Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 4, Pages: 1292-1303  
J. Environ. Treat. Tech.  
ISSN: 2309-1185  
Journal web link: http://www.jett.dormaj.com  
https://doi.org/10.47277/JETT/8(3)1303  
Industrial Composting of Commingled Municipal  
Solid Waste: A Case Study of Shiraz City, Iran  
1
1
1
2
Sama Azadi , Ayoub Karimi-Jashni *, Nasser Talebbeydokhti , Rouhollah Khoshbakht , Azadeh  
Binaee Haghighi2  
1
Department of Civil and Environmental Engineering, School of Engineering, Shiraz University, Shiraz, Fars, Iran  
2
Waste Management Organization of Shiraz Municipality, Shiraz, Fars, Iran  
Received: 19/04/2020  
Accepted: 12/09/2020  
Published: 20/12/2020  
Abstract  
Composting is a preferable treatment option for putrescible waste disposal. In the small-scale composting, the control of the process is  
easy and high quality compost is usually produced while the conditions of industrial composting and small-scale composting are so different  
especially in developing country that municipal solid waste (MSW) is collected as commingled. Unfortunately, there is still a lack of  
information and experiences regarding the successful industrial composting from commingled municipal solid waste (CMSW). Therefore,  
this study was conducted on the compost production from CMSW in Shiraz City, Iran, with the composting capacity of 100 tonnes per day.  
The common process of windrow composting was modified for industrial composting in Shiraz City. The efficiency of the modified process  
was assessed using physical, chemical, and economic analyses. In addition, the maturity and stability of produced compost was evaluated  
using different indices such as fertilizing index (FI), clean index (CI), static respiration index (SRI), cumulative respiration index (CRI), and  
2 2  
C-CO production index (C-CO Index). Finally, solutions and suggestions were presented to improve the system performance. Results  
showed that although the input putrescible waste to composting site has low homogeneity, produced compost in Shiraz City has a “good”  
quality. The produced compost with FI and CI of about 4.2 and 3.6, respectively, has high fertilizing potential and medium heavy metal  
content and can be sold without any restriction. Based on the economic analysis, poor marketing, strategies of bad marketing, lack of public  
awareness, and visible impurities, in spite of complying with the required standards, are the main reasons for the low sale price. The results  
of this study can be valuable for industrial composting in the cities where wastes are not separated at source.  
Keywords: Industrial composting, Commingled municipal solid waste, Sorting center, Economical analysis  
Introduction1  
2 3 2  
activity and are mineralized to CO , NH , H O, and incomplete  
1
humification (13, 26). If the effective parameters in the process of  
mineralization are adjusted, stable, storable, and transportable  
compost will be obtained. Otherwise, immature compost will be  
produced that adversely affects soil environment and plant  
growth.  
Generally speaking, compost quality is described based on its  
stability and maturity. Maturity relates to the phytotoxicity  
aspects of compost and determines its ability to be used  
effectively as soil fertilizer for the growth of plants. Stability  
which relates to the microbial decomposition or microbial  
respiration activity determines the resistance of the compost  
organic matter against further microbial decomposition.  
Several researchers have investigated the composting process  
of MSW. Siles-Castellano et al. (2020) studied the maturity of  
produced compost from mixed MSW in the Southeast of Spain.  
They concluded that the phytotoxicity of MSW never lost during  
composting process due to the high heavy metal content of MSW  
Putrescible waste is the main fraction of MSW stream in  
developing countries (1-5). Putrescible waste disposal in a landfill  
leads to catastrophic environmental impacts such as global  
warming by greenhouse gases emission and groundwater  
contamination by toxic leachate generation (1, 6-11).  
Furthermore, putrescible waste generation has been increased  
with population, and serious environmental threats are predicted  
to increase in the future (8, 12, 13). For these reasons, a sound  
strategy toward sustainable MSW management is the separation  
and treatment of putrescible waste.  
Various treatment methods such as incineration, anaerobic  
digestion, bioelectrochemical systems, and composting have been  
applied for waste treatment (12, 14-20). However, composting is  
a preferred treatment option for putrescible waste disposal,  
especially in large cities (21, 22). Composting not only reduces  
negative environmental impacts but also generates a good  
product, namely compost, useful for plants and soil structure (10,  
(27). Cassero et al. (2019) assessed the compost stability and  
1
3, 22-25). In the composting process, organic matters pass  
maturity during the composting process from 50 t/d source sorted  
through a thermophilic phase, which is fostered by the biological  
*
Corresponding author: Ayoub Karimi-Jashni, Department of Civil and Environmental Engineering, School of Engineering, Shiraz  
University, Shiraz, Fars, Iran. E-mail: karimi.article.2015@gmail.com  
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2020, Volume 8, Issue 4, Pages: 1292-1303  
the organic fraction of MSW in the South of Italy. They concluded  
that the quality parameters fulfilled the requirements of the Italian  
legislation but plastic content occasionally exceeded the threshold  
limit values. In addition, the produced compost was moderately  
stable and needed more aeration (28).  
and they generate 1,000 tonnes CMSW every day. Fig. 1 shows  
the mean percentage of CMSW components in Shiraz City.  
Among the generated CMSW, putrescible waste, including yard,  
food, and fruit waste, is the most substantial proportion (66%).  
The rest of the waste is paper, plastic, glass, metal, and others.  
