Evaluation of Existing And Future Zero Waste Approach in Municipal Solid Waste Management Utilizing the Zero Waste Index: Bali Province, Indonesia

The World Bank reported that around 1.3 billion tonnes of municipal waste were generated in 2011, and this amount is expected to increase to 2.2 billion tonnes by 2025. Zero Waste Index (ZWI) is a breakthrough for measuring and evaluating waste management's performance based on the concept of zero waste, where recycling is the key to determining this value. This study was conducted in a province in a developing country, namely Bali Province, Indonesia. The calculation of ZWI and energy substitution from waste management is carried out on two schemes, an optimistic scheme (basic data and percentage of waste management targets referring to the regional policy and strategy documents) and a pessimistic scheme (basic data refers to material ow analysis of waste with no increase in the percentage of waste management) from 2020 to 2025. Energy substitution is calculated on two conditions of use, namely through incinerator technology (listed in Indonesia Presidential Regulation No. 35 of 2018) and without incinerators at the Sarbagita Regional Landll. Analysis indicated that the pessimistic scheme provides a higher ZWI value of Bali Province in 2020 than the optimistic scheme, but there is no increase in the ZWI value until 2025 (the ZWI value ranges from 0.02 to 0.2) due to no increase in the percentage of solid waste management. Meanwhile, the optimistic scheme provides a lower ZWI value for Bali's Province in 2020 than the pessimistic scheme, but there is an increase in the ZWI value every year until 2025 (the ZWI value ranges from 0.004 to 0.22). In terms of energy substitution, an optimistic scheme provides energy substitution values 2-5 times greater than pessimistic schemes, with and without incinerators. However, in terms of the incinerator eciency, the pessimistic scheme provides greater eciency (2-6% eciency when using an incinerator) than the optimistic scheme (1-2% eciency when using an incinerator). The 3R (Reuse, Reduce, Recycle)-based waste management and high energy substitution potential in Bali Province can be an effective waste management solution if the stakeholders are committed to achieve the Jakstrada targets by 2025.


Introduction
Waste is the symbol of ine ciency in modern society and a representation of misallocated resources (Zaman & Lehmann, 2013). The presence of waste often creates problems in geographic attractiveness and the health of people living in an environment. Based on The World Bank, the cities around the world generate about 1.3 billion tonnes of solid waste per year. And this continues to increase to 2.2 billion tonnes by 2025 (Hoornweg & Bhada-Tata, 2012). It is approximately 84% of waste is collected in around the world, and only 15% is recycled, with most global waste still managed by land lls (Zaman, 2016). Increased population, urbanization, and economic development raised people's concerns about waste management (Levis et al., 2013).
Zero Waste (ZW) has become the alternative solution in waste management system for handling waste problems in recent decades. Policymakers have embraced the ZW concept because it encourages sustainable production and consumption, optimum recycling and resource recovery, and bans mass incineration and land lling (Zaman, 2015). Zero-waste is the conservation of all resources through responsible production, consumption, reuse, and recovery of all products, packaging, and materials without burning and discharging them to land, water, or air that threaten the environment or human health. Zero waste is different from the concept of waste as an 'end of life' product, yet, it conveys the comprehension of 'waste' as a 'resource' which produces during the intermediate phases of production and consumption activities, and thus, should be recirculated to production processes through reuse, recycle, reassemble, resell, redesign or reprocess (Zaman, 2016).
Three countries that have implemented zero waste on their waste management which are Adelaide (Australia), San Francisco (USA), and Stockholm (Swedia).
Adelaide applied zero-waste by banning plastic bags and facilitating containers for recycling which have been implemented for three decades (Zaman & Lehmann, 2013). In San Francisco, the zero waste challenge that supports solid waste systems is implemented by minimizing consumption, maximizing diversion and encouraging reuse, repair, and eco-friendly purchases of products, banning troublesome items such as plastic bags and redundant packaging to achieve zero-waste goals. One of the most important waste management policies in Stockholm, Sweden, is the ban on disposing of combustible waste and organic waste to the land ll.
Zero Waste Index (ZWI) can also be a tool to evaluate the implementation of zero waste programs based on quantitative values developed. ZWI is a tool to measure the potential of virgin materials to be balanced by zero waste management system (Zaman & Lehmann, 2013). A high ZWI value indicates a high As one of Indonesia's most desirable tourist destinations, Bali Province is surrounded by the sea and has a big impact on the sea and the aquatic environment. Increasing local and foreign tourists will also affect the amount of waste generated. Most of Bali's waste management activity still uses the old-paradigm: waste collection-transporting-disposing. Waste management in Bali Province still relies on land lls, leading to the shorter lifespan of the land ll. Most land lls are operated by an open dumping method, which results in high polluting potential towards the environment. Nowadays, the Sarbagita Regional land ll only serves the operational areas of Denpasar City, Badung Regency, Gianyar Regency, and Tabanan Regency in poor condition as it still implies the open-dumping method. Based on the Integrated Risk-Based Approach (IRBA), Sarbagita Regional land ll has the highest risk index (664.8), which implies it has the highest risk of environmental pollution, hence needing further action, either by closing or rehabilitating the land ll. Therefore, Bali needs to implement the ZW concept to tackle those waste management problems, especially in the Sarbagita region.
Currently, Bali Province has started to apply zero waste to improve its waste management. Some examples of zero waste activities are establishing a waste bank, 3R (Reuse, Reduce, Recycle) Temporary Disposal Site, and socializing the 3R program supported by the informal sector. Bali Province uses land lls as a waste nal processing technology for residual waste or those not handled by zero waste activities. There are ten land lls in Bali Province, with Sarbagita as the regional land ll. This study aims to evaluate the performance of zero waste activities in the integrated waste management system in Bali Province, starting from the generation of waste at sources to land lls by calculating the zero-waste index under two possible schemes; the scheme without any improvement in waste management and the scheme following the Regional Policy and Strategies on Municipal Solid Waste Management (from this point forward will be mention as Jakstrada). This research is expected to become a scienti c base for the government to evaluate the currently implemented waste management policies and help determine future steps to be taken, ensuring that the government and community can implement the zero-waste concept in Bali's waste management system with better performance.

