 261e335. Sørensen, P., Amato, M., 2002. Remineralisation and residual effects of N after application of pig slurry to soil. Eur. J. Agron. 16 (2), 81e95. Stevens, R., Laughlin, R., Frost, J., 1989. Effect of acidification with sulphuric acid on the volatilization of ammonia from cow and pig slurries. J. Agric. Sci. 113 (03), 389e395. Van Horne, P., Brake, J., Williams, C., 1998. Economics of controlling ammonia emission from commercial layer farms. J. Appl. Poult. Res. 7 (1), 61e68. Vlek, P., Stumpe, J., 1978. Effects of solution chemistry and environmental conditions on ammonia volatilization losses from aqueous systems. Soil Sci. Am. J. 42 (3), 416e421.
Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention Gopi Krishna Kafle a, *, Lide Chen b, **, Benton Glaze c, Terry Tindall d, Sai Krishna Reddy Yadanaparthi e a
Biological Systems Engineering, Washington State University, Pullman, WA 99164, USA Department of Biological and Agricultural Engineering, University of Idaho, Moscow, ID 83844, USA Department of Animal and Veterinary Science, University of Idaho, Moscow, ID 83844, USA d J.R. Simplot Company, Boise, ID 83702, USA e Environmental Science Program, University of Idaho, Moscow, ID 83844, USA b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 March 2015 Received in revised form 27 June 2015 Accepted 23 January 2016 Available online xxx
In the present study, the effectiveness of polymer (maleic-itaconic acid) on ammonia (NH3) emissions reduction and in retaining nitrogen (N) in fresh liquid swine manure (SM) was evaluated. The relationship between pH and NH3 emission was also determined. Different doses of polymer (namely Treatment 1 ¼ T1 ¼ 0.8 L polymer/ton of manure, Treatment 2 ¼ T2 ¼ 1.6 L polymer/ton of manure, Treatment 3 ¼ T3 ¼ 2.4 L polymer/ton of manure, and Treatment 4 ¼ T4 ¼ 3.2 L polymer/ton of manure) were added to the SM and its effects were observed for 30 d. The tests results showed significant reduction in pH for T1, T2, T3 and T4 compared to control (C). For the short term (up to 3d) T2, T3, and T4 showed significantly lower NH3 gas concentrations than C, however, for the long term (up to 10e20 d) only T4 continued to indicate significantly lower NH3 gas concentrations. Although numeric observations were reported for other treatments (T1, T2 and T3), no significant differences in NH3 gas concentrations were found. The NH3 emissions reductions were calculated in the range of 81e92%, 31e88%, 39e61%, 6 e41%, 106% to 6% for the treatment period of 1, 3, 10, 20 and 30 d, respectively. The addition of polymer resulted in no significant difference in total ammonia nitrogen (TAN) and NO 3 eN concentration. However, the addition of polymer had a significant influence on total Kjehldahl nitrogen (TKN) and soluble chemical oxygen demand (SCOD) concentration. The NH3 gas emissions strongly correlated with the manure pH (R2 ¼ 0.911e0.999). © 2016 Asian Agricultural and Biological Engineering Association. Published by Elsevier B.V. All rights reserved.
Keywords: Aerobic treatment Ammonia emissions Lagoon Nitrogen retention Polymer Swine manure
1. Introduction Swine is the most widely consumed meat product in several countries of the world, and its production is predicted to rise in the next few decades (FAO, 2012; Kafle et al., 2015; Philippe and Nicks, 2015). Livestock slurry, including swine manure (SM), is an important nutrient source for crops but its nutrient value decreases over time by significant losses of nitrogen (N), attributed greatly to the volatilization of ammonia (NH3) (Pain et al., 1987; Hartung and Phillips, 1994). The largest emitters of NH3 are China, the European
* Corresponding author. ** Corresponding author. E-mail addresses: gopikafl[email protected], (G.K. Kafle), [email protected] (L. Chen).