2
Malamis et al. (2017) studied the composting process from  
segregated household food waste for a selected area of Attica  
Region with 3,700 households. Their results indicated that heavy  
metal concentrations were within the set limits and the produced  
compost was free of pathogens. The compost had sufficient  
organic matter for soil fertilization, but considerable physical  
impurities (mainly glass) were detected in the compost due to the  
limited pre-treatment. Awasthi et al. (2014) investigated the  
impact of turning frequency and fungal consortium on the  
produced compost from 5 ton MSW. They separately collected  
vegetables, food, garden, and office waste from eight different  
zones of Jabalpur city, India. The mixing of these wastes was  
placed in four windrows with 5 m length, 1 m width, and 1.4 m  
height. Based on their results, inoculation of fungal consortium  
with weekly turning frequency accelerated the production of  
mature compost with low phytotoxicity.  
Shiraz City is 224 km in area and divided into ten municipality  
districts. Solid waste collection frequency is every other night  
with the scheme of door to door. CMSW is collected by truck and  
transferred to a transfer station and then to a processing site at  
Barmshoor site.  
Others, 14%  
Glass, 2%  
Plastic, 11%  
Metal, 2%  
Putrescible  
waste, 66%  
Paper, 5%  
A literature survey specifies that the majority of studies  
carried out on compost production from MSW are on a small scale  
while the conditions of industrial composting and small-scale  
composting are so different. In the small-scale composting, the  
quality control of compost through the process is easy and the  
produced compost usually has excellent quality. Although  
producing high-quality composts are achievable in industrial  
composting, the composition and characteristics of final products  
are usually very variable especially in developing country that  
MSW is collected as commingled (29) and putrescible waste is  
separated in the CMSWSC. When MSW is collected as  
commingled, different types of waste are mixed together  
thoroughly and compacted during transportation. This causes that  
the separated putrescible waste in the CMSWSC which is the feed  
of composting plant does not possess desirable quality and  
homogeneity. Since there is still a lack of information and  
experiences regarding industrial composting process from  
CMSW, the management and quality control of the process in  
these conditions is so difficult and faces tremendous problems (8).  
Therefore, this study aims at presenting a modified industrial  
composting method from CMSW, evaluating the quality of  
produced compost, and investigating the challenges of this  
process. This method is currently being implemented in Shiraz  
City, Iran, with the composting capacity of 100 t/d. In this study,  
first, the modified process of compost production from CMSW is  
presented. Then, the effectiveness and efficiency of the  
composting process with regard to the physical, chemical, and  
biological parameters are investigated. Next, the maturity of  
produced compost is evaluated based on the FI and CI. In  
addition, the stability of produced compost is assessed based on  
Figure. 1: Mean percentage of CMSW components in Shiraz City  
There are MSW landfill site, administrative office, research  
laboratory, biogas power plant, CMSWSC, leachate collection  
ponds, and composting and vermicomposting sites in the  
processing site at Barmshoor site. 50% of collected solid waste is  
transferred to CMSWSC, and the rest of it is transferred to the  
landfill site. At the CMSWSC, the putrescible fraction of CMSW  
is separated and transferred to composting site. It is noteworthy  
that the green waste of florists, fruit, and vegetable shops is  
separately collected and transferred to vermicomposting site.  
2
.2 Sorting process in the CMSWSC  
Two separate solid waste sorting lines are in operation in the  
CMSWSC. The first line has been in operation since 2013 and the  
second line since 2016. Each sorting line has the processing  
capacity of 250 tonnes CMSW per day. Five hundred tonnes of  
CMSW is transferred to the CMSWSC, and two front-end loaders  
dump CMSW gradually on conveyor belts. As observed in Fig. 2,  
in the first line, workers manually tear bags, and in the second  
line, the bags are torn by a device. Then, wastes pass through two  
trommel screens. Wastes, which are generally putrescible and  
smaller than 6 cm, pass through the openings of screens. Larger  
wastes are transferred to a separation area by conveyor belts. In  
this area, workers manually remove bottles and recyclable  
materials. Remaining wastes pass through a magnet for metal  
collection. Then, they pass through an air separation device for  
plastic bag removal. Remaining wastes, called rejected wastes,  
are loaded and transferred to the landfill. Putrescible wastes pass  
through a magnet for metal collection. In the first line, there is one  
magnet, and in the second line, there are two magnets. Finally,  
putrescible materials are loaded and transferred to a compost  
production site.  
2
the SRI, CRI, and C-CO Index. After that, Considering the  
incomes and costs of composting process from CMSW in the  
years of 2013 to 2016, economical analysis is conducted. Finally,  
solutions and suggestions are presented to improve the system  
performance.  
2
.3 The modified process of composting in Shiraz City  
Fig. 3 shows the methodology flowchart of industrial  
composting in Shiraz City.  
2
Materials and methods  
2
.1 Solid waste management in Shiraz City  
Shiraz City is located in the southwest of Iran with hot and  
semi-arid climate. Shiraz has a population of nearly 1.6 million  
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2020, Volume 8, Issue 4, Pages: 1292-1303  
Manual separation of  
recyclable materials  
Trommel  
screen  
Trommel  
screen  
Air separation  
device  
Manual tearing  
the bags  
Magnet  
Magnet  
Magnet  
Loading of  
separated  
putrescible waste  
CMSW  
receiving area  
Loading of  
rejected materials  
Magnet  
Bag tearing  
device  
Trommel  
screen  
Trommel  
screen  
Air separation  
device  
Magnet  
Manual separation of  
recyclable materials  
Figure. 2: A schematic view of CMSWSC in Shiraz City  
About 500 tonnes of CMSW is fed to the CMSWSC every  
day (250 tonnes for each line). About 220 to 300 tonnes of  
separated putrescible waste is transferred to the composting site  
every day. This waste is placed daily in a windrow with 200 m  
length, 4.5 m width, and 1.3 m height. After initial aeration, the  
temperature and humidity of windrows are measured. Based on  
the temperature and humidity variation, aeration program of  
windrows is determined. Usually, aeration is conducted twice in  
the first week and once a week after that. Windrows are aerated  
by Turner Topturn X53. The purpose of aeration is to control the  
temperature in the thermophilic range and help the microbial  
activities.  
