Potential of Plastic Waste Leakage to Environment in Indonesian Final Disposal

The majority of developing nations still utilize landfills as their primary method of disposing of municipal solid waste (MSW), and Indonesia is no exception to this technology. On the other hand, landfill contributes a significant fraction of plastic in the global environmental leakage from mismanaged landfill and open dumping site in Asian countries. Furthermore, Indonesia has a long history of landfill mismanagement and open dumping. The loss of plastic to the environment could lead to multisectoral impacts on the health, environment, and economy. In this paper, we analyze the current situation of landfill and the potential of plastic waste leakage from landfills to the environment using systematic review and metadata analysis using GIS in Indonesia. In addition, this study analyses potential plastic leakage based on the distance to the waterways, leachate treatment facility and landfill facility. Based on the analysis, only around 11% of the landfill were claimed as sanitary landfill, yet only 3% operated based on the sanitary landfill standard of Indonesia after the analysis. The controlled landfill is also implemented in Indonesia at around 52%, and open dumping is around 37% of total final disposal. Based on the GIS analysis, more than 20% of landfill in Indonesia are near the waterways, which increase the potential for plastic leakage. Policymakers can use the resulting study to identify and prioritise ways to stop the environmental leakage of plastics from landfills.


Introduction
Landfilling, the process of disposing municipal solid waste (MSW) in designated areas, continues to be the predominant method employed by developing countries for final disposal of solid waste [1][2][3].As a developing nation, Indonesia also employs landfilling as its primary waste management technique.In this approach, solid waste is deposited in specially engineered sites and eventually covered with layers of soil .Despite advancements in waste management practices worldwide, the continued prevalence of landfilling in Indonesia highlights the difficulties faced by developing nations in adopting more sustainable waste management strategies.Due to a number of factors-including, but not limited to, an increase in population and economic instability, as well as a lack of understanding regarding the various factors that contribute to the overall handling system-developing nations are faced with the formidable task of effectively managing their solid waste [2,4].
Landfills play a substantial role in the global environmental leakage of plastic, particularly in Asian countries where mismanaged landfill and open disposal sites are prevalent [5,6].According to estimates, between 21 and 42 percent of the world's plastic waste is deposited in landfills [7].The mismanagement of landfills and open dumping exacerbates the problem by allowing plastic waste to escape into water bodies, soil, and the atmosphere [8][9][10][11].It has been estimated that poorly managed Municipal solid waste (MSW) facilities, which include open dumps and landfills, are the largest contributor to the release of plastics into the surrounding environment.About 4.1 million Mt of the approximately 9.2 million Mt 1257 (2023) 012001 IOP Publishing doi:10.1088/1755-1315/1257/1/012001 2 of plastics believed to have been lost to the environment in 2015 was provided by poorly managed MSW facilities.This constitutes almost 45 percent of the total [12].
Previous research has demonstrated that Indonesia is one of the nations with the greatest plastic leakage rates worldwide [13][14][15].This alarming trend suggests that a substantial quantity of plastic waste from Indonesia ends up in the environment, with severe multisectoral impact such as health.Ecological, economy and social consequences.In addition, Indonesia has a lengthy history of improper landfill management and open dumping.This condition could increase the potential of plastic waste to the environment to various transport, from the wind, run-off and through the leachate [8,[16][17][18].
This study provides an overview of the current condition of landfills and also addresses the indication that plastic is leaking out of landfills in Indonesia, based on the literature that has been published.Additionally, this paper delivers an account of the current practices and management of landfills in Indonesia.In addition, this paper is followed by a discussion of research gap and potential future methods of managing landfills, all with the goal of reducing the amount of plastic pollution that escapes from landfills.

Systematic Review
This paper is a component of a larger body of research that analyzes the flow of plastic waste from land to water in Indonesia and presents its findings in the form of a review.In order to investigate the following three research issues, we searched for relevant information in two databases, namely Scopus and Web of Science.
RQ1: What is the current condition of landfill management in Indonesia?How do current conditions affect plastic leakage to the environment?RQ2: What evidence of plastic leakage originating from the Landfill in Indonesia?RQ3: Based on the condition and evidence of plastic leakage identified in RQ1 and RQ2 what are the are the core evidence gaps and, therefore, further research needs?In the Additional Information, Boolean search queries are presented (SI 1).They were streamlined using sensitivity analysis one-at-a-time to ensure the greatest number of relevant articles while lowering the amount of irrelevant sources.Articles were included or omitted based on the criteria outlined in (SI 2) Utilizing snowball and citation search approaches, further relevant material was identified.Several websites and datasets, such as the Ministry of Environmental and Forestry, Indonesia, the Ministry of Public Works and Housing, etc., were also checked for more pertinent information.

