CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 56, 2017 

A publication of 

 
The Italian Association 

of Chemical Engineering 
Online at www.aidic.it/cet 

Guest Editors: Jiří Jaromír Klemeš, Peng Yen Liew, Wai Shin Ho, Jeng Shiun Lim
Copyright © 2017, AIDIC Servizi S.r.l., 
ISBN 978-88-95608-47-1; ISSN 2283-9216 

Feedstock Amendment for the Production of Quality Compost 
for Soil Amendment and Heavy Metal Immobilisation 

Lim Li Yeea,b , Lee Chew Tin*a,b , Lim Jeng Shiunb,c, Jiří Jaromír Klemešd, Ho Chin 
Siongb,e, Nur Naha Abu Mansorf 
a
Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia (UTM), 81310 UTM Skudai, Johor Bahru, 

Johor, Malaysia 
b
UTM Low Carbon Asia Research Centre, Universiti Teknologi Malaysia (UTM), 81310 UTM Skudai, Johor Bahru, Johor, 

 Malaysia 
c
Process Systems Engineering Centre (PROSPECT), Research Institute for Sustainable Environment, Universiti Teknologi 

 Malaysia (UTM), 81310 UTM Johor Bahru, Johor, Malaysia 
d
Faculty of Information Technology and Bionics (Pázmány Péter Katolikus Egyetem, Információs Technológiai és Bionikai 

 Kar), Práter u. 50/a, 1083 Budapest, Hungary 
e
Faculty of Built Environment, Universiti Teknologi Malaysia (UTM), 81310 UTM Johor Bahru, Johor, Malaysia  

f
Faculty of Management, Universiti Teknologi Malaysia (UTM), 81310 UTM Johor Bahru, Johor, Malaysia. 
 ctlee@utm.my 

Composting is a waste management technology for recycling organic waste. A compost without detectable of 
pathogens and heavy metals can act as a soil conditioner or organic fertilizer to promote plant growth. It 
provides the soil with organic matter and nutrients, improving soil texture and water holding capacity and 
suppressing plant diseases with the presence of beneficial microorganisms. Many researchers aim to improve 
the quality of compost at a reduced process cost and composting duration. Preferably the composting process 
also offers the co-benefits of reduced environmental impact. The quality of the compost is closely related to 
the feedstock used for the composting. The feedstock ranges from bio-waste, plant- and animal-based 
agricultural waste and sometimes the organic fraction in the municipal solid waste. This paper reviews a range 
of feedstock amendment methods including the addition of bulking agent or chemical additive, inoculation with 
earthworm or microbial inoculants, and the addition of the mature compost, that could influence the 
composting process and the end product quality. The potential of immobilisation of the heavy metals in the 
waste material through composting was also discussed. 

1. Introduction 
As the backbone of many developing countries, agricultural sectors face various global challenges, including 
climate change, urbanization, and some environmental issues such as leaching and accumulation of 
pesticides and fertilizers. The performance of the conventional farming associated with the overconsumption 
of chemical fertilizers has led to some severe environmental problems. To cope with the natural leaching 
caused by the loss of around 2/3 of the applied fertilizers, high amount of fertilizers has been applied and 
resulted in the contamination of ground water (especially by nitrate, or some other pollutants such as 
pesticides) (Devassine et al., 2002). World fertiliser consumption rate had increased from 98.7 to 120 kg per 
hectare of arable land from year 2002 to 2013 (Food and Agriculture Organisation, 2016). According to the 
Department of Statistics (2016), Malaysia’s population reaches 31.7 million in 2016 with an annual growth rate 
of 1.5 % where 71 % of the total population has resided in the urban area in tandem with the rapid 
development of Malaysia. Rapid population growth and urbanisation have increased the generation of the 
solid waste. In many fast developing countries such as Malaysia, landfilling remained the main disposal 
method, i.e about 94.5 % of the collected wastes is disposed in the landfills, with a recycling and composting 
rate of 5.5 and 1 % (Periathamby et al., 2009). About 57 % of the waste is made out of organic solid waste 
(Saeed et al., 2009). 

