## 2 Material and Methods
### Environmental and Economic Cost Considerations
#### Environmental and Cost Goal and Scope  
The Goal and Scope of these LCA and LCC studies are to compare the environmental burdens and economic costs generated by the \"business-as-usual\" scenario (landfill disposal) (Scenario 1) with the valorisation of GS as a substitute for (i) feldspar in the production of ceramic paste (Scenario 2) and (ii) fine-medium inert material for structural concrete production (Scenario 3). Figure 1a-c shows the flowsheet of the scenarios studied and the corresponding systems' boundaries [28]. In this study, a \"cradle-to-grave\" approach is adopted for Scenario 1 (Figure 1a). In Scenarios 2 and 3 (Figure 1b,c), the final sludge disposal was substituted by GS valorisation as a by-product, applying the methodology of system expansion proposed by [PERSON] et al. [29]. This methodology consists of the identification of the by-product obtained that can replace potentially less sustainable products already available in the market. This approach is known as the \"avoided-burden method\". The model is elaborated considering the local reality of the sawing plant taken as a case study, in which the GS can be valorised in industrial units operating in the vicinity of the sawing plant. To assess how much the transport of the GS may affect the environmental performance of the studied system and the associated additional costs, a sensitivity analysis was performed considering that hypothetical industrial units able to re-process GS were located at 20 km (same distances to the landfill) and 50 km away from the sawing plant. Regarding the economic cost, the same approach of the system expansion was followed considering the saved money due to the avoided GS landfilling as well as the avoided revenue coming from feldspar and inert filler production for the producer of these raw materials. No additional economic revenues were prudently considered for GS \"selling\" as a by-product in Scenarios 2 and 3 since, to the authors' knowledge, a consolidated market for GS as a secondary raw material doesn't exist. All the input and output data used in the three scenarios were referred to the same functional unit--1 m\({}^{2}\) of granite slab produced. The reference scenario (Scenario 1) is based on the operational data of the R.O.P. Portuguese plant was taken as reference, which currently operates 312 days per year, 16 h per day, with an average daily granite slab production of 50 m\({}^{2}\) and one specialised worker for equipment operation [30]. The openLCA software v.1.10 [31] and the Ecoinvent database v.3.5 [22] have been used to model the three scenarios (Figure 1). The ReCiPe2016 Midpoint (H) v1.13 method was adopted [32]. All the impact categories were calculated at the \"Midpoint\" level, referred to as the corresponding equivalent of reference substances, and the \"Hierarchist\" perspective was adopted, which is based on the most common policy principles concerning the time frame and human expectations [21]. LCC intends to assess the costs of a product over its entire life cycle [33], calculating the final \"Added Value\". The final Added Value represents the sum of the value added of each activity, i.e., the difference between the cost of the output and the cost of the intermediate inputs [34; 35], representing the value that the process is creating regardless of whether the actor is paying for them [34]. Finally, to understand the cost advantages associated with the perspective of the granite slab manufacturer, a cost-benefit analysis was performed, calculating the net value obtained by subtracting the total costs from revenues and calculating the contributions to the total cost of the different sub-processes of the sawing activity. Figure 1: Model diagrams of the granite block sawing process considering (**a**) GS landfill disposal (Scenario 1), (**b**) GS valorisation as a substitute for feldspar in the ceramic industry (Scenario 2), and (**c**) GS valorisation as a substitute for inert filler in concrete production (Scenario 3). The blue dashed line represents the system boundaries.