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Ammonia and odour emitted from deep litter and fully slatted floor systems for growing-finishing pigs
b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
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Research Paper
Ammonia and odour emitted from deep litter and fully slatted floor systems for growing-finishing pigs Kaiying Wang, Bo Wei, Songming Zhu, Zhangying Ye* Department of Biosystems Engineering, School of Biosystems Engineering and Food Science, Zijingang Campus, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, PR China
article info
Two identical pig rooms, with mechanical ventilation, were used to compare the envi-
Article history:
ronmental impact of a deep litter fermentation system for growing-finishing pigs with
Received 3 November 2010
a fully slatted floor system. The pig manure in the fully slatted floor room was removed
Received in revised form
manually twice daily, but in the fermented deep litter room, no manure was removed.
29 March 2011
Indoor and outdoor temperature, relative humidity, and ammonia concentration were
Accepted 1 April 2011
measured continuously during the whole experimental period. Odour was sampled and
Published online 5 May 2011
analysed using the triangle odour bag method for 15 days during the experimental period. The performance of the pigs was not significantly different between the floor types. There were significant differences for both NH3 concentrations and emissions according to floor type ( p < 0.001). NH3 emissions from pigs raised on the slatted floor and on the fermented deep litter were 8.82 and 2.16 g d1 pig1, respectively. Emissions increased from the first period to the second by about 4.9 times for NH3 with fully slatted floor and 1.1 times for NH3 with fermented deep litter. The parameters of floor type, pig weight, outdoor temperature and ventilation rate explained most of the variability of NH3 emissions. There were significant differences in odour concentration as odour units (OU), between floor types ( p < 0.01). Mean odour concentrations during the whole experiment were 105.4 OU for the slatted floor room and 67.5 OU for the deep litter room. It was concluded that the deep litter fermentation system for pig production shows advantages in reductions of ammonia and odour. ª 2011 IAgrE. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
With intensification of livestock production, and for economic reasons, straw-bedded systems in pig production were progressively replaced by the slatted floor system since 1950 in Western Europe (Philippe, Laitat, Canart, Vandenheede, & Nicks, 2007a). However, there is currently renewed interest in litter systems because consumers are more aware about animal welfare, environmental impact and meat quality in pig production systems.
Straw is normally used as bedding material in a litter system, but sawdust, wood shavings or even paper are also used (Andersson, 1996). A deep litter fermentation system (also called ’natural pig breeding method’) places pigs over a litter bedding of a mixture with sawdust, rice hull etc. where pig wastes are composted in situ. The method was developed in Japan and microbial products were specially developed to accelerate the composting process (Fukuda, 1991), which is different from a litter based straw system (Cabaraux et al., 2009; Gilhespy et al., 2009; Nicks et al., 2004; Philippe et al., 2007a, b).
* Corresponding author. E-mail addresses: [email protected] (K. Wang), [email protected] (Z. Ye). 1537-5110/$ e see front matter ª 2011 IAgrE. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.biosystemseng.2011.04.001
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b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
Nomenclature CNH3 ENH3 Codour Fls VR RH T A
Concentration of gaseous NH3, mg m3 NH3 emission rate, g d1 pig1 Concentration of odour, OU Floor system ¼ 0 (slatted floor) ¼ 1 (deep litter) ventilation rate, m3 h1 Relative humidity, % air temperature, C the area of air outlet, m2
Litter in this fermentation system is normally accumulated in the pens and is removed after one or several animal batches. In China, compared to conventional pig houses with slatted or solid floors, building costs (especially for waste treatment) and operational costs such as water and heating in winter are often reduced when using a deep litter fermentation system (Wang & Wang, 2010). Furthermore, animal welfare appears to be improved, and it has been reported that the deep litter fermentation system has a low environmental impact (Wang & Wang, 2010). However, only a few experimental data are available regarding the impact of the deep litter fermentation system on the environment, especially in relation to emissions of pollutant gases such as ammonia (NH3) and to odour. Sheng et al. (2009) found that the NH3 concentration in a fermented deep litter pig house was significantly lower than in a solid floor house, but emissions of NH3 were not reported. Ammonia formed and emitted from pig buildings may lead to poor indoor air quality and seriously impact on the outdoor atmospheric environment as well as the natural ecosystem (Mosquera, Monteny, & Erisman, 2005). Odour produced and emitted from such intensive animal production can cause nuisance to individuals living in the vicinity of livestock farms (Chen & Hoff, 2009). In order to reduce NH3 and odour emission, it is firstly important to know the concentrations and emission rates associated with different production systems. Although gas emissions from the slatted floor system are rather well documented in pig production, there is a lack of data concerning deep litter fermentation systems and comparisons between the two systems. Therefore, the objective of this study was to compare concentrations of NH3 and odour as well as NH3 emissions from a growing-finishing pig house with two floor systems: one with slatted floors and one using fermented deep litter.
2.
Materials and methods
2.1.
Experimental room
v W n
Subscripts indoor inside pig room outdoor outside pig room in air inlet out air outlet litter deep litter
system. Each room had one pen and a floor area of each pen was 3 m2. The feeder was located toward the door of the room and the drinker was in the northwest corner of the pen (Fig. 1). The rooms were ventilated using negative pressure systems via 0.55 m diameter ventilation shaft fitted with a fan inside. The opening area of air inlet was 0.055 m2 and the air outlet was a wooden window with width of 0.55 m but a length that could be adjustable manually. For the pig pen with the deep litter fermentation system, sawdust (50% of total weight), rice hulls (40% of the total weight), rice bran (10% of the total weight) and special micro-organisms (200 g m3, composed mainly of Bacillus natto, Saccharomycetes, amylase and protease (Hangzhou New Design Biotechnology Co. Ltd, Hangzhou, China) were mixed together, and then water added until mixture content was 40%. As the mixture fermented, the temperature of mixture rose to 60 C, and then dropped to around 48 C after which fermentation was finished in two days. The fermented mixture was used for experiments after one week. The mixture was used to constitute the initial deep litter with depth of 0.8 m. During the fattening period, a fresh composted mixture was added to keep the depth at 0.8 m and manure was not removed. However, in the fully slatted floor pig pen (with 0.02 m slat and slit), manure was removed from above and beneath the slatted floor twice everyday at 8:00e8:30 and 16:30e17:00 according to the practical management procedures normally used in pig farms in China.
2.2.
Animals and feeding
Two Landrace pigs, randomly selected but with similar initial weight, were housed from December 2009 to January 2010 in each pen. All growing conditions were maintained the same for each pen. The feeds were the same for the two groups during the same growing batch. The pigs were fed twice (8:00e8:30; 16:30e17:00) before each daily manure removal. A drinking jet was installed at the height of about 200 mm (Fig. 1). The pigs were weighed at the start of the experiment with a mean body weight of 36.8 0.9 kg and also weighted at the end of experimental period.
2.3. The study was carried out in the Key Laboratory of Agriculture Environmental Engineering and Intelligent Equipment, Ministry of Chinese Agriculture, Zhejiang University. Two identical climate rooms with different floor systems were used for fattening pigs, one with a plastic fully slatted floor (50% slat area) and another with a deep litter fermentation
Mean wind speed of the outlet, m s1 Mean weight of pigs, kg The number of pigs
Measurements
The temperature and relative humidity of outdoor and room air were continuously monitored on-line with a temperature/ relative humidity (T/RH) sensor (ZDR-20, Hangzhou Zeda Instruments CO., Ltd, Hangzhou, China). The sensors were located above the pig pen at a height of 1.8 m. Ammonia
b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
205
Fig. 1 e The two experimental rooms with different floor systems: (a) plan of the experimental pig rooms; (b) cross-section of the experimental pig room with deep litter fermentation system.
concentrations were measured continuously by sensors (CGDI-1 NH3, Beijing Dongfangjihua Technology Co., Ltd, Beijing, China) with 5% precision and located at the same locations as T/RH sensor. Odour concentration of the outlet air was determined using the triangle odour bag method (GB/T 1467593, 1993), which is different from the European and American standards which use dynamic olfactometry (Watts et al., 2001). The odour measurement system used was similar to the Japanese Standard (Ministry of the Environment Government of Japan, 1999). It was conducted using 6 members of the odour panel. Each panel was given 3 bags; 1 with a sample in it and 2 without any sample (odour-free air) and asked to choose the odorous bag. If the panel member could identify the correct bag, the odour was then diluted (e.g. 30-fold, 100-fold, 300-fold) and until it became impossible to identify the bag with the odour. The sampling time was fifteen days for the whole period. Odour was sampled at 17:00 before cleaning. Sampling took about 20 s each time. Two samples were taken each day and average concentrations were used for analysis. Wind speed of air outlet was measured by using a threecup aero vane (FYF-1, Shanghai Fengyun Co., Ltd, Shanghai, China) with a mean speed of 0.30 0.03 m s1 determined across the cross-section of the air-exhaust. Ammonia emission rates were calculated based on ventilation rate and average NH3 concentrations at the inlet and outlet: ENH3 ¼ v$A$ðCout Cin Þ=n
(1)
where ENH3 is NH3 emission rate from the pig room, g d1 pig1; v is mean wind speed of the outlet, m s1; A is the area of air outlet, m2; Cout is outlet NH3 concentration, mg m3; Cin is inlet NH3 concentration, mg m3 and n is the number of pigs.
