Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 3, Pages: 1017-1022  
J. Environ. Treat. Tech.  
ISSN: 2309-1185  
Journal web link: http://www.jett.dormaj.com  
Methane Production from the Digestion of Thermally  
Treated Food Waste at 80°C  
Farizah Fadzil , Farihah Fadzil , Siti Mariam Sulaiman , A'isyah Mardhiyyah Shaharoshaha,  
Roslinda Seswoya*  
Micro Pollutant Research Centre (MPRC), Universiti Tun Hussein Onn Malaysia, 86400, Parit Raja, Johor, Malaysia  
Faculty of Civil Engineering and Built Environment, Universiti Tun Hussein Onn Malaysia, 86400, Parit Raja, Johor, Malaysia  
Received: 10/05/2020  
Accepted: 23/06/2020  
Published: 20/09/2020  
Abstract  
Food waste is the most suitable feedstock for anaerobic digestion. However, methane yield from the digestion of food waste is low.  
Therefore thermal pretreatment serves as the best solution. Also, the effect of thermal pretreatment on food waste (Malaysian dietary) before  
anaerobic digestion has low documentation. Hence this research aims to analyze the methane production and its kinetics from the digestion  
of thermally treated food waste. The result showed that thermal treatment improves the bioavailability of food waste, subsequently improve  
the methane production of food waste. The ultimate methane yield for thermally treated food waste at 80°C was 883.08 CH4/gVS higher  
than untreated food waste. The kinetic parameters observed from Modified Gompertz modeling were slightly lower from the laboratory data  
for both substrates. Thus, thermal pretreatment undoubtedly improved the anaerobic digestion of food waste.  
Keywords: Anaerobic, Food waste, Thermal, AMPTS, Gompertz  
List of symbols and unit1  
Symbols and Unit  
thrown from the residential, commercial and institutional areas,  
and it is characterized in ranges of 52 and 66 % in moisture  
Description  
content. MSW increases proportionally with population growth in  
developed and developing countries. The MSW is rising at the  
rate of 0.5-0.8 kg/person-day and is expected to exceed 9 Mt/year  
in the year 2020 [1]. The disposal of MSW in an open dumping  
area is producing environmental impacts on soil, water, and air.  
Dumping MSW on soil affecting soil fertility by reducing the crop  
yield, the degradation of organic waste in the landfill produced  
the leachate. The discharge of untreated leachate into the river  
causes groundwater contamination. Also, the landfill area  
associated with an unpleasant odor and uncontrolled release of  
methane through waste decomposition [2]. The landfill is also  
diminishing the nation's land area to 54% from the year 1990-  
AD  
Anaerobic digestion  
Organic Fraction of Municipal  
Solid Waste  
Municipal Solid Waste  
Food Waste  
OFMSW  
MSW  
FW  
Thermally treated food waste at  
FW80  
8
0°C  
BMP  
Biomethane Potential  
Automated Methane Potential  
Test II  
Total Solid  
Volatile Solid  
Chemical Oxygen Demand  
Alkalinity  
Modified Gompetrz Model  
Lag phase  
Ultimate methane yield  
Methane production rate  
AMPTS II  
TS (g/L)  
VS (g/L)  
COD (mg/L)  
2
008 in Malaysia [1]. 30% of MSW is food waste [3]. Food waste  
causes alarming problems to its surroundings due to its essence as  
material that is easy to decompose [3].  
3
(mgCaCO /L)  
GM  
(day)  
Food waste can be segregated into four groups, which are  
edible, non-edible, avoidable, and unavoidable. The edible food  
waste, also known as avoidable food and is defined as the food  
and drinks that are eaten by people. Others choose not to  
consume, whereas the non-edible and unavoidable food waste is  
the residue food preparation [4]. Food waste consists of complex  
(
(
mlCH  
mlCH  
4
4
/gVS)  
/gVS-day  
1
Introduction  
Municipal solid waste (MSW) is defined as unwanted waste  
Corresponding author: Roslinda Seswoya, (a) Micro Pollutant Research Centre (MPRC), Universiti Tun Hussein Onn Malaysia, 86400,  
Parit Raja, Johor, Malaysia; and (b) Faculty of Civil Engineering and Built Environment, Universiti Tun Hussein Onn Malaysia, 86400, Parit  
Raja, Johor, Malaysia. E-mail: roslinda@uthm.edu.my.  
1
017  
Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 3, Pages: 1017-1022  
organic compounds (e.g carbohydrate polymers, lipids, protein,  
and some other inorganic components (e.g silica) [3]. About a  
quarter of 1.3 billion food was lost along the food chain due to  
human consumption, in the way of preparation of food (e.g food  
processing factory) [5].  
The method for treating MSW includes incineration, landfill,  
and anaerobic digestion [1]. Anaerobic digestion was used for  
treating the organic fraction of municipal solid waste (OFMSW),  
particularly food waste [6]. Anaerobic digestion is a devoted  
method to manage food waste due to its high bio-methane  
potential [7]. It can develop renewable energy (methane and  
hydrogen), volatile fatty acid (VFA), and alcohol. Anaerobic  
digestion is the cost-effective treatment in managing waste  
because of high energy recovery and low environmental impact  
Gomperts Modelling [22]. Modified Gompertz is regarded as the  
kinetic model of asigmoid function, which is used for a time series  
as a mathematical model [23]. Modified Gompertz is the highest  
feature in anticipating the output of biogas, as the model has one  
of the highest fits for methane manufacturing information as a  
function of time [24]. In this model, the rate of biogas production,  
the maximum biogas production, and the lag phase can be  
estimated [25]. Gandhi et al., [18] evaluated the kinetics of  
anaerobic digestion of food waste using Modified Gompertz  
modeling, and it is reported that the ultimate biogas yield was  
improved from the digestion of thermally treated food waste at  
80°C and the lag phase was reduced significantly. Unfortunately,  
there is limited information on the anaerobic digestion of  
thermally treated food waste in Malaysia. Therefore this research  
aspiration is to study the effect of thermal pretreatment of food  
waste towards the methane yield.  