Material And Methods
Initially, the ZWI value will be calculated for Bali Province and Regency/City in Bali Province. ZWI value is calculated using the equation from previous research conducted by Zaman & Lehmann (2013); the equation is: Eq. (1) Where: MSWij = amount of waste in stream i (i = 1,2,3… n = paper, plastic, metal, etc.) which are managed by the system/institution j (j = 1,2,3… n = amount of waste reduced, recycled, managed, etc.) SFij = substitution factor for waste in stream i (i = 1,2,3,… n = n = paper, plastic, metal, etc.) which are managed by the system/institution j (j = 1,2,3… n = amount of waste reduced, recycled, managed, etc.) MSWi = total amount of waste managed (i = 1,2,3,… n = n = paper, plastic, metal, etc.) The amount of waste ow and the total amount of waste managed in Bali Province will use data from a previous study for the pessimistic scheme and modify it for the optimistic scheme. Meanwhile, the performance of the material recovery rate is calculated using the e ciency of the substitution factor for virgin material (Zaman and Lehmann, 2013), shown in Table 1. Energy from the land ll facility. A positive value represents the savings, and a negative value the demand or depletion.
Considering the performance of waste management and the low level of waste purity in Indonesia due to mixed conditions, the substitution factor will use the lowest value on the range. Apart from ZWI, energy substitution e ciency is also crucial because there will be construction and operation of incinerators at the Sarbagita Regional land ll with 1000 tonnes d − 1 capacity. This construction and operation plan is listed in Presidential Regulation No. 35 of 2018 concerning the Acceleration of the Development of Waste Processing Installation into Electrical Energy based on Green Technology. However, it is still uncertain whether this facility can operate in 2025 as targeted. Therefore, the calculation of energy substitution e ciency for the Bali Provinces and its regencies/cities will also be carried out, both when the incinerator is implemented and not implemented. In the case without an incinerator, the energy substitution sources only come from recycled materials, composting, and land lls. However, in the case of the operation incinerator facility, the energy substitution comes from recycled materials, compost, land lls, and incinerators. Therefore, the potential for energy substitution still exists even if the incinerator is not used.
The ZWI calculation methodology and energy substitution are carried out in two schemes: the optimistic and pessimistic schemes. The optimistic scheme refers to data and targets of the Jakstrada documents in 2025, with the percentage of waste handling increasing every year according to the documents. Meanwhile, the pessimistic scheme refers to existing data from a previous study projected until 2025, assuming there is no change in the percentage of waste management. The ZWI value in 2020 and 2025 of the two schemes will be compared.