Analysis of Landfill Condition based on the current Indonesian Standard
In order to gain a better understanding of the landfilling situation in Indonesia and evaluate its compliance with the standards set by the Ministry of Public Work Decree No. 03 of 2013 on Implementation of Infrastructure and Facility for Municipal Solid Waste Management, an analysis of secondary data from the SIPSN (Sistem Informasi Pengelolaan Sampah Nasional/National Waste Management Information System) and data from Ministry of Public Works and Housing from 2019 to 2022 was conducted.
SIPSN serves as a comprehensive database that collects and stores information related to waste management practices across Indonesia.By analyzing the data available in SIPSN, various aspects of landfill management, such as waste disposal practices, infrastructure conditions, and compliance with regulatory standards, can be assessed even though there are still uncertainties in this data, SIPSN is the only database available in Indonesia.
The analysis involves comparing the data obtained from SIPSN with the specific requirements outlined in the Ministry of Public Work Decree No. 03 of 2013.This decree provides guidelines and standards for the implementation of infrastructure and facilities for municipal solid waste management, including landfill design, operation, and closure.The list of data and sources is shown in Table 1 River Maps Indonesian Geospasial Agency

Analysis of Landfill Distance to the Waterways
To analyze and evaluate the distance between landfills and waterways, ArcGIS can be utilized to perform a spatial analysis and layering of the data.By employing the near (approximation distance) tool in ArcGIS, the distances between landfills and waterways can be calculated based on a specified range, such as 0.5 to 1 kilometer indicating potential risks of contamination or pollution.Current research for the minimum or maximum distance of plastic to transport is very limited, but based on previous studies shows that the plastic travel is not far from the sources and several studies using 1 km distance as the travel boundaries of plastic in river [19,20], based on this we assume the landfill less than 1 km from waterways will potentially generate plastic waste leakage to the aquatic environment.

Current condition of Landfill in Indonesia
Based on the Ministry of Public Work Decree No. 03 of 2013, there are 2 types of landfills in Indonesia, there are sanitary landfill and controlled landfill, but in the reality and practices there is third type of landfill, open dumping practices.In Indonesia, sanitary landfills are the most advanced, followed by controlled landfills with less restrictive standards.The type of landfill is determined by the number of populations for each city/regency [18].The more detailed information regarding the requirements of the landfill based on the standard is shown in SI 2. According to the literature and the national agency, there are a total of 437 landfills in Indonesia (including local and regional landfills) [21,22].In this study, only 383 Landfill data are accessible in SIPSN with facility and operating information for the years 2019 to 2022.The analysis has apparently found that most landfill facilities in Indonesia fall short in meeting these operational aspects.For example, they may lack of facilities, improper practices, and operation and even the lack adequate monitoring systems.In the data, many government regencies are claimed to be sanitary or controlled landfill but based on the more detailed analysis for each aspect have different result from the claimed type of landfill.The result of claimed and analyzed landfill in Indonesia based on the SIPSN is shown in figure 1.
Figure 1.The current condition of Landfill in Indonesia based on analysis from SIPSN data Based on the claimed design, there are 11% of sanitary landfill and 52% of controlled landfill but after the analysis there are only 3% landfill is operated as sanitary landfill and 29% as controlled landfill, it leads to the operation of open dumping to be 68% based on SIPSN data.Moreover, based on the claimed of Ministry of Public Works and Housing in 2021 more than 90% of the TPA being built based on a sanitary landfill but operating in open dumping [21].
In addition, the condition of the leachate treatment facility was evaluated using SIPSN data in this study compared to the standard.According to the MoeEF (Ministry of Environment and Forestry) Regulation Act 59 of 2016 in Indonesia, specific minimum requirements for leachate treatment facilities are mandated for controlled landfills and sanitary landfills.For controlled landfills, the minimum facility is stabilization ponds.Meanwhile, for sanitary landfills, the MoeEF Regulation Act 59 of 2016 specifies that the minimum facility for leachate treatment is biological treatment.The current condition of the leachate treatment plants in 383 landfills in Indonesia is shown in figure 2 Based on the result of analysis, around 52% of leachate treatment plants are operated in Indonesia, consisting of chemical and biological treatment plants (10%), biological treatment plants (18%) and only sedimentation plants (24.4%).Even though, half of total landfill in Indonesia have the leachate treatment plants, there are several studies shows that the treated leachate from these landfills is not comply the Indonesian standard.The previous study conducted on 14 landfill facilities found that 11 of them were below standard and the operation landfill treatment plant are in suboptimal state [17].There is a higher probability of plastic debris escaping into the environment when leachate treatment plant sites do not effectively treat the leachate [8,22,23].In the other hand, there are around 37% landfill do not have any treatment plants and 11% of landfill have unoperated leachate treatment plants.Based on this condition, there are around 48% of landfill generated untreated leachate in Indonesia and directly emit to the environment.Previous research demonstrates that leachate contributes to plastic pollution as mesoplastic and microplastic.[8,23,24].
The results of the GIS analysis indicating that more than 20% of landfills in Indonesia are located less than 1 km from waterways.The illustration of landfill location in Indonesia is shown in Figure 3.Because of this condition, there is a higher probability that plastic pollution may leak out of the landfill and into the surrounding waterways.Plastic in waterways will eventually making its way into the ocean because one of main route of plastic leakage to the sea is through the river [15,[26][27][28].Even though there are still uncertainties of measuring travel distance of plastic from the sources to the waterways, many models implied that the nearer the sources of plastic to waterways, there will be higher probability plastic will leak to aquatic environments [15,26,29]

