An Environmental Impact Framework for the Construction Stage of Municipal Solid Waste Landfill Mining: A Study on Piyungan Landfill in Indonesia

At present, the predominant method of urban waste management in Yogyakarta is centered around landfill disposal, resulting in a swift depletion of available capacity, notably at the Piyungan landfill site. Consequently, the exploration of landfill mining, a process that entails the retrieval of fully decomposed waste, is being contemplated as a potential alternative. Nevertheless, the execution of this initiative may give rise to environmental consequences. The objective of this study is to establish a comprehensive framework for assessing the ecological consequences of landfill mining operations in the initial stage of construction. The methodology encompasses a preliminary stage known as scoping, wherein potential impacts are identified and significant hypothetical impacts are assessed. Subsequently, a thorough assessment is conducted to examine the potential significant effects of the hypothetical scenario. This evaluation involves a detailed analysis of the various environmental elements and parameters associated with each activity that may serve as a potential source of impact. The present analysis employs a straightforward matrix and a flow chart. The assessment indicates that the implementation stage of landfill mining has the potential to generate substantial hypothetical effects on multiple facets of the environment, encompassing physical, chemical, biological, socio-economic, and cultural dimensions. The potential impacts encompass various factors such as air pollution, gas explosions, reduced surface air quality, odor problems, and unfavorable public attitudes and perceptions. These impacts collectively contribute to the overall consequences of the situation.


Introduction
Rapid urbanization and population growth in developing nations have resulted in a significant surge in the production of Municipal Solid Waste (MSW).The effective management of MSW poses a considerable challenge, particularly in developing nations where the existing waste management infrastructure is frequently insufficient [1].Landfill disposal is a general approach for managing MSW in the nations above.In the region of Yogyakarta, located in Indonesia, the Piyungan landfill site is experiencing a significant increase in waste accumulation daily, resulting in its imminent approach towards maximum capacity.
The concept of landfill mining, which entails retrieving completely decomposed waste from landfills, is currently being explored as a prospective remedy for the issue of excessive landfill capacity [2].This approach facilitates the retrieval of valuable resources from waste and prolongs the longevity of current 1257 (2023) 012002 IOP Publishing doi:10.1088/1755-1315/1257/1/012002 2 landfill sites.Nevertheless, the execution of landfill mining can result in substantial environmental consequences, especially throughout the construction stage.
The Environmental Impact Assessment (EIA) is a crucial instrument utilized to identify and address the potential environmental consequences associated with development projects, such as landfill mining [3].Nevertheless, a need for more all-encompassing frameworks exists when evaluating the environmental ramifications associated with the construction phase of landfill mining, particularly within the context of developing nations.Prior to making a decision on this mining option, various studies are needed, including a comprehensive environmental impact study as well as an economic study [4,5,6].It is very important to know the feasibility of environmental aspects and economic aspects.
According to regulations in Indonesia, it is stated that activities that have the potential to cause significant impacts require an analysis study on environmental impacts (UU No. 11 of 2020).This study requires a holistic evaluation of the significant hypothetical impacts that have been determined (Government Regulation No. 22 of 2021).
The Piyungan landfill one of the disposal site in Indonesia was built in between 1994-1996 and began operating since 1996.Currently the management of the Piyungan landfill is carried out by the waste management agency under the Yogyakarta Special Region Environment and Forestry Service (DLHK DIY).The Piyungan landfill has an area of 12.5 hectares consisting of 10 hectares of landfill which includes 3 zones with an area of 3 hectares for zone 1 and zone 2 and 4 hectares for zone 3. Meanwhile 2.5 hectares are used as supporting facilities in the form of offices, workshops, weighbridges, and buffer zones.The amount of waste entering the Piyungan TPST is an average of 450 tons/day to 500 tons/day, which has increased from time to time so that its capacity is soon full even though revitalization has been carried out.Therefore, it is a mining option for perfectly decomposed fill [7].
In accordance with the explanation above about the capacity of the Piyungan landfill which will soon be full and some of the age of the pile has undergone complete degradation, a mining option is possible.However, it has the potential to cause significant impacts on the environment, so that an environmental aspect study is needed.This study aims to fill the existing research gap by constructing a comprehensive framework for evaluating the environmental consequences associated with the construction phase of landfill mining.The framework's application is demonstrated by examining the Piyungan landfill in Indonesia, offering significant insights into the possible environmental consequences associated with landfill mining practices in developing nations.

Methods
In the study of the Holistic Evaluation of Environmental Impact framework includes two main stages, namely the scoping process and holistic evaluation of the significant hypothetical impacts.

Scoping Process
Scoping is an initial process to determine the scope of the problem and identify significant (hypothetical) impacts related to the activity plan.The purpose of scoping is to define the boundaries of the study area, identify significant impacts on the environment, determine the level of depth of study, determine the scope of the study, examine other activities related to the planned activities being studied.The end result of the scoping process is a significant hypothetical impact which is then analyzed using an appropriate method.Figure 1 explains the activity scoping scheme.
3 The essence of Potential Impact Identification is to estimate all impacts that could potentially occur if the activity plan is implemented at that location.In identifying these impacts it is illustrated that a worst-case scenario will occur so that a long list of impacts will be obtained.The impacts included in this long list are still diverse in nature, they can be large or small impacts, positive or negative impacts, and significant or not significant impacts.The next stage is the Potential Impact Evaluation, the essence of which is to isolate the impacts that need in-depth study to prove the hypothesis.From this Step a list of 'Significant Hypothetical Impacts (SHI)' will be generated.The criteria used in evaluating this can be used 4 criteria including: 1. Is the burden on certain environmental components already high?this can be seen from the analysis of secondary data and pre-survey results.2. Do these environmental components play a role in people's daily lives (social and economic values) and in other environmental components (ecological values) around them?This is known from the results of observations.3. Is there high community concern about the environmental component?This can be seen from the results of community consultations.4. Is there a rule or policy that was violated by the impact?This can be seen from the regulations that determine environmental quality standards As for the analysis of a hypothetical significant impact to become a significant impact or an insignificant impact based on two main things, namely the magnitude of the impact and the nature of its importance and evaluated holistically.

