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Effects of black soldier fly larvae (Diptera: Stratiomyidae) on food waste and sewage sludge composting
Journal of Environmental Management 256 (2020) 109967
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Journal of Environmental Management journal homepage: http://www.elsevier.com/locate/jenvman
Research article
Effects of black soldier fly larvae (Diptera: Stratiomyidae) on food waste and sewage sludge composting Tao Liu 1, Mukesh Kumar Awasthi **, 1, Sanjeev Kumar Awasthi, Yumin Duan, Zengqiang Zhang * College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province, 712100, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords: Black soldier fly larvae Nitrogen Food waste Sewage sludge Compost
With the rapid development of the economy and population, the improvement of life level, enormous organic wastes have been generated. Black soldier fly larvae (BSFL) treatment is an attractive management method as it provides a strategy for waste treatment while also generate biofertilizers. The aim of this study was to evaluate the BSFL processing residue quality through the physical and chemical parameters. The sewage sludge (T1) and food waste (T2) were employed with BSFL (7:1.2 ration on fresh weight basis) and without BSFL T3 and T4 was marked control and composted for 9 days. The results showed that the BSFL composting reduced the organic matter by 14.51–21.98% and the accumulation of volatile fatty acids by 10.12–28.50%. While BSFL composting greatly increased total kjeldahl nitrogen by 23.15% compared with T4, T1 remained essentially unchanged. The additive of BSFL was significantly increased the total phosphorous and potassium in T2, but T1 remained stable compared with control. These results showed that the BSFL could improve the quality of end product and promote the food waste degradation. The current study indicates that the BSFL management provides an envi ronmentally relevant alternative with very convenience in food waste. Further research should focus on residue sanitation.
1. Introduction According to the previously reported by Wang and Zeng (2017), account for 20–45% part of total municipal solid waste is food waste (FW) in Asia and European countries. It is one of the major issues to treat the FW in word, because most of the human behaviors, tremendous quantity of food wasted, resulting in serious problems of both revenue loss and environmental (Awasthi et al., 2017a). In addition, about over 40 million tons sewage sludge (SS) generated yearly from different kinds of waste water treatment plants in China. As a common practice, the ultimate destination of FW and SS was either management by direct landfills, composting or incineration (Cerda et al., 2018). The UN Food and Agriculture Organization (FAO) predicts that approximately 1.3 billion tons of food is generated each year, one-third of all food wasted for human consumption (FAO, 2011), which causes the losses of natural resources. In order to enhance sustainability and resources utilization, not only controlling the wastes of food but also transformation of FW to valuable products (Chen et al., 2019b). Mean while, SS inevitable by-product of waste water treatment plants and
cause potential environmental issue in many areas which could be due to the increasing of population and the quick rate of urbanization (Syed- Hassan et al., 2017). While composting and waste to resource by incineration are considered significantly processes for the circular management of FW and SS, the all of these methods have some potential risks of environmental (Awasthi et al., 2018). Various approaches have been effectively addressed to sustainable recycling of vast waste stream and mitigate the negative environmental and economic impacts. About the kinds of selections, this investigation pay attention to one of the more innovative biowaste recycling selections, where biowaste is fed to insect larvae - in this condition the larvae of the black soldier fly (BSF). One species of BSF, Hermetia illucens, is triggered more and more interesting after the first introduction in the 1990s (Mertenat et al., 2019). The eggs lay near food source and hatch in about 4 days and then experience the larval stage 14 days which include 5 instars, and then the BSFL is pupal and adult stage. The BSF average life cycle is 41–43 days in tropic, and the larval and prepupal stages can be extended considerably to accommodate food availability and other conditions. One reason is that, there is the ability of prodigious to consume large amounts of
* Corresponding author. ** Corresponding author. College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province, 712100, PR China. E-mail addresses: [email protected] (M.K. Awasthi), [email protected] (Z. Zhang). 1 Equally contributed by both authors in this article. https://doi.org/10.1016/j.jenvman.2019.109967 Received 16 September 2019; Received in revised form 5 December 2019; Accepted 5 December 2019 Available online 13 December 2019 0301-4797/© 2019 Elsevier Ltd. All rights reserved.
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Journal of Environmental Management 256 (2020) 109967
Table 1 Characteristics of artificial food waste in this study (dry weigh basis).
Table 2 Characteristics of composting materials used in this study.
Parameters
Noodle
Rice
Cabbage
Pork
Parameters
Sewage sludge
Food waste
Total organic carbon (%) Total nitrogen (%) Moisture content (%)
50.3 2.34 30.1
53.2 1.2 66.3
39.8 2.61 95.5
48.3 3.92 64.1
Moisture content (%) pH EC (μS/cm) DOC (g/kg) OM (%) TKN (g/kg) TP (g/kg) TK (g/kg) C/N ratio
86.12 � 0.03 6.86 � 0.02 163.7 � 19.7 0.476 � 0.16 58.69 � 0.20 20.27 � 0.56 9.30 � 0.36 3.69 � 0.17 16.43 � 0.98
83.35 � 0.44 7.05 � 0.04 217.0 � 57.78 22.98 � 0.60 99.08 � 0.22 26.82 � 0.20 1.30 � 0.27 1.61 � 0.09 20.96 � 1.01
organic waste and have been known very well. One novel process of restricting organic materials is by black soldier fly larvae (BSFL) com posting, which organic materials are transformed into larvae biomass and compost (Cickova et al., 2015). There are abundant of fat and protein in larvae biomass which can be feed animals as a protein source, while the compost could be utilized in the field as biofertilizer (Katon gole et al., 2011; Lalander et al., 2015). Diner et al. (2011) has been reported that BSFL consumed and degraded a large of organic waste to degradation up to 70%. BSFL processing is a new-style biowaste recycle technology and can convert into marketable valuable products that can conduce towards sustainable and financially. Lalander et al. (2018a) reported that the added BSFL into FW and faces, which assessed the product-value potential in four process stra tegies, and indicated that BSF treatments are similar to the most economically favorable projects. Lalander et al. (2015) proved that there is high waste of biomass transformation and efficient Salmonella spp. reduction employing of BSFL for pig manure, dog food and human feces. Rehman et al. (2017a) investigated that convert from dairy manure and soybean curd residue, which assess the demands of larvae survival rate and organic matter reduction in six treatments. Following, making organic waste with a similar protein/carbohydrate concentration, bal ance in different variations of carbohydrates has the potential to improve the process performance (Gold et al., 2018). For the more traditional treatments methods such as composting or anaerobic diges tion this message is well to determine and simplified technologies which are available under the clean development mechanism framework. Meanwhile, limited investigation on the characteristics of final bio-organic fertilizer which the BSFL bioconverted the FW and SS composting, which is not only improving the quality of composting, but also promote the composting process. However, not much investigation has done about the influence of BSFL for various kinds of organic waste composting. Presently, no reports have been conducted on the BSFL processing FW and SS as an innovative biofertilizers. Both FW and SS come from people life directly and its significantly content high moisture (about 85%), which is favorable condition for BSF growth and multi plication as well as rapid degradation of present organic matter in the source of FW and SS. Therefore, it is necessary to explore the impact of BSFL for FW and SS, and research the process of residue bioconversion into fertilizers. Based on this current investigation, the main objective was therefor to evaluate the ability of BSFL on the bioconversion FW and SS through the ultimate processing residue under the performance of physico chemical properties. In addition, we tried to find the changes of corre lation between analyzed parameters in FW and SS composting by the employed of BSFL.
EC - Electrical conductivity, DOC - Dissolved organic carbon, OM - Organic matter, TKN -Total Kjeldahl nitrogen, TP - Total Phosphorous, TK - Total po tassium. Results are the average of three repeats � standard deviation. Table 3 The survival rate of BSFL during the composting. Materials
Survival rate (%)
Food waste Sewage sludge
90.15 � 0.5 46.65 � 4.4
Table 4 Characteristics of final products in this investigation. Parameters
Sewage sludge þ BSFL
Food waste þ BSFL
Sewage sludge
Food waste
Moisture content (%) pH
75.32 � 0.19
62.99 � 0.42
7.93 � 0.09
7.36 � 0.04
76.39 � 0.29 7.21 � 0.06
EC (μS/cm)
364.2 � 10.1
109.8 � 3.9
DOC (g/kg)
1.09 � 0.35
3510 � 57.78 12.51 � 0.94
OM (%)
46.98 � 0.60
88.69 � 1.28
TKN (g/kg)
19.94 � 1.60
31.20 � 0.77
TP(g/kg)
11.06 � 0.07
11.39 � 0.76
TK(g/kg)
5.14 � 0.03
8.37 � 0.26
52.40 � 0.18 19.49 � 1.09 11.39 � 1.09 3.69 � 0.18
GI
49.86 � 1.26
82.04 � 2.39
C/N ratio
13.67 � 1.28
16.50 � 0.98
70.39 � 0.13 3.33 � 0.09 317.0 � 11.11 32.02 � 0.74 99.36 � 0.49 19.70 � 1.23 0.39 � 0.07 0.82 � 0.02 30.75 � 0.99 29.27 � 1.13
0.34 � 0.12
47.59 � 3.18 15.60 � 1.02
EC - Electrical conductivity, DOC - Dissolved organic carbon, OM - Organic matter, TKN -Total Kjeldahl nitrogen, TP - Total Phosphorous, TK - Total po tassium, GI- germination index. Results are the average of three repeats � standard deviation.
with chicken feed, and then isolated by a sieve (2.00 mm). In order to get the optimized environment, we implement the experience in the under room which the temperature was 29 � C and the humidity was 52%.