                               
 
 

 

 
   

                                                  
DOI: 10.3303/CET1756084

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Lim L.Y., Lee C.T., Lim J.S., Klemeš J.J., Ho C.S., Mansor N.N.A., 2017, Feedstock amendment for the production of 
quality compost for soil amendment and heavy metal immobilisation, Chemical Engineering Transactions, 56, 499-504  
DOI:10.3303/CET1756084   

499



Composting can be an alternative to overcome these challenges. Composting is a biological process which 
converts organic wastes into a stable organic product with high humic substances that last longer in soil. It 
involves a relatively low processing cost and less complicated technology. Composting has been widely 
practised in many developing countries however the replacement ratio of compost for chemical fertilizer is still 
low due to the inconsistency in the end quality of compost (Fan et al., 2016). Composting transforms the 
organic wastes into compost that can be used to improve soil quality, minimise soil erosion, and promote plant 
growth. Table 1 lists general requirements for organic fertiliser according to Malaysia Standard MS1517:2012. 
This paper reviews the feedstock amendment strategies during composting to enhance the end compost 
quality and the immobilisation of bioavailable heavy metal in compost and soil. 

Table 1: General requirements for organic fertiliser 

Characteristic Recommendation Range 
Moisture Content ≤ 30 % (wet weight basis) 
Organic Matter Content ≥ 50 % 
Nitrogen Content ≥ 1.5 % 
C/N Ratio ≤ 25 : 1 
Maximum Permissible Value for Heavy 
Metals 

Cr ≤ 200 mg/kg; Pb ≤ 300 mg/kg; Ni ≤ 150 mg/kg; Cd ≤ 5 
mg/kg; Hg ≤ 2 mg/kg; As ≤ 50 mg/kg 

Pathogenic Evaluation E. coli < 10 cfu/g; Pseudomonas aeruginosa < 10 cfu/g; 
Salmonella: Absent; Staphylococcus aureus < 10 cfu/g 

2. Feedstock amendments during composting 
Several amendments can be made during the composting process to improve the efficiency of the process as 
well as the quality of the final compost. A range of amendment strategies during composting has been 
reported to mitigate the emission of greenhouse gases (GHG) (Bong et al., 2016). Common amendment 
strategies include the control of the aeration rate, addition of bulking agent or chemical additive, inoculation 
with earthworm or microbial inoculants, and covered or mixed the compost with the mature compost. Table 2 
shows the positive effect of different amendments in the final compost quality. Most of the amendments gave 
more than 50 % of increment in the final nutrient concentrations with lower carbon-to-nitrogen (C/N) ratios 
indicating a better degree of waste degradation. For instance, a two-stage composting technology, amended 
with earthworm and chemical (Zhang and Sun, 2015) or matured compost (Zhang and Sun, 2016), has 
enhanced the decomposition of the recalcitrant green waste. It was likely that the beneficiary microbes in the 
mature compost improved the biochemical transformation of the organic materials, while earthworms 
enhanced the substrate availability to microbes (Lim et al., 2014). This innovative composting system has 
shortened the traditional composting period (90 - 270 d) to 30 d. 
The addition of microbial inoculant (MI) improves the degradation of the organic waste and humic substance 
formation. It is a common practice when interact with those recalcitrant organic wastes, i.e. lignocellulosic- and 
cellulosic- based wastes such as oil palm empty fruit bunches and wood bark. Previous studies indicated that 
the effect of MI for composting is more significant on the recalcitrant organic wastes than the easily 
degradable waste such as the food waste. MI enhances the initial microbial population in the waste by 
providing higher concentration of enzymes for the degradation of substrates. Single MI tends to offer a more 
specific and reproducible effect when degrading specific substrates. A similar quality of final compost was 
obtained when the sugar-cane waste by-products were inoculated with either Pleurotus sajorcaju alone or the 
mixed culture of Pleurotus sajorcaju, Trichoderma viridae, Aspergillus niger, and Pseudomonas striatum 
(Kumar et al., 2010). The effect of single or mixed MI is complicated and specific to the characteristics of the 
feedstock and operating conditions.The addition of chemical or mineral additive, such as zeolite and biochar, 
are able to increase the water and nutrient retention, reduce N volatilisation, improve aeration, enhance 
microbial activities, mitigate GHG emission, and immobilise the heavy metal in compost and soil following 
compost application (Zhang and Sun, 2015). According to Zhang and Sun (2015), zeolite have the unique 
structure that is efficient in adsorbing gases, water, nutrients, and heavy metals and stabilising the final 
compost. Covering or mixing the compost pile with the mature compost was report to reduce the GHG 
emission, the mature compost can also serve as the microbial inoculant for the next cycle of composting 
(Fukumoto et al., 2011). Although aeration rate is the main factor that influences the compost stability and 
GHG emission, it has little impact in the final compost quality (Yuan et al., 2016).  

