2.2.2. System boundary

The system boundary consists of a collection of unit processes that perform distinct functions. The general description of the system boundary is shown in Fig. 1, and the systematic approaches of LCA have been summarized in Fig. S2 of the supplementary material. The description of the system boundary for the study regions in Himachal Pradesh is demonstrated in Fig. 2. The input data utilized in the system boundary include municipal solid waste composition, energy, and mass, whereas the outputs considered are air emissions, water emissions, and emissions to soil from all the processes. The second step in conducting the LCA assessment includes the preparation of the inventory analysis, which primarily involves data collection related to the inputs and outputs of the study system. LCI involves collating specific information on inputs and outputs associated with the process, helping determine the environmental impacts [31,48]. The LCI data for the present assessment was derived from ‘in-situ’ analysis with appropriate data collected from relevant municipalities (waste generation, waste processing, transportation, and population) and utilization of the database Ecoinvent 2.2.

The general description of system boundary.

System boundary for study regions in Himachal Pradesh.

The emissions utilized for the study were determined after a thorough review of scientific literature, the database of SimaPro version 8.3.2, and the Eco-Inventory characterization method. Furthermore, the database of the software was adjusted to simulate the conditions prevalent in Himachal Pradesh. The description of scenarios and the summary details of the inventories have been presented in Table 1, Table 2, respectively. Other current data utilized in the present assessment were the population details of the study locations, waste characteristics, waste collection information, and data from open landfills. The physico-chemical characterization of waste for the study locations, as reported by the authors in another scientific literature [49], was used to determine the environmental profile of different considered scenarios for each of the study locations. Similarly, the processes involved in the transportation of MSW were also included in the system boundary, the details of which were reported and utilized by the authors in another scientific publication [2]. In summary, the data needed for the life cycle inventory were gathered from earlier reported scientific literature, the database of the software, and other relevant information collected from municipal authorities. In this respect, the outcomes can assist decision-makers in formulating efficient municipal solid waste management strategies.

Depiction of scenarios used in present study.

Life-cycle inventories for Himachal Pradesh [19,20,29].

Life-Cycle Impact Assessment (LCIA) is the third stage of the process that associates all the inputs and outputs with environmental impact categories [5,34]. The present study uses four impact categories, namely Global Warming, Acidification, Eutrophication, and Human Toxicity, using the Eco-indicator 99 (H) method. The last stage of the LCA assessment process is the interpretation of results, which reviews all the different stages during the LCA analysis. This stage summarizes all the data analyzed and checks the outcomes against the defined goals and scopes of the study. The review of LCA software is presented in the next paragraph.

The present study utilized the SimaPro software package for conducting the LCA analysis of the waste generated in the study areas. SimaPro software version 8.3.2 was used in the study and is commercial software licensed by PRe consultants, assessing the sustainable performance of a product or system. The software is also fully compliant with ISO 14040/14,044 and has complete functional abilities for computing LCI and LCIA analyses. The software has the capability to incorporate the entire MSW generation stream into its operating system and is highly specific in its input requirements. In principle, it uses data from three component sources, namely project data, library data, and general information. Thereafter, it builds the entire life cycle using the associated input data. It models the life cycle using the incorporated assemblies and input information provided. Its library functions within the software incorporate voluminous amounts of pre-defined information, including substances, materials, treatment systems, and associated impact assessment procedures used for formulating the model for a required study. The different input details are discussed separately in earlier reported literature by the authors [5]. Relevant input information regarding waste characteristics and other associated parameters from the four study locations in Himachal Pradesh were recorded in the SimaPro software. It utilized this input data to calculate possible emissions from various scenarios using the Eco-indicator 99 method and Ecoinvent database.