Dynamic System Modeling and Sustainability Strategies for Circular Economy-Based Dairy Cow Waste Management

: Dairy farming activities produce waste that can have a negative impact on the environment. The processing of livestock waste will reduce pollution and support environmental conservation programs that are currently being intensiﬁed by the West Java Provincial Government, Indonesia. An economic approach that can minimize waste and maximize resources is the circular economy (CE) approach. CE can occur at the macro-, meso-, or microlevels. The application of micro-scale CE can be carried out in a business activity. One of the micro business groups that have implemented the CE concept in Bandung Regency, West Java Province, Indonesia, is the Taruna Mukti Farmer Group, which is located in the Citarum River sub-basin area. From 2008 to 2022, this group processed 49,580 tons of cow dung into organic fertilizer. However, there has been a decline in livestock waste processing, where production reduced from 3700 tons in 2018 to 1280 tons in 2021, then to only 500 tons in 2022. Therefore, this study aims to design a sustainable strategy for livestock waste management based on CE in the Taruna Mukti Farmer Group. The method used is in-depth interviews with the Drivers, Pressure, State, Impact, Response (DPSIR) approach. In addition, this study will also describe the CE model in the management of dairy cattle waste. Key Informants come from the Farmer Group and related stakeholders. Based on the results of the study, it is known that the dairy cattle waste management model in the Taruna Mukti Farmer Group is a form of implementing the CE concept with a circular ﬂow of material and involving various stakeholders and an extensive marketing network. With the current conditions, the simulation results of processing livestock waste into organic fertilizer show a decline/unsustainability. To support the sustainability of livestock waste management, a response is needed in the form of strengthening the internal management of the Farmer Group’s organization, regular assistance and supervision from the local government and non-government organizations, and guidance regarding the marketing of organic fertilizers and ease of access to markets.


Introduction
Livestock is one of the sub-sectors that contributes to the economy in Indonesia.This is illustrated in the results of the 2013 agricultural census that the number of livestock households almost reached 13 million households.On the other hand, livestock also produces waste products.Livestock waste can cause environmental pollution.This waste can contaminate soil, water, and air [1].One type of livestock business is dairy farming.Bandung Regency is one of the largest dairy farming centers in West Java province.
The Central Bureau of Statistics of West Java data state that the total population of dairy cattle in Bandung Regency in 2021 is 27,668 heads.An adult cow can produce as much as 15 kg of solid waste per day [2].This shows that there is a potential for as much dairy cattle waste as 691.7 tons per day in Bandung Regency.If this waste is left alone, it will cause pollution, especially river pollution and the release of methane gas, which contributes to increasing global warming, so it triggers climate change, whose impacts are starting to be felt today, such as erratic weather, heatwaves in several countries, drought, and so on [3].One approach that can be used to reduce environmental pollution by dairy farm waste is the CE system approach [4].
In a CE system, resources are utilized to the maximum extent possible and minimize the waste generated by processing this waste into useful products for other sectors so as to create a circular flow of material [5].The CE can be implemented at the microlevel (business activities and consumers), mesolevel (eco-industrial area), and macrolevel (city, region, country) with the aim of achieving a sustainable economy, creating a good quality environment, economic prosperity, and social justice [6].The implementation of a CE system can support the achievement of sustainable development, which consists of three dimensions, namely, the economic dimension, the environmental dimension, and the social dimension [7].
Research related to CE implementation in the agriculture sub-sector has been carried out previously.Previous research has mostly discussed CE at the meso-and macroscales; for example, they are: adjusted the general CE framework to the agricultural sector's specificities, and analyzed the scope of the indicators available for measuring agricultural production systems' circularity performance in supporting decision-making processes [8]; studied an integrated system comprising intensive livestock and crop management compared with traditional systems, from the economic and environmental points of view [9]; researched the important role of blended traditional and modern practices in livestock keeping along with biomass management through appropriate technologies conjoined with green value chain-based enterprises for monetizable incentivization [10]; studied key challenges to ensure sustainable agriculture by managing agricultural waste in a circular bio-based economy [11]; studied the existing literature and identified the drivers and barriers for implementing the CE in the agri-food supply chain [12].
Based on previous studies, no one has examined how the CE model is implemented in the microscale agricultural sector, especially the management of dairy cattle waste.The novelty of this research is to create a CE model on micro-scale agriculture and design strategies to support the sustainability of CE implementation.The author conducted research in a farmer group named Taruna Mukti in Bandung Regency, West Java.The Taruna Mukti group is a farmer group that has implemented the CE concept, consisting of farmer groups in Cibodas Village and Cisondari Village, Pasirjambu District.The Taruna Mukti Farmer Group has activities that focus on processing dairy cattle waste in Pasirjambu District into organic fertilizer products.From 2008 to 2022, this group processed 49,580 tons of dairy cow dung into organic fertilizer.However, there has been a decline in livestock waste processing, where production has reduced from 3700 tons in 2018 to 1280 tons in 2021, then to only 500 tons in 2022.The processing of livestock waste is not only beneficial for the environment but also beneficial for the economy of farmers.However, at this time in the Taruna Mukti Farmer Group, there has been a drastic decline in fertilizer production, and production is even stopping.The author also makes a strategy to support the sustainability of CE-based livestock waste management in the Taruna Mukti Farmer Group.

Materials and Methods
The research location is in Cibodas Village and Cisondari Village, Pasirjambu District, Bandung Regency, which is the coverage area of the Taruna Mukti Farmer Group.The Taruna Mukti group became the research location because it is a pilot group in Bandung Regency that has succeeded in managing livestock waste into solid organic fertilizer products.The research method used in this study is a qualitative method which is supported by secondary data.A dynamic system approach is used to describe the CE-based model of dairy cattle waste management and predict the future organic fertilizer production of Taruna Mukti Farmer Group.The DPSIR (Drivers, Pressure, State, Impact, and Response) approach is used to analyze the sustainability strategy of dairy cattle waste management.

