Municipal solid waste (MSW) is a solid waste that is commonly described as trash or garbage that is generated daily by household, commercial establishment, industries, and others. It is regarded as an inevitable and valueless by-product due to community activities. The MSW is one of the main waste source streams beside commercial and industrial waste and construction waste. The MSW generally comprises of food waste, plastics, paper, glass, metal, landscape waste, etc. [1
]. Food waste is the major proportion of household waste in Malaysia when compared to an urban area in South-Eastern (40%) and Central Europe, which comprises about 24% of their MSW composition [2
]. The food waste needs to be reduced by half, as stated in the United Nations sustainability development goals (SDGs) 12.3 [3
]. The accumulation of food waste in MSW has created another burden to the society and urban setting [4
]. The composition and amount of MSW that are generated vary from place to place due to geographical regions urbanisation, degree of industrialisation, socioeconomic [5
], lifestyle, education, and family composition [6
]. The growth in urban population contributes to the increasing food consumption, which leads to the increasing MSW generation in Asian countries [6
]. In Medan, Indonesia, the urban population generates about 0.295 kg/person/d of MSW as compared to the suburb population with 0.18 kg/person/d [7
]. Developed countries usually produce higher MSW (522–759 kg/person/y) when compared to the developing countries 110–525 kg/person/y. The MSW may become potential threats to the environment, as it is estimated to exceed two-billion t/y globally [8
]. In Asia, more than one-million/d of MSW generated and expected to hit 1.8 million tons by 2025 [6
]. Malaysia is one of the Asian countries that has consistently recorded a remarkable economic development. Malaysia’s is about $
10,570/capita with a population of about 30 million in 2016 [9
]. As a developing country, Malaysia is experiencing an increase of urban population growth, leading to the development, rapid urbanisation and industrialisation, and finally contributes to the increment of MSW generation [10
]. In 2007, 17,000 t/d [11
] of household waste has been generated in Malaysia, which then doubled in 2012 from 1.00 to 1.33 kg/capita/d on average. This number is expected to increase by 49,670 t/d in the year 2020 [12
Education institutions are expected to drive an effort towards efficient waste management for the sustainability of the environment. Waste management is one of society’s main issues to be discussed in universities in the form of research, teaching, and outreach activities [13
]. In Malaysia, some public and private universities have studied solid waste management, such as waste management [14
], from cafeteria [15
] and office building [16
], producing a final report as an output. However, the data obtained from these studies still require lab study. The lack of comprehensive collaboration, on-site experience and understanding, and networking between the government agencies and universities are among the barriers suppressing the cradle-to-cradle strategies [17
]. Filling a gap of the MSW management is crucial to foresee the potential solution that may be provided by the university in the specific scope and its capability [13
]. As reported, the financial abilities and inadequate infrastructure are the most challenging factors in waste management due to the large amount of MSW generated [18
]. The option of appropriate treatment technology, such as biological approach, could be the best answer, as it will take care of the solid waste treatment and able to produce by-products as for green energy [19
Anaerobic digestion (AD) is likely to be one of the most promising technologies for converting organic waste into bioenergy, including methane-rich biogas [20
] and fertilizer products [21
]. In New Zealand, AD is considered to be the most attractive solution for waste management, as it is environmentally friendly, economical, and consistent with the country’s existing waste management strategy [22
]. AD is a complex biochemical process that combines chemical and physicochemical reactions in series, involves different microbial species that potentially treat organic waste, and produces renewable energy [23
]. AD using food waste as feedstock to produce bioenergy, such as biomethane [23
], biohydrogen [24
], and bioethanol [25
]. However, biogas production in Malaysia mainly focused on the palm oil industry, as it is estimated that 80% of biomass energy potential was from the palm oil industry [26
]. The energy generated is considered to be green energy, since it is produced from renewable sources that are less harmful to the environment than fossil fuels [27
]. The biogas (CH4
) is a feed-stock for electricity generation and could be used as flammable fuel for cooking and heating purposes [28
]. Capturing and utilizing methane is important in contributing to CH4
emission reduction and as a renewable energy source [29
The anaerobic digestion process consists of hydrolysis, acidogenesis, acetogenesis, and methanogenesis. The hydrolysis is known as a rate-limiting step in the process and it will determine the duration of the digestion process. The efficiency of the AD commonly evaluated according to the COD that was released from the organic fraction (biodegradable). Stoichiometrically, 1 kg of COD releases about 15.625 mol of methane gas (CH4
) at standard temperature and pressure (STP). A 1 kg COD is needed to produce 0.25 kg of methane that may generate electricity about 1.29 kWh/kg CODremoved
]. Universiti Putra Malaysia (UPM), which is one of the leading research universities in Malaysia, has committed to look out over the issues of environment and sustainability as well as to support the Malaysia National Renewable Energy Policy and Action Plan. An appropriate setting of waste management is tremendously crucial for the best practices in MSW management for green energy production. The scope of this study is to evaluate the current generation, composition, and management of MSW in Universiti Putra Malaysia as a showcase for the reference, and finally to propose improved utilization options of organic waste for the waste-to-wealth projects in Malaysia.