2.4.
2010) were used for analysis. Differences in pigs’ production performance, NH3 emission and odour concentration with regard to floor type were tested using analysis of variance (SPSS ver. 16.0, SPSS Inc., Chicago, IL, USA). Analysis of the data set was carried out by means of multiple regressions, in which the dependent variables were NH3 emissions and odour concentrations. The independent variables considered in the regression analysis were floor type, weight of the pigs, ventilation rate, outdoor and indoor temperatures, and room relative humidity. The two categories of the qualitative variable ’floor type’ were considered as dummy variables for an appropriate statistical analysis. The maximum number of independent variables that could be included in the regression model was six. However, the effects of all the parameters were not necessarily significant. A stepwise procedure (SPSS 16.0, SPSS Inc., Chicago, IL, USA) was used on all possible subset regressions. The regression models were then arranged in a decreasing order of adjusted coefficient determination (R2). The statistic ’adjusted R20 is useful for comparing regression models that have different numbers of independent variables. This method can be used for exploratory purposes, as comparison of adjusted R2 of different subset regressions gives a rough estimate of the contribution of each variable to the model (Blanes-Vidal, Hansen, Pedersen, & Rom, 2008).
Statistical analysis
Due to the data available, the data in two periods (1st: 1 December to 22 December 2009; 2nd: 15 January to 28 January
3.
Results and discussion
3.1.
Climatic characteristics of the rooms
Table 1 presents average temperature, relative humidity and ventilation rate observed in the test. The daily variation of temperature, relative humidity and ventilation rate can be seen in Fig. 2. Outdoor climate had a greater impact on indoor climate due to insufficient insulation. For both stages, the variations of indoor temperature and relative humidity were
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Stages 1st (1 Dec to 22 Dec)
Toutdoor, C Tindoor, C
Slatted floor Deep litter
Tlitter, C RHoutdoor, % RHindoor, %
Slatted floor Deep litter Slatted floor Deep litter
VR, m3 h1
9.6 11.7 11.0 22.0 76.3 69.7 75.2 360 365
2.6 2.5 2.7 1.9 11.8 11.2 10.7 11 15
2nd (15 Jan to 28 Jan) 7.7 10.9 11.1 22.2 76.8 70.3 74.5 373 374
3.2 2.6 2.8 2.0 6.9 7.2 6.7 11 4
highly related to outdoor temperature and relative humidity changes. No additional heating was applied and this resulted in temperatures in both rooms being close to outdoor the temperature. No significant differences were found for indoor temperature between floor types, which is consistent with results obtained by Correa et al. (2009). In this study, the mean litter temperature at 300 mm depth below the surface was 22.1 1.9 C when the average outdoor temperature was 8.9 2.9 C. The relative humidity in the room with slatted floor was 5.5% and 4.2% lower than that with deep litter in the two stages, respectively. Statistical analysis showed no differences in ventilation rates between floor types and experimental stages. The results indicate that the fermented deep litter can keep the lying area warm for pigs reared under the cold climate conditions. However, the higher relative humidity in the room with deep litter fermentation system needs to be considered.
3.2.
Performance of the animals
Temperature, °C
Table 2 shows the performance during the two growing periods of pigs kept on slatted floor or on fermented deep litter. In this experiment, keeping fattening pigs on the slatted floor or on the deep litter fermentation system did not cause a difference in average daily weight gain ( p > 0.05) and feed conversion ( p > 0.05). Results from the literature concerning
33 30 27 24 21 18 15 12 9 6 3 0
1st stage
Average daily weight gain, kg d1 pig1 Feed conversion (Feed intake/gain meat)
Slatted floor
Deep litter
0.74 0.50 3.3 0.4
0.73 0.57 3.4 0.7
this comparison are few and different. Several researchers compared the effects of deep litter fermentation system and solid floor system, the results showed a better performance for parameters such as higher average daily weight gain and lower feed/gain for fattening pigs kept on fermented deep litter in cold climates (Cruz, Almaguel, Mederos, & Araujo, 2009; Robert, 1997; Sheng et al., 2009; Tang, Bin, & Jia, 2009; Wu et al., 2009) or no significant differences between floor types (Correa et al., 2009; Li, Yang, & He, 2009, 2010). The results from available studies indicate that a deep litter fermentation system could be used for growing-finishing pigs due to the absence of negative effects on growth performance.
3.3.
Ammonia
Mean NH3 concentrations and emissions for each stage are listed in Table 3. The mean NH3 emission from the slatted floor room during the whole test was 8.82 g d1 pig1, however, the mean NH3 emission from the deep litter room was only 2.16 g d1 pig1. Whatever the floor type, emissions increased from the beginning to the end of the fattening periods by about 5 times for NH3 (Philippe et al., 2007a). In this study, emissions increased from the 1st to the 2nd period by about 4.9 times for NH3 with a fully slatted floor, however, it only increased 1.1 times for NH3 using fermented deep litter. There were significant differences for both NH3 concentrations and emissions between the floor types and between the experimental stages ( p < 0.001). Few data regarding the comparison of NH3 emissions from deep litter fermentation system and the slatted floor system are available in the published literature. Generally, NH3 emissions from pig housing are lower with a fully slatted floor system than with a deep litter system based on straw
2nd stage
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Time, d
420 390 360 330 300 270 240 210 180 150 120 90 60 30 0
3 -1
Floor systems
Table 2 e Performance of pigs during the experiment.
Ventilation rate, mh
Table 1 e Mean temperature, relative humidity and ventilation rate observed during the test.
Fig. 2 e Daily mean outdoor, indoor and litter temperature as well as room ventilation rates during the test. - outdoor temperature, A indoor temperature with slatted floor, > indoor temperature with deep litter, C litter temperature, , ventilation rate in room with slatted floor, 6 ventilation rate in room with deep litter.
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Stages 1st (1 Dec to 22 Dec)
CNH3, mg m3 ENH3, g d1 pig1 Codour, OU
Slatted floor Deep litter Slatted floor Deep litter Slatted floor Deep litter
0.83 0.47 3.6 2.1 89.6 60.5
2nd (15 Jan to 28 Jan)