2. Materials and methods
2.2. Black soldier fly larvae composting design
2.1. Materials collection and processing
Four of [49 (length) cm � 32 (width) cm � 14.5 (height)] opened containers which could place 7.0 kg raw materials were selected to perform this investigation and put in the room. The SS and FW were placed in a different container which named T1 and T2, respectively, and amendment with BSFL 1.2 kg (7:1.2 ration on fresh weight basis), as the treatment group. Without BSFL was named T3 (SS) and T4 (FW), as the control group. The experiment was done in triplicate. The com posting was mixed properly to the collection on 1, 3, 5, 7 and 9 days, and turn the mixture for supplying BSFL air every day. Weighting the sam ples 100 g (only the residue) from each container using small spoon, and
The SS was collected by Huayu Environmental protection water quality Cooperation Limited (Yangling, Shannxi Province, China). Ac cording to the report, the synthetic FW was ready for mixing 5.13 kg noodles, 3.95 kg rice, 3.95 kg cabbage and 1.97 kg pork in the ration of 13:10:10:5 (Wong et al., 2009), and characteristics of artificial food waste in this study were showed in Table 1. BSFL was provided by Xinyi Ecological Agriculture Technology Development Cooperation Limited (Yangling, Shanxi Province, China), and the first 6 days the BSFL was fed 2
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Journal of Environmental Management 256 (2020) 109967
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7
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n-pentanoic acid isobutyric acid
Fig. 1. The change of pH (a) and variation of VFAs (b–e) during the composting in all treatments. T1: sewage sludge þ BSFL; T2: food waste þ BSFL; T3: sewage sledge; T4: food waste.
then air dried. On the day 9, when the BSFL was ready for experience of the stage of prepupae, and then sieved them from the residue of com posting which means the experiment ended (Rehman et al., 2019). The survival of BSFL during the composting was shown in Table 3. The characteristics of raw materials and final products were listed in Tables 2 and 4, respectively.
2.3. Analytical methods The moisture content, pH, electrical conductivity (EC), dissolved organic carbon (DOC), NHþ 4 -N, NO3 -N, and germination index (GI) were determined by TMECC, (2002). To analyze the NHþ 4 -N and NO3 -N, samples were extracted with 20 mL 2 mol/L KCl (solid: extractant, 1:10 3
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Journal of Environmental Management 256 (2020) 109967
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35 30 25
DOC (g/kg)
20 15
2 1 0
0
1200
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+ NH4 -N (mg/kg)
900 750 600 450 300 150 0
0
28
(c)
24
NO3 -N (mg/kg)
20
12
8 0
2
T1
4 Time (d) 6 T3 T2
Fig. 2. The change of DOC (a), NHþ 4 -N (b) and NO3 -N (c) from different treatments during composting. T1: sewage sludge þ BSFL; T2: food waste þ BSFL; T3: sewage sledge; T4: food waste. Values are the average of three repeats and error bars indicates the standard deviation.
4
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Journal of Environmental Management 256 (2020) 109967
(m/v)) using a shaker at 180 rpm for 2 h followed by the filtration with 0.45 μm nylon syringe filter by employing of automated analyzer (Auto Analyzer 3-AA3, Germany). DOC content was determined by fresh samples were extracted at room temperature with ultra-pure water at ration 1:10 (w/v) adopting a shaker at 180 rpm for 24 h, and then filtration with 0.45 μm nylon syringe filter by the implemented of automated total organic carbon (TOC) analyzer (TOC-LCPH, Shimadzu, Japan). The VFAs were determined by fresh samples that were extracted with ultra-pure water at a ratio of 1:5 (w/v), placed in a shaker at 1 h, and then filtered with 0.22 μm nylon syringe filter from a Shimadzu GC-2014 gas chomatograph (Japan) (Yang and Choong, 2001). The parameters of total Kjeldahl nitrogen (TKN), total phosphorous (TP), total potassium (TK) and organic matter (OM) were determined by air-dried samples (TMECC, 2002). For TKN, TP and TK determination, 0.5 g dried and sieved samples were digested with 10 mL H2SO4, 1 mL HClO4, and TKN was determined by Kjeldahl apparatus (KDY-9820), TP was determined by Molybdenum-antimony colorimetric method (TMECC, 2002). The value of OM was determined by cremating of samples at 550 � C for 24 h in a muffle furnace (Lu et al., 2009).
during the beginning of composting, which the high moisture content may be created an anaerobic environment for the processing. With the addition of BSFL, the value of VFAs was reduced, T1 decreased from 1.57 to 1.41 g/kg, and T2 from 2.06 to 1.48 g/kg, which could be attributed to the VFAs as a carbon source for the BSFL and native microbial sur vival. The trend of VFAs concentration in the T1 and T2 follows a similar result by the previous reports (Liu et al., 2019; Awasthi et al., 2018). There are no strict requirements on the kinds of carbon source for waste disposition, like acetic and propionate acid have been appointed as the best carbon source (Oehmen et al., 2004). However, the T4 was increased from 1.76 to 2.30 g/kg, which because there is a high con centration of carbohydrates and provide acidic surroundings, resulting in the accumulation of VFAs. 3.2. Evaluation of DOC, NHþ 4 -N and NO3 -N during composting The changes of DOC during the composting are shown in Fig. 2a. The DOC plays a key role in all parameters which indicate the rate of com posting process and microbial activities (Awasthi et al., 2017b). Actu ally, the elevated decomposition of complex organic compounds in raw materials generated water-soluble molecules (DOC). The beginning DOC values varied in all treatments due to the different feed stocks. From the early of composting, the DOC contents in BSFL treatments increased from their levels in the raw materials to those recorded on day 3, from 1.47 to 2.26 (g/kg) in T1 and 22.98 to 24.41 (g/kg) in T2. The relevant levels (g/kg) at the end of process were 1.09 (T1), 12.51 (T2), 0.34 (T3) and 32.02 (T4). In addition, the reduced rate was 23.57, 43.59 and 28.57% in T1, T2 and T3, respectively, but the T4 was increased. However, employing of BSFL in SS was not the great influence of degradation of DOC, the reduction value of T1 was similar to the T3. The microbes utilized DOC as their energy source which could be due to the DOC decreased (Waqas et al., 2019). Meanwhile, it should be noticed, which the present investigation was BSFL treatments, which are entirely different from sawdust or biochar utilized by Diner et al. (2011), who observed a continuous DOC decreased throughout the composting. The DOC value gradually declined in BSFL treatments and the lowest DOC value was observed at the end of the composting, because of the reduced of organic carbon in the atmosphere as CO2 and the utilized of carbon as BSFL growth and survival (Rehman et al., 2017b; Awasthi et al., 2016a). Waqas et al. (2019) also reported that carbon reduction was considered an essential parameter of compost maturity. As is shown in Fig. 2b, the concentration of NHþ 4 -N elevated sharply in BSFL amended FW from the initial of composting, and attained the peak values in T1 and T2 on day 5 (438.8 mg/kg) and (1001 mg/kg), and then slowly decreased until the finish of composting due to the trans formation of NHþ 4 -N into NH3 and afterwards by its evaporation under high pH condition. Wang et al. (2018) also reported that the ammonium was generated attributed to the early disruption of the nitrogenous compounds during the beginning phase of FW degradation. The addition of BSFL into the FW compost swiftly reduced NH3 volatilization and led to accelerating in NHþ 4 -N concentrations at the starting of composting. The high value NHþ 4 -N content might be due to the low pH in FW, which promotes the conversion of NH3 into NHþ 4 -N (Pan et al., 2018). The trend of T1 was mainly due to the organic degradation and ammonification, meanwhile BSFL did not promote conversion of inorganic nitrogen to nitrate and nitrite (Awasthi et al., 2016b). The loss of NHþ 4 -N was revealed the rapid mineralization of OM and ammonification during the bio-oxidative stage of composting (Awasthi et al., 2016b). In contrast, the trend of control group was stable, which could be attributed to the without BSFL employing and the environment inhibits the native microorganism. At the end of composting, The concentration of T2 was beyond the permissible value (400 mg/kg), suggesting that the bio fertilizer was still unstable and needed to degradation. It revealed that the value of NO3 -N content was absent of all treat ments during the composting process (Fig. 2c). This result was different from the previous report during the latter phase of the composting,
2.4. Statistical analysis All the statistics were replicated three times and determined to analysis of variance (ANOVA) test (p < 0.05), and the figures were drawn by origin 2016 (Origin Lab, America). The correlation analysis among statistics was determined by the software Canoco for windows (Version 5), and the redundancy analysis (RDA) figures. 3. Results and discussions 3.1. Evaluation of pH and VFAs during the composting The changes of pH during the initial composting mainly depend on the chemical properties of raw material (Sharma and Garg, 2018). Fig. 1a, the values of pH were 7.33 and 6.86 in T1 and T3 during the initial stage. The pH values could be due to the performance of the SS (pH 6.8) (Zhang et al., 2014). In addition, the values of pH were 5.95 and 5.07 in T2 and T4, which could be attributed to the rapid decomposition of FW leads to the release of quantities of heat, and then increase the acidification rate (Wang et al., 2018). The pH in the whole process was decreased in T4, but the T2 attained to its minimum value 5.78 on day 3 while a highest value 7.36 reached on day 9. The decreased of pH which could be due to the organic acids generated by the microbial reaction (He et al., 2018). From day 3–9, the value of pH increased and attained the alkaline, which could be due to the employing of BSFL. The BSFL could utilize the VFAs as a carbon source and worked with the native microbial, resulting in the concentration of VFAs decreased (Fig. 1b–e) and the pH increased (Liu et al., 2019). The high concentration of car bohydrates in FW, caused the value of pH reduced in T4 (Awasthi et al., 2017a), decreased from 5.07 to 3.33. Compared with T2, the changes of pH were not obvious in the treatment T1 which increased from 7.33 to 7.93. This was due to the substrate of SS had not created the optimized environment for growth and survival of BSFL. Hence, the activity of BSFL didn’t contribute very much to the pH during the SS composting. During the BSFL composting, VFAs were considered to be prime producing odors (Sundberg et al., 2013). As is shown in Fig. 1b–e, VFAs are mainly composed of acetic, propionate, iso-butyrate, n-butyrate, iso-valerate and n-pentanoic acid, and organic acids play a key role in the VFAs utilization (Fang et al., 2016). During the initial phase, the peak value was 1.67, 2.26 and 1.82 g/kg in T1, T2 and T3, respectively, but the T4 reached the maximum on the last day. The activity of BSFL caused the rising temperature, the concentration of VFAs was increased that indicated the degradation of easily OM but the increased of VFAs would bring about the microbial activities and the biodegradation bar riers (Awasthi et al., 2018). The accumulation of VFAs could be due to the high moisture value (above 80%) of the substrate of SS and FW 5
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Journal of Environmental Management 256 (2020) 109967
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Total Kjeldahl nitrogen (g/kg)
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90 80 70 60
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32
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6
4
2
2 0
(b)
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2
4 Time (d) 6
8
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2
T1
4 Time (d) 6 T2 T3
Fig. 3. Organic matter (a), total Kjeldahl nitrogen (b), total phosphorous (c) and total potassium (d) from different treatments during composting. T1: sewage sludge þ BSFL; T2: food waste þ BSFL; T3: sewage sledge; T4: food waste. Values are the average of three repeats and error bars indicates the standard deviation.