gopikrishna.kafl[email protected]
Union and the United States with 15.2, 3.8 and 3.7 Tg NH3 per year, respectively (Philippe et al., 2011). Worldwide, swine farming is responsible for approximately 15% of NH3 emissions related to livestock (Olivier et al., 1998). Emissions from housings are the major source, accounting for approximately 50% of swine NH3 (Philippe et al., 2011). Loss of NH3 via volatilization from animal houses, hardstandings, and manure stores decreases the nutrient value of manure (Sørensen and Amato, 2002). The variation of NH3 emissions from manure causes variability in fertilizer efficiency which results in a decline in crop growers' reliance on manure as a source of N for plants. This may result in excess N supply to crops, risking a declination in crop quality and inclination in losses of N to the environment by leaching of nitrate (NO 3 ) and emission of nitrous oxide (N2O) and dinitrogen (N2) (Sommer et al., 2006). In addition to the monetary loss, NH3 volatilization and subsequent
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Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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deposition can cause soil acidification and ground and surface waters pollution (McCrory and Hobbs, 2001). In the livestock housing, NH3 emissions can adversely affect the performance, health, and welfare of both animals and workers (Donham and Gustafson, 1982; McCrory and Hobbs, 2001). Similarly, atmospheric NH3 emissions contribute to ecosystem fertilization, acidification, and eutrophication (NRC, 2003). The livestock manure N transformation process includes (1) mineralization of organic N into NH3, (2) assimilation of N into organic matter, (3) nitrification of N into nitrite (NO 2 ) and into NO 3 , and (4) finally, denitrification of N into dinitrogen (N2) with nitrous oxide (N2O) as a potential by-product (Philippe et al., 2011). Reduction of N losses from livestock farms should be started with proper animal feeding and management to decrease N excretion. Even with better management, a huge amount of N ends up in manure (Rotz, 2004). A major portion of this excreted N can rapidly change into NH3, which may promptly volatilize and escape into the atmosphere. Volatile loss starts soon after excretion and continues through all manure handling processes until the manure nutrients are incorporated into soil (Rotz, 2004). Ammonia volatilization is directly related to the proportion of aqueous NH3 in the total ammonia nitrogen (TAN). Generally, at a steady temperature, pH determines the equilibrium between ammonium NHþ 4 and NH3 with a lower pH favoring the NHþ 4 form and hence lower potential of NH3 volatilization (Ndegwa et al., 2008). The transformation and loss of ammonia are very sensitive to manure pH; there is almost no measurable free ammonia at pH of 4.5, relatively low loss occurs below a pH of 6.0 and very high loss occurs when the pH exceeds 8.0 (Muck and Steenhuis, 1982; Hartung and Phillips, 1994). Storage of livestock manure has been regarded as a major source of NH3 emissions (Hartung and Phillips, 1994), with reported N losses ranging from 3 to 60% of initial total N (Muck and Steenhuis, 1982; Dewes et al., 1990). Van Horne et al. (1998) reported that major part of the N entering the lagoon is lost to the atmosphere. Commonly, a series of lagoons are used where the effluents from the first become the influent of the next and there could be 70% or more of the N entering a series of lagoons lost to the atmosphere (Van Horne et al., 1998). Similarly, Harper et al. (2000) found that less than 1% of the initial N entering the first lagoon was recovered from the final lagoon and applied to cropland. Given its adverse economic and environmental impacts, reducing NH3 emissions from manure has been of great interest to academics, regulators, livestock farmers, environmentalists, and the public. Different methods have been recommended and tested for mitigating NH3 volatilization from excreted manure which include decreasing N excretion through manipulating feeding rations, decreasing volatile NH3 in the manure, and separating urine from feces to lower contact between urease and urine (Ndegwa et al., 2008). Methods for lowering volatile NH3 in manure include lowering manure pH, which shifts the equilibrium in favor of NHþ 4 over NH3; using chemical additives that bind