500



Table 2: Type of amendment made during composting and their respective effect in improving the final 
compost quality  

Refere
nce 

Study 
Area 

Composting System Waste 
Duration
(d) 

Amendment 
Nutrient content (%) 

C/N N P K 
Zhang 
and 
Sun 
(2015)  

Beijing, 
China 

Two-stage composting 
process: 
• Primary 

Fermentation (PF): 
cement containers (6 
L × 2 W × 1.5 H m) 
with automated 
turning and watering 
system 

• Second 
Fermentation (SF): 
windrow with 
trapezoidal cross-
section (2 L × 1.5 W 
× 1 H m) 

Green 
waste 

PF: 6 
SF: 24 

a) No 
amendment 

17.22 2.27 0.12 0.30

b) 0.3 % 
earthworm 
casts + 25 % 
clinoptilolite 

5.02 4.23 0.58 0.91

Zhang 
and 
Sun 
(2016)  

Beijing, 
China 

Two-stage composting 
process: 
• PF: cement 

containers (6 L × 2 
W × 1.5 H m) with 
automated turning 
and watering system

• SF: windrow with 
trapezoidal cross-
section (2 L × 1.5 W 
× 1 H m) 

Green 
waste 

PF: 6 
SF: 24 

a) No 
amendment 

-- 2.07 0.08 0.26

b) 15 % 
woodchip + 
35 % 
composted 
green waste 

-- 4.90 0.72 1.01

Lim et 
al. 
(2014)  

Selangor, 
Malaysia 

Rectangular plastic 
containers (17 cm × 14 
cm × 12 cm) 
Compost was 
periodically turned for 2 
weeks followed by a 6-
weeks 
vermicomposting 

POME 56 a) 1 part rice 
straw : 3 
parts POME 
(without 
earthworms) 

20.36 -- 0.36 1.01

b) 1 part rice 
straw : 3 
parts POME 
(with 
earthworms) 

9.64 -- 0.63 2.14

Kumar 
et al. 
(2010)  

India 60 kg pre-decomposed 
substrates (6 d) were 
subjected to compost 
(30 d) with microbial 
inoculation followed by 
vermicomposting 
(another 40 d) 

Press-
mud: 
bagasse: 
sugarcane 
trash = 1: 
1: 1 

70 a) Without 
microbial 
inoculant 

-- 0.96 0.88 0.60

b) With 
microbial 
inoculant (P. 
sajorcaju) 

-- 1.40 1.44 1.82

Awasthi 
et al. 
(2016)  

Shanxi, 
China 

130 L bench-scale PVC 
composter air was 
pumped from the 
bottom into the 
composter with a 
constant air flow about 
0.35 L h

−1 kg−1 dry 
weight during 
thermophilic phase 

dewatered 
fresh 
sewage 
sludge: 
wheat 
straw =  
1: 1 (C/N 
~25) 

56 a) No 
amendment 

25.7 1.63 0.93 2.85

   b) Amended 
with 1 % lime 
and 12% 
biochar 

11.8 2.41 1.24 2.70

 

501



According to Yuan et al. (2016), higher AR (≥ 0.3 L·kg-1 dry matter·min-1) might lead to the insufficient in 
compost sanitation, especially when running a laboratory scale composting. The insufficient heat during the 
process caused by high AR also decreased the degree of compost maturity and humification. Low (0.4 L·kg-
1·min-1) to medium (0.6 L·kg-1·min-1) AR were suggested by Rasapoor et al. (2009) when running a larger 
scale (3 m wide × 6 m long × 1.6 m high) composting process when considering from the aspect of energy 
consumption and overall compost maturity. 