0.68*** 0.12 3.0*** 0.5 34.2** 14.1
3.95 0.52 17.7 2.3 119.3 73.6
1.22*** 0.13 5.5*** 0.6 34.5** 33.2
*** means p < 0.001; ** means p < 0.01.
Temperature, °C
(Nicholson et al., 2000; Philippe et al., 2007a, b; Cabaraux et al., 2009) or sawdust (Cabaraux et al., 2009). It has been observed that high temperature and high pH in litter may lead to considerable NH3 emissions (Andersson, 1996). However, Gilhespy et al. (2009) found that the broadcast addition of 100% more straw over the entire floor in a pig house reduced NH3 emission with approximately 20%. The explanation for this was that additional straw may reduce the airflow across surfaces soiled with urine, and by immobilisation of ammonium-N. Sheng et al. (2009) found that the NH3 concentration in a fermented deep litter pig house was significantly lower than in a solid floor house. In this study, NH3 emissions were 4.1 times higher in the room with slatted floor than that with the fermented deep litter. The deep litter fermentation system placed pigs over a litter bedding where pig wastes are composted in situ and microbial products are specially developed to produce enzymes that acts on ammonium nitrogen in pig manure to stimulate fermentation. This microbial product was not added in the litter based straw as mentioned above. Fermentation caused the ammonium ions to be trapped in the bedding and converted to bacterial protein causing low gaseous ammonia concentrations (Chan, Chaw, & Lo, 1994, 1995; Cruz et al., 2009; Lavoie, Marchand, Drolet, & Gingras, 1995). Diurnal variation of NH3 concentrations from pig rooms are shown in Fig. 3. It can be seen that the variations of NH3
22 20 18 16 14 12 10 8 6 4 2 0
0
1
2
3
4
5
6
7
8
9
E ¼ 0:238VR þ 0:856W þ 0:438Toutdoor R2 ¼ 0:81; all p < 0:01
(2)
Deep litter E ¼ 0:196VR 0:111W 0:956Toutdoor R2 ¼ 0:90; all p < 0:05
10 11 12 13 14 15 16 17 18 19 20 21 22 23 Time, h
12 11 10 9 8 7 6 5 4 3 2 1 0
(3)
-3
Floor systems
concentration in the slatted floor room were related to temperature changes and manure removal. NH3 concentrations were higher before 7:00, probably due to the manure accumulation in the room during the night period, then decreased by the daily manure removal in the morning, and increased again following the temperature increase until the peak value between 13:00 and 14:00, finally decreased as temperature decreased (Aarnink, Keen, Metz, Speelman, & Verstegen, 1995, 1996). However, the changes of NH3 concentration in fermented deep litter room are very small. Fig. 4 shows daily mean NH3 emissions from pig rooms during the test. It can be seen that the variation of NH3 emissions from the slatted floor room was highly related to climatic parameters change. Nevertheless, the emissions of NH3 in the fermented deep litter room were very stable during the two stages. Table 4 shows the combination of independent variables (for a different number of variables from 1 to 6 included in the model) with higher adjusted R2, for NH3 emission as dependent variable. As expected, to a certain extent the more independent variables included in the model, the higher adjusted R2 was obtained. However, Table 4 also shows that, in some cases, the inclusion of one new variable did not improve the adjusted R2 substantially. This can occur, either because the effect of the variable is small, or because it is highly correlated with one variable that is already included in the model. According to Table 4, the four parameters that explained most of the variability of the NH3 emissions were floor type, pig weight, outdoor temperature and ventilation rate, which are usually used for estimation of NH3 emissions (Dekock, Vranken, Gallmann, Hartung, & Berckmans, 2009; Vranken, Claes, Hendriks, Darius, & Berckmans, 2004). A statistical relationship between NH3 emissions and pig weight, outdoor temperature and ventilation rate was established for slatted floor room and fermented deep litter room as follows, Slatted floor
NH3 concentration, mgm
Table 3 e Concentrations of NH3 and odour as well as NH3 emission in slatted floor and deep litter fermentation systems.
Fig. 3 e Diurnal variation of mean NH3 concentrations from pig rooms (daily removal of manure in slatted floor system). - outdoor temperature, A indoor temperature in slatted floor system, > indoor temperature in deep litter system, 6 NH3 concentration in slatted floor system, : NH3 concentration in deep litter system.
208
-1
NH3 emission, gd pig
-1
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33 30 27 24 21 18 15 12 9 6 3 0
1st stage
2nd stage
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Time, d
Fig. 4 e Daily mean NH3 emissions from pig rooms during the test. A slatted floor system, > deep litter system.
Table 4 e Best subset regressions (with higher adjusted R2) for the NH3 emission, depending on the number of the independent variables included in the model.
6 5 4 3 2 1
R2
Explicative variables
0.61 0.61 0.59 0.56 0.52 0.26
Fls Fls Fls Fls Fls Fls
W W W W W
Toutdoor Toutdoor Toutdoor Toutdoor
VR VR VR
RHindoor RHindoor
Tindoor
Fls is the floor type, 0 means slatted floor and 1 means deep litter; W is the mean weight of pigs in kg; Tindoor and Toutdoor are the indoor and outdoor temperature in C; VR is the ventilation rate in m3 h1; RHindoor is the indoor relative humidity in %.
Where, E is NH3 emission in g d1 pig1; VR is the ventilation rate in m3 h1; W is the mean weight of pigs in kg; Toutdoor is the outdoor temperature in C.
3.4.
Odour
Table 3 also shows the mean odour concentrations during the test. The mean odour concentration from the slatted floor
20
400
18 1st stage
Temperature, °C
16
350
2nd stage
300
14 12
250
10
200
8
150
6
100
4
50
2 0
Odour concentration, OU
No
room during the whole experiment was 105.4 OU, however, the mean odour concentration from the deep litter room was only 67.5 OU. Whatever the floor type, in this study, odour concentrations increased from the 1st stage to the second stage by about 1.3 times for the room with fully slatted floor and 1.2 times for the room with fermented deep litter. There were significant differences in odour concentrations between floor types ( p < 0.01), but not between experimental stages ( p > 0.05). Because the triangle odour bag method is different from the European and American standards that use dynamic olfactometry, it is difficult to compare the odour concentration levels directly. However, the main objective of this study was to compare the influence of two floor types on odour concentrations under similar pig production conditions. The available literature concerning this comparison showed that odour concentrations or emissions reduced greatly in deep litter system compared to slatted floor system (Chan et al., 1994; Chan, Chaw, and Lo (1995); Jacobson, Schmidt, Lake, & Johnson, 2003; Kaufmann, 1997; Ogink & Koerkamp, 2001; Watts et al., 2001) measured volatile odorous compounds in deep litter fermentation system by using gas chromatography and found p-cresol, indole and skatole levels were maintained and did not accumulate after 2e3 weeks when the bedding began to settle down.
16
17
18
19
20
21
22
23 24 Time, d
25
26
27
28
29
30
0
Fig. 5 e Daily mean odour concentrations from pig rooms during the test. A indoor temperature in slatted floor system, > indoor temperature in deep litter system, 6 odour concentration in slatted floor system, : odour concentration in deep litter system.
b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
Table 5 e Best subset regressions (with higher adjusted R2) for the odour concentration, depending on the number of the independent variables included in the model. No 6 5 4 3 2 1
R2 0.63 0.63 0.62 0.56 0.48 0.28
Explicative variables Fls Fls Fls Fls Fls Fls
Toutdoor Toutdoor Toutdoor Toutdoor Toutdoor
W W W W
RHindoor RHindoor RHindoor
Tindoor Tindoor
VR
Fls is the floor type, 0 means slatted floor and 1 means deep litter; W is the mean weight of pigs in kg; Tindoor and Toutdoor are the indoor and outdoor temperature in C; VR is the ventilation rate in m3 h1; RHindoor is the indoor relative humidity in %.
Diurnal variations of mean odour concentrations from pig rooms are shown in Fig. 5. It can be seen that the variations of odour concentration in the slatted floor room and deep litter room were highly related to temperature changes in the second stage. However, such a relationship was not found during the first stage. Table 5 shows the combination of independent variables (for a different number of variables from 1 to 6 included in the model) with higher adjusted R2, for odour concentration as dependent variable. As expected, to certain extent the more independent variables included in the model, the higher adjusted R2 was obtained. However, Table 5 also shows that, in some cases, the inclusion of one new variable did not improve the adjusted R2 substantially such as with indoor temperature and ventilation rate. This can occur, because the indoor temperature is highly correlated with outdoor temperature which is already included in the model and the effect of the ventilation rate is small on odour concentration as reported by Pedersen (2008). According to Table 5, the four parameters that explained most of the variability of the odour concentration were floor type, outdoor temperature, pig weight, and relative humidity. Ogink and Koerkamp (2001) found that correlations between NH3 and odour concentration (within facilities) did not show a consistent pattern. In this study, the NH3 and odour concentration showed a high correlation coefficient ðr ¼ 0:652; p ¼ 0:006 < 0:01Þ in fully slatted floor room, however, no obvious correlations between NH3 and odour concentration were found in deep litter fermentation room ðr ¼ 0:345; p ¼ 0:191 > 0:05Þ. Although the deep litter fermentation system shows advantages for pig production with respect to reduction of NH3 and odour emissions, issues such as the effect on other emissions (N2O and CH4), the supply of large quantities of bedding materials, excessive heat production resulting in high temperature at the surface of litter during summer, the choice of microorganism and effects on meat quality still exist. As a result more relevant studies are needed in future.
4.
Conclusion
Under pig production conditions in China, when compared to fully slatted floor system, the fermented deep litter system could reduce the NH3 and odour concentrations as well as NH3
209
emissions. The performance of the pigs was not significantly different according to the floor type. The four parameters that explained most of the variability of the NH3 emissions were floor type, pig weight, outdoor temperature and ventilation rate. However, the four parameters that explained most of the variability of the odour concentration were floor type, outdoor temperature, pig weight, and relative humidity. There are still some issues such as the supply of large quantities of bedding materials, excessive heat production results in high temperature at the surface of litter in summer season etc, that need to be studied.