Since Shiraz City is located in a dry climate, moisture is a  
limiting factor in the aeration of windrows. After four first weeks,  
the windrows are usually merged to keep their moisture and  
complete the thermophilic stage. Usually after 60 days, the  
transformed wastes are transferred to a secondary fermentation  
site for at least two weeks. After the completion of fermentation,  
produced materials are sieved to remove non-putrescible  
materials such as glass, metals, sand, stone, and textiles. Finally,  
produced compost is screened to classify into two sizes of smaller  
than 5 mm (0-5) and smaller than 15 mm (0-15).  
phosphorus, potassium, and C/N ratio on soil fertility is  
considered. For calculating this index, two factors of  
“desirability” and “importance” are assigned to each parameter.  
For determining the desirability factor (DF), the possible  
values of each parameter are divided into five categories and each  
category is assigned a numeric value of 1 to 5 with regard to  
desirability. For determining the importance factor (IF), based on  
scientific information and the role of each parameter in soil  
fertility, one weight is assigned to each parameter. Table 1 shows  
the values of DF and IF for each parameter. As observed, the  
organic carbon is the most important parameter; because this  
parameter directly affects the water holding capacity, porosity,  
and structure of soil and increases the biological activity of soil.  
Although nitrogen, phosphorus, and potassium are three essential  
nutrients for higher crop productivity, potassium is less critical  
than others. So, potassium is assigned lower IF than phosphorus  
and nitrogen. The FI of composts is calculated as shown in Eq. 1:  
5
∑ꢁꢃ1 퐷ꢀꢁ.ꢂꢀꢁ  
퐹푒푟푡푖푙푖푧푖푛푔 퐼푛푑푒푥 =  
(1)  
5
∑
ꢂꢀꢁ  
ꢁꢃ1  
CI is an indicator for the compost cleanliness regarding some  
heavy metals such as zinc, cadmium, chromium, copper, lead, and  
nickel. To calculate this index, the desirability and importance  
factors for each of these parameters are determined based on the  
criteria in Table 2. Cadmium has the highest importance factor  
due to its high toxicity potential for mammalians and plants. The  
CI of composts is calculated according to Eq.2:  
2
.4 The quality grade of the produced compost  
Due to the high number of quality control parameters and the  
differences in the importance of these parameters, it is difficult to  
judge the overall quality of the produced compost. To tackle this  
problem, indicators are required to evaluate the quality and  
maturity of the compost based on its chemical properties and  
effectiveness in improving the soil properties. Saha et al. (2012)  
proposed a method for determining the overall quality of the  
produced compost based on two indices of Fertilizing Index (FI)  
and Clean Index (CI). In FI, the effect of some chemical  
properties of compost such as organic carbon, total nitrogen,  
6
푗ꢃ1  
∑
퐷ꢀ푗.ꢂꢀ푗  
퐶푙푒푎푛 퐼푛푑푒푥 =  
(2)  
6
푗ꢃ1  
∑
ꢂꢀ푗  
After computing FI and CI, the compost quality is determined  
according to the classifications in Table 3.  
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2020, Volume 8, Issue 4, Pages: 1292-1303  
Transferring the separated  
putrescible waste to  
biocomposting site  
Placing the separated  
putrescible waste in a  
windrow  
No  
1
RT <1  
Yes  
1
<RT< 4  
week  
No  
Aerating  
twice a week  
Yes  
Merging two  
windrows  
Aerating  
once a week  
Aerating  
once a week  
RT< 60  
No  
Yes  
Transferring the composted  
waste to a fermentation site  
for two weeks  
Sieving to remove non-  
putrescible materials  
Sieving to classify the  
compost into two sizes  
of 0-5 mm and 0-15 mm  
1
Figure. 3: Flowchart of the proposed methodology for industrial composting in Shiraz City ( RT: retention time)  
As seen, compost is divided into seven categories with regard  
and reclaiming lawns, gardens, and uncultivated lands.  
to its quality. Composts in classes A, B, C, and D can be sold  
without any restriction. But the compost belonging to classes E,  
F, and G can only be used under special considerations. If  
compost has a low FI and all the heavy metal parameters are  
within the permissible limits, it will be non-marketable and must  
only be used as a soil conditioner. If compost’s FI and CI are  
similar to class A but even one of the heavy metal parameters is  
beyond the permissible limit, the compost will be included in  
class F and will be non-marketable. This class of compost can be  
used for growing fruitless trees and ornamental plants. If compost  
has a suitable FI but has high heavy metal content, it will be non-  
marketable and it can be used only for one time for developing  
3
Results and discussions  
3
.1 Chemical characterization of putrescible waste in Shiraz  
City  
In addition to operational parameters, some chemical  
characteristics of putrescible waste significantly affect the  
effectiveness of composting process. The most important  
parameters are Carbon/Nitrogen (C/N) ratio, moisture content,  
pH, and the amount of organic matter (OM). If these parameters  
are not in the range of optimal values, compost with undesirable  
quality and some problems such as odor and dust will be created.  
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Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 4, Pages: 1292-1303  
Fig 4 and Table 4 show the chemical analysis results of  
putrescible waste in Shiraz City. The analyses were carried out  
according to the standard methods (30). In addition, Table 4 gives  
extra information about the content of some chemical parameters  
such as total Carbon, Organic Carbon, ash, electrical conductivity  
City.  
