1749 Note: The list of air emissions estimated from the LCI phase can be expanded beyond what is presented in Table 5. However, these emissions were chosen to compare with the results of the DAE method. Figure 110 – Scope of the DAE and LCA. In addition to differences in scope, there are further differences in the EFs used to estimate CO2, NOx, and TSP emissions from resource consumption. To illustrate further, the EFs used to estimate emissions from diesel consumption are chosen, since diesel consumption is the major contributor to emissions and the most impact indicators in LCA. Additionally, diesel consumption is considered in both DAE and LCA. From Table 6, it can be observed that there are minor differences among the EFs used in the two methods. Although the differences in EFs between the two methods are small, the differences in the total emissions estimated for the cradle-to-gate system boundary are larger. This is related to the scope of the methods. Production of a resource Transport Impact indicator • GWP • ODP • AP • EP • POCP • ADP • PM On-site consumption CO2 NOx PM Material and Energy inputs Emission Material and Energy inputs CO2 – Carbon dioxide NOx – Nitrogen oxides TSP – Total Suspended Particle PM – Particulate Matter (<10µm and < 2.5µm) This box indicates the scope of LCA This box indicates the scope of the DAE estimation Method in the context of this study This box accounts for the supply chain of a resource Resource TSP Resource Emission Factors Characterization Factors (Environmental Footprint 3.0) etc. Waste Emissions Phase Change (e.g., Diesel combustion) No phase change (e.g., Rubber waste, lubricant waste, etc.) Emissions Transport and Waste Treatment Figure 109 – Steps involved in translation of LCI results to impact indicator (Baumann & Tillman, 2004). Table 40 – Emissions to air estimated from DAE and LCI for the cradle-to-gate system boundary. Emissions Unit DAE LCI phase Difference CO2 kg CO2/tonne of aggregates 8.79E-01 1.40E+00 5.16E-01 NOx kg NOx/tonne of product 9.90E-03 8.69E-03 -1.21E-03 TSP kg TSP/tonne of product 1.32E-01 9.80E-06 -1.32E-01 PM10 kg PM10/tonne of product 4.44E-02 1.08E-05 -4.44E-02 PM2.5 kg PM2.5/tonne of product 7.36E-03 4.65E-04 -6.90E-03 NOx SO2 HCl etc. Characterisation results (Impact indicator) Life Cycle Inventory results CO2 CH4 NOx SO2 CFCs P NH3 HCl etc. Classification of inventory results CO2 CH4 CFCs etc. NOx NH3 P etc. Global Warming Eutrophication Acidification
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