which was due to the nitrification process because the temperature in the container was below 40 � C which was comfortable for nitrifying bacteria (Yu et al., 2019). The NHþ 4 -N would be converted into NO3 -N with the assistance the nitrifying microbes. The temperature of this investigation was under room temperature, so that the effect of tem perature on nitrifying bacteria should be ignored. Therefore, the con centration of NO3 -N was lower than the biochar amended biosolids co-composting (Awasthi et al., 2017c; Waqas et al., 2018) and the modified bentonite amended chicken manure composting (Ren et al., 2018), which could be attributed to the addition of BSFL. Meanwhile, the concentration of NO3 -N was 21.96, 8.92, 24.98 and 8.51 mg/kg in T1, T2, T3 and T4, respectively at the finish of composting. It advised that BSFL provided an unfavorable micro-environment for nitrifying process and inhibit the N conversion from NHþ 4 -N to NO3 -N.
The similar results were also reported by Rehman et al. (2017a), who added BSFL and soybean into dairy manure composting. The results for OM reduced tendency are in accordance with the previous reports which also showed reduction in OM after BSFL composting of different vari eties of organic waste. Lalander et al. (2018b) reported the similar re sults that the BSFL was not sensitive with SS. The OM reduction may be attributed to the easily of OM transformation into VFAs during the early time, and it was used by BSFL as feed (Mertenat et al., 2019). Loss of carbon in the form of CO2 by respiration is charge of OM reduction. OM degradation can be seen as a parameter of feed stock and its trans formation into stabilized product (Sharma and Garg, 2018). As is shown in Fig. 3b, TKN content reduced in the feed stock’s of FW but the difference between BSFL treatments and control group, which could be due to the growth and survival of BSFL. However, the T2 was elevated sharply, increased from 26.86 to 31.96 g/kg after day 3 until day 7. It is because of the significant organic degradation and the composting weight is reduced and the elevated mainly as the mass concentration effect (Zhu et al., 2019). The concentration of TKN in the BSFL compost was T1 (19.94 g/kg) and T2 (30.20 g/kg) which was 5.14% and 5.03% lower than the initial nitrogen content was 21.02 and 31.80 g/kg. The similar tendency was reported by Lalander et al. (2018a), who added BSFL into FW and SS composting. Meanwhile,
3.3. Evaluation of OM, TKN, TP and TK during composting OM decreased after processing in all containers, however degree of OM reduction was different among treatments (Fig. 3a). OM reduction, as compared to initial level, was in the sequence: T2 (21.99%) > T1 (14.51%) > T3 (10.72%) > T4 (0.72%). It was showed that in T1 and T2 have higher percentage which could be due to the employing of BSFL. 6
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TP showed an uphill tendency in all treatments, except T4 (Fig. 3c). Increase in TP content was from 8.37 to 11.06 g/kg, from 1.50 to 11.39 g/kg and from 9.30 to 10.39 g/kg in T1, T2 and T3, respectively. During the composting, there is significantly difference between the substrate of FW in T2 and T4. On the day 9, the TP content of T2 was 11.39 and the control was 1.14. The tendency of T2 was dramatic which was increased sharply. Meanwhile, TK also showed an upward tendency in all treat ments, except T4 (Fig. 3d). The TK was increased from 4.86 to 5.99 g/kg, from 1.96 to 8.37 g/kg and from 3.6 to 3.79 g/kg in T1, T2 and T3, respectively. On the day 9, the TK content of T2 was 8.37 and the control was 0.82. The tendency of T2 was greatly increase. However, these re sults were opposite with the reported by Rehman et al. (2017b), which could be due to the gap of raw materials and the approaches feed. The majority increased in rate was observed in TP and TK during the BSFL FW composting, which may be due to the employing of BSFL accelera tion of the reduction in mass and degradation of organic compounds. To the contrary, the same situation was observed in control group and T1 which the concentration of TP and TK was nearly unchanged.
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4000
(b)
3.4. Evaluation of maturity parameters during composting As shown in Fig. 4a, the reduction of moisture content showed the entire time. The T1 deceased from 86.09 to 75.32%, T2 from 81.35 to 62.99%. The result of T2 was different from the reported by Kumar et al. (2018), who investigated the effect of moisture content of FW on res idue, if the initial of moisture value was 80%, the moisture of residue will not decrease. The reason why is that the experiment was carried out indoors and without mechanical aeration. Another reason is that, the BSFL significantly influence the characteristic of composting, resulting in the porosity enhanced and the evaporation of water fast (Banks, 2014). At the end of composting, moisture content of BSFL treatments was lower than the control group. However, the similar situation was found in the other parameters, which the tendency of T1 was not dramatic. Compost with suitable EC release soluble salts and pose activity ef fect on plant growth and yield. Generally, the value of EC should be less than 4000 μS/cm for the purpose of safety to use (Li et al., 2012). Fig. 4b showed the value of T2 increased greatly during the composting, increased from 587 to 3510 μS/cm, which could be attributed to the employing of BSFL. The final product EC value was lower than 4000 μS/cm, which means safely employed to soil (Chen et al., 2019a). During the composting, it is unavoidable that the BSFL could accelerate the process of degradation of organic compounds, resulting in the concen tration of soluble salts was increased (Chan et al., 2016). While employing of BSFL in T1, the T1 was stable, which the phenomenon was similar to the T3 and T4. The results showed that added the BSFL into SS was not accelerated the degradation of OM. During at the end of com posting, the value of EC was 364.5, 3510, 109.8 and 317 μS/cm in T1, T2, T3 and T4, respectively. The compost product of seed germination can not only evaluate the pyhtotoxic substance but also have a better relation with degree of compost maturity. GI is the most conventional represented parameters to assess the toxicity level of ultimate compost. Commonly, if the GI was higher 80%, the compost is indicated to be mature and safe to use (TMECC, 2002). Possibility reasons were that the decrease EC and degradation of toxic substance like organic acids and NHþ 4 -N concen tration (Wang et al., 2019). During the end of compost, the GI was 49.86%, 82.04%, 47.59% and 30.75% in T1, T2, T3 and T4 respectively (Fig. 4c). This result was evidenced that only the ultimate compost product of T2 was mature, suitable to the plant. Meanwhile, the sub strate of FW employed with BSFL had a positive effect on GI. However, employing of BSFL in T1 which the value of GI was lower 80%, considered added the BSFL into SS was negative effect on GI value. It may be due to the BSFL addition which could accelerate the decompo sition of OM in FW, which could moderate the toxicity during the FW composting.