Table 3: Effect of composting or compost for the immobilisation of heavy metal and compost quality  

Refere
nce 

Study 
Area 

Type of 
Compost 

Nutrient content (%) Experimental 
Design 

Composting Effect  
C/N HA pH 

Al 
Mamun 
et al. 
(2016) 

New 
Zealand 

Municipal 
compost 

9.10 -- 7.40 Addition of 2.5% 
compost to soil 
(Pukekohe and 
Levin soil) 

Application of compost 
decreased the Cd uptake by 
20 – 60 % (plant type: onion, 
spinach, lettuce) 

Tapia 
et al. 
(2010)  

Madrid, 
Spain 

Pruning 
waste + 
biosolids 
 (1 : 3 w/w) 
compost 

15.20 8.40 6.90 Sequential 
extraction of Cd 
from compost 
after 4-week 
incubation with 80 
or 200 mg/kg Cd 

Only 0.2 % of Cd leached out 
from the compost 

Lv et al. 
(2016)  

Shang-
hai, 
China 

Vermicompo
sted cattle 
dung (CD) 

13.60 6.23 7.90 Using sequential 
extraction to 
evaluate the 
effects of 
vermicomposting 
on the Speciation 
and mobility of 
heavy metals (Zn, 
Pb, Cr, and Cu) in 
CD and PM 

The total heavy metals in the 
final CD and PM were higher 
than the initial values and also 
the control without the worms 
(due to the concentrated of 
substrates), however 
vermicomposting decreased 
the migration and availability 
of heavy metals 

Vermicompo
sted pig 
manure 
(PM) 

13.30 5.70 7.10 

Song et 
al. 
(2014)  

Su-
zhou, 
China 

Vermicompo
sted cow 
manure/ 
mushroom 
residues  

11.32 5.62 7.57 Investigating the 
effects of 
vermicomposting 
on the mobility 
and availability of 
heavy metal 

Composting increased the 
total heavy metal 
concentration irrespective of 
the presence of earthworm in 
both cases; but the availability 
of heavy metal significantly 
decreased especially in 
vermicomposting 

Vermicompo
sted pig 
manure/ 
mushroom 
residues 

10.43 6.70 7.35 

Awasthi 
et al. 
(2016)  

Shaan
xi, 
China 

Dewatered 
fresh 
sewage 
sludge : 
wheat straw 

11.80 17.23 7.72 Evaluating the 
effect of lime and 
biochar 
amendment on 
bio-availability of 
heavy metals 

Amended compost showed 
higher humic acid (17.23 %) 
concentration which reduced 
the bio-availability of heavy 
metals (34.81 % Cu, 56.74 % 
Zn, 87.96 % Pb and 86.65 % 
Ni) and improved compost 
maturity 

Singh 
and 
Kalamd
had 
(2013)  

India Water 
hyacinth: 
cattle 
manure: 
sawdust = 6 
: 3 : 1 

-- -- 7.3-
7.7 

Determining the 
bioavailability and 
leachability of 
heavy metals (Zn, 
Cu, Mn, Fe, Ni, 
Pb, Cd and Cr) in 
compost mixed 
with lime 

Addition of lime (≤2 %) can 
enhance the composting 
temperature (to >57 °C), 
organic matter degradation 
(up to 38.5 %) and reduce the 
bioavailability and leachability 
of heavy metals (>61 %) 