Evidence of Plastic Leakage in Indonesia from the Landfill
The current study on plastic leakage from landfills in Indonesia is limited, although various studies have been conducted.The focus of the plastic emission from the landfill is still microplastic and mesoplastic, particularly from the emission of the leachate.There are no published data or studies on the precise number of macroplastic emissions from landfills to the environment, although numerous studies indicate that macroplastic emissions also occur from landfills [15,30].The study of plastic leakage from the landfill in Indonesia, is shown in Table 2. Based on the previous studies, it is indicated that microplastic emissions is occurs from the landfill leachate in Galuga Landfill [24,31] both from the leachate discharge and the river with radius 1.5 km from the landfill.It is also indicated that the concentration of microplastic near to the landfill is three times higher than other location in this study [31].Moreover, the most recent study of the microplastic concentration of the leachate treatment plant effluent, shows that the concentration of microplastic in Radengan Landfill, Mojokerto has the lowest microplastic concentration compared to the other landfill, in this location the removal efficiency of leachate treatment plant is around 75.6 %.Based on the previous study, it can be stated that landfill leachate several landfills in Indonesia emit the plastic and microplastics pollution to the environment.Furthermore, leaks in leachate collecting and treatment systems, as well as discharges from such systems, can cause microplastics present in leachate to be released into the environment.Geomembranes, also known as landfill liners, are susceptible to defects during the manufacturing and installation processes that, despite strict controls, could result in the leaking of MPs [35].
Other research, also found that the microplastic is found in dug well near to the landfill [33], the concentration of microplastic is very low compared to the other studied location, but this study can be an indication that plastic pollution also emit from the landfill to the dug well through the aquifer.Aquifer can be the pathways of microplastics to spread through environment, but the exact measurements of sources and fate is very complicated [36].The last research of plastic emissions from landfill is conducted in Benoa Bay, Bali.In this study, there several locations that studied not only near to the landfill but also far from the landfill, the result indicates that the concentration of microplastics in the location near from Suwung Landfill, Bali is the highest, around 2 -3 times higher than other locations [34], this result can be one of the indicators that plastic emissions occurs from the landfill.
Most of plastic that found in recent studies are fragmented microplastic, the presence of fragmented plastic and microplastics in Indonesia can be attributed to the breakdown of larger plastic items that originate from landfills.Plastic waste in landfills undergoes a process of degradation due to various factors, such as exposure to sunlight, physical stress, and chemical reactions [9,35,37].As a result, the plastic waste deposited in landfills gradually breaks down into smaller pieces, including microplastics.Leachate not only factor of presence of microplastic, numerous natural processes (e.g., rain and wind) also contribute to the spread of landfilled microplastics into surrounding ecosystems such as aquatic systems [5].
According to the study by Putra [38] the plastic content in landfills aged 15-20 years was found to be approximately 30%.This suggests that even after 15-20 years of being in a landfill, a significant portion of the waste present consists of plastic materials.Meanwhile, the study conducted by Kristanto [39]focused on closed landfills aged 18-20 years.The researchers found that the total plastic content in these closed landfills ranged from 28.02% to 31.58%.Based on this research the high amount of plastic in landfill could leads to the microplastic based on the degradation process, if the landfill closing is not optimal the microplastic emission will potentially be high in the landfill.Moreover, the high number practice of open dumping, where waste is disposed of in an uncontrolled and unregulated manner without proper soil cover, can lead to an increase in the quantity of leachate produced and emit the microplastic.Overall, recent studies have consistently shown that plastic and microplastic particles are found in close proximity to landfills and that the concentrations of these particles are typically higher in the surrounding environment compared to further areas.Based on the analysis, the open dumping practices are operated in around 70% of landfill, therefore the potential of plastic leak from the landfill is 70% at minimum in Indonesia.