EC ( S/cm)
3000
2000
1000
0
0
2
4 Time (d) 6
T1
100
T2
T3
8
10
T4
(c)
Germination index (%)
80
60
40
20
0
T1
T2
Treatments
T3
T4
Fig. 4. The change of moisture (a), electrical conductivity (b) and germination index (c) during the composting process of all treatments. T1: sewage sludge þ BSFL; T2: food waste þ BSFL; T3: sewage sledge; T4: food waste. Values are the average of three repeats and error bars indicates the standard deviation.
treatments amended without BSFL are expected to lose the nitrogen concentration in the final compost because of ammonium absence. The concentration of TKN decreased was attributable to the conversion of NHþ 4 -N to NO3 -N by nitrogen bacterial, NH3 emission loss and the sta bilization of compost mass (Chen et al., 2019a). However, the trend of T1 was stable which could be due to the BSFL was not sensitive to SS. 7
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Journal of Environmental Management 256 (2020) 109967
into biofertilizers, but it was not effective for SS recycling. In addition, it can be said that there is significant difference between T1 and T2. Among all the treatments, the highest TKN, TP, TK and GI were observed in FW treatments. Meanwhile, the decreased rate of OM and moisture also was found highest in FW treatments. The trend of all parameters was stable in SS treatments compared the FW group. The study demonstrated that added BSFL into FW both enhanced the total nutrient and reduced the C/N ratio compared the control group. At the ultimate of BSFL - FW processing, the range of pH (5.5–8.5) and EC (<4000 μS/ cm) was more suitable agricultural fields and potting. Though the comprehensive of initial parameters, the concentration of DOC was 0.476 g/kg in SS which be unable to provide the enough carbon source to utilize by BSFL. BSFL bioconversion could not only perform a valuable function in the form of FW management, but also generate a valuable product in the form of biofertilizer. Acknowledgements The authors are grateful for the financial support from Research Fund for International Young Scientists from National Natural Science Foundation of China (Grant No. 31750110469), China, Shaanxi Intro duced Talent Research Funding (A279021901) and The Introduction of Talent Research Start-up fund (No. Z101021904), College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China. We are also thankful to all our labo ratory colleagues and research staff members for their constructive advice and help.
Fig. 5. Correlation analysis during the composting process of all treatments. T1: sewage sludge þ BSFL; T2: food waste þ BSFL; T3: sewage sledge; T4: food waste.
As shown in Table 4, the BSFL additive could promote the degra dation of OM in T2 compared with T1. During the FW composting, the value of pH and EC were huge difference which because employing of BSFL, and the range of pH and EC are suitable for plants. While employed of BSFL could reduce the TKN compared the initial feed stock’s, the concentration of TKN was higher than the group of without BSFL at the end of composting. At the end of FW - BSFL composting, the concentration of TP and TK were increased significantly which could be due to the reduced of the mass. However, the BSFL - SS system was not obviously changed at the ultimate compost.
References Awasthi, M.K., Awasthi, S.K., Wang, Q., Wang, Z., Lahori, A.H., Ren, X., Chen, H., Wang, M., Zhao, J., Zhang, Z., 2018. Influence of biochar on volatile fatty acids accumulation and microbial community succession during biosolids composting. Bioresour. Technol. 251, 158–164. Awasthi, M.K., Selvam, A., Lai, K.M., Wong, J.W.C., 2017. Critical evaluation of postconsumption food waste composting employing thermophilic bacterial consortium. Bioresour. Technol. 245, 665–672. Awasthi, M.K., Wang, M., Pandey, A.K., Chen, H., Awasthi, S.K., Wang, Q., Ren, X., Lahori, A.H., Li, D., Li, R., Zhang, Z., 2017. Heterogeneity of zeolite combined with biochar properties as a function of sewage sludge composting and production of nutrient-rich compost. Waste Manag. 68, 760–773. Awasthi, M.K., Wang, Q., Chen, H., Wang, M., Ren, X., Zhao, J., Li, J., Guo, D., Li, D., Awasthi, S.K., Sun, X., Zhang, Z., 2017. Evaluation of biochar amended biosolids cocomposting to improve the nutrient transformation and its correlation as a function for the production of nutrient-rich compost. Bioresour. Technol. 237, 156–166. Awasthi, M.K., Pandey, A.K., Bundela, P.S., Wong, J.W.C., Li, R., Zhang, Z., 2016. Cocomposting of gelatin industry sludge combined with organic fraction of municipal solid waste and poultry waste employing zeolite mixed with enriched nitrifying bacterial consortium. Bioresour. Technol. 213, 181–189. Awasthi, M.K., Wang, Q., Ren, X., Zhao, J., Huang, H., Awasthi, S.K., Lahori, A.H., Li, R., Zhou, L., Zhang, Z., 2016. Role of biochar amendment in mitigation of nitrogen loss and greenhouse gas emission during sewage sludge composting. Bioresour. Technol. 219, 270–280. Banks, I.J., 2014. To Assess the Impact of Black Soldier Fly (Hermetia illucens) Larvae on Faecal Reduction in Pit Latrines Dissertation. London School of Hygiene & Tropical Medicine. Cerda, A., Artola, A., Font, X., Barrena, R., Gea, T., S� anchez, A., 2018. Composting of food wastes: status and challenges. Bioresour. Technol. 248, 57–67. Chan, M.T., Selvam, A., Wong, J.W.C., 2016. Reducing nitrogen loss and salinity during ‘struvite’ food waste composting by zeolite amendment. Bioresour. Technol. 200, 838–844. Chen, J., Hou, D., Pang, W., Nowar, E.E., Tomberlin, J.K., Hu, R., Chen, H., Xie, J., Zhang, J., Yu, Z., Li, Q., 2019. Effect of moisture content on greenhouse gas and NH3 emissions from pig manure converted by black soldier fly. Sci. Total Environ. 697, 133840. Chen, X., Zhao, Y., Zeng, C., Li, Y., Zhu, L., Wu, J., Chen, J., Wei, Z., 2019. Assessment contributions of physicochemical properties and bacterial community to mitigate the bioavailability of heavy metals during composting based on structural equation models. Bioresour. Technol. 289, 121657. Cickova, H., Newton, G.L., Lacy, R.C., Kozanek, M., 2015. The use of fly larvae for organic waste treatment. Waste Manag. 35, 68–80. Diner, S., Studl-Solano, N., Guti� errez, F., Zurbrügg, C., Tochner, K., 2011. Biological treatment of municipal organic waste using black soldier fly larvae. Waste Biomass Valori 2, 357–363. Fang, W., Zhang, P., Gou, X., Zhang, H., Wu, Y., Ye, J., Zeng, G., 2016. Volatile fatty acid production from spent mushroom compost: effect of total solid content. Int. Biodeterior. Biodegrad. 113, 217–221.
3.5. Relationship among environmental factors RDA was demonstrated to compare the physico-chemical and VFAs content in all of the treatments. The RDA reveled that added BSFL into FW had the greatly value of 77.59%, but the value of T1 was lower than the T3 (Fig. 5). These results were considered that employing of BSFL made the correlation significantly during the FW composting. There was positive correlation between GI, TP, TK, EC, and pH in the BSFL systems. This investigation was similar to the previous reported, which also concluded that NHþ 4 -N, VFAs, OM and DOC were negative with GI (Ren et al., 2018). The RDA was obviously indicated that all the parameters and OM have close correlation consist with Awasthi et al. (2016b). Many reports showed between the concentration of DOC, OM and the ultimate of compost maturity, and the degradation of DOC and OM represented the mature of compost (Zhou et al., 2013). At the end of the FW com posting, the concentration of TKN was not decreased obviously which could be due to the residue of mass decreased significantly, and caused the content of concentrate. This result was opposite with the report Rehman et al. (2017a). Meanwhile, the RDA also support that the cor relation between GI and TKN showed the positive relative in T2. The amendment of composting was able to enhance the degradation of FW compared the control. The positive correlation of the RDA represents that the BSFL composting system is suitable and end product stable as well as well mature for organic farming purposes. 4. Conclusion BSFL could achieve utilized and recycle the FW which conversion FW 8
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Journal of Environmental Management 256 (2020) 109967 digestion of dairy manure and chicken manure by mini-livestock (Hermetia illucens, L.). J. Environ. Manag. 196, 458–465. Ren, X., Awasthi, M.K., Wang, Q., Zhao, J., Li, R., Tu, Z., Chen, H., Awasthi, S.K., Zhang, Z., 2018. New insight of tertiary-amine modified bentonite amendment on the nitrogen transformation and volatile fatty acids during the chicken manure composting. Bioresour. Technol. 266, 524–531. Sharma, K., Garg, V.K., 2018. Comparative analysis of vermin-compost quality produced from rice straw and paper waste employing earthworm Eisenia fetida, (sav.). Bioresour. Technol. 250, 708–715. Sundberg, C., Yu, D., Franke-Whittle, I., Kauppi, S., Smårs, S., Insam, H., Romantschuk, M., J€ onsson, H., 2013. Effects of pH and microbial composition on odour in food waste composting. Waste Manag. 33, 204–211. Syed-Hassan, S.S.A., Wang, Y., Hu, S., Su, S., Xiang, J., 2017. Thermochemical processing of sewage sludge to energy and fuel: fundamentals, challenges and considerations. Renew. Sustain. Energy Rev. 80, 888–913. TMECC, 2002. Test methods for the examination of composts and composting). In: Thompson, W., Leege, P., Millner, P., Watson, M.E. (Eds.), The US Composting Council. US Government Printing Office. http://tmecc.org/tmecc/index.html. Wang, X., Zheng, G., Chen, T., Shi, X., Wang, Y., Nie, E., Liu, J., 2019. Effect of phosphate amendments on improving the fertilizer efficiency and reducing the mobility of heavy metals during sewage sludge composting. J. Environ. Manag. 235, 124–132. Wang, X., Selvam, A., Lau, S.S.S., Wong, J.W.C., 2018. Influence of lime and struvite on microbial community succession and odour emission during food waste composting. Bioresour. Technol. 247, 652–659. Wang, S., Zeng, Y., 2017. Ammonia emission mitigation in food waste composting: a review. Bioresour. Technol. 248, 13–19. Waqas, M., Nizami, A.S., Aburiazaiza, A.S., Barakat, M.A., Asam, Z.Z., Khattak, B., Rashid, M.I., 2019. Untapped potential of zeolites in optimization of food waste composting. J. Environ. Manag. 241, 99–112. Waqas, M., Nizami, A.S., Aburiazaiza, A.S., Barakat, M.A., Ismail, I.M.I., Rashid, M.I., 2018. Optimization of food waste compost with the use of biochar. J. Environ. Manag. 216, 70–81. Wong, J.W.C., Fung, S.O., Selvam, A., 2009. Coal fly ash and lime addition enhances the rate and efficiency of decomposition of food waste during composting. Bioresour. Technol. 100, 3324–3331. Yu, H., Xi, B., Khan, R., Shen, G., 2019. The changes in carbon, nitrogen components and humic substances during organic-inorganic aerobic co-composting. Bioresour. Technol. 271, 228–235. Yang, M.H., Choong, Y.M., 2001. A rapid gas chromatographic method for direct determination of short-chain (C2 - C12) volatile organic acids in foods. Food Chem. 75, 101–108. Zhou, F., Tomberlin, J.K., Zheng, L., Yu, Z., Zhang, J., 2013. Developmental and waste reduction plasticity of three black soldier fly strains (Diptera: Stratiomyidae) raised on different livestock manures. J. Med. Entomol. 50, 1224–1230. Zhang, J., Lu, F., Shao, L., He, P., 2014. The use of biochar-amended composting to improve the humification and degradation of sewage sludge. Bioresour. Technol. 168, 252–258. Zhu, L., Zhao, Y., Zhang, W., Zhou, H., Chen, X., Wei, D., Wei, Z., 2019. Roles of bacterial community in the transformation of organic nitrogen toward enhanced bioavailability during composting with different wastes. Bioresour. Technol. 285, 121326.
