Technical and Economic Planning of Landfill Mining for Refuse-Derived Fuel Production at Jatibarang Landfill

3.1 Landfill and landfill zones

The Jatibarang Landfill has a total area of 46.183 ha, with around 27.71 ha used as a garbage collection area, and the rest is supporting infrastructure such as leachate ponds. The existing passive-zone waste stock was estimated independently from the landfill design and remaining disposal capacity. Based on the calculated landfill volumes and measured waste density, the estimated stocks were 1,106,302.03 tons in Zones 1–2, 455,133.76 tons in Zone 3, and 259,006.55 tons in Zone 4, corresponding to a total estimated passive-zone stock of approximately 1.82 million tons. These values represent the estimated quantity of previously deposited waste and should not be interpreted as the landfill design capacity or remaining disposal capacity. Based on operational conditions, the landfill area consists of four passive zones, namely zones that have stopped receiving waste and have a long enough lifespan to allow landfill mining activities to be carried out. Landfill mining activities are planned to be carried out in stages based on the age of the pile and ease of operation, starting from zone 4, then zone 3, and finally zones 1–2. Passive Zones 1 and 2. The volume of the reservoir in zones 1 and 2 is estimated at 1,491,975 m³. Based on the measurement of field waste density of 741.5 kg/m³, the total mass of the landfill reached around 1.11 million tons. Taking into account the operating capacity of the equipment and working time, mining activities in this zone are projected to last longer than in other zones, at about 9 years of operation. Zone 3 has a landfill volume of 550,880 m³ corresponding to approximately 408 thousand tons of waste based on the measured field density of 741.5 kg/m³. However, for the material fraction estimation presented in Table 1, the available passive-zone stock scenario was applied, resulting in an estimated Zone 3 waste stock of 455,133.76 tons. The age of the pile and the stability of the slope conditions allow landfill mining activities to be carried out after Zone 4 is completed, with an estimated operation duration of about 4 years. Based on the passive-zone stock scenario presented in Table 1, the total waste stock potentially available for landfill mining is estimated at approximately 1.82 million tons. Using the sampled composition as a preliminary planning assumption, the potential material fractions in the passive-zone waste stock were estimated. Because zone-specific composition data were not independently available for all passive zones, these values should be interpreted as preliminary scenarios, as presented in Table 1.

The total material that has the potential to become RDF reaches around 1.34 million tons, while the decomposed soil material reaches around 129 thousand tons, which has the potential to be reused as landfill cover material. The large availability of these materials shows that landfill mining activities not only function as land rehabilitation, but also as a source of alternative energy raw materials in the long term.

3.2 Landfill risk index

The landfill-mining risk assessment was conducted using 27 parameters specified in Appendix V of the Regulation of the Minister of Public Works No. 03 of 2013, comprising landfill-site criteria, waste characteristics, and leachate characteristics. For each parameter, the partial risk score was calculated as $R I_i=W_i \times S_i$, where $W_i$ is the assigned parameter weight and $S_i$ is the corresponding sensitivity index. The total RI for each passive zone was obtained by summing the partial scores of all 27 parameters. The detailed assessment is presented in Table 2.

Table 1. Preliminary scenario of material fractions in the passive-zone waste stock

Table 2. Detailed landfill risk index (RI) assessment for the passive zones of Jatibarang Landfill

The risk assessment should therefore be interpreted together with operational controls. Slope stability requires controlled excavation geometry, work-zone restriction, and continuous observation of potentially unstable waste slopes. Landfill-gas hazards require gas monitoring before and during excavation, particularly for methane (CH₄), hydrogen sulfide (H₂S), and oxygen deficiency. Leachate exposure requires controlled handling and appropriate personal protective equipment (PPE), while groundwater protection requires maintaining control of leachate pathways and monitoring potential contamination. These controls are particularly important because the risk-index score represents a screening-level assessment rather than a direct measurement of excavation safety.

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Figure 4. Landfill mining operational scheme based on risk index (RI) assessment results

Rehabilitation decisions are made in stages, in the order of Zone 4, Zone 3, and Zones 1–2, to minimize operational disruptions and consider the life of the stockpile and the stability of the land.

3.2.1 Composition of landfill waste

The material characteristics of landfill mining products were analyzed through manual sorting of five samples at different depths. Each sample was separated into three main fractions, namely combustible, non-combustible material, and decomposed soil-like material. The recapitulation of the sorting results is presented in Table 3.