Core evidence gaps and, therefore, further research needs of plastic leakage from the disposal sites in Indonesia
One key aspect of the research gap of research in the plastic leakage from landfill to the environment is the limited number of comprehensive studies quantifying the amount of plastic waste that escapes from landfills and enters the environment.The current research is more focus to the microplastic leakage from the landfill, but the quantity of macroplastic emission to the environment is very limited and still not conducted in Indonesia.Quantifying this leakage is crucial for assessing the overall magnitude of the problem and understanding the potential environmental impacts.Secondly, the understanding the pathways through which plastic waste escapes from landfills is essential for developing effective mitigation strategies.However, there is limited research on the specific mechanisms through which plastic waste leaves landfills, such as wind dispersion, runoff, or leachate transport.Identifying these pathways can inform targeted interventions to prevent or minimize plastic waste leakage.The fate and transport of plastic waste that escapes from landfills also very important research to be conducted in future.This includes investigating how plastic waste is transported through different environmental media (such as soil, water, and air) and how it ultimately accumulates in various ecosystems, including rivers, oceans, and terrestrial.
Further research is needed to assess the ecological and health impacts of plastic waste leakage from landfills.This includes studying the effects of plastic pollution on wildlife, biodiversity, and ecosystem functioning, as well as evaluating potential human health risks associated with the ingestion or exposure to plastic waste.The research gap also extends to the development and evaluation of effective mitigation strategies.There is a need for studies that investigate and compare different waste management practices, engineering solutions, and policy interventions aimed at reducing plastic waste leakage and its environmental impact.Another aspect of the research gap is the limited availability of long-term monitoring data on plastic waste leakage from landfills.Continuous monitoring is essential for assessing the effectiveness of waste management measures, tracking trends over time, and understanding the longterm consequences of plastic waste leakage on the environment.

Conclusion
In conclusion, the analysis indicates that the majority of waste disposal in Indonesia consists of open dumping, accounting for 68% of the total.Controlled landfill accounts for 29%, while sanitary landfill represents only 3% of waste disposal practices.The presence of mesoplastic and microplastic particles has been observed in all studied locations in Indonesia, with higher concentrations near landfills.The potential of plastic leakage from the open dumping landfill is very high in Indonesia due to the lack of management and operation, potentially at minimum 70% of all of landfill in Indonesia will generate the microplastic to the Environment.
Moving forward, it is essential to do additional studies in order to comprehend the mechanisms and quantities of plastic (macroplastic) leakage, particularly from landfills.Additionally, research on closed landfill management, including the impact and effective management strategies, is necessary to address the legacy waste and potential environmental risks associated with closed landfill sites.Furthermore, the development of robust regulations and policies is crucial to improve waste management practices and mitigate the adverse impact of plastic pollution on the environment and human health.

Figure 3 .
Figure 3. Location of Landfill in Indonesia[25] Because of this condition, there is a higher probability that plastic pollution may leak out of the landfill and into the surrounding waterways.Plastic in waterways will eventually making its way into the ocean because one of main route of plastic leakage to the sea is through the river[15,[26][27][28].Even though there are still uncertainties of measuring travel distance of plastic from the sources to the waterways, many models implied that the nearer the sources of plastic to waterways, there will be higher probability plastic will leak to aquatic environments[15,26,29].
Figure 3. Location of Landfill in Indonesia[25] Because of this condition, there is a higher probability that plastic pollution may leak out of the landfill and into the surrounding waterways.Plastic in waterways will eventually making its way into the ocean because one of main route of plastic leakage to the sea is through the river[15,[26][27][28].Even though there are still uncertainties of measuring travel distance of plastic from the sources to the waterways, many models implied that the nearer the sources of plastic to waterways, there will be higher probability plastic will leak to aquatic environments[15,26,29].

Table 1 .
. List Data and Sources

.
Figure 2. The current condition of leachate treatment plant in Indonesia based on SIPSN data

Table 2 .
The study of plastic leakage from the landfill in Indonesia