System Dynamics Modeling Approach
The modeling of the dairy farming solid waste management system based on a CE uses qualitative research methods in descriptive and exploratory forms.Descriptive research has the aim of explaining something by describing, recording, analyzing, and interpreting the conditions that occur in the dairy cattle waste management system in the Taruna Mukti Farmer Group.The dynamic system approach in this study uses a causal loop diagram model to describe the CE model [13].The CLD approach defines the causal relationship between a set of elements that run in the system.The basic elements of CLD consist of variables (factors) and arrows.Variables are conditions, situations, actions, or decisions that affect and can be influenced by other variables.Variables can be quantitative (measurable) and qualitative [14].The CLD method is useful for explaining interdependencies in various situations.The causal relationship between these variables shows two possibilities, namely: the possibility of the relationship moving in the same direction (+/R = Reinforcing) or moving in the opposite direction (−/B = Balancing).The stages of the CLD approach used to describe the dairy cattle waste management model based on a CE are as follows [15]:

System Identification and Conceptualization
The initial stage in developing a CLD system is to identify variables in the system [16].The structure of the model is created by building a CLD (causal loop diagram) in the form of a cause-and-effect diagram for the management of dairy cattle solid waste based on a CE.

Stock-Flow Diagram (SFD) Model Formulation
In this study, the formulation of the SFD model uses a computer program tool in the form of Powersim Studio v7 software.Creating the model structure is performed by building flow diagrams or SFDs (stock-flow diagrams) to proceed to the simulation stage.Before building a flow chart, it is necessary to distinguish between variables or parameters that will be used as stock (accumulation) and flow (flow) that can change the stock value [17].The SFD model is based on secondary data available on the dairy cattle waste management system in the Taruna Mukti Farmer Group.In SFDs, mathematical formulas are applied.

• Model Simulation and Validation
After the model formulation stage, validation and model simulation were carried out.This stage is the stage of assigning a value to the initial variable whose value is known.System dynamics uses mathematical equations to describe a system in a model.The simulation model must be equipped with the correct mathematical equations, units, and initial conditions so that it can be run.The result obtained will be the appropriate relationship between the variables in the diagram.
As shown in Figure 1, the initial stage in developing a CLD system is to identify the elements in the system.This stage is the stage of determining the elements in modeling.A stock-flow diagram (SFD) is created based on secondary data, which differentiates the variables or parameters that will be used as stock (accumulation) and flow which can change the value of the stock.After the model formulation stage, the model validation and simulation stages are carried out.These stages are the stages of giving value to the initial variable, whose value is known.System dynamics use differential equations to describe a system in a model [15].For example, the mathematical equation for the amount of livestock waste that is wasted is equal to the amount of livestock waste produced minus the amount of livestock waste that is managed as fertilizer.
Model validation is carried out in accordance with the modeling objectives, namely, by comparing the dynamic behavior of the model with real system conditions.If the model is considered valid, then this model can be used as a representative of the real system.Validation in this modeling is performed by comparing the behavior of the model with the real system (quantitative behavior pattern comparison), namely, the MAPE (mean absolute percentage error) test.MAPE is a measure of accuracy related to time series.MAPE is always expressed as a percentage.MAPE is formulated as follows [18]: Notes: Model validation is carried out in accordance with the modeling objectives, namely, by comparing the dynamic behavior of the model with real system conditions.If the model is considered valid, then this model can be used as a representative of the real system.Validation in this modeling is performed by comparing the behavior of the model with the real system (quantitative behavior pattern comparison), namely, the MAPE (mean absolute percentage error) test.MAPE is a measure of accuracy related to time series.MAPE is always expressed as a percentage.MAPE is formulated as follows [18]: Notes: Ai = real data Fi = simulation result data n = period and amount of data The informants selected to create a model of dairy cattle waste management based on a CE include the management of the Taruna Mukti Group, members of farmers, the village government, the Bandung district government, business partners, and consumers of organic fertilizer.Supporting data and literature come from notes, activity reports, scientific journals, and other documents related to livestock waste management in the Taruna Mukti Group.

DPSIR Analysis
A qualitative method with the DPSIR approach is used to design a CE-based dairy waste management strategy.The DPSIR method was developed by the European Environment Agency (EEA) and has been widely used to conduct analyses related to the environment and environmental carrying capacity [19].The DPSIR method is carried out by outlining drivers (causing factors), pressure (pressure/driving factors/catalysts that accelerate changes in the condition of a situation), states (initial conditions), impact The informants selected to create a model of dairy cattle waste management based on a CE include the management of the Taruna Mukti Group, members of farmers, the village government, the Bandung district government, business partners, and consumers of organic fertilizer.Supporting data and literature come from notes, activity reports, scientific journals, and other documents related to livestock waste management in the Taruna Mukti Group.

DPSIR Analysis
A qualitative method with the DPSIR approach is used to design a CE-based dairy waste management strategy.The DPSIR method was developed by the European Environment Agency (EEA) and has been widely used to conduct analyses related to the environment and environmental carrying capacity [19].The DPSIR method is carried out by outlining drivers (causing factors), pressure (pressure/driving factors/catalysts that accelerate changes in the condition of a situation), states (initial conditions), impact (impact of these changes), and responses (responses from related stakeholders/subjects) to these changes [20].
Drivers or driving factors in the management of solid waste in dairy farming are livestock productivity factors.This causes pressure on the environment that causes state conditions, namely, environmental pollution by livestock waste.Then, there is an impact in the form of environmental degradation due to livestock waste on the environment.Therefore, responses are needed, namely, efforts to carry out sustainable livestock waste management.Qualitative data analysis is carried out through three stages, namely data reduction/condensation, data presentation, and drawing conclusions.Then, a cross-check was carried out through field observations.Data were obtained from observation, and then poured into documentation and notes.After performing a cross-check through observation in the field.The data that have been validated are then included in the research discussion.
The sources of data in the qualitative method of this DPSIR approach are informants and literature related to the research.The selection of informants was conducted using a purposive sampling technique by considering their relevance and competence to the management of livestock waste at Taruna Mukti Farmer Group, Bandung Regency.Informants came from the management and members of the Taruna Mukti Farmer Group, the local government, and farmer group partners.The results of the semi-structured interviews were triangulated to ensure the validity of the data.In addition, this research is also supported by secondary data such as data on environmental conditions, milk prices, livelihoods, milk production, production, and sales of organic fertilizers.