Acknowledgements The authors appreciate the supports by the National Natural Science Foundation of China (Grant No.30571357). We would also like to thank the anonymous reviewers for their insightful comments on the manuscript which enabled it to be significantly improved.
references
Aarnink, A. J. A., Keen, A., Metz, J. H. M., Speelman, L., & Verstegen, M. W. A. (1995). Ammonia emission patterns during the growing periods of pigs housed on partially slatted floors. Journal of Agricultural Engineering Research, 62(2), 105e116. Aarnink, A. J. A., VandenBerg, A. J., Keen, A., Hoeksma, P., & Verstegen, M. W. A. (1996). Effect of slatted floor area on ammonia emission and on the excretory and lying behaviour of growing pigs. Journal of Agricultural Engineering Research, 64(4), 299e310. Andersson, M. (1996). Performance of bedding materials in affecting ammonia emissions from pig manure. Journal of Agricultural Engineering Research, 65, 213e222. Blanes-Vidal, V., Hansen, M. N., Pedersen, S., & Rom, H. B. (2008). Emissions of ammonia, methane and nitrous oxide from pig houses and slurry: effects of rooting material, animal activity and ventilation flow. Agriculture, Ecosystems and Environment, 124(3e4), 237e244. Cabaraux, J. F., Philippe, F. X., Laitat, M., Canart, B., Vandenheede, M., & Nicks, B. (2009). Gaseous emissions from weaned pigs raised on different floor systems. Agriculture. Ecosystems and Environment, 130(3e4), 86e92. Chan, D. K. O., Chaw, D., & Lo, C. Y. Y. (1994). Management of the sawdust litter in the pig-on-litter system of pig waste treatment. Resources Conservation and Recycling, 11(1e4), 51e72. Chan, D. K. O., Chaw, D., & Lo, C. Y. Y. (1995). Development of an environmentally-friendly and cost- effective system for the treatment of waste in pig farming. Supplement to the Journal of Sun Yatsen University Forum, 3, 11e16. Chen, L., & Hoff, S. J. (2009). Mitigation odours from agricultural facilities: a review of literature concerning biofilters. Applied Engineering in Agriculture, 25(5), 751e766. Correa, E. K., Bianchi, I., Ulguim, R. D., Correa, M. N., GilTurnes, C., & Lucia, T. (2009). Effects of different litter depths on environmental parameters and growth performance of growing finishing pigs. Ciencia Rural, 39(3), 838e843. Cruz, E., Almaguel, R. E., Mederos, C. M., & Araujo, C. G. (2009). Deep bedding system in the swine production at small scale. Revista Cientifica-Facultad de Ciencias Veterinarias, 19(5), 495e499.
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Dekock, J., Vranken, E., Gallmann, E., Hartung, E., & Berckmans, D. (2009). Optimisation and validation of the intermittent measurement method to determine ammonia emissions from livestock buildings. Biosystems Engineering, 104, 396e403. Fukuda, T. (1991). Utilization of fermentation products in the pig-onlitter system of pig farming. Japan: Japanese Council for the Propagation and Promotion of Fermentation Products. Gilhespy, S. L., Webb, J., Chadwick, D. R., Misselbrook, T. H., Kay, R., Camp, V., Retter, A. L., & Bason, A. (2009). Will additional straw bedding in buildings housing cattle and pigs reduce ammonia emissions. Biosystems Engineering, 102, 180e189. GB/T 14675-93. (1993). Standards on air quality - determination of odour - triangle odour bag method. Beijing: China standard press. Jacobson, L. D., Schmidt, D. R., Lake, J. K., & Johnson, V. J. (2003). ASAE Publication Number 701P1403. In H. Keener (Ed.), Ammonia, hydrogen sulfide, odour, and PM10 emissions from deep-bedded hoop and curtain-sided pig finishing barns in Minnesota. Kaufmann, R. (1997). Pig fattening on a sawdust bedding: optimised from the technical, but doubtful from the environmental point of view. 13th Conference of the International-Society-forLivestock-Husbandry - Appropriate Housing Systems for Farm Animals: Newer Developments and Solutions, 23-25 October, 1997, Tanikon, Switzerland, 45, 64e72. Lavoie, J., Marchand, G., Drolet, J. Y., & Gingras, G. (1995). Biological and chemical contamination of the air in a growerfinisher pig building using deep-litter systems. Canadian Agricultural Engineering, 37(3), 195e203. Li, J. F., Gu, C. M., Yu, J. Q., Cai, Y. H., & Shen, J. Q. (2010). Contrast test on effects of deep-litter systems for growing-finishing pigs with conventional system. Shanghai Journal of Animal Husbandry and Veterinary Medicine, 1, 45e46. Li, R. L., Yang, S. L., & He, Y. (2009). Comparsion on effects of deeplitter systems for growing-finishing pigs with conventional system. Guizhou Agricultural Sciences, 37(11), 122e124. Ministry of the Environment Government of Japan. (1999). Calculation method of odor Index and odor Intensity. Environment Agency Notification No. 18 of 1999.. Mosquera, J., Monteny, G. J., & Erisman, J. W. (2005). Overview and assessment of techniques to measure ammonia emissions from animal houses: the case of the Netherlands. Environmental Pollution, 135(3), 381e388. Nicholson, F. A., Williams, J. R., Chambers, B. J. (2000). Ammonia losses from straw and slurry based manure management systems. In: American Society of agricultural Engineers (Ed.), Air pollution from agricultural operations, Proceedings of the second International Conference. 9e11 October, 2000, Des Moines, USA, 18e24.
Nicks, B., Laitat, M., Farnir, F., Vandenheede, M., De´siron, A., Verhaeghe, C., & Canart, B. (2004). Gaseous emissions from deep-litter pens with straw or sawdust for fattening pigs. Animal Science, 78, 99e107. Ogink, N. W. M., & Koerkamp, P. W. G. G. (2001). Comparison of odour emissions from animal housing systems with low ammonia emission. Water Science and Technology, 44(9), 245e252. Pedersen, P. (2008). Perstrup pig house with partial under floor air evacuation and in-house separation of faeces and urine. In Agricultural & Biosystems Engineering for a Sustainable World e Proceedings of AgEng2008 International Conference on Agricultural Engineering, 23e25 June 2008, Crete, Greece. Paper No. OP-920 on Proceeding CD. Philippe, F. X., Laitat, M., Canart, B., Vandenheede, M., & Nicks, B. (2007a). Comparison of ammonia and greenhouse gas emissions during the fattening of pigs, kept either on fully slatted floor or on deep litter. Livestock Science, 111, 144e152. Philippe, F. X., Laitat, M., Canart, B., Vandenheede, M., & Nicks, B. (2007b). Gaseous emissions during the fattening of pigs kept either on fully slatted floors or on straw flow. Animal, 1(10), 1515e1523. Robert, K. (1997). Deep litter fermentation systems for fattening pigs (technical improvements, nutrient balance). 5th International Symposium on Livestock Environment (ILES V), May 29e31, 1997, Bloomington, MN, 718e724. Sheng, Q. K., Wang, C., Wu, Y., Guo, J. F., Zhao, H. B., & Zhang, G. Z. (2009). Effects of deep-litter systems on environment in swine house and swine productivity in cold seasons. Acta Ecologae Animalis Domastici, 30(1), 82e85. Tang, W. L., Bin, S. Y., & Jia, J. S. (2009). Effects of deep-litter systems on production performance and economic benefit for growing-finishing pigs. Hunan Journal of Animal Science & Veterinary Medicine, 4, 13e15. Vranken, E., Claes, S., Hendriks, J., Darius, P., & Berckmans, D. (2004). Intermittent measurements to determine ammonia emissions from livestock buildings. Biosystems Engineering , 88(3), 351e358. Wang, Y. X., & Wang, T. (2010). Progress and application of biology bed in pigs raising. Progress in Veterinary Medicine, 31(S), 193e196. Watts, P. J., Nicholas, P. J., McGahan, E. J. (2001). A review e Australian and international developments in the assessment and management of piggery odours. 8th Biennial Conference of the Australasian-Pig-Science-Association, 25e28 November, 2001, Adelaide, Australia, 8, 51e65. Wu, H. Y., Qiao, M., Guo, W. Z., Peng, X. W., Song, Z. X., Guo, R., & Mei, S. Q. (2009). Research on effects of deep-litter systems for growing-finishing pigs. Hubei Agricultural Sciences, 48(12), 3090e3094.
