Efforts to Reduce Carbon Emissions from TPS3R and Rumah Kompos Facilities: Case Study in Surabaya

A majority of the solid waste produced in Surabaya is handled by the Surabaya Environmental Agency (Dinas Lingkungan Hidup, DLH). This process includes sorting, and colleting waste from local sources, transporting waste to and treating waste in local facilities, as well as final processing of waste done in landfills. Each of these processes will produce its own amount and type of GHG emissions. This study focuses on the emission coming from local facilities used to treat waste, namely TPS3R and Rumah Kompos. These facilities receive waste from local communities and produce compost and recyclable materials, creating GHG emissions in the process. This research estimates how much GHGs are emitted from these facilities from its compost production and energy consumption using available tools, and then compare its emission to the amount of waste that it processes. This comparison will show how much GHG each facility emits for every ton of solid waste handled (Facility Emission Factor, EF) which equates to its waste handling performance. Results show that the lowest EF achievable by TPS3R and Rumah Kompos facilities in Surabaya is 0.210- and 1.988-ton CO2eq/ton waste, respectively. This performance level is used as a baseline for increasing the amount of waste treated in these facilities with no additional emission load. When this estimation is applied, the total waste treated in Surabaya could increase by 11%, treating an additional 691 tons of waste per year and reducing waste going to landfills, which in turn reduces overall emissions of the waste sector.


Introduction
Every step of Municipal Solid Waste (MSW) management produces Green House Gases (GHGs) in its process, which contribute to the already present effect of climate change [1].Nevertheless, MSW management is a crucial part of every sizable settlement in the world.This case study will look at MSW management in Surabaya, the second largest city in Indonesia with a daily solid waste production of over 2000 tons, resulting in over 811 thousand tons of solid waste every year [2].A majority of the solid waste produced in Surabaya is handled by the Surabaya Environmental Agency (Dinas Lingkungan Hidup, DLH), which defines MSW management as MSW Reduction at Source and MSW Handling.Handling of MSW is done by sorting and collecting waste from sources to various Transfer Facilities (Tempat Penampungan Sementara, TPS), transporting it to and treating it in Treatment Facilities such as 3R-based Facilities (Tempat Pengelolaan Sampah dengan Prinsip 3R, TPS3R) and composting houses (Rumah Kompos, Rukom), and final processing done in Landfills (Tempat Pemrosesan Akhir, TPA) [2].1307 (2024) 012011 IOP Publishing doi:10.1088/1755-1315/1307/1/012011 2 Currently, more than 75% of MSW produced in Surabaya is going to the city landfill, producing landfill gas in large quantities [2], [3].The remaining 15% is converted into compost and recycled products in Treatment Facilities, the majority of which being DLH-owned facilities.This research focuses on MSW Management activities done in TPS3R and Rukom, which receive solid waste from various TPSs and waste sources around the city, treat it by composting and sorting for recyclable materials, and transport its residue to the landfill for final processing.
TPS3R and Rukom facilities produce emissions in two primary ways, electricity usage and compost production.Electricity usage comes from utilizing equipment such as conveyer belts and shredders, while compost produces emission from aerobic digestion.As an example, A study by Lou conducted in 2008 estimated an Emission Factor of around 0.323 ton CO2eq/ton waste for composting facilities, including its operational activities [4]; Meanwhile, Jackson and Line did practical measurements of a windrow composting facility which resulted in an EF of around 0.183 CO2eq/ton waste [5].It is theorized that similarly sized facilities will produce the same amount of emission when active for the same amount of time, and that the capacity of each facility is proportional to the emission it produces.When calculated alongside the amount of solid waste each facility treats, an Emission Factor (EF) can be defined for each facility.A comparison is then done between these facilities to determine the lowest EF they can achieve, and by simulating the performance on other facilities of the same category, we hope to present hypothesized capacities of DLH-owned MSW treatment facilities in Surabaya based on the GHG emission it produces.Using this method, this research aims to reduce the amount of solid waste going to landfills by increasing TPS3R and Rukom capacities to treat more solid waste, and optimizing the treatment done in these facilities to release the least amount of GHGs.