Since microorganisms require 30 units of C per unit of N, the  
good amount of C/N ratio to begin the composting process is  
between 25 and 35. Higher C/N ratio contents lead to a decrease  
in the rate of putrescible waste decomposition, and lower contents  
result in the release of bad smells due to the loss of N in the form  
of ammonia or nitrous compounds. The content of C/N ratio in  
the putrescible waste of Shiraz City is equal to the reasonable  
amount of 24.2.  
(EC), total Nitrogen (TN), Phosphorous (P), Potassium (K),  
Sodium (Na), Magnesium (Mg), Iron (Fe), Copper (Cu),  
Manganese (Mn), Zinc (Zn), Chromium (Cr), Lead (Pb),  
Cadmium (Cd), and Nickel (Ni) in the putrescible waste of Shiraz  
Table 1: Criteria for determining desirability and importance factors of fertilizing index (Saha et al. 2012)  
*
DF  
Fertilizing parameter  
Unit  
IF**  
5
4
3
2
1
g g- %dw*  
1
>20.0  
>1.25  
>0.60  
>1.00  
<10.1  
15.1-20.0  
1.01-1.25  
0.41-0.60  
0.76-1.00  
10.0-15  
12.1-15.0  
0.81-1.00  
0.21-0.40  
0.51-0.75  
15.1-20  
9.1-12.0  
0.51-0.80  
0.11-0.2  
0.26-0.50  
20.1-25  
<9.1  
<0.51  
<0.11  
<0.26  
>25  
5
3
3
1
3
Total organic C  
Total N  
-
1
g g %dw  
-1  
g g %dw  
-1  
Total P  
Total K  
C/N ratio  
mg.kg dw  
-
*
DF: Desirability Factor ** IF: Importance Factor  
Table 2: Criteria for determining desirability and importance factors of the clean index (Saha et al. 2012)  
DF  
I
HM*  
Unit  
5
4
3
2
1
0
F
1
2
5
3
1
3
mg.kg- dw*  
1
<151  
<51  
<0.3  
<51  
<21  
<51  
151-300  
51-100  
0.3-0.6  
51-100  
21-40  
301-500  
101-200  
0.7-1.0  
101-150  
41-80  
501-700  
201-400  
1.1-2.0  
151-250  
81-120  
151-250  
701-900  
401-600  
2.0-4.0  
251-400  
121-160  
251-350  
>900  
>600  
>4.0  
>400  
>160  
>350  
Zn  
Cu  
Cd  
Pb  
Ni  
-
1
mg.kg dw  
-
1
mg.kg dw  
-
1
mg.kg dw  
-
1
mg.kg dw  
-
1
Cr  
mg.kg dw  
51-100  
101-150  
*
HM: Heavy Metal  
Table 3. Compost classification with regard to its quality (Saha et al. 2012)  
Fertilizing  
Clean Index + The status of  
heavy metal parameters  
Compost  
quality  
Class  
Selling status  
Use restrictions  
Index  
>3.5  
>4.0 + All parameters of heavy  
A
B
C
D
E
F
metals are within the  
permissible limits  
Best  
Marketable  
-
>4.0 + All parameters of heavy  
3.1 to 3.5  
>3.5  
metals are within the  
permissible limits  
Very good  
Good  
Marketable  
-
-
-
3
.1 to 4.0 + All parameters of  
heavy metals are within the  
permissible limits  
Marketable  
3
.1 to 4.0 + All parameters of  
3.1 to 3.5  
<3.1  
heavy metals are within the  
permissible limits  
Any value+ All heavy metal  
parameters are within the  
permissible limits  
Medium  
Bad  
Marketable  
Can be applied as a soil  
conditioner  
Non-marketable  
Non-marketable  
>4.0 + At least one of the heavy  
Can be used for growing  
fruitless trees and ornamental  
plants  
>3.5  
metal parameters is out of the  
permissible limits  
Bad  
Can be used only for once for  
developing and reclaiming  
lawns, gardens, and uncultivated  
lands  
<
4.0 + At least one of the heavy  
G
>3.5  
metal parameters is out of the  
permissible limits  
Bad  
Non-marketable  
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2020, Volume 8, Issue 4, Pages: 1292-1303  
Water is a vital ingredient for microorganisms to carry out  
their enzyme activities. The good amount of moisture is between  
Shiraz City putrescible waste is rich in organic matter (88.7%)  
and contains low ash content (7.7%). Ash is the inorganic portion  
of putrescible waste and includes different inorganic minerals  
such as Mn, Mg, Ca, Fe, and Na. During the composting process,  
complex organic matters are transformed to simpler components  
which lead to a decrease in organic matter content and an increase  
in ash content.  
5
0% and 65%. Lower moisture contents result in a significant  
reduction in microbial activities and higher contents lead to the  
appearance of anaerobic conditions. As observed, the average  
initial moisture content for the putrescible waste of Shiraz City is  
8
8.1, 87.5, 67.9, and 75.4% in spring, summer, autumn, and  
winter, respectively. The reason for the higher moisture content  
in spring and summer is the high amount of fruit and vegetable  
waste in these seasons. However, due to an increase in  
temperature during the process, a large amount of moisture  
evaporates, and its amount can be adjusted to the acceptable  
range.  
3.2 The amount of compost production  
Between 2013 and 2015, one separation line with the capacity  
of 250 t per day had been in operation. The second line with the  
capacity of 250 t per day has been put into operation in 2016.  