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Research Paper
Ammonia and odour emitted from deep litter and fully slatted floor systems for growing-finishing pigs Kaiying Wang, Bo Wei, Songming Zhu, Zhangying Ye* Department of Biosystems Engineering, School of Biosystems Engineering and Food Science, Zijingang Campus, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, PR China
article info
Two identical pig rooms, with mechanical ventilation, were used to compare the envi-
Article history:
ronmental impact of a deep litter fermentation system for growing-finishing pigs with
Received 3 November 2010
a fully slatted floor system. The pig manure in the fully slatted floor room was removed
Received in revised form
manually twice daily, but in the fermented deep litter room, no manure was removed.
29 March 2011
Indoor and outdoor temperature, relative humidity, and ammonia concentration were
Accepted 1 April 2011
measured continuously during the whole experimental period. Odour was sampled and
Published online 5 May 2011
analysed using the triangle odour bag method for 15 days during the experimental period. The performance of the pigs was not significantly different between the floor types. There were significant differences for both NH3 concentrations and emissions according to floor type ( p < 0.001). NH3 emissions from pigs raised on the slatted floor and on the fermented deep litter were 8.82 and 2.16 g d1 pig1, respectively. Emissions increased from the first period to the second by about 4.9 times for NH3 with fully slatted floor and 1.1 times for NH3 with fermented deep litter. The parameters of floor type, pig weight, outdoor temperature and ventilation rate explained most of the variability of NH3 emissions. There were significant differences in odour concentration as odour units (OU), between floor types ( p < 0.01). Mean odour concentrations during the whole experiment were 105.4 OU for the slatted floor room and 67.5 OU for the deep litter room. It was concluded that the deep litter fermentation system for pig production shows advantages in reductions of ammonia and odour. ª 2011 IAgrE. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
With intensification of livestock production, and for economic reasons, straw-bedded systems in pig production were progressively replaced by the slatted floor system since 1950 in Western Europe (Philippe, Laitat, Canart, Vandenheede, & Nicks, 2007a). However, there is currently renewed interest in litter systems because consumers are more aware about animal welfare, environmental impact and meat quality in pig production systems.
Straw is normally used as bedding material in a litter system, but sawdust, wood shavings or even paper are also used (Andersson, 1996). A deep litter fermentation system (also called ’natural pig breeding method’) places pigs over a litter bedding of a mixture with sawdust, rice hull etc. where pig wastes are composted in situ. The method was developed in Japan and microbial products were specially developed to accelerate the composting process (Fukuda, 1991), which is different from a litter based straw system (Cabaraux et al., 2009; Gilhespy et al., 2009; Nicks et al., 2004; Philippe et al., 2007a, b).
* Corresponding author. E-mail addresses: [email protected] (K. Wang), [email protected] (Z. Ye). 1537-5110/$ e see front matter ª 2011 IAgrE. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.biosystemseng.2011.04.001
204
b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
Nomenclature CNH3 ENH3 Codour Fls VR RH T A
Concentration of gaseous NH3, mg m3 NH3 emission rate, g d1 pig1 Concentration of odour, OU Floor system ¼ 0 (slatted floor) ¼ 1 (deep litter) ventilation rate, m3 h1 Relative humidity, % air temperature, C the area of air outlet, m2
Litter in this fermentation system is normally accumulated in the pens and is removed after one or several animal batches. In China, compared to conventional pig houses with slatted or solid floors, building costs (especially for waste treatment) and operational costs such as water and heating in winter are often reduced when using a deep litter fermentation system (Wang & Wang, 2010). Furthermore, animal welfare appears to be improved, and it has been reported that the deep litter fermentation system has a low environmental impact (Wang & Wang, 2010). However, only a few experimental data are available regarding the impact of the deep litter fermentation system on the environment, especially in relation to emissions of pollutant gases such as ammonia (NH3) and to odour. Sheng et al. (2009) found that the NH3 concentration in a fermented deep litter pig house was significantly lower than in a solid floor house, but emissions of NH3 were not reported. Ammonia formed and emitted from pig buildings may lead to poor indoor air quality and seriously impact on the outdoor atmospheric environment as well as the natural ecosystem (Mosquera, Monteny, & Erisman, 2005). Odour produced and emitted from such intensive animal production can cause nuisance to individuals living in the vicinity of livestock farms (Chen & Hoff, 2009). In order to reduce NH3 and odour emission, it is firstly important to know the concentrations and emission rates associated with different production systems. Although gas emissions from the slatted floor system are rather well documented in pig production, there is a lack of data concerning deep litter fermentation systems and comparisons between the two systems. Therefore, the objective of this study was to compare concentrations of NH3 and odour as well as NH3 emissions from a growing-finishing pig house with two floor systems: one with slatted floors and one using fermented deep litter.
2.
Materials and methods
2.1.
Experimental room
v W n
Subscripts indoor inside pig room outdoor outside pig room in air inlet out air outlet litter deep litter
system. Each room had one pen and a floor area of each pen was 3 m2. The feeder was located toward the door of the room and the drinker was in the northwest corner of the pen (Fig. 1). The rooms were ventilated using negative pressure systems via 0.55 m diameter ventilation shaft fitted with a fan inside. The opening area of air inlet was 0.055 m2 and the air outlet was a wooden window with width of 0.55 m but a length that could be adjustable manually. For the pig pen with the deep litter fermentation system, sawdust (50% of total weight), rice hulls (40% of the total weight), rice bran (10% of the total weight) and special micro-organisms (200 g m3, composed mainly of Bacillus natto, Saccharomycetes, amylase and protease (Hangzhou New Design Biotechnology Co. Ltd, Hangzhou, China) were mixed together, and then water added until mixture content was 40%. As the mixture fermented, the temperature of mixture rose to 60 C, and then dropped to around 48 C after which fermentation was finished in two days. The fermented mixture was used for experiments after one week. The mixture was used to constitute the initial deep litter with depth of 0.8 m. During the fattening period, a fresh composted mixture was added to keep the depth at 0.8 m and manure was not removed. However, in the fully slatted floor pig pen (with 0.02 m slat and slit), manure was removed from above and beneath the slatted floor twice everyday at 8:00e8:30 and 16:30e17:00 according to the practical management procedures normally used in pig farms in China.
2.2.
Animals and feeding
Two Landrace pigs, randomly selected but with similar initial weight, were housed from December 2009 to January 2010 in each pen. All growing conditions were maintained the same for each pen. The feeds were the same for the two groups during the same growing batch. The pigs were fed twice (8:00e8:30; 16:30e17:00) before each daily manure removal. A drinking jet was installed at the height of about 200 mm (Fig. 1). The pigs were weighed at the start of the experiment with a mean body weight of 36.8 0.9 kg and also weighted at the end of experimental period.
2.3. The study was carried out in the Key Laboratory of Agriculture Environmental Engineering and Intelligent Equipment, Ministry of Chinese Agriculture, Zhejiang University. Two identical climate rooms with different floor systems were used for fattening pigs, one with a plastic fully slatted floor (50% slat area) and another with a deep litter fermentation
Mean wind speed of the outlet, m s1 Mean weight of pigs, kg The number of pigs
Measurements
The temperature and relative humidity of outdoor and room air were continuously monitored on-line with a temperature/ relative humidity (T/RH) sensor (ZDR-20, Hangzhou Zeda Instruments CO., Ltd, Hangzhou, China). The sensors were located above the pig pen at a height of 1.8 m. Ammonia
b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
205
Fig. 1 e The two experimental rooms with different floor systems: (a) plan of the experimental pig rooms; (b) cross-section of the experimental pig room with deep litter fermentation system.
concentrations were measured continuously by sensors (CGDI-1 NH3, Beijing Dongfangjihua Technology Co., Ltd, Beijing, China) with 5% precision and located at the same locations as T/RH sensor. Odour concentration of the outlet air was determined using the triangle odour bag method (GB/T 1467593, 1993), which is different from the European and American standards which use dynamic olfactometry (Watts et al., 2001). The odour measurement system used was similar to the Japanese Standard (Ministry of the Environment Government of Japan, 1999). It was conducted using 6 members of the odour panel. Each panel was given 3 bags; 1 with a sample in it and 2 without any sample (odour-free air) and asked to choose the odorous bag. If the panel member could identify the correct bag, the odour was then diluted (e.g. 30-fold, 100-fold, 300-fold) and until it became impossible to identify the bag with the odour. The sampling time was fifteen days for the whole period. Odour was sampled at 17:00 before cleaning. Sampling took about 20 s each time. Two samples were taken each day and average concentrations were used for analysis. Wind speed of air outlet was measured by using a threecup aero vane (FYF-1, Shanghai Fengyun Co., Ltd, Shanghai, China) with a mean speed of 0.30 0.03 m s1 determined across the cross-section of the air-exhaust. Ammonia emission rates were calculated based on ventilation rate and average NH3 concentrations at the inlet and outlet: ENH3 ¼ v$A$ðCout Cin Þ=n
(1)
where ENH3 is NH3 emission rate from the pig room, g d1 pig1; v is mean wind speed of the outlet, m s1; A is the area of air outlet, m2; Cout is outlet NH3 concentration, mg m3; Cin is inlet NH3 concentration, mg m3 and n is the number of pigs.
