Characterization of composted chicken manures discharged from farms in South Korea
Article information
Abstract
In this study, the characteristics as well as the maturity and stability of chicken manure collected from nine chicken farms in South Korea during the summer and winter seasons of 2014 are evaluated. The physicochemical parameter values of the manure, such as BOD, NO3-N and PO4-P etc. were determined using the Korea Standard test Method, HPLC, and APHA standard methods. The results showed that the alkalinity content and COD concentration in winter chicken manure were higher than those of summer chicken manure. The moisture content of summer manure was positively correlated with almost all of the other parameters of the manure, whereas it was negatively correlated with almost all of the other parameters in the winter manure. According to the criterion of C/N ratio, chicken manure indicated good quality compost. However, composted chicken manure showed immature and unstable compost when considering the criteria of the NH4-N/NO3-N ratio and NH4-N concentrations.
1. Introduction
The poultry population is increasing every year, causing an increase in the amount of remaining manure [1]. In addition, poultry contamination is a typical agricultural waste and has become a major source of rural pollution, while chicken manure has become the main source of poultry waste [2].
Composted animal manures (such as farmyard manure and chicken manure) represent a valuable resource, if managed appropriately; they are excellent fertilizers for crops and forages, and can be used to replace significant amounts of mineral fertilizers [3–5]. Chicken manure increases the electrical conductivity (EC) and cation exchange capacity (CEC) of soil, and the growth of cantaloupe cultivars, silage maize, and mentha spicata [6–8]. On the other hand, livestock and poultry manures containing a high proportion of biodegradable organic matter, nutrients, and pathogens have potential negative impacts on the environment [2, 9]. Leaching of nitrate and possible pathogens transferred to the ground water from manure storage facilities or from fields are particular threats to drinking water quality [10]. Qing Liao et al. [11] estimated the loss of biochemical oxygen demand (BOD5), chemical oxygen demand (COD), and ammonia nitrogen (NH4-N) of livestock and poultry manure, and assumed that these contaminants were a considerable threat to the water environment. Moreover, the application of unstable and immature compost manure can affect nitrogen immobilization in the soil, restrict plant growth, and cause phytotoxic effects [12–15]. Therefore, in order to deal with these problems, several researchers have assessed the quality of composted manures, which were then appropriately applied for the best productivity and to protect the environment based on the physicochemical parameter properties of the composts [1, 8, 11]. The study of the value of the parameters in chicken manure is fundamental for providing a database for adequate use for crops and pollution control.
The aim of this study was to analyze the parameter contents and to determine the characteristics of composted chicken manure samples collected from nine farms in South Korea during the summer and winter seasons of 2014.
2. Materials and Methods
2.1. Manure Sample Collection
Composted chicken manure samples were collected from 9 farms located in South Korea during the summer and winter of 2014. One sample from each farm was taken randomly from 4 to 6 holes in the manure store location, then mixed and kept in a plastic bag.
2.2. Sample Preparation and Analysis
The samples were air-dried, ground to pass through a 0.1 mm sieve and treated with distilled water at a manure to water ratio of 1:10 (w/v) in a 50 ml plastic conical tube. The tube was tightly capped and shaken at 200 rpm for 48 hours. The liquid samples were then used to analyze the COD, BOD, nitrate nitrogen (NO3-N), NH4-N, phosphate phosphorus (PO4-P) and total kjeldahl nitrogen (TKN). The moisture content, total organic carbon (TOC), COD, BOD, total nitrogen (T-N), and total phosphorus (T-P) were analyzed using the Korea Standard Test Method [16].
The concentration of NO3-N and PO4-P were analyzed using high performance liquid chromatography (HPLC) with a conductivity detector (WATER 432, column Allsep Anion 7μm GRACE), a Mobile Phase (with suppresser) 0.85mM sodium bicarbonate (NaHCO3), and a 0.9mM sodium carbonate (Na2CO3) solution. The concentrations of NH4-N, TKN, and alkalinity were analyzed according to American Public Health Association (APHA) standard methods [17].
2.3. Statistical Analysis
Statistical analysis was conducted using R software (version 3.1.2). The differences between the values of parameters in the winter manure and summer manure were tested using the t-test at a significant level of 5%. The relationships between the phys-icochemical parameters in chicken manures were determined using the correlation analysis method.