Overview of Taruna Mukti Farmer Group
The research location is in Cibodas Village and Cisondari Village, Pasirjambu District, Bandung Regency, which is the area of the Taruna Mukti Farmer Group.In general, the geographical and topographical conditions of the Cibodas and Cisondari villages are hilly areas and rice fields accompanied by protected forests with an altitude of 1000 to 1200 m above sea level with an average temperature ranging from 18 • C to 28 • C. Cibodas Village and Cisondari Village are located at the foot of the hill and are included in the Ciwidey subwatershed which is one of the Citarum River sub-watersheds.Cisondari Village and Cibodas Village are the centers of dairy farming in Pasirjambu District.Dairy farmers sell milk to the Pasirjambu Cow Village Unit Cooperative at the current price of 5870 IDR per liter.Milk from KUD Pasirjambu is then sold to the milk processing industry.
Cibodas Village and Cisondari Village as centers for dairy farming in Pasirjambu District produce waste in the form of cow dung.Taruna Mukti Farmer Group processes waste into organic fertilizer.The formation of the Taruna Mukti Farmer Group aims to provide stimulation to the community about the potential of dairy cattle dung that has not been optimally utilized by farmers, reduce environmental pollution by utilizing cow dung waste to be used as other more useful materials through community empowerment, as well as develop business utilization.
Taruna Mukti Farmer Group is a farmer group that focuses on processing organic fertilizers.The Taruna Mukti Farmer Group has been processing livestock waste into organic fertilizer since 2008.The farmer group buys cow dung from the farmer for 50 IDR per kg.The number of workers in the Taruna Mukti Farmer Group is 30 people, consisting of 20 technical people and 10 management people.Apart from producing organic fertilizers, the Taruna Mukti Farmer Group is also active in social activities.Some of the profits are allocated for activities such as: compensation for orphans and poor people, free medical treatment, mass circumcision, the repair of worship facilities, and the provision of food barns.The Taruna Mukti Farmer Group purchased 1800 m 2 of rice fields, all of which were allocated for distribution to the Cibodas community.Each rukun warga (RW) receives 150 kg of rice.The distribution of the rice is arranged by the RW heads to be given to the less fortunate residents.Currently, there are 7 tons of grain in the rice barn.
The activities of the Taruna Mukti Farmer Group support various aspects of development such as economic, social, and environmental, as well as supporting village food security.In the economic aspect, farmers receive additional income from the sale of livestock manure.In the social aspect, the existence of the Taruna Mukti Farmer Group has created new job opportunities, reduced unemployment, and been involved in social activities.In the environmental aspect, processing livestock waste into organic fertilizer can reduce environmental pollution, including water, soil, and air pollution.Meanwhile, in the aspect of food security, organic fertilizer is useful for agriculture and food crops, and the existence of food barn activities is beneficial for village food security, especially for vulnerable families.The optimal utilization and processing of livestock waste can create added value economically.The environmental awareness of livestock waste and its utilization is influenced by the knowledge and skills of the community as well as socialization from the local government about the importance of processing livestock waste in terms of the health, environment, and also economic benefits that can be obtained [21].