502



3. Immobilisation of heavy metal by compost 
Intensification of industrialisation and urbanisation, and the intensive use of chemical fertiliser, herbicide, 
pesticide, and fungicide, have caused the contamination of many agricultural soils with heavy metals (Khairiah 
et al., 2012). These heavy metals can lead to severe health issue if they enter the food chain via the 
vegetables and animal feedstock. Composting can be a potential solution to overcome this issue. Composting 
has been reported to immobilise the heavy metals in the waste. Table 3 shows the effect of composting on the 
immobilisation of heavy metal in the contaminated waste and soil. With the formation of humic substances 
(HS), composting can reduce the bioavailability of heavy metals. HS are physically and chemically 
homogeneous mixture with relatively high molecular mass and stability. The present of carboxyl and hydroxyl 
groups in HS allowed their strong interaction with heavy metals. The concentration of heavy metals increased 
during the composting process due to the concentrated effect of substrates, however the bio-availability of the 
heavy metal was significantly decreased. Reduced bio-availability of the heavy metal is crucial to avoid the 
uptake by the plants. All reviews on the immobilisation of heavy metal by the amendment methods are 
summarised in Table 3. 
Apart of the presence of HS, pH is another key factor that affects the mobility of heavy metal. The higher the 
pH of the compost (pH 6 and above), the more stable the insoluble complexes formed between heavy metals 
and the organic matters (Tapia et al., 2010). According to Al Mamun et al. (2016), the uptake of Cd by plants 
has been reduced by 30 – 60 % at a higher pH of the soil (at pH 6.2) following the application of compost. The 
application of amendments, such as earthworm inoculation and alkaline materials and mineral additives, into 
compost also improved the immobilisation of heavy metal.  The mineral additives can improve the heavy 
metals binding by the stable organic matter while the addition of alkaline material, such as lime, can increase 
the compost pH and these further lead to the decrease in the bioavailability of heavy metals (Singh and 
Kalamdhad, 2013).  
Vermicomposting combined the positive effects by the earthworms and microorganisms. Vermicomposting 
could offer a higher degree of humification (Lv et al., 2016), as it could directly or indirectly accelerate the 
humification process through their digestion, burrowing or simulating (Song et al., 2014). Earthworms can also 
bio-accumulate the heavy metal in their bodies. Vermicomposting seems to be more efficient in decomposing 
the waste with heavy metals contamination and to produce better quality compost with higher humus content 
and less phytotoxicity, and within a shorter period of composting. 

4. Conclusions 
Composting can be a viable and effective treatment for organic waste management. With the application of 
feedstock amendments for composting, higher rates of composting, assimilation of nutrient contents and the 
immobilisation of heavy metals could be achieved. Future study should intensify the potential of microbial and 
earthworms to achieve high efficiency for the immobilisation of heavy metals content for the composting of 
organic waste followed by the plant uptake study on the bio-available of heavy metals.   

Acknowledgments  

The authors acknowledge research grants from the Ministry of Higher Education (MOHE) Malaysia with grant 
no. 7301.4B145 and 2546.15H25; and from Universiti Teknologi Malaysia with the grant no. 2546.14H65 and 
2501.10H28.  The authors also acknowledge the funding and support from JICA-JST-SATREPS entitled 
“Development of Low Carbon Scenarios in Asian Region” and support from the Faculty of Information 
Technology and Bionics, Pázmány Péter Catholic University in Budapest, Hungary. 

Reference  

Al Mamun S., Chanson G., Muliadi, Benyas E., Aktar M., Lehto N., McDowell R., Cavanagh J., Kellermann L., 
Clucas L.,  Robinson B., 2016, Municipal composts reduce the transfer of Cd from soil to vegetables, 
Environmental Pollution 213, 8-15. 

Awasthi M.K., Wang Q., Huang H., Li R., Shen F., Lahori A.H., Wang P., Guo D., Guo Z., Jiang S.,  Zhang Z., 
2016, Effect of biochar amendment on greenhouse gas emission and bio-availability of heavy metals 
during sewage sludge co-composting, Journal of Cleaner Production 135, 829-835. 

Bong C.P.C., Lim L.Y., Ho W.S., Lim J.S., Klemeš J.J., Towprayoon S., Ho C.S., Lee C.T., 2016, A review on 
the global warming potential of cleaner composting and mitigation strategies, Journal of Cleaner 
Production, DOI: 10.1016/j.jclepro.2016.07.066. 