Data Collection
Data of MSW treatment facilities was obtained from the DLH internal database, including a list of all 9 TPS3R and 26 Rukom facilities.The data required from each facility includes waste input, amount of processed waste (in composting and recycling), and residue from each facility in tons of waste per year over a 5 year period between 2017 and 2021, as well as amount and type of equipment utilized in each facility.Out of these facilities, some have incomplete data and thus needs to be discounted from calculation.This leaves 9 TPS3R and 22 Rukom facilities as the sample size.
The equipment used in these facilities are standardized by the DLH, so electricity usage can be determined from the power requirement of each equipment and how many of them are used in the facility.Informal interviews were also conducted to various facility workers to determine the rate of usage for each equipment.

Composting Emissions
Composting refers to the conversion of organic waste into compost for soil through aerobic digestion, producing compost, water, as well as CO2.As a side note, poor management of composting sites can result in the production of CH4 and N2O, although studies have shown that the amount is negligible [6].GHG emission from the composting processes is dependent on the materials being composted, from MSW to sludge to manure.Higher Degradable Organic Carbon (DOC) levels result in higher GHG emissions.Practical measurements have resulted in Emission Factors around 0.183 to 0.193 ton CO2eq/ton of mixed waste composted [4].This EF is combined to define the composting emissions by a simple formula of: Ecomposting = Emissions produced from aerobic digestion of compost (CO2eq/year) EFcomposting= Emission Factor of composting process (CO2eq/ton waste composted) Waste Composted = Amount of waste composted in facility (ton waste/year) 2.2 kW 4.5 hours Data for the power requirements are obtained from technical specifications of the equipment used, as the type and build are standardized across DLH facilities.Meanwhile, the usage time is obtained from interviews conducted with facility workers.This data is then combined with the EF of electricity usage in Surabaya to obtain the emission produced for equipment usage in each facility.Most recently in 2019, the Indonesian Ministry of Energy and Mineral Resources recommended an EF of 0.001183 ton CO2eq/kWh for electricity usage in Surabaya [7].It should be noted that this EF can fluctuate depending on the performance of the electric grid that year, and the Ministry has announced its goal to decrease the EF of electricity usage in the following years.This EF is then utilized along with usage duration and energy requirements identified to define the equipment emissions (Eequipment, CO2eq/year) for these facilities using the below equation for a given equipment (i), taking account the number of equipment used (N, units), its usage duration (D, hours), and its power consumption (P, kW), where 261 is the number of workdays in a year:

Expected Facility Emission and Emission Factor
The expected facility emission will then equal to the emission from composting combined with the emission from electricity usage, This number is 'expected' because accurate data cannot be obtained for practical equipment usage duration (D) for each facility in a given day.The duration is therefore assumed to be universal, which will in turn theorize the amount of emission created by these facilities should they undergo a standard business day.The EF of each facility is generally defined by the total emission they produce divided by the amount of MSW that goes through processing, expressed in the below equation: Facility EF = the emission factor of each facility (CO2eq/ton waste processed) Expected Emission = Expected amount of emission from each facility (CO2eq/year) Processed Waste = Amount of waste processed by facility (ton waste/year) This will reflect the existing number of usage time and amount of composting done, and use it to weigh the composting and electricity emission factor.Some facilities might have lower than average equipment usage duration, which indicates lower performance.Data for these lower usage rates may not be available, but the measurement of facility EF serves as a workaround for this problem.It is assumed that the "Usage time" given in Table 1 is the standard usage we expect to happen from a regular work day; and therefore, the emission of each facility will be standardized according to this average.Meanwhile, the data for the amount of product recycled and composted are available to represent the facility performance; and by comparing said data with the emission for each facility, we are able to obtain an Emission Factor (EF) that serves as a performance indicator for each facility, reflecting the amount of waste they are processing when compared to the amount of emission they are expected to produce in a standard business day.
After the EF of each facility is determined, a comparison can be made between facilities in the same category (TPS3R or Rukom) to identify which facilities have the least CO2 produced per ton of waste processed.This measurement of optimal EF is used as a proxy to show the optimal performance of that facility type, and can then be used to simulate how much waste can be treated if every facility runs with optimal EF using the below formula: Expected Waste Capacity = Amount of waste treated if performance is uniform (ton waste/year) Expected Emission = Emission produced in the facility with standard equipment usage (ton CO2eq/year) Optimal EF = The lowest EF in the facility category (TPS3R or Rukom, ton CO2eq/ton waste)