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9
Contents lists available at ScienceDirect
Journal of Environmental Management journal homepage: http://www.elsevier.com/locate/jenvman
Research article
Effects of black soldier fly larvae (Diptera: Stratiomyidae) on food waste and sewage sludge composting Tao Liu 1, Mukesh Kumar Awasthi **, 1, Sanjeev Kumar Awasthi, Yumin Duan, Zengqiang Zhang * College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province, 712100, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords: Black soldier fly larvae Nitrogen Food waste Sewage sludge Compost
With the rapid development of the economy and population, the improvement of life level, enormous organic wastes have been generated. Black soldier fly larvae (BSFL) treatment is an attractive management method as it provides a strategy for waste treatment while also generate biofertilizers. The aim of this study was to evaluate the BSFL processing residue quality through the physical and chemical parameters. The sewage sludge (T1) and food waste (T2) were employed with BSFL (7:1.2 ration on fresh weight basis) and without BSFL T3 and T4 was marked control and composted for 9 days. The results showed that the BSFL composting reduced the organic matter by 14.51–21.98% and the accumulation of volatile fatty acids by 10.12–28.50%. While BSFL composting greatly increased total kjeldahl nitrogen by 23.15% compared with T4, T1 remained essentially unchanged. The additive of BSFL was significantly increased the total phosphorous and potassium in T2, but T1 remained stable compared with control. These results showed that the BSFL could improve the quality of end product and promote the food waste degradation. The current study indicates that the BSFL management provides an envi ronmentally relevant alternative with very convenience in food waste. Further research should focus on residue sanitation.
1. Introduction According to the previously reported by Wang and Zeng (2017), account for 20–45% part of total municipal solid waste is food waste (FW) in Asia and European countries. It is one of the major issues to treat the FW in word, because most of the human behaviors, tremendous quantity of food wasted, resulting in serious problems of both revenue loss and environmental (Awasthi et al., 2017a). In addition, about over 40 million tons sewage sludge (SS) generated yearly from different kinds of waste water treatment plants in China. As a common practice, the ultimate destination of FW and SS was either management by direct landfills, composting or incineration (Cerda et al., 2018). The UN Food and Agriculture Organization (FAO) predicts that approximately 1.3 billion tons of food is generated each year, one-third of all food wasted for human consumption (FAO, 2011), which causes the losses of natural resources. In order to enhance sustainability and resources utilization, not only controlling the wastes of food but also transformation of FW to valuable products (Chen et al., 2019b). Mean while, SS inevitable by-product of waste water treatment plants and
cause potential environmental issue in many areas which could be due to the increasing of population and the quick rate of urbanization (Syed- Hassan et al., 2017). While composting and waste to resource by incineration are considered significantly processes for the circular management of FW and SS, the all of these methods have some potential risks of environmental (Awasthi et al., 2018). Various approaches have been effectively addressed to sustainable recycling of vast waste stream and mitigate the negative environmental and economic impacts. About the kinds of selections, this investigation pay attention to one of the more innovative biowaste recycling selections, where biowaste is fed to insect larvae - in this condition the larvae of the black soldier fly (BSF). One species of BSF, Hermetia illucens, is triggered more and more interesting after the first introduction in the 1990s (Mertenat et al., 2019). The eggs lay near food source and hatch in about 4 days and then experience the larval stage 14 days which include 5 instars, and then the BSFL is pupal and adult stage. The BSF average life cycle is 41–43 days in tropic, and the larval and prepupal stages can be extended considerably to accommodate food availability and other conditions. One reason is that, there is the ability of prodigious to consume large amounts of
* Corresponding author. ** Corresponding author. College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province, 712100, PR China. E-mail addresses: [email protected] (M.K. Awasthi), [email protected] (Z. Zhang). 1 Equally contributed by both authors in this article. https://doi.org/10.1016/j.jenvman.2019.109967 Received 16 September 2019; Received in revised form 5 December 2019; Accepted 5 December 2019 Available online 13 December 2019 0301-4797/© 2019 Elsevier Ltd. All rights reserved.
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Table 1 Characteristics of artificial food waste in this study (dry weigh basis).
Table 2 Characteristics of composting materials used in this study.
Parameters
Noodle
Rice
Cabbage
Pork
Parameters
Sewage sludge
Food waste
Total organic carbon (%) Total nitrogen (%) Moisture content (%)
50.3 2.34 30.1
53.2 1.2 66.3
39.8 2.61 95.5
48.3 3.92 64.1
Moisture content (%) pH EC (μS/cm) DOC (g/kg) OM (%) TKN (g/kg) TP (g/kg) TK (g/kg) C/N ratio
86.12 � 0.03 6.86 � 0.02 163.7 � 19.7 0.476 � 0.16 58.69 � 0.20 20.27 � 0.56 9.30 � 0.36 3.69 � 0.17 16.43 � 0.98
83.35 � 0.44 7.05 � 0.04 217.0 � 57.78 22.98 � 0.60 99.08 � 0.22 26.82 � 0.20 1.30 � 0.27 1.61 � 0.09 20.96 � 1.01
organic waste and have been known very well. One novel process of restricting organic materials is by black soldier fly larvae (BSFL) com posting, which organic materials are transformed into larvae biomass and compost (Cickova et al., 2015). There are abundant of fat and protein in larvae biomass which can be feed animals as a protein source, while the compost could be utilized in the field as biofertilizer (Katon gole et al., 2011; Lalander et al., 2015). Diner et al. (2011) has been reported that BSFL consumed and degraded a large of organic waste to degradation up to 70%. BSFL processing is a new-style biowaste recycle technology and can convert into marketable valuable products that can conduce towards sustainable and financially. Lalander et al. (2018a) reported that the added BSFL into FW and faces, which assessed the product-value potential in four process stra tegies, and indicated that BSF treatments are similar to the most economically favorable projects. Lalander et al. (2015) proved that there is high waste of biomass transformation and efficient Salmonella spp. reduction employing of BSFL for pig manure, dog food and human feces. Rehman et al. (2017a) investigated that convert from dairy manure and soybean curd residue, which assess the demands of larvae survival rate and organic matter reduction in six treatments. Following, making organic waste with a similar protein/carbohydrate concentration, bal ance in different variations of carbohydrates has the potential to improve the process performance (Gold et al., 2018). For the more traditional treatments methods such as composting or anaerobic diges tion this message is well to determine and simplified technologies which are available under the clean development mechanism framework. Meanwhile, limited investigation on the characteristics of final bio-organic fertilizer which the BSFL bioconverted the FW and SS composting, which is not only improving the quality of composting, but also promote the composting process. However, not much investigation has done about the influence of BSFL for various kinds of organic waste composting. Presently, no reports have been conducted on the BSFL processing FW and SS as an innovative biofertilizers. Both FW and SS come from people life directly and its significantly content high moisture (about 85%), which is favorable condition for BSF growth and multi plication as well as rapid degradation of present organic matter in the source of FW and SS. Therefore, it is necessary to explore the impact of BSFL for FW and SS, and research the process of residue bioconversion into fertilizers. Based on this current investigation, the main objective was therefor to evaluate the ability of BSFL on the bioconversion FW and SS through the ultimate processing residue under the performance of physico chemical properties. In addition, we tried to find the changes of corre lation between analyzed parameters in FW and SS composting by the employed of BSFL.