3. Results and Discussion
3.1. Physicochemical Properties of Composted Chicken Manure
The moisture content in the summer chicken manure and in the winter chicken manure from farms in South Korea ranged from 14.18% to 78.74% with a mean of 26.90% and from 12.70% to 81.00% with a mean value of 38.40%, respectively, while the content of alkalinity in the winter manure with a mean of 76,570 mg/kg was significantly (p < 0.05) higher than that in the summer manure with a mean value of 46,116 mg/kg. A familiar trend with alkalinity was observed. The COD concentrations in chicken manure in winter (ranging from 344,000 mg/kg to 424,000 mg/kg with a mean of 388,444 mg/kg) was significantly (p < 0.05) higher than the concentration of COD in the summer chicken manure, which ranged from 224,000 mg/kg to 328,000 mg/kg with a mean of 279,111 mg/kg. It is clear that under the effect of temperature, the evaporation of water in manure in the summer is higher than that of in the winter; thus, the moisture content of manure in winter was higher than that in summer. The higher alkalinity content of manure in winter than that in summer clearly reflects the general tendency that alkalinity (high pH) in a lower temperature condition is usually higher than that in a higher temperature [18]. According to Wenche Bergland et al. [19], the temperature significantly influences manure quality during storage. Dissolved organics are generated by the disintegration and hydrolysis of particles during storage in the warmest season, but not at winter temperatures. Therefore, organic matters of composted chicken manure in South Korea were dissolved and a greater amount of organic matter was lost in summer than in winter, resulting in a higher COD concentration of manure in winter than that in summer.
Related to the group of nitrogen, organic carbon, and phosphorous nutrients, PO4-P concentrations ranged from 2,798 mg/kg to 24,253 mg/kg, whereas the T-P contents ranged from 11,263 mg/kg to 32,735 mg/kg. TOC contents in different types of chicken manures fluctuated in a narrow range, around 300,000 mg/kg, while the concentrations of NO3-N and NH4-N widely fluctuated from 166 mg/kg to 1,546 mg/kg and from 259 mg/kg to 10,213 mg/kg, respectively. The TKN concentrations ranged from 8,138 mg/kg to 36,856 mg/kg and the T-N contents ranged from 25,220 mg/kg to 75,330 mg/kg. Nitrogen (N) and phosphorus (P) are indispensable for sustainability in agriculture [20, 21]. They have been shown to improve soil fertility and enhance crop productivity [8, 22, 23]. However, the use of an inappropriate application rate can cause environmental risks [11, 20]. For these reasons, in order to prevent and reduce risks to human health and the environment, in some countries such as Austria and Belgium, regulations have been established for the maximum amount of nitrogen supply using compost (290 kg N/ha in crop soil and 350 kg N/ha in pastures, 800 – 100 kg N/ha in crops with the addition of inorganic fertilization, and 250 kg N/ha in maize crops). In other countries, preventive measures have even established for P input (Sweden 22–35 kg/ha per year and Denmark, 20 kg/ha per year) [14]. Therefore, composted chicken manure from farms in South Korea needs to be calculated and applied appropriately for different types of soils, plants, and crops in order to gain the best productivity as well as protect the environment.
Correlation coefficients (r) were compared between the physicochemical parameters of composted chicken manure. These are presented in Table 1 and Table 2 and in Fig. 1 and Fig. 2. It is noted that no significant correlation was observed between alkalinity and almost all other parameters in the summer chicken manure, while TOC correlated with the other parameters except for NO3-N. The moisture content showed the closest correlation with T-P (r = 0.73), the second closest with NH4-N (r = 0.68) and the third closest with PO4-P (r = 0.62). COD was significantly correlated with the C/N ratio (r = 0.76) (Table 1 and Fig. 1).
Correlations Matrix between Physicochemical Parameters in Summer Chicken Manure Samples
Correlations Matrix between Physicochemical Parameters in Winter Chicken Manure Samples
Relationships between physiochemical parameters in summer chicken manure samples collected from nine farms in South Korea in 2014.
Relationships between physiochemical parameters in winter chicken manure samples collected from nine farms in South Korea in 2014.
The concentration of PO4-P in winter chicken manure only correlated with T-P (r = 0.79) (Table 2 and Fig. 2). Moisture content was strongly, positively correlated with C/N ratio (r = 0.8) and significantly, negatively correlated with alkalinity (r = −0.60), BOD (r = −0.63), NH4-N (r = −0.50), TKN (r = −0.72), and T-N (r = −0.77). Thus, an increase in moisture content increases the C/N ratio, but the value of alkalinity, BOD, NH4-N, TKN, and T-N will decrease, and vice versa. A significant negative correlation was observed between alkalinity and C/N ratio (r = −0.70), whereas alkalinity was positively correlated with NH4-N (r = 0.78) and T-N (r = 0.72).
It is interesting to note that the moisture content of manure in summer was positively correlated with almost all of the other parameters (Table 1), while it was negatively correlated with almost all of the other parameters in the winter season (Table 2). This result has been considered to be the consequence of temperature and effective microorganism (EM) activity [24]. The activity of EM results in a higher content of N, P, and K etc. in compost manure [25]. The higher moisture content of manure in the warm summer temperature leads to an increase in EM growth as well as a greater EM activity. This results in higher contents of PO4-P, T-P, NH4-N, and TKN, etc. of the manure in this study. This is why moisture content was positively correlated with almost all other parameters. In contrast, in the cold conditions in winter, if the moisture content in the manure is higher, the temperature of the manure is lower, and the EM activity in manure is thus restricted. This phenomenon causes lower contents of TOC, NH4-N, TKN, and TN, etc. in the manure. This indicates a negative correlation between moisture content and the content of various parameters in winter manure.
