Comparative Study of The Life Cycle Assessment Model for Agricultural Solid Waste Management: Case Studies in East Ungaran and West Ungaran Districts, Semarang

The increase in population affects the production of available food; this also increases agricultural activities and the waste produced. Improper agricultural waste management harms the environment, so a good agricultural waste management strategy is needed. The areas that are the object of study are East Ungaran and West Ungaran Districts, Semarang Regency. This area has great potential in the agricultural sector. This plan aims to analyze the existing conditions, volume, and mass balance of agricultural waste and their environmental impact using the life cycle assessment (LCA) and material flow analysis (MFA) methods to determine the appropriate strategy for managing agricultural solid waste. It is planned to manage agricultural solid waste using two alternative solutions, which are then compared using the LCA method using the SimaPro application and the Analytical Hierarchy Process (AHP) method involving two experts in the agricultural sector. Based on the analysis, processing agricultural solid waste as bokashi fertilizer and silage livestock feed is the most suitable method and is of interest to farmers.


Introduction
Population growth is estimated to reach 9,1 billion in 2050.This will lead to an increase in food production by 70% [1], increase agricultural activities, and have an impact on the waste produced [2].The negative consequences of agricultural waste do not have a spontaneous impact on the environment or living things but can gradually become one of the main contributors to climate change to global warming if not appropriately handled; in one of the Asian countries, Pakistan, most agricultural waste is burned or destroyed [3].Therefore, waste management is needed so that the agricultural waste produced can be safely returned to the environment, and to ensure sustainable agriculture, resilient rural regions, and productive farming [3][4][5].Generally, waste is divided into easily decomposed and nondegradable waste [6][7][8].In general, agricultural product processing waste has a high carbohydrate content but a low protein content and a high starch content with little fiber.Agricultural and plantation waste can be bulky, fibrous, low digestibility, and low protein [9,10].The design of an agricultural waste management strategy must have data on the source, quantity, and type of agricultural waste produced [11][12][13].Various methods of analysis of environmental management systems are currently available for making decisions.Life cycle assessment is a method for identifying and calculating the 1248 (2023) 012013 IOP Publishing doi:10.1088/1755-1315/1248/1/012013 2 amount of energy use, natural resources, and disposal as well as evaluating and making improvements to be implemented [14][15][16][17][18][19].In this study, the environmental impact of agricultural solid waste processing technology is determined utilizing a life cycle assessment (LCA) and the appropriate agricultural solid waste processing strategy, which has the best environmental impact in Semarang Regency.Morever, material flow analysis (MFA) is used for waste management to determine whether the given objectives have been achieved.The highest-potential processes and flows are also identified through an MFA balance [20][21][22].The data from the processing and analysis results will produce outputs for the planning stage of an effective and efficient agricultural solid waste management strategy in the Semarang Regency area as a form of developing an existing agricultural solid waste management system.Agricultural waste management

Data collection technique
The necessary data were obtained through direct observation, institutional surveys, questionnaires, and interviews.The data sources used were the Semarang Regency Environmental Service, the Semarang Regency Central Bureau of Statistics, the Semarang Regency Agriculture and Agriculture Office, and the Semarang Regency Regional Development Planning Agency.

Data processing and analysis techniques
This method includes the preparation stage, the data analysis stage, and the planning stage.At the preparation stage, a field survey was conducted to determine the existing conditions, such as handling agricultural waste.The survey was carried out using a questionnaire survey and direct surveys.The survey results obtained were analyzed for later use in planning.Next is the data analysis stage, where the primary data obtained will be processed through an assessment of existing conditions, an analysis of livestock and plant population projections, an analysis of the amount of livestock manure generation, and an analysis of data on the amount of crop residue produced.The last stage is the planning stage, where the data from the previous processing will be used to determine alternative planning strategies for agricultural solid waste management and environmental impact analysis.

Material flow analysis (MFA)
MFA analysis was performed using STAN (substance flow analysis) software.The flow of agricultural solid waste material in East Ungaran and West Ungaran sub-districts is in tons every four months based on the farmers' harvest frequency

Life Cycle Assessment
Environmental impact analysis is carried out using the LCA method.In this plan, the technology being compared is existing management technology with composting technology using the Bokashi method and an anaerobic digester through the Simapro application.Data analysis was carried out using the CML-IA baseline/World 2000 method.The limits used were cradle-to-gate, so the calculation was limited to the environmental impact of the processing of agricultural solid waste that was carried out.