2.4.
2010) were used for analysis. Differences in pigs’ production performance, NH3 emission and odour concentration with regard to floor type were tested using analysis of variance (SPSS ver. 16.0, SPSS Inc., Chicago, IL, USA). Analysis of the data set was carried out by means of multiple regressions, in which the dependent variables were NH3 emissions and odour concentrations. The independent variables considered in the regression analysis were floor type, weight of the pigs, ventilation rate, outdoor and indoor temperatures, and room relative humidity. The two categories of the qualitative variable ’floor type’ were considered as dummy variables for an appropriate statistical analysis. The maximum number of independent variables that could be included in the regression model was six. However, the effects of all the parameters were not necessarily significant. A stepwise procedure (SPSS 16.0, SPSS Inc., Chicago, IL, USA) was used on all possible subset regressions. The regression models were then arranged in a decreasing order of adjusted coefficient determination (R2). The statistic ’adjusted R20 is useful for comparing regression models that have different numbers of independent variables. This method can be used for exploratory purposes, as comparison of adjusted R2 of different subset regressions gives a rough estimate of the contribution of each variable to the model (Blanes-Vidal, Hansen, Pedersen, & Rom, 2008).
Statistical analysis
Due to the data available, the data in two periods (1st: 1 December to 22 December 2009; 2nd: 15 January to 28 January
3.
Results and discussion
3.1.
Climatic characteristics of the rooms
Table 1 presents average temperature, relative humidity and ventilation rate observed in the test. The daily variation of temperature, relative humidity and ventilation rate can be seen in Fig. 2. Outdoor climate had a greater impact on indoor climate due to insufficient insulation. For both stages, the variations of indoor temperature and relative humidity were
206
b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
Stages 1st (1 Dec to 22 Dec)
Toutdoor, C Tindoor, C
Slatted floor Deep litter
Tlitter, C RHoutdoor, % RHindoor, %
Slatted floor Deep litter Slatted floor Deep litter
VR, m3 h1
9.6 11.7 11.0 22.0 76.3 69.7 75.2 360 365
2.6 2.5 2.7 1.9 11.8 11.2 10.7 11 15
2nd (15 Jan to 28 Jan) 7.7 10.9 11.1 22.2 76.8 70.3 74.5 373 374
3.2 2.6 2.8 2.0 6.9 7.2 6.7 11 4
highly related to outdoor temperature and relative humidity changes. No additional heating was applied and this resulted in temperatures in both rooms being close to outdoor the temperature. No significant differences were found for indoor temperature between floor types, which is consistent with results obtained by Correa et al. (2009). In this study, the mean litter temperature at 300 mm depth below the surface was 22.1 1.9 C when the average outdoor temperature was 8.9 2.9 C. The relative humidity in the room with slatted floor was 5.5% and 4.2% lower than that with deep litter in the two stages, respectively. Statistical analysis showed no differences in ventilation rates between floor types and experimental stages. The results indicate that the fermented deep litter can keep the lying area warm for pigs reared under the cold climate conditions. However, the higher relative humidity in the room with deep litter fermentation system needs to be considered.
3.2.
Performance of the animals
Temperature, °C
Table 2 shows the performance during the two growing periods of pigs kept on slatted floor or on fermented deep litter. In this experiment, keeping fattening pigs on the slatted floor or on the deep litter fermentation system did not cause a difference in average daily weight gain ( p > 0.05) and feed conversion ( p > 0.05). Results from the literature concerning
33 30 27 24 21 18 15 12 9 6 3 0
1st stage
Average daily weight gain, kg d1 pig1 Feed conversion (Feed intake/gain meat)
Slatted floor
Deep litter
0.74 0.50 3.3 0.4
0.73 0.57 3.4 0.7
this comparison are few and different. Several researchers compared the effects of deep litter fermentation system and solid floor system, the results showed a better performance for parameters such as higher average daily weight gain and lower feed/gain for fattening pigs kept on fermented deep litter in cold climates (Cruz, Almaguel, Mederos, & Araujo, 2009; Robert, 1997; Sheng et al., 2009; Tang, Bin, & Jia, 2009; Wu et al., 2009) or no significant differences between floor types (Correa et al., 2009; Li, Yang, & He, 2009, 2010). The results from available studies indicate that a deep litter fermentation system could be used for growing-finishing pigs due to the absence of negative effects on growth performance.
3.3.
Ammonia
Mean NH3 concentrations and emissions for each stage are listed in Table 3. The mean NH3 emission from the slatted floor room during the whole test was 8.82 g d1 pig1, however, the mean NH3 emission from the deep litter room was only 2.16 g d1 pig1. Whatever the floor type, emissions increased from the beginning to the end of the fattening periods by about 5 times for NH3 (Philippe et al., 2007a). In this study, emissions increased from the 1st to the 2nd period by about 4.9 times for NH3 with a fully slatted floor, however, it only increased 1.1 times for NH3 using fermented deep litter. There were significant differences for both NH3 concentrations and emissions between the floor types and between the experimental stages ( p < 0.001). Few data regarding the comparison of NH3 emissions from deep litter fermentation system and the slatted floor system are available in the published literature. Generally, NH3 emissions from pig housing are lower with a fully slatted floor system than with a deep litter system based on straw
2nd stage
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Time, d
420 390 360 330 300 270 240 210 180 150 120 90 60 30 0
3 -1
Floor systems
Table 2 e Performance of pigs during the experiment.
Ventilation rate, mh
Table 1 e Mean temperature, relative humidity and ventilation rate observed during the test.
Fig. 2 e Daily mean outdoor, indoor and litter temperature as well as room ventilation rates during the test. - outdoor temperature, A indoor temperature with slatted floor, > indoor temperature with deep litter, C litter temperature, , ventilation rate in room with slatted floor, 6 ventilation rate in room with deep litter.
207
b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
Stages 1st (1 Dec to 22 Dec)
CNH3, mg m3 ENH3, g d1 pig1 Codour, OU
Slatted floor Deep litter Slatted floor Deep litter Slatted floor Deep litter
0.83 0.47 3.6 2.1 89.6 60.5
2nd (15 Jan to 28 Jan)