EC - Electrical conductivity, DOC - Dissolved organic carbon, OM - Organic matter, TKN -Total Kjeldahl nitrogen, TP - Total Phosphorous, TK - Total po tassium. Results are the average of three repeats � standard deviation. Table 3 The survival rate of BSFL during the composting. Materials
Survival rate (%)
Food waste Sewage sludge
90.15 � 0.5 46.65 � 4.4
Table 4 Characteristics of final products in this investigation. Parameters
Sewage sludge þ BSFL
Food waste þ BSFL
Sewage sludge
Food waste
Moisture content (%) pH
75.32 � 0.19
62.99 � 0.42
7.93 � 0.09
7.36 � 0.04
76.39 � 0.29 7.21 � 0.06
EC (μS/cm)
364.2 � 10.1
109.8 � 3.9
DOC (g/kg)
1.09 � 0.35
3510 � 57.78 12.51 � 0.94
OM (%)
46.98 � 0.60
88.69 � 1.28
TKN (g/kg)
19.94 � 1.60
31.20 � 0.77
TP(g/kg)
11.06 � 0.07
11.39 � 0.76
TK(g/kg)
5.14 � 0.03
8.37 � 0.26
52.40 � 0.18 19.49 � 1.09 11.39 � 1.09 3.69 � 0.18
GI
49.86 � 1.26
82.04 � 2.39
C/N ratio
13.67 � 1.28
16.50 � 0.98
70.39 � 0.13 3.33 � 0.09 317.0 � 11.11 32.02 � 0.74 99.36 � 0.49 19.70 � 1.23 0.39 � 0.07 0.82 � 0.02 30.75 � 0.99 29.27 � 1.13
0.34 � 0.12
47.59 � 3.18 15.60 � 1.02
EC - Electrical conductivity, DOC - Dissolved organic carbon, OM - Organic matter, TKN -Total Kjeldahl nitrogen, TP - Total Phosphorous, TK - Total po tassium, GI- germination index. Results are the average of three repeats � standard deviation.
with chicken feed, and then isolated by a sieve (2.00 mm). In order to get the optimized environment, we implement the experience in the under room which the temperature was 29 � C and the humidity was 52%.
2. Materials and methods
2.2. Black soldier fly larvae composting design
2.1. Materials collection and processing
Four of [49 (length) cm � 32 (width) cm � 14.5 (height)] opened containers which could place 7.0 kg raw materials were selected to perform this investigation and put in the room. The SS and FW were placed in a different container which named T1 and T2, respectively, and amendment with BSFL 1.2 kg (7:1.2 ration on fresh weight basis), as the treatment group. Without BSFL was named T3 (SS) and T4 (FW), as the control group. The experiment was done in triplicate. The com posting was mixed properly to the collection on 1, 3, 5, 7 and 9 days, and turn the mixture for supplying BSFL air every day. Weighting the sam ples 100 g (only the residue) from each container using small spoon, and
The SS was collected by Huayu Environmental protection water quality Cooperation Limited (Yangling, Shannxi Province, China). Ac cording to the report, the synthetic FW was ready for mixing 5.13 kg noodles, 3.95 kg rice, 3.95 kg cabbage and 1.97 kg pork in the ration of 13:10:10:5 (Wong et al., 2009), and characteristics of artificial food waste in this study were showed in Table 1. BSFL was provided by Xinyi Ecological Agriculture Technology Development Cooperation Limited (Yangling, Shanxi Province, China), and the first 6 days the BSFL was fed 2
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Fig. 1. The change of pH (a) and variation of VFAs (b–e) during the composting in all treatments. T1: sewage sludge þ BSFL; T2: food waste þ BSFL; T3: sewage sledge; T4: food waste.
then air dried. On the day 9, when the BSFL was ready for experience of the stage of prepupae, and then sieved them from the residue of com posting which means the experiment ended (Rehman et al., 2019). The survival of BSFL during the composting was shown in Table 3. The characteristics of raw materials and final products were listed in Tables 2 and 4, respectively.
2.3. Analytical methods The moisture content, pH, electrical conductivity (EC), dissolved organic carbon (DOC), NHþ 4 -N, NO3 -N, and germination index (GI) were determined by TMECC, (2002). To analyze the NHþ 4 -N and NO3 -N, samples were extracted with 20 mL 2 mol/L KCl (solid: extractant, 1:10 3
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Fig. 2. The change of DOC (a), NHþ 4 -N (b) and NO3 -N (c) from different treatments during composting. T1: sewage sludge þ BSFL; T2: food waste þ BSFL; T3: sewage sledge; T4: food waste. Values are the average of three repeats and error bars indicates the standard deviation.
4
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Journal of Environmental Management 256 (2020) 109967
(m/v)) using a shaker at 180 rpm for 2 h followed by the filtration with 0.45 μm nylon syringe filter by employing of automated analyzer (Auto Analyzer 3-AA3, Germany). DOC content was determined by fresh samples were extracted at room temperature with ultra-pure water at ration 1:10 (w/v) adopting a shaker at 180 rpm for 24 h, and then filtration with 0.45 μm nylon syringe filter by the implemented of automated total organic carbon (TOC) analyzer (TOC-LCPH, Shimadzu, Japan). The VFAs were determined by fresh samples that were extracted with ultra-pure water at a ratio of 1:5 (w/v), placed in a shaker at 1 h, and then filtered with 0.22 μm nylon syringe filter from a Shimadzu GC-2014 gas chomatograph (Japan) (Yang and Choong, 2001). The parameters of total Kjeldahl nitrogen (TKN), total phosphorous (TP), total potassium (TK) and organic matter (OM) were determined by air-dried samples (TMECC, 2002). For TKN, TP and TK determination, 0.5 g dried and sieved samples were digested with 10 mL H2SO4, 1 mL HClO4, and TKN was determined by Kjeldahl apparatus (KDY-9820), TP was determined by Molybdenum-antimony colorimetric method (TMECC, 2002). The value of OM was determined by cremating of samples at 550 � C for 24 h in a muffle furnace (Lu et al., 2009).