Goal and scope
The purpose of this plan is to determine the environmental impact of the existing management and the two processing alternatives that can be carried out by farmers in West Ungaran and East Ungaran Districts.The study was conducted with Simapro software using the CML-IA baseline/World 2000 method.An environmental impact analysis study with LCA was carried out for this plan.Figures 1, 2,  3, and 4 show the limits of the agricultural solid waste treatment planning system.

Life cycle inventory
An inventory of the life cycle model of the LCA is made based on primary and secondary data that has been obtained from observations and interviews.The data is grouped into three main groups, namely input, output, and emission.

Life cycle impact assessment
Planning using the Life Cycle Assessment method is calculated using the CML-IA baseline/World 2000 method with the Global Warming parameter (GWP100a) on the SimaPro application.Table 1 shows that biogas processing using an anaerobic digester has the smallest global warming impact compared to composting and existing conditions.

Analytical hierarchy process (AHP)
The selection of alternative strategies for managing agricultural solid waste is carried out to determine the best and most suitable strategy for managing agricultural solid waste.The selection of alternative strategies for managing agricultural solid waste is based on several factors, namely environmental impact, land requirements, financing, operations, and farmers' preferences.Then the objectives and factors are processed to determine the best alternative strategy using Expert Choice software with the AHP method to determine strategies for managing agricultural solid waste in East Ungaran and West Ungaran Districts.In the process, several experts are interviewed regarding the specified criteria.

Result and discussion
A comparative LCA model of the existing treatment (open combustion), bokashi technology, and anaerobic digester technology has been developed.In processing agricultural solid waste by open burning, crop residues in the form of rice straw, rice husks, corn stover, and corn cobs act as the main input.The environmental impact tested is calculated based on one ton of crop residue.Farmers use as much as 30% of the crop residue as additional animal feed, and the remaining 70% is burned.To process agricultural solid waste by open dumping, livestock manure from cows and goats is the main input.The environmental impact is tested based on one ton of livestock manure.
In the processing of agricultural solid waste using the composting scenario (bokashi fertilizer) and animal feed (silage), the remaining crop residues in the form of chopped rice straw and rice husks, as well as cow and goat manure, are all composted.Stoves and corn cobs are chopped and then reprocessed into animal feed using the fermentation method to become silage animal feed.Assuming the amount of waste is 2 tons, with an allocation of 1.5 tons for compost and 0.5 tons for animal feed.
In the processing of agricultural solid waste using the anaerobic digester scenario, all agricultural solid waste (chopped crop residue and livestock manure) is put into the reactor.Assuming the amount of waste is 2 tons, consisting of 1 ton of crop residue and 1 ton of livestock manure, to understand emission sources and their pathways, a network diagram of processing alternatives can be seen in figures 5; 6; and 7.The selection of agricultural solid waste management strategies is based on several considerations: environmental impact, land requirements, financing, operations, and farmers' preferences.The Analytical Hierarchy Process (AHP) method was used to choose alternative strategies for managing agricultural solid waste, which was processed using Expert Choice software.
The goal is to choose the best strategy for managing agricultural solid waste in West Ungaran and East Ungaran Districts.Criteria that need to be considered in alternative strategies are farmer preferences, operations, financing, land requirements, and environmental impacts; the alternatives for the solution to this goal are anaerobic digesters, composting (bokashi), and animal feed.The results of the AHP method utilizing the five criteria, as said earlier, showed that bokashi and animal feed are better alternative strategies for agricultural solid waste management in West Ungaran and East Ungaran Districts.Bokashi and animal feed scored 62%, while the anaerobic digester alternative scored 38%.Thus, alternative strategies for managing agricultural solid waste in East Ungaran and West Ungaran Districts that will be planned are composting using the Bokashi technique and animal feed processing.

Conclusion
The existing condition of agricultural solid waste management in Semarang Regency, especially in East Ungaran and West Ungaran Districts, includes open burning for plant residues and landfilling for livestock manure.After analyzing using LCA and MFA, it is known that the anaerobic digestion method has the smallest environmental impact of the two proposed alternatives.However, due to the superiority of the composting (bokashi) and animal feed (silage) methods in terms of financing, operations, and farmer preferences, as evidenced by the Analytical Hierarchy Process (AHP) method, the management strategy chosen in this plan is composting (bokashi) and animal feed (silage).

Figure 2 .
Figure 2. Limitation of the existing treatment system: stockpiling.

Figure 3 .
Figure 3. Limitations of the composting planning system (bokashi fertilizer) and animal feed.

Figure 4 .
Figure 4. Limitations of the biogas planning system.

Figure 8 .
Figure 8. Outline results of selection of alternatives.