NH4eN; and applying biological nitrification-denitrification to convert NHþ 4 into non volatile N-species such as NO 2 , NO3 , or gaseous N (Ndegwa et al., 2008). Other methods for mitigating NH3 emissions target emitting surfaces, and include capturing air using physical covers and treating the captured air using bio-filters or/and scrubbers (Ndegwa et al., 2008; Kafle and Chen, 2014; Kafle et al., 2015), and manure subsurface injection during land application. Manure collection facility designs and appropriate facility management are also essential for abating NH3 emissions (Ndegwa et al., 2008). Earlier studies have clearly demonstrated the effectiveness of pH reduction in the mitigation of NH3 volatilization from different livestock manures (Ndegwa et al., 2008). Acidification of swine and cattle slurries from a pH of 8 to a pH of 1.6 using H2SO4 reduced NH3 emissions progressively and completely stopped NH3 volatilization
at a pH of 5.0 in pig slurries and at a pH of 4.0 in cattle slurries (Molloy and Tunney, 1983). Jensen (2002) maintained a pH of 5.5 using H2SO4 in swine slurry in full-scale sow-confinement housings with slatted floors and manure pits under-the-floor. In a similar study, Stevens et al. (1989) used H2SO4 to acidify cow and swine slurries to pHs of 5.5 and 6.0, respectively. Ammonia volatilization was reported to be effectively reduced by 95% in the lab and by 82% in the field under such pH conditions. In another study, NH3 loss reductions of 14e57% were reported by Pain et al. (1990) when the pH of cattle slurry was lowered to 5.5. More Than Manure (MTM), a maleic-itaconic copolymer product, was developed by Specialty Fertilizer Products (Verdesian Life Sciences, Cary, NC 27513) for improving manure fertilizer use and reducing NH3 emission from manure. The objectives of this study were to: (1) evaluate the effect of the polymer (MTM) on mitigating NH3 gas emissions from fresh liquid SM, (2) evaluate the effect of the polymer on retaining N in liquid SM, and (3) to derive the relationship between pH and NH3 gas emissions. 2. Materials and methods 2.1. Swine manure and polymer Fresh SM was collected from a commercial swine farm (swine nursery barn) in Kimberly, Idaho on March 14, 2014. A shallow pit with depth of 0.6 m was constructed below the slatted floor to collect manure and washing water. Around 60e70% of total volume in the shallow pit was drained to the lagoons every 5 d. The manure was sampled from a drained pipe connected to a lagoon. The collected manure was then transported back to the University of Idaho Twin Falls Research and Extension Center. The characteristics of SM are shown in Table 1. The polymer was prepared from the mixture of maleic-itaconic copolymer partial calcium salt and maleic-itaconic copolymer partial ammonium salt, 30e60% w/w total solids solution in water. The pH, specific gravity and freezing range of the polymer was 3.0, 1.2 and 5 C, respectively. 2.2. Experimental setup and design The experimental setup for the tests is shown in Fig.1. The collected manure was mixed before being randomly distributed into 16 twenty-liter buckets. Five liters of manure were placed in each bucket without any pretreatments. Three of the 16 buckets were randomly chosen to be controls and treatments with four different doses (namely Treatment 1 ¼ T1 ¼ 0.8 L polymer/ton of manure, Treatment 2 ¼ T2 ¼ 1.6 L polymer/ton of manure, Treatment 3 ¼ T3 ¼ 2.4 L polymer/ton of manure, Treatment Table 1 Characteristics of swine manure used for the tests. The manure was stored in a shallow pit below slatted floor for around five days in pig nursery barn. Parameter
Units
Mean ± SD
Total solids (TS) Volatile solids (VS) VS/TS pH Total volatile fatty acids (TVFA) Alkalinity (mg/L) Crude protein (CP)a Crude fiber (CF)a Ether extract (EE)a C/N ratioa
% %
5.5 4.7 0.86 6.18 7956 1952 26.88 20.40 9.40 12:1
mg/L mg/L % TS % TS % TS
± ± ± ± ± ± ± ± ±
0.2 0.1 0.02 0.05 346 246 0.88 0.29 0.06
SD: Standard deviations. a Adapted from Kafle and Chen, 2014.
Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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Fig. 1. Experiment setup and ammonia measurement apparatus (a) numbered empty bucket, (b) bucket with 5 L of liquid swine manure, (c) bucket lid with two two-inch diameter holes, (d) closed buckets in lab (e) Ogwa passive sampler; (f) gas detection pump and tubes.