Causal Loop Diagram Model on Dairy Cow Waste Management
The identification and conceptualization of the system with a system dynamics approach focuses on the pattern of cause-and-effect relationships that occur due to the influence of feedback from the results of activities or conditions of one system component to another.Based on the results of the study, we created the following causal loop diagram model of the livestock waste management system in the Taruna Mukti Farmer Group, Pasirjambu District, Bandung Regency (Figure 2).CLD-R2 can be explained by the fact that that the livestock waste that is managed will be the raw material and support the production of organic fertilizer.Increasing the amount of production supports the processing of livestock waste into more organic fertilizers.CLD-R2 is a form of "loop reinforcing", which is mutually reinforcing where the increase in fertilizer production causes the need for raw materials to increase, as well as more livestock waste that is managed.The CE concept in the agriculture sector emphasizes the redesign of production, by promoting the recycling of waste, some of which becomes organic fertilizer [30].The application of technology in waste management produces organic fertilizers as a substitute for inorganic fertilizers and is more CLD-R1 can be explained by the fact that that dairy farms in the Taruna Mukti Farmer Group area produce cow dung.Cow dung is the main raw material for organic fertilizer products.Organic fertilizers are useful for agriculture.Agriculture produces waste in the form of crop residues such as rice straw, corn straw, and soybean straw.This straw can be used as animal feed either given directly or processed into silage/fermented feed.One of the alternative feed sources for livestock is agricultural waste [22].Optimizing the use of agricultural waste can help provide cattle feed [23].Furthermore, processing agricultural waste into cattle feed can overcome the shortage of grass as the main feed for the cattle business [24].
The form of CLD-R1 is an application of the CE concept by maximizing the utilization of resources and minimizing wasted waste.CLD-R1 involves the dairy farming sector and the agricultural sector, where organic fertilizer is beneficial for agriculture, and agricultural waste is beneficial for livestock.CE is a design resulting from integrated waste management involving various sectors [25].The conceptual analysis of the CE shows a strong relationship with sustainable production, waste management, and recycling [26].
CLD-B1 can be explained that dairy farming in the Taruna Mukti Farmer Group area produces livestock waste where not all livestock waste has been managed.Based on interview results, this is partly due to the lack of awareness of farmers to manage livestock waste.Government support is important for farming, this support can be in the form of adequate transportation facilities and infrastructure, adequate farming equipment, smooth marketing, business capital, and assistance [27].The government support in the form of guidance and counseling had a significant effect on improving the function of farmer groups [28].CLD-B1 is a form of "loop balancing" where the effect is the opposite; when the awareness of the Taruna Mukti Farmer Group farmers regarding waste management is lacking, the amount of unmanaged waste increases so that support from the government and other stakeholders is needed.To achieve an optimal increase in the commercial production of organic fertilizers, government support is needed through organic fertilizer policies, funding, the development of an efficient quality control system, and also market strategies [29].
CLD-R2 can be explained by the fact that that the livestock waste that is managed will be the raw material and support the production of organic fertilizer.Increasing the amount of production supports the processing of livestock waste into more organic fertilizers.CLD-R2 is a form of "loop reinforcing", which is mutually reinforcing where the increase in fertilizer production causes the need for raw materials to increase, as well as more livestock waste that is managed.The CE concept in the agriculture sector emphasizes the redesign of production, by promoting the recycling of waste, some of which becomes organic fertilizer [30].The application of technology in waste management produces organic fertilizers as a substitute for inorganic fertilizers and is more environmentally friendly.Utilizing livestock manure in compost will indirectly increase people's income and welfare [31].
CLD-B2 can be explained that the utilization of agricultural waste as animal feed can reduce the cost of dairy cattle feed.Reducing feed costs can increase the profitability of a dairy farming business.The greater profit of dairy farming causes the business to continue to exist, which is also supported by factors of environmental conditions and the potential of natural resources, milk prices, and human resources.For the development of dairy cattle agribusiness, it must be able to increase the profits received by farmers.Every dairy farmer tries to make their agribusiness run efficiently and economically so that it can increase profits [32].If heat stress is experienced by dairy cattle for a long time, it will have an effect on decreasing milk production by 0.6 kg to 1.4 kg for every 1 • C increase in air temperature.Environmental conditions that are in accordance with the availability of feed will keep the productivity of dairy cattle belonging to members of the Taruna Mukti Farmer Group in good condition [33].
CLD-R3 can be explained by the fact that that the processing of livestock waste into organic fertilizer by the Taruna Mukti Farmer Group can reduce environmental pollution which will improve the quality of the environment.Organic fertilizers are useful for agriculture.Agriculture produces residual agricultural waste that can be used as animal feed.Organic fertilizers are also useful for forest reforestation.Forests can provide animal feed and improve environmental quality.The Taruna Mukti Farmer Group also indirectly contributes to the reforestation of forests because it is a supplier of fertilizer for several environmental NGOs.Reduced environmental pollution and the reforestation of forests can improve the quality of the environment.The processing of livestock waste into organic fertilizer is beneficial in reducing environmental pollution, so it is expected to eliminate potential impacts on the environment [34].Reforestation activities are beneficial for adding ecological value, adding aesthetic value, and obtaining economic benefits [35].
Reforestation is an inexpensive way to meet several international environmental goals such as mitigating climate change, reversing landscape degradation, and restoring biodiversity restoration [36].
CLD-B3 can be explained by the fact that that the increase in organic fertilizer production can increase the absorption of labor.An increasing number of workers can reduce the number of unemployed people.Decreasing unemployment can reduce poverty.Smaller poverty creates better socioeconomic conditions for the community.In the organic fertilizer business, the Taruna Mukti Farmer Group employs 30 people.The increase in marketing and sales of organic fertilizer for the Taruna Mukti Farmer Group can increase income, which also has an impact on socio-economic conditions.From the economic aspect, the use of waste has an impact on the income of farmers [37].The organic fertilizer business is one of the businesses in the agricultural sector that deserves to be developed to create jobs [38].Processing waste into organic fertilizers will increase farmers' income, support sustainable agriculture, and reduce the ecological footprint due to the use of inorganic fertilizers [39].
CLD-R4 can be explained by the fact that that the increase in the income of the Mukti cadet farmer group can support the social activities of the Farmer Group.These activities include compensation for orphans and the poor, free medical treatment, mass circumcision, the repair of worship facilities, and food barns.These activities contribute to creating better socio-economic conditions for farmers and other communities.Farmer Groups have a role in increasing farmers' income, assisting farmers in running their agricultural wheels, and can also be a forum for farmers to exchange information about agricultural science [40].
CLD-R5 can be explained by the fact that that the increase in the marketing of organic fertilizer products by Taruna Mukti Farmer Group will increase the need for the transportation/delivery of organic fertilizer.The Farmer Group cooperates with a delivery service provider at a cost of 150 IDR per kg of fertilizer.The truckload of one shipment is about 7 tons of fertilizer.Some of the organic fertilizer consumer partners of the Farmer Group, namely, non-governmental organizations (NGOs), engaged in the environmental sector, such as the Family NGO, the Green Archipelago Movement, Peduli Rakyat Kecil, and Mercy-USA.This indirectly contributes to the reforestation of the Farmer Group.Farmer groups also contribute directly to reducing environmental pollution so that environmental quality is maintained.If the waste is not treated, it has the potential to cause environmental pollution, which has an impact on the quality of the environment and the quality of life of farmers and livestock and can trigger social conflicts [41].
CLD-R6 can be explained by the fact that that the social activities of the Taruna Mukti Farmer Group, one of which is the provision of food barns, can maintain food security in the village.Moreover, more and more marketing and sales of organic fertilizers to various consumers/partners in various regions can support the agricultural sector and contribute to creating food security in these areas.Organic fertilizers play an important role in the management of food crop agriculture, especially rice [42].The use of organic fertilizers is needed to improve soil quality, especially those related to the number of bacteria that are beneficial for growth and the increased production of food crops [43].The Taruna Mukti Farmer Group has contributed to supporting rice farming, especially in the Bandung Regency, West Bandung Regency, and Karawang Regency.Other agricultural and plantation commodities that have been supplied with fertilizer by the Farmer Group include cassava, coffee, tea, corn, porang (an export commodity), avocados, herbal plants (jamu), horticulture, and so on.
The livestock waste management system at Taruna Mukti Farmer Group applies CE concepts such as reduce, reuse, recycling/upcycling, and repair.The processing of livestock waste and the use of agricultural waste to become animal feed can reduce waste.Processing livestock waste is also a recycling/upcycling process in which livestock waste is converted into organic fertilizer products.In the organic fertilizer production process, used sacks of fertilizer are also reused to package fertilizer.Farmers also repair damaged production equipment such as hoes, shovels, and waste carts.The 3R concept (Reuse, Reduce, Recycle) is a solution to reduce industrial waste, community waste, and family (household) waste [44].