Table 5 shows the separated putrescible waste from CMSW in the  
CMSWSC (input waste to the composting site) and the produced  
compost in different years.  
Based on the results shown in Table 5, about 50 percent of  
input CMSW to the CMSWSC is transferred to the composting  
site. Furthermore, the weight of produced compost is about 36  
percent of input putrescible waste to the composting site. It is  
worth mentioning that about 35 percent of rejected waste is the  
untorn bags of CMSW that contain putrescible waste as well.  
Most of the separated recyclable materials in the CMSWSC are  
plastics contaminated with putrescible waste. If the source  
separation strategy is implemented and recyclable materials are  
separated from putrescible wastes, not only time and energy will  
be saved, but also the cotamination problem of recyclable  
materials will also be solved.  
100  
8
8.1%  
87.5%  
7
5.4%  
80  
60  
40  
20  
0
6
7.9%  
Spring  
Summer  
Autumn  
Winter  
Figure. 4: The average moisture content (%) of Shiraz City putrescible  
waste in each season  
Since microorganisms are active in the 5.5-8.0 pH range,  
putrescible waste has to be adjusted for pH in this range for  
supporting good microbial activities during the composting  
process. However, a slightly acidic pH is favorable in the initial  
stage of the composting process. Therefore, the pH of 5.4 for the  
putrescible waste of Shiraz City is appropriate.  
Table 5: The mean amount of separated putrescible waste and  
produced compost from 2013 to 2016  
Input wastes  
to the  
CMSWSC  
Separated  
putrescible waste  
in the CMSWSC  
Mean produced  
compost (t/d)  
year  
(
t/d)  
(t/d)  
115  
124  
123  
262  
2
2
2
013  
014  
015  
250  
250  
250  
500  
40  
44  
45  
97  
Table 4: The results of chemical analysis of Shiraz City  
putrescible waste  
Parameter  
Organic Matter  
Total Carbon  
Organic Carbon  
Ash  
Unit  
Average content  
88.7  
51.1  
48.5  
7.7  
g g %dw*  
-
1
2016  
-
1
g g %dw  
3
.3 Physical and chemical analysis of the produced compost in  
Shiraz City  
To investigate the quality of produced compost, physical and  
chemical analysis were conducted at different months of 2015 and  
016. Composite method was used for sampling. A sample from  
the surface, a sample from the center, and a sample from the  
bottom of the compost stack was collected; the samples were  
mixed together and a quarter of mixed sample was sent to a  
laboratory. As the results of physical analysis show (Table 6),  
glass comprises a significant percentage of impurities in the  
produced compost due to the lack of source separation of glass.  
Despite many efforts to collect glass manually at the CMSWSC,  
a small fraction of broken glass remains in the produced compost  
and reduces the compost quality. Furthermore, although the  
weight percentage of plastic is not noticeable, its volume is  
considerable. Plastic in the compost, which depresses the compost  
market, is immediately recognized at first glance.  
-
1
g g %dw  
-
1
g g %dw  
C/N ratio  
pH  
-
-
24.3  
5.4  
2
EC  
ds/m  
%dw  
%
mg.kg dw  
mg.kg dw  
11.6  
2.1  
0.3  
5,643.5  
31,800  
5,345  
2,177.5  
5,360.5  
48  
150  
328  
0
61  
1.85  
31.4  
Total Nitrogen  
Phosphorous  
Potassium  
Calcium  
Sodium  
Magnesium  
Iron  
Copper  
Manganese  
Zinc  
Chromium  
Lead  
Cadmium  
Nickel  
-
1
-
1
-
1
mg.kg dw  
-1  
mg.kg dw  
-1  
mg.kg dw  
-1  
mg.kg dw  
-1  
mg.kg dw  
-
1
mg.kg dw  
mg.kg dw  
mg.kg dw  
mg.kg dw  
-
1
-
1
The use of immature compost as a soil fertilizer can have  
harmful effects on the soil and plants functioning due to high  
content of salts and unstable organic compounds (30-32).  
Hindering the plant growth and inducing anaerobic conditions in  
-
1
-
1
mg.kg dw  
1
297  
Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 4, Pages: 1292-1303  
the soil are two of the most important adverse effects (32-34).  
Different researchers disagree on the parameters used for  
evaluating the degree of compost maturity (31). Some parameters  
used in the literature to determine a compost maturity are: C/N  
ratio, pH, electrical conductivity, moisture content, total organic  
matter, total nitrogen, etc (35). Table 7 shows the amount of  
maturity parameters for compost produced in Shiraz City and the  
allowance of each parameter based on compost quality standards  
in Iran. Considering that a first-class compost covers a compost  
with particle size up to 8 mm, quality parameters of 0-5 and 0-15  
mm produced compost have to be controlled based on the first-  
class and second-class standards, respectively. As can be seen in  
Table 7, only the C/N ratio of 0-15 mm compost is not within the  
permissible limits. However, based on the literature, an  
acceptable maturity is obtained for C/N ratio less than or equal to  
Producing a stabilized end-product is of great important in  
composting process. The stability of produced compost depends  
on its microbial respiration activity. Table 8 shows the amount of  
two important types of pathogen and three indicators related to  
the compost stability for produced compost in Shiraz City. As  
observed, E.coli and Salmonella pathogens in the produced  
compost are within the permissible limit. Three studied stability  
indicators are static respiration index (SRI), cumulative  
respiration index (CRI), and C-CO  
maximum rate of oxygen uptake over 24 h, cumulative amount of  
oxygen consumed after 7 d, and the total C-CO produced after  
2
which represent the  
2
the 7 days incubation period, respectively (36-38). More details  
about the calculation method of these indicators and their  
recommended limits for very, moderately, and least stable  
compost are addressed in the Komilis et al. (2011). The lower the  
amount of these indicators, the lower the microbial respiration  
activity and consequently the more stable the produced compost  
[36]. Based on the amount of these indicators and their  
recommended limits, 0-5 and 0-15 mm compost are characterized  
as “very stable” and “moderately stable”, respectively.  
