ELECTRONIC SUPLEMENTARY MATERIAL
Life Cycle Inventory Analysis of Granite Production from cradle-to-gate
Joan-Manuel F. Mendoza1,*, Feced Maria1, Gumersindo Feijoo2, Alejandro Josa3,4, Xavier Gabarrell1,5, and Joan Rieradevall1,5
1 Sostenipra (ICTA-IRTA-Inèdit). Institute of Environmental Science and Technology (ICTA), School of Engineering (ETSE), Universitat Autònoma de Barcelona (UAB). Campus de la UAB, Bellaterra (Cerdanyola del Vallès), 08193 Barcelona, Catalonia, Spain.
2 Department of Chemical Engineering, School of Engineering, University of Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain.
3 Institute of Sustainability (IS.UPC), Technical University of Catalonia-Barcelona Tech (UPC), Campus Nord, Building VX, Plaça Eusebi Güell, 6,
08034 Barcelona, Catalonia, Spain.
4 Department of Geotechnical Engineering and Geosciences, School of Civil Engineering (ETSECCPB), Technical University of Catalonia-Barcelona Tech (UPC), Campus Nord, C/ Jordi Girona 1-3, Building D2, 08034 Barcelona, Catalonia, Spain.
5 Department of Chemical Engineering, School of Engineering (ETSE), Universitat Autònoma de Barcelona (UAB), Campus de la UAB, Bellaterra (Cerdanyola del Vallès), 08193 Barcelona, Catalonia, Spain.
*Corresponding author: - Tel. (+34) 935813760 – Fax. (+34) 935868008
This file contains further inventory data related to the case study. It is structured as follows:
ESM 1. Production volumes (2010) of the quarries and processing facilities analyzed
ESM 2. Detailed description of the production chain and technological coverage
ESM 3. Quantification of the net production of granite products and wastes per each unit process of the granite processing stage
ESM 4. LCI data per quarried granite block
ESM 5. LCI data per processed granite block
ESM 6. LCI data of sanding, flaming and bush-hammering unit processes on a granite block basis
ESM 7. Disaggregated LCI data of the production chain from cradle to gate of one square meter of finished granite tiles with dimensions of 60 x 40 x 2 cm
ESM 1. Production volumes (2010) of the quarries and processing facilities analyzed
Granite quarries / Quarry A / Quarry B / Quarry C / TOTALNACE / 08.11 / 08.11 / 08.11 / 08.11
Operating area - Ha / 4.14 / 15.41 / 16.76 / 36.31
Quarried granite - m3 / 10,628 / 11,424 / 26,000 / 48,052
Equivalence in commercial blocks – units (8.67 m3/unit) / 1,226 / 1,318 / 2,999 / 5,542
Processing facilities / Facility A / Facility B / Facility C / TOTAL
NACE / 23.70 / 23.70 / 23.70 / 23.70
Processed granite – m2 (total production) / 318,813 / 281,096 / 281,497 / 881,406
Sawn granite - m2 (slabs) / 318,813 / 221,659 / 281,497 / 821,969
Finished granite - m2 (slabs) / 290,968 / 281,096 / 231,007 / 803,071
Polished granite - m2 (slabs) / 258,126 / 190,985 / 143,300 / 592,411
Sandblasted granite - m2 (slabs) / 19,492 / 63,022 / 0 / 82,514
Flamed granite - m2 (slabs) / 12,250 / 27,089 / 87,707 / 127,046
Bush-hammered granite - m2 (slabs) / 1,100 / 0 / 0 / 1,100
Cut granite - m2 (tiles) / 54,043 / 13,200 / 115,274 / 182,517
The production volume of the processing facilities is divided into the net production volume from each of the unit processes of granite processing: granite sawing, granite finishing and granite cutting. The total production volume of processing facilities A and C corresponds to the total amount of granite slabs that leave the sawing process. For cases A and C a large part of the granite slabs receive a finishing application but only a share of them passes directly to the cutting tiles. Facility B has produced a higher amount of finished granite slabs than those leaving the sawing process. In this case, the facility has received sawn granite slabs from intermediate sawing facilities. The entire amount of granite slabs that left the sawing process received a finishing application and subsequently a few of them are cut into tiles.