The sampling dataset consisted of five depth-specific samples obtained from a single trench, with one sample representing each nominal depth from 1 to 5 m. Because no replicate samples were collected at the same depth and no independent zone-specific sampling was conducted, the dataset was not intended to statistically characterize the spatial heterogeneity of all passive landfill zones. The results are therefore used as a preliminary characterization to support engineering planning and scenario estimation. The combined analysis of the five depth-specific samples resulted in 73.52% combustible material, 19.36% non-combustible material, and 7.12% soil-like material. These values represent the composition of the sampled material. Because the available sampling data do not provide independent zone-specific samples for all passive zones, these composition values are treated as a preliminary characterization rather than a statistically representative composition of the entire passive-zone stock. The dominance of combustible materials shows that most of the old waste still has a fairly high energy content even though it has undergone a degradation process in the landfill. The existence of non-combustible fractions is mainly derived from inorganic materials such as glass, metals, and other inert materials that do not contribute to the calorific value, but still have the potential to be separated and recycled. Meanwhile, the soil-like material fraction is the result of long-term decomposition of organic matter that can be reused as cover soil in landfill rehabilitation activities. The composition indicates that the waste pile in the passive zone of the Jatibarang Landfill has a high potential for the use of recovery materials, especially as raw materials for RDF, because the proportion of flammable fractions is much larger than inert residues. These results form the basis for the fuel quality analysis at the next stage.

Table 3. Composition of the sampled landfill-mining material

Table 4. Characteristics and variability of Refuse-Derived Fuel (RDF) from landfill-mining samples compared with SNI 9313:2024

3.3 Quality of waste as a landfill

The characteristics of landfill mining RDF raw materials were analyzed to evaluate their suitability as an alternative fuel for the cement industry. The parameters tested included moisture content, calorific value, ash content, total sulfur, chlorine, and mercury, and were then compared to the SNI 9313:2024 standard. The laboratory results in Table 4 were obtained from five separately identified samples (LM1–LM5), corresponding to the sampled depth intervals, rather than from a single composite sample. The reported values therefore represent the arithmetic mean of the five samples (n = 5).

The calorific value obtained in this study was also compared with values reported for landfill-mined and MSW-derived RDF. Prihartanto et al. [28] reported calorific values of 18.75–20.88 MJ/kg for the coarse combustible fraction of landfill-mined waste, while a previous study at Jatibarang Landfill reported approximately 2,980 kcal/kg (12.47 MJ/kg) after treatment [26]. Following further quality improvement, landfill-mined RDF with optimized combustible composition reached approximately 25.23 MJ/kg [29]. The post-drying gross calorific value obtained in the present study, 6,664.82 kcal/kg (approximately 27.90 MJ/kg), is therefore relatively high for landfill-mined RDF but remains within the upper range reported for MSW-derived RDF.

The relatively high calorific value is primarily attributed to feedstock selection and moisture reduction. The sampled material contained a high combustible fraction (73.52%), while soil-like and non-combustible materials were removed before RDF preparation. In addition, drying reduced the mean moisture content from 38.65% to 5.59%, substantially increasing the energy content per unit mass. The age of the landfill may also have contributed indirectly because prolonged degradation preferentially reduces readily biodegradable organic matter, leaving a relatively larger proportion of persistent combustible materials such as plastics and textiles. However, landfill age alone should not be interpreted as the direct cause of the high calorific value, as waste composition, contamination with soil-like material, and moisture conditions also strongly influence fuel quality.

The five depth-specific samples showed measurable between-sample variability. Moisture content before drying ranged from 33.65 wt.% to 45.93 wt.%, whereas after drying it decreased to a narrower range of 5.16 wt.% to 6.17 wt.%. Gross calorific value showed greater variation, ranging from 2,397.27 to 6,162.51 kcal/kg before drying and from 4,179.20 to 8,896.25 kcal/kg after drying. Ash content ranged from 11.51 wt.% to 19.06 wt.%, while sulfur, chlorine, and mercury remained consistently below the SNI 9313:2024 limits across all five samples. The observed variability, particularly in calorific value, reflects the heterogeneous characteristics of landfill-mined material across sampling depths and should be considered when estimating RDF quality and full-scale process performance.