2
5.  
Table 6: The physical analysis of produced compost in Shiraz  
City (2015–2016)  
Weight  
percentage for  
Weight  
Parameters  
percentage for 0-  
mm compost  
3.4 Determining the quality grade of the produced compost in  
Shiraz City  
0
-15 mm  
5
compost  
0.8  
0.5  
0.2  
4.4  
Table 9 presents computed FI and CI for the produced 0-5 and  
Plastic  
Metal  
Textile  
Glass  
0.2  
0.5  
0.1  
1.4  
0
-15 mm composts in Shiraz City. Based on the results, the  
produced composts in Shiraz City belong to Class C and have  
good” quality. The produced composts have high fertilizing  
“
potential and medium heavy metal content. It is worth mentioning  
that the main reason for the low CI is the high cadmium content,  
which is the most crucial factor. If the cadmium content decreases  
The total percentage  
of impurities  
The allowance of  
impurities  
2
6
.1  
5.9  
12  
-1  
to below 0.6 mg.kg dw, the CI will increase to 4 and a compost  
with the best quality will be produced.  
Table 7: The amount of maturity parameters for produced compost in Shiraz City (2015- 2016)  
Second class  
standard  
<20  
>25  
>15  
1-1.5  
<50  
10-15  
6-8  
0-5 compost of  
Shiraz City  
<5  
37.2  
21.9  
1.5  
54.9  
15.4  
7.8  
0-15 compost of Shiraz  
First class standard  
parameter  
Unit  
City  
<15  
60.4  
31.3  
1.3  
40.7  
25.4  
7.9  
Grain size  
Organic matter  
Organic Carbon  
Total Nitrogen  
Ash  
C/N ratio  
pH  
mm  
<8  
>35  
>25  
1.25-1.66  
<50  
g g %dw  
-
1
-
1
g g %dw  
-
1
g g %dw  
-
1
g.g %dw  
-
-
15-20  
6-8  
EC  
Potassium  
Zn  
Phosphorous  
Cd  
SAR  
Cu  
Mn  
Pb  
Ni  
Cr  
Moisture  
ds/m  
mg.kg dw  
<8  
<14  
4.6  
0.8  
239.9  
0.6  
1.8  
0.3  
43  
56.4  
50.9  
15.4  
0
4.7  
1.1  
262.6  
0.7  
1.8  
0.3  
76.9  
56  
53.8  
14  
0
-
1
0.5-1.8  
<1300  
1-3.8  
<10  
<10  
<650  
-
<200  
<120  
<150  
<15  
0.5-1.8  
<1300  
0.3-3.8  
<10  
<10  
<650  
-
<200  
<120  
<150  
<35  
-
1
mg.kg dw  
-1  
g.g %dw  
-1  
mg.kg dw  
-
-
1
mg.kg dw  
mg.kg dw  
-
1
-
1
mg.kg dw  
-1  
mg.kg dw  
-1  
mg.kg dw  
%dw  
8.8  
23.6  
1
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2020, Volume 8, Issue 4, Pages: 1292-1303  
Table 8: The stability parameters of produced compost in Shiraz City (2015- 2016).  
Biological parameters  
E.coli  
Salmonella  
SRI24  
Unit  
MPN/g  
MPN/4g  
Iran standard  
1×10  
3
-
-
0-5 mm compost  
<3  
0
70.9  
1.5  
1.7  
0-15 mm compost  
11  
0
128.4  
3.5  
2.4  
3
-
1 -1  
mg O dry kg h  
g O dry kg  
g C-CO  
dry kg-1  
2
-
1
CRI  
C-CO  
7
2
2
2
-
Table 9: FI, CI, and the quality of produced composts in Shiraz City.  
Shiraz compost  
Fertilizing Index  
Clean Index + The status of heavy metal parameters  
Class Compost quality  
0
-5 mm  
4.3  
3.9 + All parameters of heavy metals within the standard range  
C
Good quality  
0
-15 mm  
4.2  
3.6 + All parameters of heavy metals within the standard range  
C
Good quality  
3
.5 Cost and income from industrial composting in Shiraz City  
The cost per unit weight of the produced compost in Shiraz  
Shiraz City which is far from residential areas, historic sites,  
airports, and water resources. The availability of fuel for  
machinery is another opportunity. The monthly cost of fuel, oil,  
and filter change, depreciation of tires, vehicle insurance, repairs,  
and maintenance is about 0.02 of each machine price. Recently, a  
fresh wave has been launched among people who tend to eat  
organic foods which may be a great opportunity for industrial  
composting in Shiraz City.  
City was calculated around 1,133 Iranian R. (0.03 US $) in 2015  
Table 10). This cost includes the wages of workers,  
(
depreciations, and investments. As observed, much of the cost is  
associated with the investment in the CMSWSC construction.  
The statistics of produced compost show that the weight ratio  
of 0-15 mm compost to 0-5 mm compost was five. The sale price  
of 0-15 and 0-5 mm compost was 0.016 and 0.021 US $/kg,  
respectively. The sale price was not changed from 2013 to 2016.  
Table 11 shows the average income from selling the 0-5 and 0-15  
mm produced compost as well as the total income from  
composting in Shiraz City in different years.  