Department of Statistics Malaysia, 2016, Current population estimates, Malaysia, 2014 - 2016 
<www.statistics.gov.my/index.php?r=column/cthemeByCat&cat=155&bul_id=OWlxdEVoYlJCS0hUZzJyRU
cvZEYxZz09&menu_id=L0pheU43NWJwRWVSZklWdzQ4TlhUUT09> accessed 15.08.2016 

503



Devassine M., Henry F., Guerin P., Briand X., 2002, Coating of fertilizers by degradable polymers, 
International Journal of Pharmaceutics 242(1–2), 399-404. 

Fan Y.V., Lee C.T., Klemeš J.J., Bong C.P.C.,  Ho W.S., 2016, Economic assessment system towards 
sustainable composting quality in the developing countries, Clean Technologies and Environmental Policy 
DOI: 10.1007/s10098-016-1209-9. 

Food and Agriculture Organization, 2016, Fertilizer consumption (kilograms per hectare of arable land) <data. 
worldbank.org/indicator/AG.CON.FERT.ZS?end=2013&start=2002&view=chart>accessed 20.09.2016 

Fukumoto Y., Suzuki K., Kuroda K., Waki M.,  Yasuda T., 2011, Effects of struvite formation and nitratation 
promotion on nitrogenous emissions such as NH3, N2O and NO during swine manure composting, 
Bioresource Technology 102 (2), 1468-1474. 

Khairiah J., Tharmendren M.S.M., Habibah J., Zulkefly H., Kamal W.I.W.,  Ismail B.S., 2012, Heavy metal 
content in paddy soils of Ketara, Besut, Terengganu, Malaysia, World Applied Sciences Journal 19 (2), 
183-191. 

Kumar R., Verma D., Singh B.L., Kumar U.,  Shweta, 2010, Composting of sugar-cane waste by-products 
through treatment with microorganisms and subsequent vermicomposting, Bioresource Technology 101 
(17), 6707-6711. 

Lim S.L., Wu T.Y., Clarke C., 2014, Treatment and Biotransformation of Highly Polluted Agro-industrial 
Wastewater from a Palm Oil Mill into Vermicompost Using Earthworms, Journal of Agricultural and Food 
Chemistry 62 (3), 691-698. 

Lv B., Xing M., Yang J., 2016, Speciation and transformation of heavy metals during vermicomposting of 
animal manure, Bioresource Technology 209, 397-401. 

Periathamby A., Hamid F.S., Khidzir K., 2009, Evolution of solid waste management in Malaysia: impacts and 
implications of the solid waste bill, 2007, Journal of Material Cycles and Waste Management 11 (2), 96-
103. 

Rasapoor, M., Nasrabadi, T., Kamali, M., Hoveidi, H., 2009, The effects of aeration rate on generated compost 
quality, using aerated static pile method, Waste Management 29 (2), 570-573. 

Saeed M.O., Hassan M.N., Mujeebu M.A., 2009, Assessment of municipal solid waste generation and 
recyclable materials potential in Kuala Lumpur, Malaysia, Waste Management 29 (7), 2209-2213. 

Singh J., Kalamdhad A.S., 2013, Effects of lime on bioavailability and leachability of heavy metals during 
agitated pile composting of water hyacinth, Bioresource Technology 138, 148-155. 

Song X., Liu M., Wu D., Qi L., Ye C., Jiao J., Hu F., 2014, Heavy metal and nutrient changes during 
vermicomposting animal manure spiked with mushroom residues, Waste Management 34 (11), 1977-83. 

Tapia Y., Cala V., Eymar E., Frutos I., Gárate A.,  Masaguer A., 2010, Chemical characterization and 
evaluation of composts as organic amendments for immobilizing cadmium. Bioresource Technology, 101 
(14), 5437-5443. 

Yuan J., Chadwick D., Zhang D., Li G., Chen S., Luo W., Du L., He S., Peng S., 2016, Effects of aeration rate 
on maturity and gaseous emissions during sewage sludge composting, Waste Management, DOI: 
10.1016/j.wasman.2016.07.017. 

Zhang L., Sun X., 2015, Effects of earthworm casts and zeolite on the two-stage composting of green waste, 
Waste Management 39, 119-129. 

Zhang L., Sun X., 2016, Influence of bulking agents on physical, chemical, and microbiological properties 
during the two-stage composting of green waste, Waste Management 48, 115-126. 

504