4 ¼ T4 ¼ 3.2 L polymer/ton of manure) of the polymer, respectively. The polymer doses were chosen based on the polymer manufacturer's recommendation. The remaining bucket was used for a time series test. The time series test was utilized to determine if the passive samplers reached their saturation capacities within a period of 24 h, therefore, no polymer was applied to the time series test bucket. 2.3. Analytical methods The NH3 gas concentrations for the duration of 24 h were measured using Ogawa passive samplers (Ogawa & Co. USA Inc., Pompano Beach, FL) (Fig.1e). The NH3 gas absorbed in the filter of the passive sampler was analyzed using a Quickchem 8500 system (QuickChem 8500, Lachat Instruments, Milwaukee, WI). The QuickChem 8500 system reported NH4eN concentrations as mg/l. The NH3 gas concentrations for day 1 to 30 was measured using detection tubes and a gas pump (Gastec Co. Ltd.) (Fig.1f). The detection ranges of the NH3 gas tubes were 0.5e75.0 ppm. The CO2, CH4 and N2 concentrations in the headspace of each bucket were measured using a Gas Chromatography (Agilent 7980A, Agilent Technologies, CA) following the method described by Kafle and Chen (2016). TAN, total Kjehldahl nitrogen (TKN), NO 2 eN, NO 3 eN, and soluble chemical oxygen demand (SCOD) were analyzed using a spectrophotometer (DR 5000, Hach, USA). The total volatile fatty acids (TVFA) and alkalinities were determined using a Hach titrator (Kim and Kafle, 2010; Kafle and Kim, 2011). 2.4. Test procedure and conditions After pouring manure into the buckets and applying the
treatments, all of the 16 buckets were covered with lids. Two twoinch holes were made on each lid for placing passive samplers into and pulling passive samplers out of the headspace of each bucket. These holes also allowed for the measurement of pH in each bucket. Five passive samplers were placed in the headspace of each control and treatment bucket. Seven passive samplers were placed in the headspace of the time series test bucket. After passive samplers were placed in the headspace of each bucket, all the buckets were sealed by sticky tape and were kept at the University of Idaho Twin Falls Research and Extension Center during the test periods. The temperatures in the lab were maintained between 20 and 22 C during the test. During the first 24 h test period, at 2, 4, 8, 12, and 24 h, a passive sampler was pulled out from the control and treatment test buckets, respectively; at 2, 4, 6, 8, 10, 12, and 24 h, a passive sampler was pulled out from the time series test bucket, respectively. Immediately after removing the passive samplers, sampler filters (part No. 3 in the passive sampler- Fig. 1e) were transferred using clean forceps into 15-ml centrifuge tubes and were stored in a refrigerator for later analysis. Manure pH was measured after a passive sampler was pulled out from a bucket. Manure was mixed for 1 min using a stick after measuring manure pH and before sampling 30e40 ml of manure which was used for chemical analysis. After all the passive sampler samples were collected, the 15 ml centrifuge tubes were brought to the United States Department of AgricultureeAgriculture Research Service (USDA-ARS) Northwest Irrigation and Soils Research Center located in Kimberly, Idaho for analysis on the following day. The CO2 concentrations in the bucket head spaces were found in the range of 3.6e13.0% during the test period of 1e30 d. The N2 gas concentrations in the bucket head spaces were in the range of
Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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alkalinity, and NH3 gas in the bucket head spaces was determined by using single factor ANOVA (Analysis of Variance) in Excel software 2007. If the calculated F value is higher than the tabulated F value, Least Significant Difference (LSD) was calculated to judge whether two or more averages were significantly different at levels of a ¼ 0.05 and a ¼ 0.01 (Kafle and Kim, 2013; Kafle et al., 2013, 2014). 