Fig. 5 illustrates the difference of cost and income from  
composting in different years. As seen, income is less than the  
compost production cost. The main reasons are poor marketing  
strategies for selling the produced compost and the lack of loyal  
customer. People and farmers in Shiraz City often mistakenly  
know compost as “manure” or “fertilizer” while they have  
entirely different characteristics. They are unaware that manure  
may destroy young plants and continuous application of chemical  
fertilizer leads to a decrease in the soil nitrogen content due to  
leaching, an increase in the soil bulk density, and consequently  
soil degradation (1, 22, 39, 40). They must be informed that the  
use of compost as a soil conditioner leads to 1) an increase in the  
content of organic matter and soil moisture, and activities of soil  
12  
1
0
8
6
4
2
0
Cost Income  
2
013  
2014  
2015  
2016  
year  
Figure 5: The cost and income from industrial composting in Shiraz City  
The greatest strength of the compost production from Shiraz  
City CMSW is that it is a step towards sustainable development.  
Although many environmental projects like industrial composting  
in Shiraz City may initially be non-economic, they have a lot of  
moral values in protecting the environment, and even they have  
high value in the long term by protecting resources and  
prolonging the useful lifetime of landfill. Another strength of  
composting in Shiraz City is that about 70% of the generated  
waste is putrescible and the C/N ratio of putrescible waste is in  
the acceptable range. Therefore, investment in the production of  
compost is wise. Also, necessary equipment for separating  
putrescible waste and producing compost is manufactured in the  
country, and there is no need to import any special equipment  
causing a decrease in investment levels, composting challenges,  
and error of the process. The development of this process creates  
many job positions for Shiraz citizens. In addition to those who  
are involved in the transportation of produced compost,  
marketing, and the department of composting management in the  
municipality, 46 workers have been employed in the sorting  
center and composting site. Compost production reduces the need  
for chemical fertilizers which may cause irreversible damage to  
public health and environment.  
enzymes  
(e.g.  
protease,  
arylsuiphatase,  
alkaline  
phosphomonoesterase, phosphodiesterase, and deaminas), soil  
microbial biomass, and soil respiration (41), 2) remediation of  
toxic pollutants such as pesticides and heavy metals in the soil by  
various fungi and bacteria present in the compost (42), 3) the  
prevention of nutrients leaching by increasing the soil aggregate  
stability (43, 44), 4) an increase in the plant growth by enhancing  
the uptake of required nutrients such as potassium and nitrate  
through the plant roots (45, 46), 5) an increase in the plants  
systemic resistance against variant environmental conditions (7,  
4
7, 48), 6) the eradication of plant diseases and soil pathogens  
(48), and 7) an increase in the defense system of plants (49-51).  
3
.6 Assessment of composting in Shiraz City  
The most considerable opportunity of industrial composting  
in Shiraz City is related to the weather conditions. Semi-arid and  
hot climate of Shiraz City causes the monthly mean air  
temperature to be between 7 and 30̊C and average relative  
humidity to be between 24% and 60%. Another opportunity is that  
enough land with low groundwater level has been found around  
1
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2020, Volume 8, Issue 4, Pages: 1292-1303  
Table 10: Cost of compost production in Shiraz City in 2015  
Description of cost  
Cost type  
Monthly cost (US $)  
16,000.00  
Investment  
Depreciations and O&M cost  
5 workers  
1 driver  
4 truck  
1 Bobcat  
1 loader  
Investment  
Depreciations and O&M cost  
Investment  
Depreciations  
The cost of 15,000 kWh consumption per  
month  
CMSWSC construction cost  
Labor cost  
2,453.33  
8,548.80  
Transportation cost of putrescible material within  
the site  
Aeration cost  
6,933.33  
5,691.45  
800.00  
Screening cost  
Power consumption cost  
Total monthly cost (US $)  
Total weight of produced compost (kg/mon)  
Composting cost per kg (US $)  
40,426.91  
1,338,333  
0.03  
Table 11: Income from the sale of compost from 2013 to 2016  
Total income  
from  
composting (US  
Compost type Produced  
Selling  
Income from  
compost selling  
(US $)  
Input waste to  
CMSWSC (t/d)  
Produced  
compost (t/y)  
Year  
(grain size  
mm)  
compost in each price  
type (t/y)  
(US $/kg)  
$
)
0
0
0
0
0
0
0
0
-5  
-15  
-5  
-15  
-5  
-15  
-5  
2,460  
12,300  
2,678  
13,392  
2,677  
13,383  
5,901  
0.016  
0.021  
0.016  
0.021  
0.016  
0.021  
0.016  
0.021  
39,360  
258,300  
42,848  
281,232  
42,832  
281,043  
94,416  
619,584  
2
2
2
2
013  
014  
015  
016  
250  
250  
250  
500  
14,760  
16,070  
16,060  
35,405  
297,660  
324,080  
323,875  
714,000  
-15  
29,504  
The lack of administrative support and a framework for legal  
borne diseases only exert adverse effects on site labors providing  
they do not work according to health and safety laws, codes, and  
regulations. The lack of shelter for the composting site leads to  
rapid evaporation of putrescible waste moisture. So, it is  
necessary to merge the windrows after four weeks so that their  
moisture is kept.  
Based on the assessments, the following suggestions may be  
considered by managers who have the same experience to  
transform weaknesses to strengths and minimize threats to ensure  
the sale of produced compost:  
rules is the most important factor which threatens the industrial  
composting in Shiraz City. The production of compost from  
CMSW is still not a priority and no financial aid is allocated to  
this project. The potential advantages of this project will appear  
by an accurate planning after a long time and until then financial  
assistance from the government is needed to get the project off  
the ground. Another threat is that municipal authorities do not pay  
attention to the quality of the produced compost regarding  
compost appearance and the absence of glass and plastic. This  
will gradually lose the confidence of customers (end users).  
