examining the MSDS4 of xanthate. Xanthate may decompose to products like CS 2 and H2S; however, these are not officially GHG emissions and are unlikely to convert into CO2 or other GHG. Other potential scope 1 emissions could be from fossil fuel combustion (e.g., backup generators, or mobile equipment). However, no significant fuel consumers exist within the system boundary; accordingly, Scope 1 emissions are assumed to be zero. 4.2.2 Scope 2 emissions: Scope 2 emissions refer to indirect emissions from the generation of purchased electricity, steam, heating, and cooling consumed within the system boundary [5]. Electricity is used throughout the plant, across all units. To estimate GHG emissions from electricity use, power usage data for each plant unit are collected, along with the appropriate EF. According to the IPCC Guidelines [12], the EF must be location-specific, hence the Chilean grid EF from Ecoinvent of 0.5628 kg CO2e/kWh is selected (see Table 1 for comparison across all three case studies). 4.2.3 Scope 3 emissions: Scope 3 emissions refer to all other indirect emissions, such as those from the production of purchased goods [4]. In this study, these include the production of materials that wear in the grinding plant units (mill liners and grinding media) and the reagents consumed in the flotation and dewatering units. Wear materials: The manufacturing of wear materials generates GHG emissions and must be accounted for in the LCA. At this stage, data on these materials are required: the wear rate (i.e., how fast they deteriorate, in g/kWh of mill operation), as well as the EF for producing the wear material (in kg CO2e/kg of material). The wear rates of the mill liners and grinding media were collected as primary data. To obtain the EF (secondary data), the liner and ball mill materials must be known. These are made of chromium-molybdenum (CrMo) steel, but since Ecoinvent does not provide an EF for CrMo, the EF for low-alloyed steel (2.123 kg CO₂e/kg) is used as proxy5. Ecoinvent’s system boundary covers steel production only up to the point of cast steel, so additional processing is required to form the final liners and balls into the specific shape/size/specifications. Therefore, the EF for ‘forged steel’ (1.252 kg CO₂e/kg) is added to account for the forging process. Assuming 1 tonne of steel yields 1 tonne of low-alloyed steel, the total estimated EF for CrMo steel is 3.375 kg CO₂e/kg [(2.123 + 1.252) kg CO₂e/kg]. 5 As suggested by Metso experts 4 https://reviewboard.ca/upload/project_document/EA0809-004_MSDS_for_Potassium_Amyl_Xanthate.PDF 212
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