Holistic impact evaluation framework
Holistic evaluation in environmental impact studies is intended to determine environmental feasibility or infeasibility.Holistic evaluation is used to evaluate the relationship and interaction of predicted environmental impacts as a whole in order to determine the characteristics of the total impact on the environment.
This holistic evaluation was carried out using 2 methods, namely using the simple matrix method with an approach to the results of impact prediction (magnitude and significant nature of the impact) and a flowchart to see the extent of the study of the linkages and interactions of significant impacts.

Impact Evaluation with a Simple Matrix
In a holistic evaluation using the Simple Matrix, an approach to the value or quantity of environmental quality can be carried out which is converted into a scale of environmental quality and the significance of the impact.The criteria for determining significant impact evaluations to determine whether or not significant impacts are managed and monitored, are as presented in The evaluation can show the extent to which the study of the linkages and interactions of hypothetical significant impacts on all stages of activity includes the frequency, duration and intensity of impacts in the same space and time.In order to obtain a slice of conclusion where the magnitude and significant nature of the impact of the most dominant business and/or activity plan has an impact on environmental components.In essence, the magnitude of impact is a combination of data-driven analyses, stakeholder feedback, and expert judgment.
Data Sources for Determining the Magnitude of Impact, including:

Impact Evaluation with Flowchart
The flowchart method can show the relationship between one significant impact and another significant impact (continuation impact).The use of flowcharts can show holistically between one type of impact that arises and the various activity components that cause the impact, and/or shows one type of activity component that can cause various types of impact.From the flow of significant impacts it can be seen that the primary impacts lead to further impacts (secondary, tertiary and so on), so that impact control measures can be carried out appropriately.

Result and Discussions
It is known that the capacity of the Piyungan landfill is increasingly limited.If efforts are not made to increase it, in 2022 it will be full [8].Efforts that can be made include land conversion or mining of heaps that have been decomposed stably.
As explained in point 2, that in order to carry out an activity including mining activities in landfills it is necessary to carry out an environmental impact assessment in which a holistic assessment is required.Referring to Figure 1, a series of potential impacts and SHI can be shown in Table 2. Particularly SHI during the construction phase of Piyungan landfill mining activities can be described as follows:

Mobilization of equipment and materials
In Mining This activity certainly requires a variety of equipment both for excavation and transportation of excavated products.With an area of 10 ha and an estimated depth of 10 m, 1,000,000 m 3 will be produced so that the activity of mobilizing equipment and materials will have an important hypothetical impact in the form of air pollution (odor, dust, CH 4 , CO 2 ) and negative attitudes and perceptions of the community.Air pollution can cause health problems so that negative public perceptions will emerge [9].

Stockpile Excavation Activities
At this stage, the significant hypothetical impacts include the decline in the quality of river water around the Piyungan landfill which is the outlet for the Leachate treatment.Another SHI is a Gas Explosion, this is obtained from various studies that landfill waste in landfill contains a lot of trapped gases and will explode when the pile is exposed [10].The emergence of community attitudes and perceptions is also estimated to be SHI, this is shown from the condition of the community around the Piyungan landfill which is quite vulnerable to all existing activities.This is because all this time they feel that the existence of the Piyungan landfill often causes social and environmental problems [11].

Placement at disposal site
The placement of mining products is an important part of the activity to study, this has the potential to cause air pollution, odors and a decrease in the quality of surface water in the vicinity.So far, they often complain about the existence of landfills.In summary, the results of a holistic evaluation of the magnitude and nature of significant impacts on construction are shown in Table 3, while the holistic evaluation using a flowchart is shown in Figure 2.

Conclusions
Based on a series of information on the existing condition of the Piyungan landfill which has the potential to be used for landfill mining, a study on holistic environmental impact assessment is needed.In the assessment process starting from identifying potential impacts, evaluating using the five criteria according to Government Regulation Number 22 of 2021, followed by evaluating using a matrix and flowchart.It was concluded that the potential impacts evaluated resulted in successive SHI Air Pollution, Gas Explosion, Decreased surface water quality, Occurrence of odors, Attitudes and public perceptions as the end of all impacts that occur.

Figure 1
Figure 1 Schematic of the scoping process in an environmental impact assessment study.

Figure 2 .
Figure 2. Summary of impact evaluation results using a flowchart

Table 1 .
The

Table 1 .
1. Baseline Data Collection: Before any project begins, it's essential to understand the existing environmental conditions.This might involve: a. Groundwater quality data from existing wells.b.Ambient air quality measurements.c.Soil analysis.d.Traffic counts.e. Biodiversity surveys.2. Technical Reports: Design and feasibility studies for the landfill can provide data on proposed sizes, depths, operational procedures, and expected waste quantities and types.3. Literature and Case Studies: Previous studies and similar projects can provide insights and data that can be used for predictions and assumptions.4. Stakeholder Consultations: Input from the local community, experts, and authorities can provide qualitative data on potential impacts, especially those that might not be immediately quantifiable like cultural or visual impacts.Impact Evaluation Determination Criteria and Categories

Table 2 .
Summary of Potential Impacts and SHI Construction Phase

Table 3 .
Summary of holistic impact evaluation using the matrix