0.68*** 0.12 3.0*** 0.5 34.2** 14.1
3.95 0.52 17.7 2.3 119.3 73.6
1.22*** 0.13 5.5*** 0.6 34.5** 33.2
*** means p < 0.001; ** means p < 0.01.
Temperature, °C
(Nicholson et al., 2000; Philippe et al., 2007a, b; Cabaraux et al., 2009) or sawdust (Cabaraux et al., 2009). It has been observed that high temperature and high pH in litter may lead to considerable NH3 emissions (Andersson, 1996). However, Gilhespy et al. (2009) found that the broadcast addition of 100% more straw over the entire floor in a pig house reduced NH3 emission with approximately 20%. The explanation for this was that additional straw may reduce the airflow across surfaces soiled with urine, and by immobilisation of ammonium-N. Sheng et al. (2009) found that the NH3 concentration in a fermented deep litter pig house was significantly lower than in a solid floor house. In this study, NH3 emissions were 4.1 times higher in the room with slatted floor than that with the fermented deep litter. The deep litter fermentation system placed pigs over a litter bedding where pig wastes are composted in situ and microbial products are specially developed to produce enzymes that acts on ammonium nitrogen in pig manure to stimulate fermentation. This microbial product was not added in the litter based straw as mentioned above. Fermentation caused the ammonium ions to be trapped in the bedding and converted to bacterial protein causing low gaseous ammonia concentrations (Chan, Chaw, & Lo, 1994, 1995; Cruz et al., 2009; Lavoie, Marchand, Drolet, & Gingras, 1995). Diurnal variation of NH3 concentrations from pig rooms are shown in Fig. 3. It can be seen that the variations of NH3
22 20 18 16 14 12 10 8 6 4 2 0
0
1
2
3
4
5
6
7
8
9
E ¼ 0:238VR þ 0:856W þ 0:438Toutdoor R2 ¼ 0:81; all p < 0:01
(2)
Deep litter E ¼ 0:196VR 0:111W 0:956Toutdoor R2 ¼ 0:90; all p < 0:05
10 11 12 13 14 15 16 17 18 19 20 21 22 23 Time, h
12 11 10 9 8 7 6 5 4 3 2 1 0
(3)
-3
Floor systems
concentration in the slatted floor room were related to temperature changes and manure removal. NH3 concentrations were higher before 7:00, probably due to the manure accumulation in the room during the night period, then decreased by the daily manure removal in the morning, and increased again following the temperature increase until the peak value between 13:00 and 14:00, finally decreased as temperature decreased (Aarnink, Keen, Metz, Speelman, & Verstegen, 1995, 1996). However, the changes of NH3 concentration in fermented deep litter room are very small. Fig. 4 shows daily mean NH3 emissions from pig rooms during the test. It can be seen that the variation of NH3 emissions from the slatted floor room was highly related to climatic parameters change. Nevertheless, the emissions of NH3 in the fermented deep litter room were very stable during the two stages. Table 4 shows the combination of independent variables (for a different number of variables from 1 to 6 included in the model) with higher adjusted R2, for NH3 emission as dependent variable. As expected, to a certain extent the more independent variables included in the model, the higher adjusted R2 was obtained. However, Table 4 also shows that, in some cases, the inclusion of one new variable did not improve the adjusted R2 substantially. This can occur, either because the effect of the variable is small, or because it is highly correlated with one variable that is already included in the model. According to Table 4, the four parameters that explained most of the variability of the NH3 emissions were floor type, pig weight, outdoor temperature and ventilation rate, which are usually used for estimation of NH3 emissions (Dekock, Vranken, Gallmann, Hartung, & Berckmans, 2009; Vranken, Claes, Hendriks, Darius, & Berckmans, 2004). A statistical relationship between NH3 emissions and pig weight, outdoor temperature and ventilation rate was established for slatted floor room and fermented deep litter room as follows, Slatted floor
NH3 concentration, mgm
Table 3 e Concentrations of NH3 and odour as well as NH3 emission in slatted floor and deep litter fermentation systems.
Fig. 3 e Diurnal variation of mean NH3 concentrations from pig rooms (daily removal of manure in slatted floor system). - outdoor temperature, A indoor temperature in slatted floor system, > indoor temperature in deep litter system, 6 NH3 concentration in slatted floor system, : NH3 concentration in deep litter system.
208
-1
NH3 emission, gd pig
-1
b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
33 30 27 24 21 18 15 12 9 6 3 0
1st stage
2nd stage
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Time, d
Fig. 4 e Daily mean NH3 emissions from pig rooms during the test. A slatted floor system, > deep litter system.
Table 4 e Best subset regressions (with higher adjusted R2) for the NH3 emission, depending on the number of the independent variables included in the model.
6 5 4 3 2 1
R2
Explicative variables
0.61 0.61 0.59 0.56 0.52 0.26
Fls Fls Fls Fls Fls Fls
W W W W W
Toutdoor Toutdoor Toutdoor Toutdoor
VR VR VR
RHindoor RHindoor
Tindoor
Fls is the floor type, 0 means slatted floor and 1 means deep litter; W is the mean weight of pigs in kg; Tindoor and Toutdoor are the indoor and outdoor temperature in C; VR is the ventilation rate in m3 h1; RHindoor is the indoor relative humidity in %.
Where, E is NH3 emission in g d1 pig1; VR is the ventilation rate in m3 h1; W is the mean weight of pigs in kg; Toutdoor is the outdoor temperature in C.
3.4.
Odour
Table 3 also shows the mean odour concentrations during the test. The mean odour concentration from the slatted floor
20
400
18 1st stage
Temperature, °C
16
350
2nd stage
300
14 12
250
10
200
8
150
6
100
4
50
2 0
Odour concentration, OU
No
room during the whole experiment was 105.4 OU, however, the mean odour concentration from the deep litter room was only 67.5 OU. Whatever the floor type, in this study, odour concentrations increased from the 1st stage to the second stage by about 1.3 times for the room with fully slatted floor and 1.2 times for the room with fermented deep litter. There were significant differences in odour concentrations between floor types ( p < 0.01), but not between experimental stages ( p > 0.05). Because the triangle odour bag method is different from the European and American standards that use dynamic olfactometry, it is difficult to compare the odour concentration levels directly. However, the main objective of this study was to compare the influence of two floor types on odour concentrations under similar pig production conditions. The available literature concerning this comparison showed that odour concentrations or emissions reduced greatly in deep litter system compared to slatted floor system (Chan et al., 1994; Chan, Chaw, and Lo (1995); Jacobson, Schmidt, Lake, & Johnson, 2003; Kaufmann, 1997; Ogink & Koerkamp, 2001; Watts et al., 2001) measured volatile odorous compounds in deep litter fermentation system by using gas chromatography and found p-cresol, indole and skatole levels were maintained and did not accumulate after 2e3 weeks when the bedding began to settle down.
16
17
18
19
20
21
22
23 24 Time, d
25
26
27
28
29
30
0
Fig. 5 e Daily mean odour concentrations from pig rooms during the test. A indoor temperature in slatted floor system, > indoor temperature in deep litter system, 6 odour concentration in slatted floor system, : odour concentration in deep litter system.
b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
Table 5 e Best subset regressions (with higher adjusted R2) for the odour concentration, depending on the number of the independent variables included in the model. No 6 5 4 3 2 1
R2 0.63 0.63 0.62 0.56 0.48 0.28
Explicative variables Fls Fls Fls Fls Fls Fls
Toutdoor Toutdoor Toutdoor Toutdoor Toutdoor
W W W W
RHindoor RHindoor RHindoor
Tindoor Tindoor
VR
Fls is the floor type, 0 means slatted floor and 1 means deep litter; W is the mean weight of pigs in kg; Tindoor and Toutdoor are the indoor and outdoor temperature in C; VR is the ventilation rate in m3 h1; RHindoor is the indoor relative humidity in %.
Diurnal variations of mean odour concentrations from pig rooms are shown in Fig. 5. It can be seen that the variations of odour concentration in the slatted floor room and deep litter room were highly related to temperature changes in the second stage. However, such a relationship was not found during the first stage. Table 5 shows the combination of independent variables (for a different number of variables from 1 to 6 included in the model) with higher adjusted R2, for odour concentration as dependent variable. As expected, to certain extent the more independent variables included in the model, the higher adjusted R2 was obtained. However, Table 5 also shows that, in some cases, the inclusion of one new variable did not improve the adjusted R2 substantially such as with indoor temperature and ventilation rate. This can occur, because the indoor temperature is highly correlated with outdoor temperature which is already included in the model and the effect of the ventilation rate is small on odour concentration as reported by Pedersen (2008). According to Table 5, the four parameters that explained most of the variability of the odour concentration were floor type, outdoor temperature, pig weight, and relative humidity. Ogink and Koerkamp (2001) found that correlations between NH3 and odour concentration (within facilities) did not show a consistent pattern. In this study, the NH3 and odour concentration showed a high correlation coefficient ðr ¼ 0:652; p ¼ 0:006 < 0:01Þ in fully slatted floor room, however, no obvious correlations between NH3 and odour concentration were found in deep litter fermentation room ðr ¼ 0:345; p ¼ 0:191 > 0:05Þ. Although the deep litter fermentation system shows advantages for pig production with respect to reduction of NH3 and odour emissions, issues such as the effect on other emissions (N2O and CH4), the supply of large quantities of bedding materials, excessive heat production resulting in high temperature at the surface of litter during summer, the choice of microorganism and effects on meat quality still exist. As a result more relevant studies are needed in future.
4.