3. Results and discussion 3.1. Effect of polymer on manure pH and COD concentration The pH values after 2 h of polymer addition were measured to be 6.14, 6.03, 5.86, 5.71, and 5.48 for C, T1, T2, T3 and T4, respectively. Statistically, no significant difference (p > 0.05) was found in pH between the C and T1 but pH was significantly lower (p < 0.01) for all other treatments compared to the C (Table 2). pH values remained constant for up to 3 d and increased thereafter (Fig. 2a). Significant differences in manure pH among the treatments T2, T3, T4 and C were observed up to 10 d, but not for times longer than 10 d. Thus, it can be concluded that polymer addition showed a positive effect on pH reduction for up to 10 d only for doses up to 3.2 L/ton manure. Fig. 2b and c shows the TVFA and alkalinity concentration of manure during treatment period of 3e30 d. Polymer addition increased the TVFA and decreased the alkalinity concentration of the manure. Statistically, T3 and T4 showed significantly higher TVFA and T2, T3, and T4 showed significantly lower alkalinity concentrations compared to the control (Fig.2 and Table 2). During 3e10 d there was a slight increase in alkalinity for all the treatments and a decrease in TVFA (except for T4) and thereafter the trend was rapid for both TVFA (decrease) and alkalinity (increase). The regular increase in manure pH after d 3e10 can be supported by the increase in the alkalinity and decrease in TVFA (Rani et al., 2012; Rani et al., 2013; Kafle et al., 2014). Similar to TVFA, the SCOD concentration of SM increased with the addition of the polymer. The SCOD concentration measured after 2 h duration increased 2.3e36.1% for all treatments (Fig. 2d). Statistically, no significant difference (p > 0.05) in SCOD concentration was found for T1 and T2 but the SCOD concentration for T3 and T4 was significantly higher than the control. For the first 10 d (except for the time period of 12 h), concentration was almost constant for all the treatments. The C and T1 showed significantly lower SCOD concentrations between 20 and 30 d of the treatment period.
Table 2 Results of ANOVA and least significant difference (LSD) analysis. Parameter Fig. 2. (a) pH; (b) total volatile fatty acids (TVFA); (c) alkalinity; (d) soluble chemical oxygen demand (SCOD) for different doses of polymer at different duration of time. C, T1, T2, T3, and T4 represents 0, 0.8, 1.6, 2.4, 3.2 L polymer/ton of manure, respectively. The values are means ± standard deviations (vertical bars, n ¼ 3rd deviations).
75.4e82.7% during the test period of 1e30 d. The methane gas concentrations were less than 1% and not detected in the most of the cases. This represents aerobic condition in all the buckets. 2.5. Statistical analysis The statistical significance of differences in the manure average pH, TAN, NO 3 eN and NO2 eN, TKN, TN, SCOD, VFA, and
pH TAN NO 3 N TKN SCOD NH3 gasa NH3 gasb TVFA Alkalinity
Units
mg/L mg/L mg/L mg/L mg/L (NH4eN) ppm 0e10d 10e30d mg/L mg/L
LSD
p-value
a ¼ 0.05
a ¼ 0.01
0.17 84 1.2 120 1547 0.83 0.6 2.65 456 251
0.23 111 1.7 161 2043 1.11 0.79 3.57 606 333
2.65E-44 3.06E-14 0.008397289 3.5442E-05 0.004559 5.80E-19 0.006766 0.000484 4.3421E-18 1.88E-27
TAN: total ammonia nitrogen; TKN: total Kjeldahl nitrogen; SCOD: soluble chemical oxygen demand; TVFA: total volatile fatty acids. a Measured using Ogwa passive sampler. b Measured using Gastec detection tubes.
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found. For the treatment period of 2e20 d, only T4 showed significantly higher (p < 0.01) TKN concentration than the control, but for the treatment period of 30 d, three treatments (T2, T3 and T4) showed significantly higher (p < 0.01) TKN concentration than the control. Among the three treatments (T2, T3 and T4), T3 showed significantly higher (p < 0.01) TKN concentration compared to other two treatments for the treatment period of 30 d. Similar to TAN and TKN, the manure NO 3 eN concentration increased after adding the polymer. For the treatment period of 1e10 d, T3 and T4 showed significantly higher NO 3 eN concentrations compared to the control. For the treatment period of 20e30 d only T4 showed higher (p < 0.05) NO 3 eN concentration than the control. 3.3. Effect of polymer on NH3 gas emissions from liquid SM The NH3 gas concentrations (measured as NH4eN concentrations) measured over a 24 h period using passive samplers are shown in Fig. 4. The linear relationship between the NH4-N concentration and the treatment period indicated that the passive samplers did not reach their saturation points during the 24 h passive sampler test period (Fig. 4a). For treatment period of up to 8 h, no significant difference in NH3 gas concentration was observed. For the 12 h test period, only T4 showed significantly
Fig. 3. (a) Total ammonia nitrogen (TAN); (b) nitrate-N (NO 3 N); (c) total Kjeldahl nitrogen (TKN) for different doses of polymer at different duration of time. C, T1, T2, T3, and T4 represents 0, 0.8, 1.6, 2.4, and 3.2 L polymer/ton of manure, respectively. The values are means ± standard deviations (vertical bars, n ¼ 3rd deviations).