Facility 'Emission Factor' to Indicate Performance
Seen in Table 2 and Table 3 are emission and waste data for TPS3R and Rukom facilities.Expected emission is shown in ton CO2eq/year showing emission totals from Ecomposting and Eequipment.Amount of waste processed, which is acquired from DLH internal data, shows the facility performance measured in ton waste processed/year, and both parameters are used to calculate the facility EF based on equation (3), shown in ton CO2eq/ton waste: From the TPS3R facility category shown in Table 2, the facility with the most emission is also the facility with the most waste processed, which is Super Depo Sutorejo.The opposite is also true, with the lowest emission and least waste processed both being Pemilahan Bratang.This is in line with Equation ( 4), where the expected emission is proportional to the amount of processed waste.However, when the EF is calculated to show the ratio between these two parameters, a different hierarchy starts to show.Pemilahan Bratang has the highest EF of 289 ton CO2eq/ton waste, but instead of Super Depo Sutorejo, which is the biggest facility in terms of waste processed, the facility with the lowest EF is TPS3R Tambak Osowilangun, treating 814 tons of waste while producing 170 ton CO2eq every year for an EF of 0.210 ton CO2eq/ton waste.This shows that there is a difference in performance between these facilities, leading to some facilities producing more emission per ton waste processed than others.The same calculation for the Rukom category is shown in Table 3  The Rukom facility category in Table 3 shows very similar emission values, most of them hovering around 15.5 ton CO2eq/year with the exception of Rukom Jambangan with 31.3 ton CO2eq/year.This is due to the majority of their emission coming from equipment use, which only varies based on number of available equipment in the facility.Meanwhile, Rukom Jambangan is the only facility in the Rukom category to operate two organic shredders instead of one, hence the difference in emission.Despite the similarities in emission values, the amount of waste these Rukom facilities treat differ greatly from each other, with the least being Rukom Mbah Ratu treating 0.5 ton waste/year, compared to Rukom Wonorejo II which treats more than 16 times that amount, at 8.6 ton waste/year.This naturally causes significant differences between facility EF.The Facility with the highest EF is not Rukom Jambangan with its high emission value, but instead it is Rukom Mbah Ratu, simply because it does not treat enough waste compared to the others.Rukom Jambangan has the third most waste treated at 3.64 ton waste/year, resulting in an EF of 10.220 ton CO2eq/ton waste.This is still not the lowest EF, as two other facilities can treat more with less equipment, namely Rukom Keputran that treats 4.35 ton waste/year for an EF of 3.7 ton CO2eq/ton waste, and the facility with the lowest EF as well as highest amount of waste treated, Rukom Wonorejo II with an EF of 1.998 ton ecCO2/ton waste.
Nevertheless, it can be seen that these differences in EF between facilities in their category are mostly due to the amount of processed waste entering and exiting the facility.When the same equipment is used for the same amount of time, then they will produce the same amount of emission-this is the facility's expected emission.However, the same cannot be said for the amount of waste that they process using said equipment.When the equipment is available and is expected to be active, but not used to its capacity, is the difference in performance between these facilities.
In other studies, such as one conducted in Depok, Indonesia by Kristanto and Kowen in 2019, Facilities like Rukom and TPS3R has an EF of about 0.05 ton CO2eq/year [8], with values ranging from 0.074 to 4.448 ton CO2eq/year in other studies [9], [10] depending on type of equipment used and its usage rate.Other than equipment specification, other factors that can result to different EF between IOP Publishing doi:10.1088/1755-1315/1307/1/0120116 facilities include the method of composting used.Several studies have shown that pile mixing done during composting can increase GHG emissions up to 20% both in household waste and dairy manure composting [11], [12].