ESM 2. Detailed description of the production chain and technological coverage
Granite quarrying A granite bench is removed from a deposit by a combination of drilling, blasting and cutting operations. The first operation consists of the drilling of two boreholes in the ground plane and one borehole in the vertical plane for the subsequent passage of the diamond wire to begin cutting the stone. The boreholes are created by using probe drives that are driven by air compressors powered by diesel. The preparation of the boreholes requires between 24 and 36 h. Subsequently, electric-powered diamond wire machines begin cutting the vertical planes of the bench. The cutting speeds of these machines range from 2 to 7 m2 h-1. A series of boreholes separated by 80 cm each are created along the perimeter of the ground plane. The boreholes are filled with gun powder and detonating cord (6–12 g m-1) to create a pushing action on the stone. Detonators and safety fuses are used to initiate blasting. The process of lifting the granite bench requires from 48 to 72 h.
The subdivision of the granite bench into primary granite blocks is performed by the application of the following two techniques:
· Drilling and blasting. Pneumatic hammers driven by electrically powered air compressors or diesel-powered backhoes equipped with drills are employed. The drilling process can utilise the full height of the bench (10–14 m), or an average length of 6 m, with a spacing of approximately 30 cm. The separation of the primary granite block from the bench requires a small amount of gun powder and/or a detonating cord.
· Cutting. A diamond wire cutting machine is used to obtain thinner granite blocks (~ 6 m). These blocks are easier to cut into commercial blocks, which eliminates an intermediate cutting step. The use of diamond wire cutting machines achieves higher efficiencies.
The primary granite block is dumped on the ground of the quarry to subdivide them into commercial granite blocks (quarry marketable products) with suitable dimensions for transporting and handling in processing industries. A sand or clay bed is created to cushion the impact and prevent stone breakage. A diesel-powered loader is used to prepare the sand or clay bed and a backhoe equipped with a mechanical arm is used to dump the primary block on the ground. Boreholes with 15-cm spacings and approximate lengths of 1.4 m are drilled using hydraulic hammers to define cleavage planes. Pneumatic hammers driven by a compressed air circuit are used to introduce steel shims and wedges in the boreholes to break the stone. The granite blocks are squared using pneumatic hammers and/or diamond wire. The dimensions of the granite blocks are conditioned by the characteristics of the machinery that is employed to saw the blocks in the processing industries. The average dimensions of the commercial granite blocks that are quarried and processed are 1.7 m high, 3 m long and 1.7 m wide (8.67 m3). A continuous stream of cooling water during the drilling and cutting operations is required to dissipate the heat generated by the process, as sufficiently elevated temperatures can cause significant machine and material damage. The final phase in granite quarrying consists of washing the commercial blocks and inspecting and classifying them prior to their storage in or transportation to processing facilities. Granite of insufficient quality or handling size is utilised in producing masonry products, sent to a crushing facility for the production of aggregate for construction applications, or stored on-site for future site reclamation. Commercial blocks are transferred to storage using diesel-powered loaders. Due to legal concerns, a truck can only transport a single commercial block per voyage.