during the beginning of composting, which the high moisture content may be created an anaerobic environment for the processing. With the addition of BSFL, the value of VFAs was reduced, T1 decreased from 1.57 to 1.41 g/kg, and T2 from 2.06 to 1.48 g/kg, which could be attributed to the VFAs as a carbon source for the BSFL and native microbial sur vival. The trend of VFAs concentration in the T1 and T2 follows a similar result by the previous reports (Liu et al., 2019; Awasthi et al., 2018). There are no strict requirements on the kinds of carbon source for waste disposition, like acetic and propionate acid have been appointed as the best carbon source (Oehmen et al., 2004). However, the T4 was increased from 1.76 to 2.30 g/kg, which because there is a high con centration of carbohydrates and provide acidic surroundings, resulting in the accumulation of VFAs. 3.2. Evaluation of DOC, NHþ 4 -N and NO3 -N during composting The changes of DOC during the composting are shown in Fig. 2a. The DOC plays a key role in all parameters which indicate the rate of com posting process and microbial activities (Awasthi et al., 2017b). Actu ally, the elevated decomposition of complex organic compounds in raw materials generated water-soluble molecules (DOC). The beginning DOC values varied in all treatments due to the different feed stocks. From the early of composting, the DOC contents in BSFL treatments increased from their levels in the raw materials to those recorded on day 3, from 1.47 to 2.26 (g/kg) in T1 and 22.98 to 24.41 (g/kg) in T2. The relevant levels (g/kg) at the end of process were 1.09 (T1), 12.51 (T2), 0.34 (T3) and 32.02 (T4). In addition, the reduced rate was 23.57, 43.59 and 28.57% in T1, T2 and T3, respectively, but the T4 was increased. However, employing of BSFL in SS was not the great influence of degradation of DOC, the reduction value of T1 was similar to the T3. The microbes utilized DOC as their energy source which could be due to the DOC decreased (Waqas et al., 2019). Meanwhile, it should be noticed, which the present investigation was BSFL treatments, which are entirely different from sawdust or biochar utilized by Diner et al. (2011), who observed a continuous DOC decreased throughout the composting. The DOC value gradually declined in BSFL treatments and the lowest DOC value was observed at the end of the composting, because of the reduced of organic carbon in the atmosphere as CO2 and the utilized of carbon as BSFL growth and survival (Rehman et al., 2017b; Awasthi et al., 2016a). Waqas et al. (2019) also reported that carbon reduction was considered an essential parameter of compost maturity. As is shown in Fig. 2b, the concentration of NHþ 4 -N elevated sharply in BSFL amended FW from the initial of composting, and attained the peak values in T1 and T2 on day 5 (438.8 mg/kg) and (1001 mg/kg), and then slowly decreased until the finish of composting due to the trans formation of NHþ 4 -N into NH3 and afterwards by its evaporation under high pH condition. Wang et al. (2018) also reported that the ammonium was generated attributed to the early disruption of the nitrogenous compounds during the beginning phase of FW degradation. The addition of BSFL into the FW compost swiftly reduced NH3 volatilization and led to accelerating in NHþ 4 -N concentrations at the starting of composting. The high value NHþ 4 -N content might be due to the low pH in FW, which promotes the conversion of NH3 into NHþ 4 -N (Pan et al., 2018). The trend of T1 was mainly due to the organic degradation and ammonification, meanwhile BSFL did not promote conversion of inorganic nitrogen to nitrate and nitrite (Awasthi et al., 2016b). The loss of NHþ 4 -N was revealed the rapid mineralization of OM and ammonification during the bio-oxidative stage of composting (Awasthi et al., 2016b). In contrast, the trend of control group was stable, which could be attributed to the without BSFL employing and the environment inhibits the native microorganism. At the end of composting, The concentration of T2 was beyond the permissible value (400 mg/kg), suggesting that the bio fertilizer was still unstable and needed to degradation. It revealed that the value of NO3 -N content was absent of all treat ments during the composting process (Fig. 2c). This result was different from the previous report during the latter phase of the composting,
2.4. Statistical analysis All the statistics were replicated three times and determined to analysis of variance (ANOVA) test (p < 0.05), and the figures were drawn by origin 2016 (Origin Lab, America). The correlation analysis among statistics was determined by the software Canoco for windows (Version 5), and the redundancy analysis (RDA) figures. 3. Results and discussions 3.1. Evaluation of pH and VFAs during the composting The changes of pH during the initial composting mainly depend on the chemical properties of raw material (Sharma and Garg, 2018). Fig. 1a, the values of pH were 7.33 and 6.86 in T1 and T3 during the initial stage. The pH values could be due to the performance of the SS (pH 6.8) (Zhang et al., 2014). In addition, the values of pH were 5.95 and 5.07 in T2 and T4, which could be attributed to the rapid decomposition of FW leads to the release of quantities of heat, and then increase the acidification rate (Wang et al., 2018). The pH in the whole process was decreased in T4, but the T2 attained to its minimum value 5.78 on day 3 while a highest value 7.36 reached on day 9. The decreased of pH which could be due to the organic acids generated by the microbial reaction (He et al., 2018). From day 3–9, the value of pH increased and attained the alkaline, which could be due to the employing of BSFL. The BSFL could utilize the VFAs as a carbon source and worked with the native microbial, resulting in the concentration of VFAs decreased (Fig. 1b–e) and the pH increased (Liu et al., 2019). The high concentration of car bohydrates in FW, caused the value of pH reduced in T4 (Awasthi et al., 2017a), decreased from 5.07 to 3.33. Compared with T2, the changes of pH were not obvious in the treatment T1 which increased from 7.33 to 7.93. This was due to the substrate of SS had not created the optimized environment for growth and survival of BSFL. Hence, the activity of BSFL didn’t contribute very much to the pH during the SS composting. During the BSFL composting, VFAs were considered to be prime producing odors (Sundberg et al., 2013). As is shown in Fig. 1b–e, VFAs are mainly composed of acetic, propionate, iso-butyrate, n-butyrate, iso-valerate and n-pentanoic acid, and organic acids play a key role in the VFAs utilization (Fang et al., 2016). During the initial phase, the peak value was 1.67, 2.26 and 1.82 g/kg in T1, T2 and T3, respectively, but the T4 reached the maximum on the last day. The activity of BSFL caused the rising temperature, the concentration of VFAs was increased that indicated the degradation of easily OM but the increased of VFAs would bring about the microbial activities and the biodegradation bar riers (Awasthi et al., 2018). The accumulation of VFAs could be due to the high moisture value (above 80%) of the substrate of SS and FW 5
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Fig. 3. Organic matter (a), total Kjeldahl nitrogen (b), total phosphorous (c) and total potassium (d) from different treatments during composting. T1: sewage sludge þ BSFL; T2: food waste þ BSFL; T3: sewage sledge; T4: food waste. Values are the average of three repeats and error bars indicates the standard deviation.
which was due to the nitrification process because the temperature in the container was below 40 � C which was comfortable for nitrifying bacteria (Yu et al., 2019). The NHþ 4 -N would be converted into NO3 -N with the assistance the nitrifying microbes. The temperature of this investigation was under room temperature, so that the effect of tem perature on nitrifying bacteria should be ignored. Therefore, the con centration of NO3 -N was lower than the biochar amended biosolids co-composting (Awasthi et al., 2017c; Waqas et al., 2018) and the modified bentonite amended chicken manure composting (Ren et al., 2018), which could be attributed to the addition of BSFL. Meanwhile, the concentration of NO3 -N was 21.96, 8.92, 24.98 and 8.51 mg/kg in T1, T2, T3 and T4, respectively at the finish of composting. It advised that BSFL provided an unfavorable micro-environment for nitrifying process and inhibit the N conversion from NHþ 4 -N to NO3 -N.
The similar results were also reported by Rehman et al. (2017a), who added BSFL and soybean into dairy manure composting. The results for OM reduced tendency are in accordance with the previous reports which also showed reduction in OM after BSFL composting of different vari eties of organic waste. Lalander et al. (2018b) reported the similar re sults that the BSFL was not sensitive with SS. The OM reduction may be attributed to the easily of OM transformation into VFAs during the early time, and it was used by BSFL as feed (Mertenat et al., 2019). Loss of carbon in the form of CO2 by respiration is charge of OM reduction. OM degradation can be seen as a parameter of feed stock and its trans formation into stabilized product (Sharma and Garg, 2018). As is shown in Fig. 3b, TKN content reduced in the feed stock’s of FW but the difference between BSFL treatments and control group, which could be due to the growth and survival of BSFL. However, the T2 was elevated sharply, increased from 26.86 to 31.96 g/kg after day 3 until day 7. It is because of the significant organic degradation and the composting weight is reduced and the elevated mainly as the mass concentration effect (Zhu et al., 2019). The concentration of TKN in the BSFL compost was T1 (19.94 g/kg) and T2 (30.20 g/kg) which was 5.14% and 5.03% lower than the initial nitrogen content was 21.02 and 31.80 g/kg. The similar tendency was reported by Lalander et al. (2018a), who added BSFL into FW and SS composting. Meanwhile,
3.3. Evaluation of OM, TKN, TP and TK during composting OM decreased after processing in all containers, however degree of OM reduction was different among treatments (Fig. 3a). OM reduction, as compared to initial level, was in the sequence: T2 (21.99%) > T1 (14.51%) > T3 (10.72%) > T4 (0.72%). It was showed that in T1 and T2 have higher percentage which could be due to the employing of BSFL. 6
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TP showed an uphill tendency in all treatments, except T4 (Fig. 3c). Increase in TP content was from 8.37 to 11.06 g/kg, from 1.50 to 11.39 g/kg and from 9.30 to 10.39 g/kg in T1, T2 and T3, respectively. During the composting, there is significantly difference between the substrate of FW in T2 and T4. On the day 9, the TP content of T2 was 11.39 and the control was 1.14. The tendency of T2 was dramatic which was increased sharply. Meanwhile, TK also showed an upward tendency in all treat ments, except T4 (Fig. 3d). The TK was increased from 4.86 to 5.99 g/kg, from 1.96 to 8.37 g/kg and from 3.6 to 3.79 g/kg in T1, T2 and T3, respectively. On the day 9, the TK content of T2 was 8.37 and the control was 0.82. The tendency of T2 was greatly increase. However, these re sults were opposite with the reported by Rehman et al. (2017b), which could be due to the gap of raw materials and the approaches feed. The majority increased in rate was observed in TP and TK during the BSFL FW composting, which may be due to the employing of BSFL accelera tion of the reduction in mass and degradation of organic compounds. To the contrary, the same situation was observed in control group and T1 which the concentration of TP and TK was nearly unchanged.
