170 INTERPRETATION This is the final phase in LCA, where the results from LCI, LCIA, or both are summarized and discussed (ISO, 2006a). During this phase, the LCIA and LCI results are analysed to identify the primary contributors to environmental impact, such as specific processes, resources, or waste. The outcome of this phase provides aggregate producers with the necessary insights to support decision-making. The detailed description of applying LCA to quantify the impacts from aggregates production is described in a handbook developed during the ROTATE project (Gowda et al., 2025). COMMON BASIS FOR COMPARISON To ensure comparability between the DAE and LCA, it is essential to establish a common basis for their application. This includes defining a common functional unit for the assessment and system boundary. SYSTEM BOUNDARY A system boundary defines which operations are included or excluded in the study. In this study, the cradle-to-gate system boundary has been assessed. Aggregate production includes operations such as rock extraction through excavation for sand and gravel or drilling and blasting to extract crushed rock; material handling (loading, transport, and feeding); and production processes (crushing and classification at the crushing plant). The operations included in the cradle-to-gate system boundary are highlighted within the dashed green box in Figure 6. FUNCTIONAL UNIT The functional unit serves as the reference unit for quantifying the inputs and outputs of the system under study (Baumann & Tillman, 2004). In LCA, the most commonly used functional unit is 1 tonne (1000 kg) of the product produced at the site. For the DAE method, emissions are estimated for the annually produced quantity of the product during operations, which could be an important source of air emissions. To compare the results of both the LCA and DAE methods common unit of 1 tonne of aggregates produced at the site was used. COMPARISON OF RESULTS The DAE method can calculate emissions of CO2, NOx, CH4, CO, TSP, PM, and several heavy metals to the air. Within the scope of this work, only emissions related to TSP, PM10, PM2.5, NOx, and CO2 have been estimated through the DAE method. Table 2 presents an overview of the emissions estimated from different sources in a quarry using the DAE method. To present the results coherently for subsequent comparison with LCA, it is assumed that emissions to air from drilling, blasting, and explosive use are included in the extraction operations. Diffuse dust and emissions of TSP, PM, NOx, and CO2 from fuel combustion generated from internal quarry transportation, material handling, and wind erosion from stockpiles are considered part of material handling operations. Emissions from material processing are included in the production process.
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