Conclusion
Under pig production conditions in China, when compared to fully slatted floor system, the fermented deep litter system could reduce the NH3 and odour concentrations as well as NH3
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emissions. The performance of the pigs was not significantly different according to the floor type. The four parameters that explained most of the variability of the NH3 emissions were floor type, pig weight, outdoor temperature and ventilation rate. However, the four parameters that explained most of the variability of the odour concentration were floor type, outdoor temperature, pig weight, and relative humidity. There are still some issues such as the supply of large quantities of bedding materials, excessive heat production results in high temperature at the surface of litter in summer season etc, that need to be studied.
Acknowledgements The authors appreciate the supports by the National Natural Science Foundation of China (Grant No.30571357). We would also like to thank the anonymous reviewers for their insightful comments on the manuscript which enabled it to be significantly improved.
references
Aarnink, A. J. A., Keen, A., Metz, J. H. M., Speelman, L., & Verstegen, M. W. A. (1995). Ammonia emission patterns during the growing periods of pigs housed on partially slatted floors. Journal of Agricultural Engineering Research, 62(2), 105e116. Aarnink, A. J. A., VandenBerg, A. J., Keen, A., Hoeksma, P., & Verstegen, M. W. A. (1996). Effect of slatted floor area on ammonia emission and on the excretory and lying behaviour of growing pigs. Journal of Agricultural Engineering Research, 64(4), 299e310. Andersson, M. (1996). Performance of bedding materials in affecting ammonia emissions from pig manure. Journal of Agricultural Engineering Research, 65, 213e222. Blanes-Vidal, V., Hansen, M. N., Pedersen, S., & Rom, H. B. (2008). Emissions of ammonia, methane and nitrous oxide from pig houses and slurry: effects of rooting material, animal activity and ventilation flow. Agriculture, Ecosystems and Environment, 124(3e4), 237e244. Cabaraux, J. F., Philippe, F. X., Laitat, M., Canart, B., Vandenheede, M., & Nicks, B. (2009). Gaseous emissions from weaned pigs raised on different floor systems. Agriculture. Ecosystems and Environment, 130(3e4), 86e92. Chan, D. K. O., Chaw, D., & Lo, C. Y. Y. (1994). Management of the sawdust litter in the pig-on-litter system of pig waste treatment. Resources Conservation and Recycling, 11(1e4), 51e72. Chan, D. K. O., Chaw, D., & Lo, C. Y. Y. (1995). Development of an environmentally-friendly and cost- effective system for the treatment of waste in pig farming. Supplement to the Journal of Sun Yatsen University Forum, 3, 11e16. Chen, L., & Hoff, S. J. (2009). Mitigation odours from agricultural facilities: a review of literature concerning biofilters. Applied Engineering in Agriculture, 25(5), 751e766. Correa, E. K., Bianchi, I., Ulguim, R. D., Correa, M. N., GilTurnes, C., & Lucia, T. (2009). Effects of different litter depths on environmental parameters and growth performance of growing finishing pigs. Ciencia Rural, 39(3), 838e843. Cruz, E., Almaguel, R. E., Mederos, C. M., & Araujo, C. G. (2009). Deep bedding system in the swine production at small scale. Revista Cientifica-Facultad de Ciencias Veterinarias, 19(5), 495e499.
210
b i o s y s t e m s e n g i n e e r i n g 1 0 9 ( 2 0 1 1 ) 2 0 3 e2 1 0
Dekock, J., Vranken, E., Gallmann, E., Hartung, E., & Berckmans, D. (2009). Optimisation and validation of the intermittent measurement method to determine ammonia emissions from livestock buildings. Biosystems Engineering, 104, 396e403. Fukuda, T. (1991). Utilization of fermentation products in the pig-onlitter system of pig farming. Japan: Japanese Council for the Propagation and Promotion of Fermentation Products. Gilhespy, S. L., Webb, J., Chadwick, D. R., Misselbrook, T. H., Kay, R., Camp, V., Retter, A. L., & Bason, A. (2009). Will additional straw bedding in buildings housing cattle and pigs reduce ammonia emissions. Biosystems Engineering, 102, 180e189. GB/T 14675-93. (1993). Standards on air quality - determination of odour - triangle odour bag method. Beijing: China standard press. Jacobson, L. D., Schmidt, D. R., Lake, J. K., & Johnson, V. J. (2003). ASAE Publication Number 701P1403. In H. Keener (Ed.), Ammonia, hydrogen sulfide, odour, and PM10 emissions from deep-bedded hoop and curtain-sided pig finishing barns in Minnesota. Kaufmann, R. (1997). Pig fattening on a sawdust bedding: optimised from the technical, but doubtful from the environmental point of view. 13th Conference of the International-Society-forLivestock-Husbandry - Appropriate Housing Systems for Farm Animals: Newer Developments and Solutions, 23-25 October, 1997, Tanikon, Switzerland, 45, 64e72. Lavoie, J., Marchand, G., Drolet, J. Y., & Gingras, G. (1995). Biological and chemical contamination of the air in a growerfinisher pig building using deep-litter systems. Canadian Agricultural Engineering, 37(3), 195e203. Li, J. F., Gu, C. M., Yu, J. Q., Cai, Y. H., & Shen, J. Q. (2010). Contrast test on effects of deep-litter systems for growing-finishing pigs with conventional system. Shanghai Journal of Animal Husbandry and Veterinary Medicine, 1, 45e46. Li, R. L., Yang, S. L., & He, Y. (2009). Comparsion on effects of deeplitter systems for growing-finishing pigs with conventional system. Guizhou Agricultural Sciences, 37(11), 122e124. Ministry of the Environment Government of Japan. (1999). Calculation method of odor Index and odor Intensity. Environment Agency Notification No. 18 of 1999.
Nicks, B., Laitat, M., Farnir, F., Vandenheede, M., De´siron, A., Verhaeghe, C., & Canart, B. (2004). Gaseous emissions from deep-litter pens with straw or sawdust for fattening pigs. Animal Science, 78, 99e107. Ogink, N. W. M., & Koerkamp, P. W. G. G. (2001). Comparison of odour emissions from animal housing systems with low ammonia emission. Water Science and Technology, 44(9), 245e252. Pedersen, P. (2008). Perstrup pig house with partial under floor air evacuation and in-house separation of faeces and urine. In Agricultural & Biosystems Engineering for a Sustainable World e Proceedings of AgEng2008 International Conference on Agricultural Engineering, 23e25 June 2008, Crete, Greece. Paper No. OP-920 on Proceeding CD. Philippe, F. X., Laitat, M., Canart, B., Vandenheede, M., & Nicks, B. (2007a). Comparison of ammonia and greenhouse gas emissions during the fattening of pigs, kept either on fully slatted floor or on deep litter. Livestock Science, 111, 144e152. Philippe, F. X., Laitat, M., Canart, B., Vandenheede, M., & Nicks, B. (2007b). Gaseous emissions during the fattening of pigs kept either on fully slatted floors or on straw flow. Animal, 1(10), 1515e1523. Robert, K. (1997). Deep litter fermentation systems for fattening pigs (technical improvements, nutrient balance). 5th International Symposium on Livestock Environment (ILES V), May 29e31, 1997, Bloomington, MN, 718e724. Sheng, Q. K., Wang, C., Wu, Y., Guo, J. F., Zhao, H. B., & Zhang, G. Z. (2009). Effects of deep-litter systems on environment in swine house and swine productivity in cold seasons. Acta Ecologae Animalis Domastici, 30(1), 82e85. Tang, W. L., Bin, S. Y., & Jia, J. S. (2009). Effects of deep-litter systems on production performance and economic benefit for growing-finishing pigs. Hunan Journal of Animal Science & Veterinary Medicine, 4, 13e15. Vranken, E., Claes, S., Hendriks, J., Darius, P., & Berckmans, D. (2004). Intermittent measurements to determine ammonia emissions from livestock buildings. Biosystems Engineering , 88(3), 351e358. Wang, Y. X., & Wang, T. (2010). Progress and application of biology bed in pigs raising. Progress in Veterinary Medicine, 31(S), 193e196. Watts, P. J., Nicholas, P. J., McGahan, E. J. (2001). A review e Australian and international developments in the assessment and management of piggery odours. 8th Biennial Conference of the Australasian-Pig-Science-Association, 25e28 November, 2001, Adelaide, Australia, 8, 51e65. Wu, H. Y., Qiao, M., Guo, W. Z., Peng, X. W., Song, Z. X., Guo, R., & Mei, S. Q. (2009). Research on effects of deep-litter systems for growing-finishing pigs. Hubei Agricultural Sciences, 48(12), 3090e3094.