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3.4. Evaluation of maturity parameters during composting As shown in Fig. 4a, the reduction of moisture content showed the entire time. The T1 deceased from 86.09 to 75.32%, T2 from 81.35 to 62.99%. The result of T2 was different from the reported by Kumar et al. (2018), who investigated the effect of moisture content of FW on res idue, if the initial of moisture value was 80%, the moisture of residue will not decrease. The reason why is that the experiment was carried out indoors and without mechanical aeration. Another reason is that, the BSFL significantly influence the characteristic of composting, resulting in the porosity enhanced and the evaporation of water fast (Banks, 2014). At the end of composting, moisture content of BSFL treatments was lower than the control group. However, the similar situation was found in the other parameters, which the tendency of T1 was not dramatic. Compost with suitable EC release soluble salts and pose activity ef fect on plant growth and yield. Generally, the value of EC should be less than 4000 μS/cm for the purpose of safety to use (Li et al., 2012). Fig. 4b showed the value of T2 increased greatly during the composting, increased from 587 to 3510 μS/cm, which could be attributed to the employing of BSFL. The final product EC value was lower than 4000 μS/cm, which means safely employed to soil (Chen et al., 2019a). During the composting, it is unavoidable that the BSFL could accelerate the process of degradation of organic compounds, resulting in the concen tration of soluble salts was increased (Chan et al., 2016). While employing of BSFL in T1, the T1 was stable, which the phenomenon was similar to the T3 and T4. The results showed that added the BSFL into SS was not accelerated the degradation of OM. During at the end of com posting, the value of EC was 364.5, 3510, 109.8 and 317 μS/cm in T1, T2, T3 and T4, respectively. The compost product of seed germination can not only evaluate the pyhtotoxic substance but also have a better relation with degree of compost maturity. GI is the most conventional represented parameters to assess the toxicity level of ultimate compost. Commonly, if the GI was higher 80%, the compost is indicated to be mature and safe to use (TMECC, 2002). Possibility reasons were that the decrease EC and degradation of toxic substance like organic acids and NHþ 4 -N concen tration (Wang et al., 2019). During the end of compost, the GI was 49.86%, 82.04%, 47.59% and 30.75% in T1, T2, T3 and T4 respectively (Fig. 4c). This result was evidenced that only the ultimate compost product of T2 was mature, suitable to the plant. Meanwhile, the sub strate of FW employed with BSFL had a positive effect on GI. However, employing of BSFL in T1 which the value of GI was lower 80%, considered added the BSFL into SS was negative effect on GI value. It may be due to the BSFL addition which could accelerate the decompo sition of OM in FW, which could moderate the toxicity during the FW composting.
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Fig. 4. The change of moisture (a), electrical conductivity (b) and germination index (c) during the composting process of all treatments. T1: sewage sludge þ BSFL; T2: food waste þ BSFL; T3: sewage sledge; T4: food waste. Values are the average of three repeats and error bars indicates the standard deviation.
treatments amended without BSFL are expected to lose the nitrogen concentration in the final compost because of ammonium absence. The concentration of TKN decreased was attributable to the conversion of NHþ 4 -N to NO3 -N by nitrogen bacterial, NH3 emission loss and the sta bilization of compost mass (Chen et al., 2019a). However, the trend of T1 was stable which could be due to the BSFL was not sensitive to SS. 7
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into biofertilizers, but it was not effective for SS recycling. In addition, it can be said that there is significant difference between T1 and T2. Among all the treatments, the highest TKN, TP, TK and GI were observed in FW treatments. Meanwhile, the decreased rate of OM and moisture also was found highest in FW treatments. The trend of all parameters was stable in SS treatments compared the FW group. The study demonstrated that added BSFL into FW both enhanced the total nutrient and reduced the C/N ratio compared the control group. At the ultimate of BSFL - FW processing, the range of pH (5.5–8.5) and EC (<4000 μS/ cm) was more suitable agricultural fields and potting. Though the comprehensive of initial parameters, the concentration of DOC was 0.476 g/kg in SS which be unable to provide the enough carbon source to utilize by BSFL. BSFL bioconversion could not only perform a valuable function in the form of FW management, but also generate a valuable product in the form of biofertilizer. Acknowledgements The authors are grateful for the financial support from Research Fund for International Young Scientists from National Natural Science Foundation of China (Grant No. 31750110469), China, Shaanxi Intro duced Talent Research Funding (A279021901) and The Introduction of Talent Research Start-up fund (No. Z101021904), College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi Province 712100, China. We are also thankful to all our labo ratory colleagues and research staff members for their constructive advice and help.
Fig. 5. Correlation analysis during the composting process of all treatments. T1: sewage sludge þ BSFL; T2: food waste þ BSFL; T3: sewage sledge; T4: food waste.
As shown in Table 4, the BSFL additive could promote the degra dation of OM in T2 compared with T1. During the FW composting, the value of pH and EC were huge difference which because employing of BSFL, and the range of pH and EC are suitable for plants. While employed of BSFL could reduce the TKN compared the initial feed stock’s, the concentration of TKN was higher than the group of without BSFL at the end of composting. At the end of FW - BSFL composting, the concentration of TP and TK were increased significantly which could be due to the reduced of the mass. However, the BSFL - SS system was not obviously changed at the ultimate compost.
References Awasthi, M.K., Awasthi, S.K., Wang, Q., Wang, Z., Lahori, A.H., Ren, X., Chen, H., Wang, M., Zhao, J., Zhang, Z., 2018. Influence of biochar on volatile fatty acids accumulation and microbial community succession during biosolids composting. Bioresour. Technol. 251, 158–164. Awasthi, M.K., Selvam, A., Lai, K.M., Wong, J.W.C., 2017. Critical evaluation of postconsumption food waste composting employing thermophilic bacterial consortium. Bioresour. Technol. 245, 665–672. Awasthi, M.K., Wang, M., Pandey, A.K., Chen, H., Awasthi, S.K., Wang, Q., Ren, X., Lahori, A.H., Li, D., Li, R., Zhang, Z., 2017. Heterogeneity of zeolite combined with biochar properties as a function of sewage sludge composting and production of nutrient-rich compost. Waste Manag. 68, 760–773. Awasthi, M.K., Wang, Q., Chen, H., Wang, M., Ren, X., Zhao, J., Li, J., Guo, D., Li, D., Awasthi, S.K., Sun, X., Zhang, Z., 2017. Evaluation of biochar amended biosolids cocomposting to improve the nutrient transformation and its correlation as a function for the production of nutrient-rich compost. Bioresour. Technol. 237, 156–166. Awasthi, M.K., Pandey, A.K., Bundela, P.S., Wong, J.W.C., Li, R., Zhang, Z., 2016. Cocomposting of gelatin industry sludge combined with organic fraction of municipal solid waste and poultry waste employing zeolite mixed with enriched nitrifying bacterial consortium. Bioresour. Technol. 213, 181–189. Awasthi, M.K., Wang, Q., Ren, X., Zhao, J., Huang, H., Awasthi, S.K., Lahori, A.H., Li, R., Zhou, L., Zhang, Z., 2016. Role of biochar amendment in mitigation of nitrogen loss and greenhouse gas emission during sewage sludge composting. Bioresour. Technol. 219, 270–280. Banks, I.J., 2014. To Assess the Impact of Black Soldier Fly (Hermetia illucens) Larvae on Faecal Reduction in Pit Latrines Dissertation. London School of Hygiene & Tropical Medicine. Cerda, A., Artola, A., Font, X., Barrena, R., Gea, T., S� anchez, A., 2018. Composting of food wastes: status and challenges. Bioresour. Technol. 248, 57–67. Chan, M.T., Selvam, A., Wong, J.W.C., 2016. Reducing nitrogen loss and salinity during ‘struvite’ food waste composting by zeolite amendment. Bioresour. Technol. 200, 838–844. Chen, J., Hou, D., Pang, W., Nowar, E.E., Tomberlin, J.K., Hu, R., Chen, H., Xie, J., Zhang, J., Yu, Z., Li, Q., 2019. Effect of moisture content on greenhouse gas and NH3 emissions from pig manure converted by black soldier fly. Sci. Total Environ. 697, 133840. Chen, X., Zhao, Y., Zeng, C., Li, Y., Zhu, L., Wu, J., Chen, J., Wei, Z., 2019. Assessment contributions of physicochemical properties and bacterial community to mitigate the bioavailability of heavy metals during composting based on structural equation models. Bioresour. Technol. 289, 121657. Cickova, H., Newton, G.L., Lacy, R.C., Kozanek, M., 2015. The use of fly larvae for organic waste treatment. Waste Manag. 35, 68–80. Diner, S., Studl-Solano, N., Guti� errez, F., Zurbrügg, C., Tochner, K., 2011. Biological treatment of municipal organic waste using black soldier fly larvae. Waste Biomass Valori 2, 357–363. Fang, W., Zhang, P., Gou, X., Zhang, H., Wu, Y., Ye, J., Zeng, G., 2016. Volatile fatty acid production from spent mushroom compost: effect of total solid content. Int. Biodeterior. Biodegrad. 113, 217–221.
3.5. Relationship among environmental factors RDA was demonstrated to compare the physico-chemical and VFAs content in all of the treatments. The RDA reveled that added BSFL into FW had the greatly value of 77.59%, but the value of T1 was lower than the T3 (Fig. 5). These results were considered that employing of BSFL made the correlation significantly during the FW composting. There was positive correlation between GI, TP, TK, EC, and pH in the BSFL systems. This investigation was similar to the previous reported, which also concluded that NHþ 4 -N, VFAs, OM and DOC were negative with GI (Ren et al., 2018). The RDA was obviously indicated that all the parameters and OM have close correlation consist with Awasthi et al. (2016b). Many reports showed between the concentration of DOC, OM and the ultimate of compost maturity, and the degradation of DOC and OM represented the mature of compost (Zhou et al., 2013). At the end of the FW com posting, the concentration of TKN was not decreased obviously which could be due to the residue of mass decreased significantly, and caused the content of concentrate. This result was opposite with the report Rehman et al. (2017a). Meanwhile, the RDA also support that the cor relation between GI and TKN showed the positive relative in T2. The amendment of composting was able to enhance the degradation of FW compared the control. The positive correlation of the RDA represents that the BSFL composting system is suitable and end product stable as well as well mature for organic farming purposes. 4. Conclusion BSFL could achieve utilized and recycle the FW which conversion FW 8
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