Another threat is related to the citizens’ attitude towards compost  
and chemical fertilizer. Scant attention of the vast majority of  
people about the environment and the importance of its protection  
causes that people do not support buying the compost. Therefore,  
effective marketing plays a vital role in the success of this project.  
The most considerable weakness of composting in Shiraz City  
is that the MSW is collected without any source separation. If the  
glass and plastic are separated at the source, the composting  
efficiency will increase significantly. The emission of greenhouse  
Planning for source separation of wastes before further  
development of the composting project that increases the  
quality of produced compost, reduces composting costs and  
the amount of waste transferred to the landfill, and increases  
the production of compost.  
Due to the glass problems in compost, it is recommended that  
the glass is separated in the source and collected separately or  
it is effectively removed from the CMSWSC.  
Marketing and introducing compost benefits to customers for  
increasing the incomes from composting by achieving a  
dynamic composting industry.  
4 2 3  
gases such as CH , CO , and NH is another weakness in this  
process. However, based on the recommendation of some  
researchers, CO does not contribute in global warming since it is  
Encouraging citizens to cooperate with the Solid Waste  
Management Department.  
Informing farmers about the agricultural applications of  
compost including keeping soil moisture, applying as a soil  
2
generated in a biological process (51, 52). Since the composting  
site is far from residential areas, unpleasant odors and vector-  
1
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Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 4, Pages: 1292-1303  
conditioner, reducing soil erosion, and mulching after  
seeding.  
Notifying forest development authorities about the  
application of compost to reduce irrigation requirements and  
mulching of forest lands to suppress weeds during the  
growing period of trees.  
Utilizing compost as good quality topsoil for quick  
development of lawns in the boulevards and road shoulders  
especially in Shiraz City which has a high demand for  
landscaping.  
Training fishery operators for applying compost as a factor  
for the rapid growth of phytoplankton and, consequently, the  
rapid growth of fish.  
Ethical issue  
Authors are aware of, and comply with, best practice in  
publication ethics specifically with regard to authorship  
(avoidance of guest authorship), dual submission, manipulation  
of figures, competing interests, and compliance with policies on  
research ethics. Authors adhere to publication requirements that  
submitted work is original and has not been published elsewhere  
in any language.  
Competing interests  
The authors declare that there is no conflict of interest that  
would prejudice the impartiality of this scientific work.  
Informing farmers about the dangers of using chemical  
fertilizers and animal manure.  
Implementing policies for increasing the price of chemical  
fertilizers.  
Authors’ contribution  
All authors of this study have a complete contribution for data  
collection, data analyses and manuscript writing  
Ensuring the quality of produced compost for the customers.  
Advising greenhouse managers for applying the compost as a  
soil conditioner and reducing water requirements.  
Applying the produced compost as a biofilter at the  
composting site and daily cover in landfill.  
References  
1
.
Oviedo-Ocaña E, Dominguez I, Torres-Lozada P, Marmolejo-  
Rebellón L, Komilis D, Sanchez A. A qualitative model to evaluate  
biowaste composting management systems using causal diagrams: A  
case study in Colombia. Journal of Cleaner Production.  
The government has a vital role in achieving an efficient  
2
016;133:201-11.  
composting process. The government can ensure the  
sustainability of composting by providing loans, encouraging  
organic farming, and creating a favorable market.  
2
3
4
.
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Elango D, Thinakaran N, Panneerselvam P, Sivanesan S.  
Thermophilic composting of municipal solid waste. Applied Energy.  
2009;86(5):663-8.  
Tun MM, Juchelkova D. Assessment of solid waste generation and  
greenhouse gas emission potential in Yangon city, Myanmar. Journal  
of Material Cycles and Waste Management. 2018;20(3):1397-408.  
Ghosh A, Debnath B, Ghosh SK, Das B, Sarkar JP. Sustainability  
analysis of organic fraction of municipal solid waste conversion  
techniques for efficient resource recovery in India through case  
studies. Journal of Material Cycles and Waste Management.  
4
Conclusions  
This study was conducted on the industrial composting  
process from CMSW in Shiraz City, Iran, by a modified windrow  
composting method. In Shiraz City with a population of 1.5  
million people, 1,000 tonnes of CMSW is collected and  
transferred to the processing site at Barmshoor site every day. In  
processing site, 500 tonnes of 1000 tonnes collected commingled  
solid waste is transported to CMSWSC and the rest of it is  
transferred to a landfill site. Data showed that about 50% of the  
CMSW is being separated as putrescible waste in the CMSWSC.  
The weight of produced compost was about 36% of input  
putrescible waste to the composting site. Based on the CI and FI,  
the produced compost in Shiraz City by the proposed method  
belongs to Class C and has a “good” quality. Produced compost  
has a high fertilizing potential and medium heavy metal content  
and can be sold without any restriction. Despite many efforts for  
manual collection of glass at the CMSWSC, a small fraction of  
broken glass remains in the produced compost. The weight  
percentage of plastic in produced compost is not noticeable, but  
its volume is considerable. Plastic in the compost, which  
depresses the compost market, is immediately recognized at first  
glance. Although these physical impurities in the produced  
compost are within the permissible limits, effective removal of  
glass and plastics is necessary for the production of higher quality  
compost. Furthermore, the stability of produced compost was  
2
018;20(4):1969-85.  
5
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