ZWI for pessimistic schemes
In the pessimistic condition scheme, ZWI in Bali Province will be calculated using the material ow analysis (MFA) of waste from Bali Province, as shown in This data describes the ow of existing waste management in Bali Province. The amount of waste generation used in the 2020 ZWI calculation is the generation shown by the recycler section, which is 109,896.80 tonnes yr − 1 , with 13.36% of the total generation. Based on Bali Province's MFA, a projection of waste generation is carried out until 2025, but the percentage of waste management is assumed to remain the same every year. The results of ZWI calculations will be displayed in the form of a time series to see the pattern of ZWI value for an area each year until 2025.

ZWI optimistic scheme
The second scheme uses an optimistic scheme with the management target referring to the Jakstrada documents for regencies/city in Bali Province. Each regency and city in Bali Province have already established their own Jakstrada as guidance on municipal solid waste management with targets at 2025. The targets are: reducing waste by 30% of total waste generation and waste handling by 70% of total waste generation. ZWI in this scheme is calculated following the planned annual waste generation rate as stated in the Jakstrada documents at the regency/city level. Like the pessimistic scheme, the optimistic scheme also calculates and analyzes the energy substitution e ciency, with and without incinerator.

ZWI of Bali Province and its regencies/cities on pessimistic scheme
The ZWI of Bali Province and regencies/cities in Bali Province is calculated according to Eq. (1). The amount of waste generated that will be used in the calculation is equal to the "recycler" sector, as shown in Fig. 1, which is 128,087.48 tonnes yr − 1 . The data regarding waste composition, both at sources and land lls, shown in Fig. 2 & Fig. 3.
The amount of recycled waste from the material ow analysis is used to calculate the ZWI in 2020. The waste generation is then projected according to population growth to calculate the ZWI in 2025. Under the pessimistic scheme, it is assumed that the percentage of recycled waste from managed generated waste is stagnant and constant at 24.53%. E ciencies of virgin material substitution used in this calculation are the lowest in the range (Table 1) as Indonesia is categorized low in virgin material substitution management. The ZWI of Bali Province on pessimistic scheme year 2020 and year 2025 shown in Table 2 and Table 3.  The ZWI value of Bali province in the existing condition scheme is obtained at 0.09 or 9%, meaning that from 100% of handled waste in Bali province, 9% of waste can be recycled and can be used as alternative virgin material. According to the ZWI value prediction in previous studies conducted by Zaman & Swapan (2016), Indonesia is estimated to be in the low ZWI category (0.06-0.10). Compared with the results obtained from the calculation, which is 0.09, this gure is in the range estimated by Zaman (2016). The predicted gure is the ZWI for Indonesia as a whole nation; in other words, this gure is the average index for all regions in Indonesia. As one of the provinces with a proper and developing waste management level, Bali Province is reasonable to have the ZWI slightly under the highest number in Indonesia's projected average ZWI.
Meanwhile, the ZWI of Bali Province based on the projection of 2025 is still the same as 2020. It means that, in 2025, the amount of substitute virgin materials recovered is still the same as in 2020. This result is expected as the percentage of recycled waste stays stagnant year to year, while the amount of generated waste increases each year.
There are 8 (eight) regencies and 1 (one) city in Bali Province: Denpasar City, Badung Regency, Gianyar Regency, Tabanan Regency, Jembrana Regency, Buleleng Regency, Klungkung Regency, Bangli Regency, and Karangasem Regency. Using a similar method with the Bali Province, the ZWI of each regency and city is calculated from 2020 and 2025, as shown in Table 4. The percentage of recovered substitute virgin materials is shown in Table 5. Classi ed nations around the world according to each nation's respective ZWI. This study follows the same classi cation to classify each regency/city in Bali Province according to the ZWI in 2020 and 2025 ( Fig. 4 and Fig. 5). According to the classi cation, regencies/cities in Bali Province are classi ed in very low ZWI (i.e., Denpasar City, Klungkung Regency, and Buleleng Regency), low ZWI (i.e., Gianyar Regency, Tabanan Regency, dan Badung Regency), and medium ZWI (i.e., Jembrana Regency, Karangasem Regency, and Bangli Regency). By using the ZWI value of each regencies/cities, some of the regencies in Bali Province is classi ed as low class and some other is classi ed as high class. However, it shows a different result if the ZWI from the Bali Province data is used, which is 0.09, which classi es the Bali Province as low class. This discrepancy shows a data gap between the government's level, which affects the region's classi cation into two different classi cations. The Sarbagita Regional land ll (also known as Suwung Land ll) is a land ll that serves four regions: Denpasar City, Badung Regency, Gianyar Regency, and Tabanan Regency. Waste generated from those four regions will be transported to the Suwung Land ll and reduces the possibility of collecting recyclable materials from the source. Although the recyclable collection is performed on the land ll by scavengers, it is not as easy as the collection performed from the lower level (e.g., transfer station, households, etc.) as the land ll waste is heavily mixed in enormous mass and volume. This issue affects the recycling performance in 4 (four) regions as it becomes harder to perform the collection for recyclable materials (only performed by waste banks and 3R transfer stations with low rate). In the end, it also lowered the value of ZWI, as shown in the ZWI classi cation; those four regions are classi ed as very low and low.
Besides ZWI, the energy substitution e ciency is also calculated on the scheme. The primary difference between ZWI and energy substitution is that ZWI sees waste as an alternative for raw/virgin materials to make products; meanwhile, the energy substitution calculation views waste as a potential source to produce energy. This is why thermal processes do not contribute to the ZWI calculation but contribute to determining the energy substitution e ciency (Table 1). There are 2 (two) applied cases for calculating energy substitution e ciency; (1) incinerator facilities are implemented in certain land lls in Bali Province, and (2) incinerator facilities are not implemented.
Incinerator facilities are planned to be implemented in Suwung Land ll following the Presidential Regulation no. 35/2018 regarding Acceleration of the Development of Waste Processing Installation into Electrical Energy based on Green Technology. The Suwung Land ll covers the area of Sarbagita (Denpasar City, Badung Regency, Gianyar Regency, and Tabanan Regency); therefore, it is assumed that the waste which the incinerator will process comes from the 4 (four) regions. Table 6 shows the value of energy substitute for 4 (four) regions or Suwung Land ll, with and without incinerator facilities. implementation. This is supported by the fact that Denpasar city is Bali's capital that generates a larger amount of combustible waste than other locations.
Meanwhile, the recycling activities are not as potential in Denpasar City as most generated waste is transported to the Suwung Land ll. This makes the ZWI value of these regions low, but the energy substitution value high as there is a large amount of input waste and could be utilized in the land ll. The value of energy substitution will be discussed further on the comparison between the two schemes.