3.4 Mass balance of landfill mining

The mass balance analysis was carried out to evaluate the distribution of material flows at each stage of processing landfill-mined waste into RDF at the RDF IWPF Jatibarang facility. The calculation was based on the planned daily operating capacity during the operational period. The processing flow includes material reception, sorting and separation, drying, shredding, and compaction until the final RDF product is obtained. The calculated input and output mass flows for each processing stage are summarized in Figure 5. The mass flow distribution is shown in Figure 5.

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Figure 5. Mass balance

The material from landfill mining entering the facility was 470.08 tons/day. Based on the measured composition of the sampled landfill-mining material presented in Table 3, the incoming material consisted of 73.52 wt.% combustible material, 19.36 wt.% non-combustible material, and 7.12 wt.% soil-like material. The measured combustible fraction of 73.52 wt.% was used as the preliminary combustible recovery fraction in the mass-balance calculation. Screening efficiency was not experimentally measured; therefore, no additional dry-solid loss due to screening was assumed in the preliminary mass balance. Accordingly, the initial separation stage produced approximately 345.60 tons/day of combustible material, 91.01 tons/day of non-combustible material, and 33.47 tons/day of soil-like material. Therefore, the mass balance at this stage satisfies the conservation relationship: 470.08 = 345.60 + 91.01 + 33.47 tons/day. The combustible fraction of 345.60 tons/day was subsequently directed to the drying process. The drying mass balance was recalculated on a conserved dry-solids basis using the measured moisture contents of 38.65% before drying and 5.59% after drying. The dry-solid mass entering the dryer was calculated as 345.60 × (1 − 0.3865) = 212.03 tons/day. Assuming that the drying process removes only moisture and does not cause a significant loss of dry solids, the mass of material leaving the dryer was calculated as 212.03/(1 − 0.0559) = 224.58 tons/day. Therefore, approximately 121.02 tons/day of water is removed through evaporation during drying. The dried material of 224.58 tons/day is subsequently transferred to the shredding and compaction stages. No significant material loss was assumed during these mechanical processes because they primarily modify particle size and bulk density. Accordingly, the final RDF production is estimated at 224.58 tons/day under the stated material-composition and moisture assumptions.

Based on the corrected RDF production capacity of 224.58 tons/day, annual RDF production was calculated using 260 effective operating days per year. The remaining days were allocated for scheduled maintenance, equipment inspection, operational downtime, and non-operating periods. Accordingly, the annual RDF production is estimated at 58,390.80 tons/year. This annual production value is used consistently throughout the material balance, revenue analysis, cash-flow calculation, and financial-feasibility assessment.

3.5 Capacity planning

Planning the capacity of the RDF IWPF facility begins with a material balance analysis to determine the amount of waste flow at each stage of the process. This data is the basis for determining the capacity and number of equipment units, as well as the dimensions of the required building.

3.5.1 Landfill mining yield transportation capacity

Transportation of excavated material from the landfill-mining area to the RDF IWPF facility was evaluated separately from the transportation of the final RDF product to the cement plant. The landfill-mining operation generates approximately 470.08 tons/day of material that must be transferred to the RDF IWPF facility. Two dump trucks are planned for this internal transportation stage, each with a nominal payload capacity of 25 tons per loaded trip. Therefore, the minimum number of loaded trips required is 470.08/25 = 18.80, rounded up to 19 loaded trips/day in total. With two operating trucks, this corresponds to approximately 9–10 loaded trips per truck per day.

The actual transport capacity depends on the one-way haul distance between the excavation area and the RDF IWPF facility, travel speed, loading and unloading time, queuing time, and operational availability. These parameters are therefore considered in determining the truck cycle time and standby requirement.

3.5.2 Processing capacity at Integrated Waste Processing Facility Refuse-Derived Fuel

The waste that arrives at the RDF IWPF then goes through a series of processing processes. The calculation of the capacity of each stage is carried out sequentially by considering the material reduction factor in each process. A recapitulation of the input and output capacities in each processing area is presented in Table 5.

3.5.3 Determination of number of equipment units

The equipment requirements were reassessed based on the corrected material flow and the available operating capacity of each processing unit. The RDF IWPF is designed with four parallel processing lines. Following the corrected mass balance, the total material entering the shredding stage is 224.58 tons/day, corresponding to approximately 56.15 tons/day per production line.