Stock-Flow Diagram Results
A stock-flow diagram is a form of livestock waste management system flow diagram created by entering numerical data or mathematical formulas on each component.The livestock waste treatment system of organic fertilizer in the Taruna Mukti Farmer Group consists of several subsystems including the raw material subsystem as an input, the production subsystem, and the marketing subsystem.The agribusiness of organic fertilizer production is three sub-sectors that are economically interrelated.The three sub-sectors are the input availability sub-sector, the production sub-sector, and the product marketing sub-sector [45].
The formulation of the stock-flow diagram model is based on the livestock waste treatment subsystem, which is supported by secondary data.The model is formulated mathematically in the form of a flow chart.The following is the formulation of the stock-flow diagram model for the management of the Taruna Mukti Farmer Group's livestock waste: The SFD model (Figure 3) is formed based on indicators that have secondary data (numeric data).In this case, it includes raw material subsystem data, production, marketing, and the sales of organic fertilizer as a product of livestock waste processing.The results of the validation SFD obtained the deviation level between the simulation results and factual data with an average MAPE yield of 16.3%.The resulting MAPE has a value between 10% and 20%, which means it is considered good to represent actual conditions.The interpretation of the MAPE guidelines is as follows: if the MAPE value is less than 10% it is a "highly accurate" forecast.If the MAPE value is between 10% and 20%, it is a "good" forecast.If the value of MAPE is between 20 and 50%, it is a "reasonable" forecast.If the value of MAPE is higher than 50%, it is an "inaccurate" forecast [18].MAPE states the percentage of prediction error results against actual demand during a certain period, which will provide information on the percentage of errors that are too high or too low.The smaller the MAPE percentage level, the more accurate the prediction [46].
A raw material subsystem is a subsystem that is influenced by the availability of raw materials in the production of organic fertilizers.The main raw material for organic fertilizer is cow dung.The availability of raw material for dairy cow dung is influenced by the population of dairy cows in Cibodas Village and Cisondari Village.The population of dairy cattle in the two villages in 2021 is 512 heads.Cow waste is used as a raw material to be processed into organic fertilizer.A good organic fertilizer production system can support sales and income [47].
The production subsystem is a subsystem consisting of a series of organic fertilizer production processes.This subsystem produces output in the form of 40 kg of organic fertilizer products.This subsystem is also affected by the costs incurred to produce organic fertilizers such as the price of cow dung, labor costs, electricity costs, and additional materials.The price of cow dung is 50 IDR per kg of fertilizer, labor costs are 200 IDR per kg of fertilizer, and additional costs and fixed costs are 200 IDR.In a meeting regarding the production cost capital needs, the Taruna Mukti Farmer Group obtained a capital loan from Bank BJB West Java.
forecast [18].MAPE states the percentage of prediction error results against actual demand during a certain period, which will provide information on the percentage of errors that are too high or too low.The smaller the MAPE percentage level, the more accurate the prediction [46].A raw material subsystem is a subsystem that is influenced by the availability of raw materials in the production of organic fertilizers.The main raw material for organic fertilizer is cow dung.The availability of raw material for dairy cow dung is influenced by the population of dairy cows in Cibodas Village and Cisondari Village.The population of dairy cattle in the two villages in 2021 is 512 heads.Cow waste is used as a raw material to be processed into organic fertilizer.A good organic fertilizer production system can support sales and income [47].
The production subsystem is a subsystem consisting of a series of organic fertilizer production processes.This subsystem produces output in the form of 40 kg of organic fertilizer products.This subsystem is also affected by the costs incurred to produce organic fertilizers such as the price of cow dung, labor costs, electricity costs, and additional materials.The price of cow dung is 50 IDR per kg of fertilizer, labor costs are 200 IDR per kg of fertilizer, and additional costs and fixed costs are 200 IDR.In a meeting regarding the production cost capital needs, the Taruna Mukti Farmer Group obtained a capital loan from Bank BJB West Java.
The production subsystem is important because the potential of livestock manure cannot be utilized optimally if the production subsystem is carried out incorrectly.The right production subsystem can produce good-quality organic fertilizer [48].The products The production subsystem is important because the potential of livestock manure cannot be utilized optimally if the production subsystem is carried out incorrectly.The right production subsystem can produce good-quality organic fertilizer [48].The products produced by the Taruna Mukti Farmer Group are solid organic fertilizers without producing waste.The used sacks of organic fertilizer packaging are also used as containers for refertilizer (extension of product use).Figure 4 shows the flow of the organic fertilizer production process at the Taruna Mukti Farmer Group.produced by the Taruna Mukti Farmer Group are solid organic fertilizers without producing waste.The used sacks of organic fertilizer packaging are also used as containers for re-fertilizer (extension of product use).Figure 4 shows the flow of the organic fertilizer production process at the Taruna Mukti Farmer Group.The series of organic fertilizer production begins by mixing cow dung, leftover forage, and ash with a ratio of 80%:15%:5%.After being mixed, a decomposer is added for the composting process.The composting process lasts for about 3 weeks and is characterized by compost material that does not smell and is not hot.Then, the compost material is stirred and harvested.Then, the finished compost is ground and then sifted.The packaged compost is then stored in the warehouse and is ready to be sent to The series of organic fertilizer production begins by mixing cow dung, leftover forage, and ash with a ratio of 80%:15%:5%.After being mixed, a decomposer is added for the composting process.The composting process lasts about 3 weeks and is characterized by compost material that does not smell and is not hot.Then, the compost material is stirred and harvested.Then, the finished compost is ground and then sifted.The packaged compost is then stored in the warehouse and is ready to be sent to consumers/partners.The process of making compost (composting) can be performed by aerobic or anaerobic methods.Compost material can come from plant residues and animal waste.The composting process is carried out by lowering the C/N of organic matter until it is equal to the C/N of the soil.The advantages of compost are environmental friendliness, its ability to increase farmers' income, and its ability to increase soil fertility by repairing soil physical damage due to excessive use of inorganic (chemical) fertilizers [49].The results of the organic fertilizer laboratory test for Taruna Mukti Farmer Group have a C/N value of 17 with a C-Organic of 22.49%.Research and Development of Agriculture (2011) states that a good C/N ratio is between 15 and 20.
The marketing and income subsystem of the Taruna Mukti Farmer Group is a subsystem that is influenced by the number of sales, marketing costs, and product delivery, and also the amount of income earned by the Taruna Mukti Farmer Group.Marketing is a form of coordination that is needed from a series (stages) of activities or in the movement of the flow of products and services from the hands of primary producers to the hands of final consumers [50].The Taruna Mukti Farmer Group markets its products to consumers directly or through third parties.Farmer groups have also partnered with NGOs related to greening the environment by supplying fertilizer to those in need such as the Gerakan Nusantara Hijau, LSM Kerabat, Peduli Rakyat Kecil, and Mercy-USA.The following is a picture of the marketing area for the Taruna Mukti Farmer Group's organic fertilizer marketing area.