ZWI of Bali Province and its regencies using optimistic scheme
The optimistic scheme is a scheme based on the waste management targets in Jakstrada documents by 2025. The existing and projected data of waste generation in Jakstrada from each regency/city in Bali Province is used, assuming there is no change in data composition, both at sources and land lls. ZWI calculation is the same as the pessimistic scheme from 2020 to 2025 and compared between 2020 and 2025 shown in Table 7 and Table 8. The ZWI calculation in 2020 is 0.05 or 5% and 0.07 or 7% in 2025. With this scheme, there is an increase of 2% for ZWI in Bali Province in 5 ( ve) years. This increase follows the assumption that the targets of Jakstrada are achieved (30% reduction and 70% handling). It is also assumed that 30% of total waste generation is successfully recycled to be virgin material in 2025. Thus, there is an increase in the value of ZWI. Same as Bali Province, ZWI for each regency/city also increases, as shown in Table 9. The ZWI average of the regencies/cities is not too different from the ZWI in Bali Province, which is still in the very low ZWI class and low ZWI class. Table 9 also shows a decrease in ZWI value in certain years in each location (i.e., Denpasar city from 2020 to 2021, Badung Regency from 2021 to 2022, Gianyar Regency from 2021 to 2022, etc.). The ZWI value decrease is caused by the increasing amount of waste generation but not followed by an increase in waste management capacity for reduction or recycling. Therefore, instead of reduction or recycling, the increased waste will enter the land ll.
The calculations and time series graphs in Fig. 6 show that Bali's regencies/cities' ZWI value in the optimistic scheme ranges from 0.004 to 0.22. Tabanan Regency held the highest ZWI value, and Bangli Regency had the lowest ZWI value. In this scheme, Tabanan Regency has a high ZWI value because, based on Jakstrada data, this regency is making great use of existing recycling facilities, such as 3R transfer station, unit waste Bank, main waste bank, and even the waste recovered by scavengers at nal processing is the highest compared to other regencies/cities. Waste composting in Tabanan Regency is also the highest in nal processing compared to other regencies.
Meanwhile, Bangli Regency has a low ZWI value due to very few recycling and composting facilities based on Jakstrada data. Figure 7 and Referring to the ZWI value classi cation reported by Zaman and Swapan (2016), this scheme in the year 2025, the regencies/cities in Bali Province can be categorized into very low ZWI value (i.e., Denpasar City, Bangli Regency, Karangasem Regency), low ZWI value (Gianyar Regency and Buleleng Regency), and ZWI medium (i.e., Badung Regency, Klungkung Regency, Tabanan Regency, and Jembrana Regency). Based on the average ZWI value of regencies/cities in Bali Province, the ZWI value for Bali Province is in the low ZWI value. This scheme also shows the calculations of energy substitutions obtained from the two conditions, such as implementing and not implementing incinerator as shown in Table 10. Incinerator usage contributes a higher energy substitution value than the condition without incinerator usage. However, the increase in value is not high, with only a maximum of 2%. This result was obtained because for the pessimistic scheme, the 3R approach is preferable to a thermal process like incineration. Thus, it causes less e ciency in incineration as the waste is expected to be successfully recovered into virgin materials through the 3R activities.