[
3]. Besides, anaerobic digestion is the biochemical method that  
occurs when there is no oxygen at all [8]. The absence of oxygen  
is a significant difference between anaerobic and aerobic  
digestion [9]. Anaerobic digestion involves several biochemistry  
processes, such as hydrolysis, acidegenosis, acetogenesis, and  
methanogenesis [10]. The implementation of anaerobic digestion  
can improve the economic feasibility and become an  
environmentally sustainable solution in managing waste [11]. For  
instance, methane from anaerobic digestion can replace fossil fuel  
power used and reduce greenhouse emissions [12].  
2
Material and Methodology  
2
.1 Substrate and inoculum  
The food waste was collected from a cafeteria. The collected  
food waste consists of cooked food such as meat, rice, bone, and  
vegetables [26]. Impurities such as bone, tissue, and plastic were  
manually removed and sorted [11]. The fresh food waste was  
collected for two days. The collection during this period is due to  
the cafeteria operation period. The special treatment such as  
sterilization is not conducted on food waste. Then, the fresh food  
waste was diluted with tap water at a ratio of 1:1 for food waste  
slurry preparation [27]. After that, the food waste was  
homogenized with the aid of kitchen blender [22]. The food waste  
was filled in a 1 L glass bottle (Schott Duran) and then was  
thermally treated in the oven at 80°C for about 1.5 hours [13].  
After 1.5 hours, the bottle was left to cool at room temperature  
before it was used for biochemical methane potential (BMP) test  
The ultimate methane yield from the digestion of food waste  
is low [13] because the solubilization of particulate matter to  
simple monomer during the hydrolysis stage of the anaerobic  
digestion process requires a long time and thus making this step  
problematic [14]. Pretreatment was applied to enhance the biogas  
production and overcome problems during the hydrolysis stage of  
anaerobic digestion of food waste. The pretreatment methods are  
mechanical, biological, chemical, and thermal [13]. Thermal  
o
pretreatment was introduced at a mild temperature of 55 to 90 C  
[
15]. Thermal pretreatment increased the organic particle  
[
13].  
Anaerobically digested sludge used as inoculum was collected  
solubilization, subsequently making it more assessable by  
anaerobic microbes [13].  
from an anaerobic digester treating POME. The sludge was stored  
in a plastic container and refrigerated at 4°C prior used for BMP  
testing [28].  
Thermal pretreatment is a proven approach, as it improved the  
digestion process [16]. The characteristics of food waste such as  
COD, carbohydrate, and protein were also enhanced as well as  
methane production after undergoing thermal pretreatment [17].  
Gandhi et al., [18] observed an improvement in protein  
solubilization after the thermal pretreatment process. According  
to Jin et al., [19], the changes in pH after thermal pretreatment are  
lesser in low temperature and higher in high temperature  
depending on the duration of the pretreatment. Longer period with  
the high temperature of pretreatement, increased the release of  
organic acid, making the pH of the substrate to reduce [19].  
Thermally treated food waste obtained a higher value of total  
solids, volatile solids, and chemical oxygen demand (COD) than  
the untreated food, indicated that the thermal pretreatment  
increased bioavaiability. Bioavailability makes the thermally  
treated food waste easily digested subsequently resulted in higher  
methane yield [20]. Meanwhile, according to Ariunbaatar et al.,  
2
.2 Biodegradability assay (biochemical methane potential)  
BMP is a well known effective technique for evaluating the  
rate of methane transformation of organic matter [29]. The batch  
test was conducted by practicing Automated Methane Potential  
System Test System II (AMPTS II), as shown in Figure 1  
[1][26][30]. The system serves swift service of measuring  
biomethane flow and ultra-low biogas in determining biogas  
potential [30].  
The digestibility of food waste was studied through a series of  
batch anaerobic digester conducted using a 500ml digester with a  
mass of 400g [31]. The value of substrate and inoculums added  
into the mixture were calculated based on VS [31]. Substrate and  
inoculums were mixed at inoculum to substrate ratio of 2.0 [28].  
This ratio is recommended to avoid the inhibitory effect [32]. The  
pH of each reactor was recorded between 7.2 to 7.4. This pH is in  
the range for anaerobic digestion, which is from 6.5 to 7.5 [33].  
The reactor was flushed with nitrogen for two minutes to provide  
an anaerobic condition [30]. Mesophilic state (37±0.5°C) was  
maintained by a thermostatic water bath incubator [26]. The  
reactor was stirred with a mechanical mixing at 90rpm [18].  
[
13], the thermal pretreatment at 80°C for 1.5 hours produces  
higher methane yields than untreated food waste. The difference  
in methane yield between untreated food waste and thermally  
treated food waste at 80°C was about 221.5 ml CH /gVS.  
4
Kinetic analysis is implemented to predict and express the  
performance of anaerobic digestion systems [21]. The kinetic  
analysis of anaerobic digestion can be accomplished using First  
Order Kinetic, the Logistic Function Model, and Modified  
1
018