Future Fertilizer Production Model Simulation
The dynamic system scenario is a picture of conditions that can occur in the future that can be used to make decisions or steps that need to be taken in real conditions.The scenario used is based on the currently available resources and the same number of sales as today.Based on the dynamic system simulation results, the projection of organic fertilizer production in 2023 is 1256.79tons; in 2024, it is 1233.88tons; in 2025, it is 1211.38; in 2026, it will be 1189.29 tons; and in 2027, it will be 1167.61tons.
Based on the research results, it is known that there are no problems in the subsystem of organic fertilizer raw materials because the availability of dairy cow manure in the Cibodas and Cisondari villages is still sufficient for organic fertilizer production and is supported by the availability of dairy cow manure in other villages in Pasirjambu District.In the production subsystem, there are no constraints on production costs and production capacity.Gapoktan's fertilizer factory capacity reaches 1000 tons per month.In the marketing subsystem, there is a problem where fertilizer marketing continues to decline [51].Gapoktan needs to improve its marketing strategy.One type of marketing strategy is the marketing mix strategy, which is a method to achieve marketing objectives by fulfilling consumer needs and desires through the exchange of goods.The marketing mix strategy is designed in an integrated manner to produce the desired response in the target market which consists of four Ps, namely, product, price, place, and promotion [52].

The Linkages between the CLD Model and DPSIR Analysis
The CLD model has a relationship with DPSIR analysis where each approach is based on a causal relationship.A causal loop diagram (CLD) is a diagram that describes the relationship between elements in a system, whereas DPSIR analysis also shows a causal relationship but is more specific by dividing the elements into several categories, namely, drivers, pressure, state, impact, and response [53].CLD describes the interaction between complex elements simplified by using assumptions, which are obtained based on the results of data processing and data analysis [54]. Figure 5

Drivers
Dairy cattle production activities which are supported by environmental conditions, natural resource potential, skills, and livelihoods are the driving factors for the emergence of pressure on the environment in Cibodas Village and Cisondari Village.The average temperature, which ranges from 18 °C to 28 °C, is a suitable environmental condition for dairy farming of the Friesian Holstein (PFH) breed.This type of dairy cow comes from the subtropics, namely, the Netherlands, which was later developed in Indonesia.The topography of the village in the form of hilly areas, rice fields, and forests can support the availability of dairy cattle feed.Agricultural land, plantations, and forestry are sources of forage/grass needed to meet the feed needs of dairy cows.Breeders can take grass from the rice fields, straw from the rest of the plantation, or grass in the forest for animal feed.Besides being supported by potential feed resources, dairy farming activities are also supported by human resources where the majority of the people in Cibodas Village and Cisondari Village work as farmers and ranchers with long experience.
The increasing price of milk every year also supports the dairy farming business to remain stable.An increase in milk prices received a positive supply response from farmers.This means that the level of production produced by farmers will be stable with an increase in prices because farmers receive more sources of capital to support the basic Based on Figure 5, it can be seen that dairy farming activities to produce milk are supported by environmental conditions, and the potential of natural resources, milk prices, and human resources are the driving factors for environmental change.Livestock activities cause pressure on the environment with livestock waste and resource exploitation.This causes the current condition in the Taruna Mukti Farmer Group area where there is livestock waste that has been processed into organic fertilizer and organic waste that has not been processed.Livestock waste that is processed into organic fertilizer has a positive impact, whereas the waste that is just thrown away has a negative impact.Currently, there is a decrease in fertilizer production in farmer groups, so the amount of untreated waste is increasing.Therefore, a response is needed so that the processing of livestock waste can run optimally.
3.6.Sustainability Strategy for Dairy Cattle Waste Management Using DPSIR Analysis 3.6.1.Drivers Dairy cattle production activities which are supported by environmental conditions, natural resource potential, skills, and livelihoods are the driving factors for the emergence of pressure on the environment in Cibodas Village and Cisondari Village.The average temperature, which ranges from 18 • to 28 • C, is a suitable environmental condition for dairy farming of the Friesian Holstein (PFH) breed.This type of dairy cow comes from the subtropics, namely, the Netherlands, which was later developed in Indonesia.The topography of the village in the form of hilly areas, rice fields, and forests can support the availability of dairy cattle feed.Agricultural land, plantations, and forestry are sources of forage/grass needed to meet the feed needs of dairy cows.Breeders can take grass from the rice fields, straw from the rest of the plantation, or grass in the forest for animal feed.Besides being supported by potential feed resources, dairy farming activities are also supported by human resources where the majority of the people in Cibodas Village and Cisondari Village work as farmers and ranchers with long experience.
The increasing price of milk every year also supports the dairy farming business to remain stable.An increase in milk prices received a positive supply response from farmers.This means that the level of production produced by farmers will be stable with an increase in prices because farmers receive more sources of capital to support the basic needs of a more optimal dairy cattle business.The increased selling price of milk also has a significant positive effect on the ability to finance animal feed [55].
The price of milk in the Pasirjambu KUD increases every year, in 2018 the price of milk was IDR 4630 per liter, in 2019, IDR 4730 per liter, in 2020, IDR 5100 per liter, in 2021, it will be IDR 5670 per liter, and in 2022, it will increase to IDR 5870 per liter.
The price is still quite promising for a dairy farming business.Apart from milk yields, farmers also have dairy cow calves which have a selling price of around 5-9 million IDR per head, which are about 4-9 months old (already weaned).With the condition and potential of available natural resources, farmers and ranchers become the livelihood of most residents in the Cibodas and Cisondari villages.
The farmers' interest in investing in dairy cattle cultivation is due to the daily nature of the results of the dairy cattle business which already has certainty on the milk payment mechanism; with a good management pattern, the investment returns quickly, because every year, the breeder will obtain results in the form of calves.Then, in the next two years, the first calves are ready to produce results [56].The level of milk price received by farmers is closely related to the process of farming; its feasibility level is being periodically pursued, so it is hoped that it will increase the interest of farmers to increase their farm productivity dynamically with adequate price incentives.The rational determination of milk prices at the farmer level will be responded to by increasing their productivity, and this condition will in turn increase the income of farmers [57].