Comparison between ZWI of Bali Province on two schemes
Page 10/17 The pattern of municipal waste management in Bali Province for both schemes is obtained after the ZWI calculation. The ZWI value between optimistic and pessimistic scheme from 2020 to 2025 will be compared to identify the changing pattern and achievement of the 3R based waste management in regencies/cities of Bali Province as shown in Fig. 9.
From the comparison, the average ZWI value of 2020 in pessimistic schemes is higher than the optimistic scheme. It happens because the data used for the pessimistic scheme is data from a previous study regarding material ow analysis in Bali Province; hence the data is closer to the actual practice done on the sites. Meanwhile, the data used for the optimistic scheme is data from Jakstrada documents which use a standardized per capita waste generation approach. Therefore, the data are less likely to represent the actual condition and more of a projection.
The average ZWI value of Bali Province in 2025 is the same for both schemes; however, further analysis shows a difference in the ZWI development pattern. Even though the initial ZWI is high in a pessimistic scheme, there is no improvement in ZWI value to 2025. This scheme assumes that there will be no change in waste management and recycling percentage for every location, hence no change in ZWI despite an annual increase in waste generation. On the other hand, optimistic schemes give a lower value of initial ZWI with a changing pattern from year to year for every location. According to the Jakstrada documents, the generated waste will be reduced to 30% by 2025 using 3R activities. This target affects the value of ZWI as it changes following the target of waste reduction by 3R activities in 2025. Therefore, the ZWI value is not affected by the initial data and waste generation rate used for the calculation, but it is affected by the increase of waste management utilizing the 3R or zero-waste-based activities. Nevertheless, it is still imperative to have a reliable and valid database to determine and evaluate the current condition of waste management.
Additionally, the energy substitution values between the two schemes are also compared. Both comparisons consider the case where the incinerator is applied and not applied in Sarbagita Regional Land ll/Suwung Land ll as shown in Table 11.

Conclusion
According to the analysis, the pessimistic scheme shows a higher value of initial ZWI than the optimistic scheme in 2020, but the value is stagnant and does not increase by 2025 (ZWI value ranges from 0.02 to 0.2) because there is no improvement in recycling and waste management percentage. On the other hand, the optimistic scheme gives a lower value of initial ZWI than the pessimistic scheme, but the value keeps increasing until 2025 following the target in Jakstrada documents (ZWI value ranges from 0.004 to 0.22).
For energy substitution, an optimistic scheme gives an energy substitution value 2-5 times higher than the pessimistic scheme, both with and without an incinerator. However, if the incinerator is to be implemented, the pessimistic scheme gives better e ciency (2-6% higher than without the incinerator) compared to the optimistic scheme (only 1-2% higher than without the incinerator).
From an optimistic scheme, the waste management utilizing the 3R approach gives signi cant results, as shown by ZWI improvement from year to year. The optimistic scheme also gives a relatively higher energy substitution value from the energy substitution variable and can be utilized further. The 3R based waste management and energy substitution potential in Bali Province may become the solution for effective municipal solid waste management under the condition that every stakeholder is committed to achieve the Jakstrada targets by 2025.
Declarations Figure 1 Material ow analysis of Bali Province in 2020 Average waste percentage composition in land lls