3.2. Effect of polymer on manure nitrogen composition TKN accounted for more than 98% of the manure total N and the rest was in the forms of NO 3 eN and NO2 eN. The NO2 eN concentration in the manure was less than 5% of NO3 eN (data not shown). Fig. 3 shows the TAN, TKN and NO 3 eN concentrations for the control and treatments at different durations of time. The TAN concentration was recorded higher for the treatments than the control for entire test periods. Statistically, for the duration of 24 h all the treatments (except T1) showed significantly higher TAN than the control. For the treatment period up to 10 d, T2, T3, and T4 maintained significantly higher TAN concentrations than the control, however, there was no significant difference among T2, T3 and T4. For the treatment period of 20e30 d, only T4 showed significantly higher TAN than the control. Addition of polymer increased the TKN concentration in the manure. For the treatment period of 24 h, no significant difference in TKN concentration was
Fig. 4. Results of 24 h ammonia emissions experiment using Ogwa passive sampler (a) time series test; (b) ammonia gas concentration for different doses of polymer for treatment period of 24 h. Ammonia gas concentration was expressed as NH4eN (mg/L). C, T1, T2, T3, and T4 represents 0, 0.8, 1.6, 2.4, and 3.2 L polymer/ton of manure, respectively. The values are means ± standard deviations (vertical bars, n ¼ 3rd deviations).
Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
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Table 3 NH3 gas concentrations (ppm) and NH3 gas emissions reduction (%) for different treatments measured using gas detection tubes during treatment period of 1e30 days. The values are expressed as mean (standard deviation, n ¼ 3). Treatment period
1d
3d
10 d
NH3 gas emissions concentration (ppm) C 2.6(0.1) 1.6(0.3) 1.8(0.2) T1 0.5(0.0) 1.1(0.5) 2.5(0.8) T2 0.3(0.0) 0.5(0.1) 1.9(0.2) T3 0.2(0.0) 0.3(0.2) 1.5(0.5) T4 0.2(0.0) 0.2(0.1) 0.7(0.1) NH3 gas emissions reduction compared to control (%) T1 81 31 39 T2 88 69 6 T3 92 81 17 T4 92 88 61
20 d
30 d
8.2(2.0) 5.8(2.0) 7.7(2.3) 7.1(2.4) 4.8(1.6)
9.0(1.4) 18.5(4.9) 12.0(7.1) 11.8(6.7) 9.5(4.2)
29 6 13 41
106 33 31 6
C: 0.0 L polymer/ton of manure; T1: 0.8 L polymer/ton of manure; T2: 1.6 L polymer/ ton of manure; T3: 2.4 L polymer/ton of manure; T4: 3.2 L polymer/ton of manure.
lower (p < 0.01) NH3 gas concentrations than the control. For the 24 h test period T2, T3 and T4 showed significantly lower (p < 0.01) NH3 concentration than the control. The NH3 emissions were reduced by 38.8e69.5% corresponding to polymer dose of 1.6e3.2 L/
ton of manure. For the 24 h treatment period no significant difference (p > 0.05) was found between the ammonia concentrations of T2 and T3, however, T4 was significantly lower than both T2 and T3 (p < 0.01). T1 showed significantly higher NH3 gas concentration than control for treatment period of 4, 6 and 12 h. This result was not expected and the reason needs to be investigated. The NH3 gas concentrations measured using gas detection tubes for duration of 1e30 d are shown in Table 3. Table 3 also shows the calculated NH3 gas emissions reduction percentages for different treatments and for different treatment periods. Data from day 1e3 showed significantly lower ammonia gas concentration (p < 0.05) for the treatments T2, T3 and T4 compared to the control (Tables 2 and 3). Data from day 10 to day 20 showed that only the treatment T4 had significant lower NH3 gas concentrations than the control. The treatments showed no effect on NH3 emissions based on the samples collected on day 30. Thus, test results showed that NH3 gas emissions reduction increased with increase in polymer dose but decreased with increase in treatment period length. The ammonia gas emissions reductions were calculated in the range of 81e92%, 31e88%, 39e61%, 6e41%, 106% to 6% for the treatment period of 1, 3, 10, 20 and
Fig. 5. Relationship between pH and NH3 gas emissions using data of (a) C; (b) T1; (c) T2; (d) T3; (e) T4; (f) C, T1, T2, T3 & T4. C, T1, T2, T3, and T4 represents 0, 0.8, 1.6, 2.4, and 3.2 L polymer/ton of manure, respectively.
Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005
G.K. Kafle et al. / Engineering in Agriculture, Environment and Food xxx (2016) 1e7
30 d, respectively (Table 3). 3.4. Relationship between pH and NH3 emissions Fig. 5 shows the relationship between pH and NH3 gas emissions. The NH3 gas emissions increased as manure pH increased. The relationship between NH3 gas emissions and pH followed a secondary order polynomial line. The correlation coefficients (R2) were found in a range of 0.911e0.999 when deriving the relationship using each individual treatment data (Fig. 5aee) and to be 0.917 (Fig. 5f) when the relationship was derived using all treatments data together. Although it is well known that pH is one of the major parameters influencing NH3 volatilization, this study, in addition to those by Avnimelech and Laher (1977) and Vlek and Stumpe (1978) indicate that the potential NH3 loss from an NH4eN solution is proportional to its total alkalinity. Similarly, Husted et al. (1991) also derived a close relationship between reduction in total alkalinity and a decrease in ammonia loss when various pH depressing additives were employed for cattle slurry. This study results also supports the relationship between alkalinity and NH3 gas emissions. After the treatment period of 10 d the alkalinity concentration was increased rapidly for all the cases and there was found similar rapid increase in NH3 emissions for all the cases (Fig. 2c). 4. Conclusions The addition of the polymer showed positive effects in reducing NH3 emissions and retaining N contents in the liquid SM. For the test period of 30 d, the polymer treatments (T1, T2, and T3, 0.8e2.4 L polymer/ton of manure) showed no significant difference in TAN and NO 3 eN concentration and showed significant increase (p < 0.01) in the TKN concentration of the liquid SM. Polymer doses in the range of 1.6e3.2 L/ton of manure showed significant effect on NH3 emissions reduction for the treatment period less than 10 d. The NH3 gas emissions reduction increased with increase in polymer dose and maximum reductions were calculated in the range of 61e92% for treatment period up 10 d for the highest tested dose of 3.2 L/ton manure. The SM pH was decreased with increasing the polymer dose and the relationship between NH3 emissions and manure pH followed a secondary order polynomial line with R2 ¼ 0.911e0.999. This study showed feasibility for using polymer for the short term (<10 d) treatment of the liquid SM at polymer doses in the range of 1.6e3.2 L/ton of manure. For the long term treatment of liquid SM, polymer can be added to SM at an interval of 3e10 d depending on the polymer dose. The tests performed in this study served as a preliminary investigation. However, the data obtained from this study could be the basis for the long term evaluation of the polymer and can also be useful in designing field scale treatment of the liquid SM stored in lagoons using the polymer. Acknowledgments This research was supported by the College of Agricultural and Life Sciences, University of Idaho and the J.R. Simplot Agribusiness Company. References Avnimelech, Y., Laher, M., 1977. Ammonia volatilization from soils: equilibrium considerations. Soil Sci. Am. J. 41 (6), 1080e1084. Dewes, T., Schmitt, L., Valentin, U., Ahrens, E., 1990. Nitrogen losses during the storage of liquid livestock manures. Biol. Wastes 31 (4), 241e250. Donham, K.J., Gustafson, K.E., 1982. Human occupational hazards from swine confinement. In: Annals of the American Conference of Governmental Industrial Hygienists, pp. 137e142.
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Please cite this article in press as: Kafle, G.K., et al., Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention, Engineering in Agriculture, Environment and Food (2016), http://dx.doi.org/10.1016/j.eaef.2016.01.005