Pressure
The Pasirjambu sub-district is one of the centers for dairy farming in Bandung Regency in addition to the Ciwidey, Pangalengan, Arjasari, Rancabali, Cilengkrang, and Kertasari sub-districts.The productivity of dairy cows can cause pressure on the environment.Dairy cows need water resources either to clean the barn, bathe the cows, or drink.Every day, the dairy cows are cleaned, especially before milking.Dairy cows also need a lot of drinking water to produce milk.In addition to water resources, dairy cows also need feed resources in the form of forage and concentrates.Dairy cows need feed of at least 10% of their body weight.To support milk production, adequate consumption of feed and drink is required.
The provision of forage in dairy cow rations is about 10% of body weight.Forage given to dairy cows can be in the form of elephant grass, king grass, Bengal grass, rice straw, lamtoro, alfalfa, and sugarcane leaf shoots [58].Forage is the main source of feed for dairy cattle, so increasing milk production for dairy cattle must be followed by an increase in the supply of sufficient forage both in quantity and quality [59].
Dairy cow milk production in Pasirjambu District in 2017 was 3.22 L, in 2018, it was 2.99 million liters, in 2019, it was 2.10 million liters, in 2020, it was 1.88 million liters, and in 2021, it was 1.88 million liters.In addition to producing milk, dairy cattle business activities also cause other problems, namely, livestock waste.Livestock waste can be in the form of solid waste (derived from leftover feed and cow dung), liquid waste, or gas waste.
Livestock waste pollute the environment in terms of soil, water, and air.The processing of livestock waste can overcome these problems, but it takes a strong commitment from the parties involved so that all livestock waste can be processed either into organic fertilizer, biogas, or other products.

State
The current condition is that the processing of dairy cattle waste in the Taruna Mukti Farmer Group, which includes Cibodas Village and Cisondari Village, has not been maximized, and there has been a decrease in organic fertilizer production, so more cow dung has not been processed.A lot of cow dung is left to accumulate in the barn or is dumped into waterways and rivers.Cow dung that is allowed to accumulate in the pen can cause odor pollution and invite disease-carrying animals such as flies.Meanwhile, cow dung dumped into rivers can cause river silting.The silting of the river can reduce the capacity of the river to water so that during the rainy season the river water will overflow and cause flooding.
Cow dung waste that is thrown into the river will have an impact on silting the river or disrupting the life of river water biota in addition to the comfort impact on local residents.Cow dung thrown into the river will cause water pollution, which would certainly interfere with public health.Cow dung dumped in this open space will have an impact on soil and air pollution because animal dung contains methane gas, which is a source of GHG (greenhouse gas) emissions and will affect global warming.Therefore, a solution is needed to process livestock waste, one of which is an organic fertilizer product [60].
In 2018, the production of organic fertilizer for the Mukti cadets farmer group was 3700 tons with sales of 3500 tons, in 2019, it was 2100 tons with sales of 1800 tons, in 2020, it was 3100 tons with sales of 3000 tons, then decreased in 2021 to 1280 tons with sales of 1200 tons, and in 2022, 500 tons with sales of 250 tons.Based on the results of interviews and interviews, it is known that there are several factors that make it difficult for the Taruna Mukti Farmer Group to develop livestock waste, including: (1) Regeneration of the ineffective farmer group management.The Taruna Mukti Farmer Group was initiated and chaired by the late Mr. Uus Permana who is the most influential person in the Farmer Group.However, since his death, a new chairman has not yet been elected.The slow regeneration of the management and the inactivity of the existing management make it difficult for the current activities of the Farmer Group to run.(2) Lack of assistance and supervision from the village government.Based on the results of the interview, it is known that the village government rarely provides assistance and supervision.The village government only accompanies when there is monitoring from the agriculture office or the environment service or other agencies in Bandung Regency, so there has been no initiative from the village government itself to commit to helping develop the Taruna Mukti Farmer Group.Even the Bandung Regency offices have not routinely been monitored, so the development of the Farmer Group is not monitored.(3) Marketing that is not yet effective.Most of the sales of organic fertilizers rely on work contracts with partners/third parties so that the amount of organic fertilizer production adjusts to the appropriate amount in the contract.When the contract expires, the organic fertilizer factory does not produce, and in the following year, it is not necessarily possible to obtain another work contract.In addition, there are still some organic fertilizers that are sold directly to farmers or direct consumers.Organic fertilizers are sold in bulk without a brand.Currently, the Farmer Group has created its own brand with the name "Kosa Plus".However, until now, the distribution permit has not been issued by the Ministry of Trade, so the product cannot be circulated in the market.