Granite processing The operations related to granite processing can be divided into three major unit processes: sawing (primary cutting), finishing (surface treatment), and (secondary) cutting (and/or shaping). Prior to the sawing process, the granite blocks may need to be squared to remove lumps and their dimensions may require adjustments to optimise the yield of production. During the sawing process, the granite block is cut into slabs with dimensions defined by the dimensions of the granite block. Their thicknesses, however, are defined by customer demand, which determines the number of granite slabs produced per sawn block. The processing facilities use gang saw machines to saw the granite blocks. Gang saws are the most widely used technology for the mass production of granite slabs with thicknesses of 2–3 cm. In the gang saw machines, a granite block is eroded by the action of a steel blade mounted in a heavy frame, which is moved back and forth at high speeds by a transmission mechanism. The steel blades are typically 5 mm thick, 100 mm wide and 3,000–3,500 mm long. The length of the blades is dependent on the dimensions of the gang saw, which are typically 2,000–2,100 mm high, 3,500–5,500 mm wide and 3,000–3,500 mm long. Gang saws have an installed power that ranges from 95 kW to 165 kW. Sawing a granite block into slabs requires 48 h to 72 h. A water flow of 80 litres h-1 to 200 litres h-1 is required. In the process of granite sawing, the function of the water input is to refrigerate the steel blades used to erode the stone and remove the fines generated during the process. Water also contains a load of steel grit, which causes stone cutting as a result of the thrust force generated by the steel blades. The water also contains hydrated lime to raise the viscosity of the fluid and maintain the grit in suspension. The hydrated lime also minimises oxidation. To guarantee the efficiency of the process, the excess of granite fines and the worn grit in the water need to be removed periodically. The fluid is sent to a cyclone in which heavier particles are deposited on the bottom of the tank. This fraction is mixed with additions of the new abrasive mixture and returned to the gang saw. The finer mixture passes to a decanter where coagulants and flocculants are added to accelerate the process of decantation. Carbon dioxide is also added to reduce the alkalinity of the wastewater. The carbon dioxide reacts with the calcium hydroxide to produce calcite. Two fractions are generated upon separation: clarified water and granite sludge that contains the finely ground stone, worn grit, steel blade particles and calcite. Clarified water is sent back to the production line, whereas the granite sludge is sent to filter press devices where granite sludge is partially dried. As a result, granite sludge cakes catalogued as inert non-hazardous wastes are generated, collected and transported to an authorised landfill. The moisture content of granite sludge cakes are typically in the range of 35%–40% in weight.
After the sawing process, granite slabs can either pass directly to the finishing line to obtain a specific texture on the surface of the stone or bypass the finishing process and go directly to the cutting line once the granite product is determined to have a “natural” appearance and the texture generated by the sawing process fulfils the function required in construction. An array of finishing applications exists. The following finishing processes conducted by the processing facilities are considered in this study:
· Polishing. The treatment of the surface of the stone with progressively finer abrasive grains. A smooth and shiny finish surface is generated with almost zero porosity. Polishing is the most common finishing process applied to granite products. Polished granite slabs are used for indoor flooring and indoor and outdoor cladding. Polishing machines have an installed power of approximately 375 kW. Approximately 80 m2 h-1 can be polished. A continuous stream of 1,500 litres h-1 of cooling water is required.
· Sandblasting. A sandblasted finish is achieved by projecting silica sand or corundum on the surface of the stone through a nozzle at high speeds and variable air pressures. Depending on the pressure applied and the abrasive flow, the process provides a finer or thicker finished surface. Sandblasted granite tiles are typically used in indoor and outdoor cladding. Sandblasting machines have an installed power of approximately 130 kW. Approximately 200 m2 h-1 can be sandblasted. Cooling water is not required.
· Flaming. This process involves the application of a flame at approximately 2,800 ºC through a torch on the surface of the stone, which causes the detachment of small chips or splinters. The process is performed automatically in special chambers, whose main component is a mobile oxy-propane torch. It provides a rough, vitreous, undulating and irregular surface that is resistant to atmospheric chemical alteration. Flamed granite tiles are typically utilised in outdoor paving due to their anti-slipping properties. Flaming machines have an installed power of 4.5 kW and a process speed of 30 m2 h-1. A continuous stream of 100 to 450 litres h-1 of cooling water is required.
· Bush-hammering. A previously flattened surface is repeatedly hit with a hammer that contains one or more bushes with small pyramidal teeth. Although it can be performed manually, jackhammers are often used, which are moved either manually or automatically over the surface of the stone. As a result, a rough flat and slightly irregular surface with small craters is obtained. Bush-hammered granite tiles are mainly applied in outdoor paving projects due to their anti-slipping properties. The installed power is approximately 4.5 kW and approximately 20 m2 h-1 can be bush-hammered. The process does not require water.
The last step in granite processing consists of cutting the granite slabs into granite tiles of desired dimensions, which is accomplished using electric-powered diamond disc saws. Diamond disc saws have an installed power of approximately 190 kW. The diameter of diamond discs can vary but their average thickness is 2.5 mm. A continuous stream of cooling water is also required in production. Granite tiles are packed using wooden pallets, boards and crates. Steel slings fasteners are also applied.