Optimal Facility Performance
The EF written in the above tables might not be reflective of actual working conditions (because of said differences in working hours and electricity usage), but it serves as a proxy to optimize the facility to be as efficient as possible based on existing data.After the EF is determined, a comparison can be made between facilities in the same category (TPS3R or Rukom) to identify which facilities have the least CO2 produced per ton of waste processed.In the TPS3R category, using TPS3R Tambak Osowilangun EF of 0.210 ton CO2eq/ton waste, other facilities can increase their processed waste capacity to various degrees, ranging from 3% (TPS3R Gunung Anyar) to 38% (Pemilahan Bratang) of the current processed waste.This comparison is given in Figure 1 below: Figure 1.Theorized Capacity Increase for TPS3R Facilities In the Rukom category, the Rukom Wonorejo II is most efficient with an EF of 1.988 ton CO2eq/ton waste.This performance is above and beyond any other composting houses, with its next in line being Rukom Keputran with 3.757 ton CO2eq/ton waste.This makes the capacity increase in composting houses quite significant when compared to TPS3R facilities.For detailed report, see Figure 2 below: Figure 2. Theorized Capacity Increase for Rukom Facilities Together, The TPS3R and Rukom facilities receive an average of 12599.9tons of waste every year.From this, 6179.2 tons of it is processed, approximately 49%.With the theoretical capacities implemented, the total processing capacity becomes 6870.9 tons, or 55% of Surabaya's annual waste production.This increase in processing capacity will in turn decrease the amount of waste going to landfills.This is an improvement not only in the quality of solid waste management, but also in the waste sector's overall contribution to global emissions.Reducing the waste load of landfills is considered beneficial to the solid waste management system as it will result in lower environmental impact, lower consumption of energy resources, and lower economic costs [13], [14].Not to mention many landfills in Indonesia currently operates more similarly to controlled dumping sites rather than sanitary landfills, making them even more unfavorable in other cities than in Surabaya [15].And in terms of emissions, various studies have shown that landfilling, both sanitary and uncontrolled, are by far the biggest contributor of emissions from the waste sector [16].On top of that, scenarios that decrease the amount of waste going into landfills will result in an overall decrease in emissions, even if the alternative processing methods produce its own emissions [17].If implemented correctly, it can increase the amount of waste processed throughout Surabaya by 11% of its current capacity.Reducing the amount of residue going into the landfill by the same amount, from 6380 tons to 5673.1 tons/year, processing an additional 691.8 tons of waste.The difference can be seen in Figure 3 below: These items are affected by the increased capacities proposed in this research.When the DLH facilities implement increased capacities, they will see an increase in the amount of waste treated with material recycling (Item 1 & 2).Assuming the collection and handling rate does not increase, an increase in efficiency also means a decrease in the amount of residue that gets sent to landfills (Item 3).All in all, the increase in efficiency proposed will function in accordance with the goals of waste management done by the DLH in Surabaya.

Conclusion
Based on their respective GHG emissions, we hypothesize increased capacities of DLH-owned MSW treatment facilities in Surabaya.This is done by calculating each facility's EF and comparing their performance.When processing emissions are calculated for every facility, TPS3R Tambak Osowilangun and Rukom Wonorejo II has the lowest EF in their categories, with an EF of 0.210-and 1.988-ton CO2eq/ton waste, respectively.Therefore, we propose this be utilized to increase facility efficiency in order to emit less GHGs per ton of waste processed.When implemented, these emission factors are able to demonstrate an 11% increase of waste treatment without increasing GHG emissions, going from 6179 tons of waste treated per year to 6870.9 tons.

Figure 3 .
Increase of Processed Waste in SurabayaThis theoretical performance data is then compared to the DLH performance targets stated in Perwali Surabaya No. 64 Tahun 2018.Out of the six indicators set by the DLH for increased performance stated in the Perwali, three items are relevant: (1) Increase in the amount of municipal solid waste delivered to waste treatment facilities to be recycled (material and/or energy); (2) Increase in the amount of municipal solid waste treated with material recycling; (3) Decrease in the amount of municipal solid waste processed in landfills.

Table 1 .
Out of them, this research will focus on ones that use electricity to treat waste, namely conveyor belts, organic waste shredder, and hydraulic press.Seen in Table1below are the power specification and usage time for each type of equipment: Equipment Usage Time and Power Consumption

Table 3 .
below: Emission Factors for Rukom Facilities