3.2. Assessment of Maturity and Stability of Composted Chicken Manure
In relation to compost, stability and maturity are two terms usually used to describe the rates of the decomposition and transformation of the organic matter in the compost. Compost maturity is used to describe product quality, while compost stability is strongly related to the rate of microbial activity in the compost [26]. In a number of researches, the C/N ratio is used as an index of compost stability as well as an indicator of compost maturity [12, 27]. In the present study, the C/N ratios ranged from 4.07 in summer layer manure at farm L-4 to 13.90 in the winter layer of manure at farm L-3 (Table 3). According to Bernal et al. [12] and Iglesias-Jiménez and Pérez-García [28], a C/N ratio lower than 12 after the composting process indicated a good degree of maturity and suitability for addition to soil. Moreover, almost all the C/N ratios in the manure samples in this research were found to be lower than 12, indicating that the manure can be considered as ready to be applied. Only the C/N ratio in winter layer manure at farm L-3 (13.90) was higher than 12, indicating that the compost manure at this farm was unstable.
C/N Ratio and NH4-N/NO3-N Ratio in Broiler Chicken Manure and Layer Chicken Manure
Besides the C/N ratio, the NH4-N/NO3-N ratio and NH4-N concentrations are used as indexes for assessing compost stability and compost maturity. The value of NH4-N/NO3-N < 0.16 denoted very stable or mature compost [12]. In this study, the NH4-N/NO3-N ratios ranged from 1.44 to 91.31, which did not meet the requirement for the degree of maturity of less than 0.16. This means that the compost manures in all farms were unstable and immature. However, the California Compost Quality Council (CCQC) [29] categorizes mature compost into three levels based on the NH4-N/NO3-N ratios: NH4-N/NO3-N < 0.5 (very mature), 0.5 ≤ NH4-N/NO3-N ≤ 3.0 (mature), and NH4-N/NO3-N > 3.0 (immature). Compared to the NH4-N/NO3-N ratios in this research, only the NH4-N/NO3-N ratio in winter layer manure at farm L-3 (1.44) showed that the compost had reached a mature level, whereas the other NH4-N/NO3-N ratios showed that the compost was at an immature level. However, Rui Guo et al. [15] suggested that the NH4/NO3 ratio may not be suitable as a maturity index for manure composts, and this should be further studied. On the other hand, a high concentration of NH4-N in a compost indicates instability [30]. According to Zucconi and de Bertoldi [31], the maximum NH4-N concentration in a mature compost should be less than 400 mg/kg. In the present study, the concentration of NH4-N in winter layer manure at farm L-1 (259 mg/kg) was less than 400 mg/kg, while the others were higher. Therefore, only winter layer manure at farm L-1 reached a maturity level for compost according to the NH4-N concentration criterion (< 400 mg/kg).
In general, the composted chicken manures in the present study were not ready for use when considering the criteria of the NH4-N/NO3-N ratios and the NH4-N concentration. Stable and mature compost can be used to enhance soil fertility and plant growth. In contrast, the application of unstable and immature compost can fix nitrogen in the soil, restrict plant growth, and cause phytotoxic effects [12–15]. In this research, the NH4-N/NO3-N ratios and the concentrations of NH4-N were high, while the NH4-N concentrations were obviously higher than the NO3-N concentrations. Even the concentrations of NO3-N in winter layer chicken manure at farm B-1, farm L-1, farm L-2, farm L-4, farm L-5, and farm L-6 were not detected. The NH4-N/NO3-N ratio and NH4-N concentrations are still high, indicating that nitrification is not complete [12]. The nitrification process oxidizes NH4-N to NO2-N and then NO3-N during composting, which leads to a decrease in NH4-N and an increase in NO3-N; thus, the NH4-N/NO3-N ratio is lower in mature compost [12, 15, 27, 32, 33]. Hence, the chicken manure in farms in South Korea needs to be composted longer and the NH4-N/NO3-N ratio and the concentration of NH4-N should be decreased to meet the required values before applying. In addition, at the end of the compost process, the concentration of NH4-N should be lower than that of NO3-N. As mentioned above, NH4-N positively correlated with the moisture content in the summer chicken manure and alkalinity in the winter chicken manure. Therefore, the NH4-N concentration may be decreased by reducing the moisture content in the summer chicken manure and alkalinity in the winter chicken manure.
4. Conclusions
The alkalinity content and COD concentration in winter chicken manure were higher than those of the summer chicken manure. In the summer chicken manure, no correlations were observed between alkalinity and almost all other parameters; TOC was correlated with the other parameters except for NO3-N, while COD was correlated with the C/N ratio. In the winter chicken manure, a significant, negative correlation was observed between alkalinity and the C/N ratio but positively correlated with NH4-N and T-N. The moisture content of the summer manure was positively correlated with almost all of the other parameters, while it was negatively correlated with almost all of the other parameters in the winter season. According to the criterion of the C/N ratio, chicken manure from farms in South Korea indicated the potential for good quality compost. However, the composted chicken manure was immature and unstable when considering the criteria of the NH4-N/NO3-N ratio and the NH4-N concentration.