Each production line is equipped with one Double Shaft Shredder with a rated capacity of 10 tons/hour. At the previously assumed operating time of 5.5 hours/day, the available capacity would be only 55 tons/day per unit, which is insufficient for the required load of 56.15 tons/day. Therefore, the effective operating schedule of the shredder was 6.0 hours/day. Under this operating schedule, each shredder provides a rated daily capacity of 60 tons/day, corresponding to a utilization rate of approximately 93.6% and an available capacity margin of approximately 6.4%.

The capacities and power requirements of the trommel screen, rotary dryer, shredder, compactor, and supporting equipment are evaluated against their respective process loads. The total electrical supply requirement should be determined from the simultaneous connected load of all electrically driven equipment, including appropriate motor starting and power-factor allowances, rather than from the nominal plant capacity alone.

3.5.4 Calculation of area requirements

The RDF IWPF facility is planned within a building footprint of approximately 147.5 m × 46 m, corresponding to a total operational area of 6,785 m². The facility area was determined from the space requirements of the main processing zones, material-storage areas, internal vehicle circulation, equipment access, safety separation, and environmental-control facilities.

The area requirement for each processing zone was determined from the daily material throughput, estimated bulk volume, storage or retention period, allowable pile height, equipment footprint, and additional maneuvering space. For example, the reception area was calculated based on a material volume of approximately 158.49 m³/day per line, a storage height of 2 m, one day of temporary retention, and approximately 40.96 m² of additional operational space, resulting in a calculated requirement of approximately 120.21 m² per line. For preliminary design purposes, this value was rounded to 150 m² per line.

The facility layout distinguishes the waste-reception and temporary-storage zone, material-separation area, drying area, shredding and RDF-compaction area, RDF-product storage, residue storage, hazardous-material temporary storage, leachate collection and drainage facilities, and supporting operational areas. Separate internal truck circulation routes are provided to reduce interference between incoming landfill-mining material and outgoing RDF-product transportation.

Safety provisions are incorporated into the preliminary layout by maintaining separation between material-storage and thermal-processing areas, providing emergency access routes, and preventing obstruction of vehicle and personnel circulation. Dust-generating processing areas, particularly screening and shredding, are designated for local dust-control and ventilation systems. Drainage from waste-reception and residue-handling areas is directed toward the leachate-collection system rather than being discharged directly to the surrounding ground.

The layout and area allocations presented in this study represent a preliminary engineering design. Final fire-separation distances, ventilation rates, drainage dimensions, hazardous-material storage requirements, and emergency-access dimensions should be verified during detailed engineering in accordance with the applicable fire-safety, occupational-safety, environmental, and building regulations.

3.6 Cost Budget Plan analysis

The cost analysis in the planning of the RDF IWPF aims to provide an overview of the funding needs, both for the construction stage and for operations and maintenance during the project period. The Cost Budget Plan (RAB) is prepared by grouping costs into two main components, namely initial investment costs and variable costs. Furthermore, an analysis of potential income and calculation of financial feasibility indicators were carried out to assess the profitability of the project.

3.6.1 Initial investment costs

The initial investment cost includes all expenses required before the facility can operate, including the cost of building construction, procurement of basic equipment and fleet, and the provision of PPE for workers. The recapitulation of initial investment costs is presented in Table 6.

Construction costs. The calculation of construction costs for the development of the 6,785 m² RDF IWPF refers to the 1st edition of the Central Java Provincial Construction Work Unit Price (MAS PETRUK) of 2025. The construction works include site preparation, foundation works, drainage construction, building structure, wall installation, roofing, and electrical works, with a total estimated cost of IDR 7,001,485,252.70. The construction period is preliminarily estimated at six months. A detailed construction schedule and S-curve would be developed during the detailed engineering design phase.

Table 6. Recapitulation of the initial investment cost of Refuse-Derived Fuel Integrated Waste Processing Facility (RDF IWPF)

Equipment, fleet, and personal protective equipment costs. The next initial investment component is the procurement of main equipment for the processing process at IWPF and a fleet for landfill mining and distribution activities, with a total cost of Rp 7,464,064,640.00. In addition to equipment, the investment also includes the provision of PPE for 99 workers with a total cost of IDR 79,873,200.00.

3.6.2 Variable costs

Variable costs are costs incurred on a regular basis during the life of the plant, the amount of which can change over time. Variable cost components include operational costs and maintenance costs.