2. Materials and Methods
2.1. Field Survey Activity
UPM is a world-renowned centre of learning and it is one of the leading research universities in Malaysia. Its main campus is in Serdang, Selangor next to Malaysia’s administrative capital city, Putrajaya. In 2018, UPM was ranked at 202 of world university ranking and 34 of Asian university rankings by Quacquarelli Symonds (QS) World University Rankings 2018/2019 [30
]. In general, UPM consists of 19,000 students and 2,274 academies staff, with another 1,000 supporting staff making up to 23,000 people at one time [30
]. UPM is predicted to receive a tonnage amount of MSW generated daily from the students and staffs through their administrative activities and daily life due to the huge population in the campus [13
]. The tonnage generation of MSW has caused the management to spend over USD 480,000 a year on waste management. About 50–55% of the allocation is used to pay the contractor and local municipalities and the rest of the allocation is used for public and street cleansing. The actual waste management cost in UPM might be higher than the stated budget, since the other waste, such as hazardous and clinical waste generated from laboratories and medical centres, are separately handled by Occupational Safety and Health Management Office UPM.
The survey involved in three major groups: (1) residential and colleges, (2) administrative offices, and (3) restaurant premises. The administrative offices include department offices, faculty offices, and centres in UPM compound (Table S1
and Table S2
). The student staying at colleges and staff staying at quarters were the main respondent from the residential and colleges group. The main organic contributors were predicted from the restaurant and cafeteria inside the campus. All of the data obtained were evaluated and quantified to represent the statistical acceptance for assessment.
The study of MSW generation in UPM campus consists of three main stages: (1) estimation of the MSW generation via questionnaire and interview, (2) organic waste sampling and quantification, and (3) analysis of the chemical composition of the organic fractions.
Different sets of questions were prepared and disseminated via face-to-face interview or an online survey to the targeted respondent. The questionnaires comprised three parts; general info, waste management, and awareness programme. The questions were mainly based on the MSW composition and management, on-going awareness program, future and budget allocation. The questions to the restaurant representatives were mainly focused on the operation handling and the amount of organic fraction generated from their premises. Independent experts from a different background validated all of the questions (refer to the acknowledgement section).
2.3. Statistical Analysis of the Questionnaires
IBM SPSS Statistics software was used to validate the survey questions by conducting a reliability test to obtain the α-value [31
]. This α-value will determine whether or not the questions will produce a stable and consistent answer to avoid the respondents from giving a random answer. Referring to Krejcie and Morgan [32
], the sample size for survey distribution should be between 377–379, since the UPM population is between 20,000–30,000.
2.4. Sampling Activities of Waste Generation from the Restaurant
Sampling was carried out within the UPM compound. The sampling activities consist of two different periods, at first, the sampling was conducted during normal semester running with full student capacity (October–February) and the second stage during the fasting month. Eleven and five restaurants were chosen for MSW generation sampling at the first and second stages. During the fasting month, most of the restaurants are closed in the daytime and are open from 4.00 pm until midnight. The sampling was done for each consecutive day for each restaurant. The MSW was collected from the restaurant premises then segregated, according to an organic fraction (left-over food, kitchen refuse, including vegetables and meat) and an inorganic fraction (plastic, paper, glass, fabric, metal, and tetra pak). During the survey activities, the MSW was quantified and segregated daily for one week for each restaurant. The data that are presented are the daily average of each premise. For the anaerobic digestion process, the collection and segregation process was every 2 d prior to use in anaerobic digestion for biogas production.
2.5. Physical and Chemical Analysis of Organic MSW
The organic fraction was characterized based on its physical and chemical properties, such as total solids (TS), volatile solid (VS), moisture content, chemical oxygen demand (COD), and total Kjeldahl nitrogen (TKN). For the moisture content, TS and vs. the analyses were immediately done after the segregation completed. However, the COD and TKN were done after the grinding process (Section 2.7
). All of the analysis was referred to the Standard Methods for the Examination of Water and Wastewater, American Public Health Association APHA [33
]. For the COD analysis, a 2 mL of a slurry sample of the organic fraction (Section 2.7
) was added in COD digestion vials (HACH) and digested at 150 °C and measured with spectrophotometer DR3900. The TKN was measured while using 4500-Norg B test kit (HACH), according to the manufacturer protocol. All of the analysis was done in triplicate from independent samples to represent average data.
2.6. Biogas Production Potential
The number of organic wastes that were generated from the restaurants was used as an indicator to evaluate biogas generation through anaerobic digestion. The COD and total organic (VS) fed into the anaerobic digester were measured daily based on the amount in kg of organic waste fed daily to the anaerobic digester. From the amount of COD and total organic (VS) measured, the potential methane and green energy generation were quantified, based on stoichiometry [28
2.7. Biogas Pilot Plant Set-up
The pilot plant consists of three main sections, which are a food grinder, 15 m3
anaerobic digester, and 10m3
gas storage balloon. The pilot plant was built in the Biorefinery complex located inside UPM. Figure 1
shows the flow of the process for the conversion of organic waste to biogas. The cow dung was used as a starter (inoculum) for the anaerobic digester process. Approximately 50% of the reactor was filled with the inoculum and water (1:1 ratio). The biogas generated was flushed out for three cycles in order to acclimatize the inoculum to ensure the anaerobic condition in the digester. After the acclimatization process completed, the reactor was fed with organic waste as the main substrate. The collected MSW was segregated into organic and inorganic fractions. Subsequently, organic fraction ground into slurry form by mixing with water (1:1 ratio). The slurry organic fraction then fed into the anaerobic digester for the anaerobic fermentation process. The biogas was channelled through a piping system into the flow gas meter to measure the volume generated. The biogas was stored in a gas storage balloon for further application.
2.8. Start-up Biogas Production
The reactor was gradually fed with organic slurry until reaching the maximum capacity of 15 m3. A fed-batch strategy was applied to avoid any shock to the digester. The initial feeding rate was 50 kg/d and gradually increase to 25 kg/d. To determine the organic loading rate, COD and vs. were measured to monitor the digester progress. The other parameters, such as pH and temperature, were measured daily for monitoring purpose.