Impact
The impact caused by the presence of livestock waste is divided into two, namely, positive and negative impacts.The positive impact of livestock waste is that livestock waste becomes the main raw material for fertilizers that are beneficial for the agricultural sector, can increase the income of farmers, and create jobs for the surrounding community, thereby reducing unemployment.The Taruna Mukti Farmer Group sells fraudulent organic fertilizer at a price of 700 IDR per kg with production and delivery costs of 600 IDR.This means that the profit obtained by the Taruna Mukti Farmer Group is 100 IDR per kg of organic fertilizer.
The total profit of the Taruna Mukti Farmer Group in the last 5 years is IDR 861,500,000.This will certainly increase the income of farmer group members.In addition, the Farmer Group buys wet cow dung for 50 IDR per kg.From 2008 to 2022, the Taruna Mukti Farmer Group purchased around 79,328 tons of wet cow dung from farmers.This means that the income of the farmers from selling cow dung totals IDR 3,966,400,000.In addition, the Taruna Mukti Farmer Group also has social activities such as donations for orphans and poor people, free medical treatment, mass circumcision, the repair of worship facilities, and the provision of food barns of 150 kg of rice per rukun warga (RW).
Negative impacts arise when dairy cattle waste has not been processed or managed optimally.The impact that occurs due to the management of livestock waste that has not been optimal; namely, the amount of livestock waste that is disposed of directly is increasing, which causes environmental pollution.The Taruna Mukti Farmer Group, as the only group for processing livestock waste in the Cibodas and Cisondari villages, is currently in a production vacuum.This worsens the condition of livestock waste management.Livestock waste that is directly discharged into waterways leading to the Cisondari River will cause pollution.Cow dung can cause the death of river biota, which disrupts the ecosystem.Livestock waste can cause negative impacts such as methane gas pollution (which is discharged through feces, belch, and wind) and can also be a growing medium for pathogenic bacteria that are harmful to humans.Therefore, technology is needed to process livestock waste into new products that have added value and at the same time minimize the negative impact of waste [61].

Response
The response that should be carried out by the local government is to provide assistance and rearrange the activities of the Taruna Mukti Farmer Group.In addition, it should also support the marketing of organic fertilizers so that production can run continuously.Based on the interview result, it also requires the activeness of the administrators and members of the Farmer Group to commit to developing the activities of the Farmer Group.Cooperation and partnerships with third parties are also needed for marketing development.The market is the last key in business development for farming activities because if there is no market, the production produced by farmers will not provide benefits and contribute to increasing income and welfare for farming families.Therefore, the market will greatly determine the sustainability of the farming business [62].
The government response needed by the Taruna Mukti Farmer Group is in the form of empowering breeders/farmers.In Law No. 19 of 2013 article 1 paragraph 2, it is stated that farmer empowerment encompasses all efforts to improve the ability of farmers to carry out better farming activities through education and training, counseling and assistance, developing systems and means of marketing agricultural products, and consolidation and guarantees agricultural land area, easy access to knowledge, information technology, and capacity and institutional strengthening.Based on the results of the study, it is known that the empowerment needed by the Taruna Mukti Farmer Group is primarily in mentoring, marketing, and institutional strengthening.Mentoring is a strategy commonly used by governments and non-profit institutions in an effort to improve the quality of human resources so that they are able to identify themselves as part of the problems they are experiencing and seek alternative solutions to the problems they face [63].
In order to strengthen the institutions of Farmer Groups, besides requiring guidance from the government, it also requires the active participation of members of the Taruna Mukti Farmer Group, or what is known as community-based participation.Community-based participation an active process in which a community directly participates in planning, implementing, and evaluating development activities or programs that they have with the aim of growing their independence and increasing their income and development.The participation of breeders who are members of the Taruna Mukti Farmer Group is the participation of farmers with full awareness and responsibility to develop the business of processing dairy cattle waste into organic fertilizer products so that they are economically, socially, and environmentally beneficial [64].

Conclusions
Based on the results of the study, it is known that the dairy cattle waste management model in the Taruna Mukti Farmer Group is a form of implementing the CE concept with a circular flow of material and involving various stakeholders and an extensive marketing network.With the current conditions, the simulation results of processing livestock waste into organic fertilizer show a decline/unsustainability.To support the sustainability of livestock waste management, a response is needed in the form of strengthening the internal management of the Farmer Group organization, regular assistance and supervision from the local government and non-government organizations, and guidance regarding the marketing of organic fertilizers and ease of access to markets.

Figure 1 .
Figure 1.Stages of dynamic systems approach.

Figure 2 .
Figure 2. CLD model on CE-based dairy cattle waste management in the Taruna Mukti Farmer Group.

Figure 2 .
Figure 2. CLD model on CE-based dairy cattle waste management in the Taruna Mukti Farmer Group.

Figure 3 .
Figure 3. Stock-flow diagram on livestock waste management for Taruna Mukti Farmer Group.

Figure 3 .
Figure 3. Stock-flow diagram on livestock waste management for Taruna Mukti Farmer Group.

Figure 4 .
Figure 4. Process flow of solid organic fertilizer production.

Figure 4 .
Figure 4. Process flow of solid organic fertilizer production.

Figure 5 .
Figure 5.The relationship between CLD in dynamic systems and the DPSIR approach.

Figure 5 .
Figure 5.The relationship between CLD in dynamic systems and the DPSIR approach.