Operating cost. Operating costs were recalculated using the corrected RDF production and operating assumptions. Fuel and electricity requirements were linked to equipment operating hours, drying requirements, and transportation activities, while maintenance and labor costs were adjusted according to the annual operating schedule. Operational costs include the need for electricity, fuel, labor salaries, and consumables (RDF straps). The calculation of operational costs is carried out by taking into account various assumptions, such as the base price and annual escalation. Electricity demand, based on the Determination of Electricity Tariff Adjustment for 2025, is calculated based on the total power and operating hours of all electrical equipment, with the basic electricity tariff for 6,600 VA – 200 kVA power of IDR 1,444.70 per kWh. Electricity consumption is calculated for each electrically driven processing unit from its rated motor power, number of operating units, effective operating hours, and assumed load factor. The total daily electricity demand is obtained by summing the energy consumption of the trommel screens, shredders, compactors, conveyors, and auxiliary electrical equipment. The corresponding maximum simultaneous electrical demand is also used to verify the adequacy of the proposed electrical supply capacity. Fuel Costs: Fuel needs are calculated for transportation fleets and heavy equipment, with the base price of diesel in 2027 projected at IDR 15,745 per liter (assuming an escalation of 7.6% per year from the price in 2024 [26]. The use of rotary dryers uses industrial biodiesel (B40) at different prices. Labor Costs: The needs of 99 workers with various qualifications, ranging from heavy equipment operators, sorters, to factory heads, are allocated salary costs based on the Semarang City Unit Price Standard (Semarang City Mayor No. 12 of 2025). The total salary cost per year is estimated to reach IDR 3,289,920,000.00. Cost of Consumables: RDF products that have been compacted into bales require a strap. With dimensions of 1.2 m × 1.2 m × 1.2 m and a weight of 10 tons, the need for rope per bale is 32 meters, with a total cost of IDR 416,000.00 per bale.

Maintenance costs and depreciation of tools. Maintenance costs are allocated to maintain the optimal performance of all machines and machines throughout their lifetime. This cost is calculated based on a certain percentage of the purchase price of the tool, which is 5–15% [33], with specific values adjusted based on the capacity and function of each tool. In addition to routine maintenance costs, the depreciation (depreciation) of the equipment is also calculated. Depreciation is calculated using the straight-line method, referring to the AHSP PUPR (Permen PUPR No. 1 of 2022) with a residual value percentage of 10% and the economic life of the tool of 15 years. Although it is not a cash expense, the value of depreciation is important for further financial analysis such as tax calculations and net cash flow.

Recapitulation of variable costs and escalation. Variable costs are not fixed and will increase every year due to inflation and other factors. The escalation rate assumptions used in this analysis are as follows:

•Electricity requirement: 0.10% per year

•Fuel needs: 7.6% per year [26]

•Officer's salary: 2% per annum

•Maintenance fee: 1.22% per year

The escalation-adjusted variable costs from the first year of operation (2027) to the 15th year (2041) were incorporated into the cash flow analysis to evaluate the financial feasibility of the RDF IWPF facility.

3.6.3 Integrated Waste Processing Facility income analysis

The income of RDF IWPF comes from two main sources, namely the sale of RDF products and the sale of sorted glass and metal materials. RDF production is estimated at 58,390.80 tons/year, based on a corrected daily RDF output of 224.58 tons/day and 260 effective operating days per year. This production value is used consistently in the subsequent revenue and financial analyses. Glass and metal materials that can be sold are 23,667.21 tons per year. The base-case RDF selling price of IDR 450,000/ton was adopted from the reported RDF price range of approximately IDR 300,000–500,000/ton [34]. This value represents a planning assumption rather than a confirmed contract price with the intended off-taker, assuming an average price increase of 1.22% per year following changes in the rupiah exchange rate. The recapitulation of IWPF income is presented in Table 7.

3.6.4 Financial feasibility analysis

The financial feasibility analysis is carried out by compiling the balance of income and cash flow during the life of the project (2026–2041), as well as calculating feasibility indicators such as Net Present Value (NPV), Internal Rate of Return (IRR), and Payback Period. The uncertainty associated with the RDF selling price and feedstock characteristics was evaluated through the sensitivity analysis presented in this section.

Profit and Loss Balance. The income statement describes net income after deducting variable costs each year. Income before tax is obtained from the difference between total income and total variable costs.

Table 7. Recapitulation of Refuse-Derived Fuel Integrated Waste Processing Facility (RDF IWPF) income in 2027-2041