173 RESULTS AND DISCUSSION This section presents the results obtained from the two methods. Furthermore, this section presents the underlying reasons for the differences observed between the results. EMISSIONS ESTIMATED USING DAE The results for the cradle-to-gate system boundary from DAE show that the majority of emissions originate from material handling operations, which ranged between 66% and 94% (see Table 4). Diffuse dust emissions are, for the most part, associated with internal transport operations. Additionally, it can be observed that the CO2 and NOx emissions during the production process are not reported in Table 4. This is because the processing circuit used for the production process is powered by electricity supplied from the grid, and the DAE method does not account for emissions associated with electricity generation (secondary emissions). ENVIRONMENTAL IMPACT QUANTIFIED USING LCA From the LCIA phase of LCA, environmental impacts from producing 1 tonne of aggregates were quantified for a cradle-to-gate system boundary. Table 5 presents the results for several impact indicators from the LCIA phase of LCA. From Table 5, it can be observed that the majority of the cradle-to-gate impact originated from material handling operations across all of the indicators (except ODP and EP-freshwater indicators). The contribution from material handling ranged between 65% to 98% of the total impact. This contribution was mainly Figure 7 – Processing circuit of the quarrying site. Crushing plant Drilling and Balsting Loading Transport Feeding P2 P3 P4 P5 P6 P7 P8 P9 B1 C1 S1 HSC1 HSC2 HSC3 HSC4 B1 S3 S4 S6 S5 C2 C3 C4 WL T T B2 S2 P1 Material flow B Bin C Conveyor P Product S Screen T Truck WL Wheel Loader HSC Horizontal Shaft impact Crusher
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