Virgin PP Fibre
The virgin PP is produced commercially from olefin monomers (propylene). Two techniques (liquid propylene pool process and gas phase polymerisation) are normally used for the production of PP in Australia (LyondellBasell 2012). Three main virgin PP granulate manufacturers (Kemcor Resins, Montell Clyde and Montell Geelong) form the basis of the Australasian Unit Process LCI data available in the SimaPro 8.0 database (Grant and Grant 2011d). As shown in Fig. 6.3, Kemcor Resins extracts propylene from gasoil, while Montell Clyde extracts propylene through catalytic cracking from naphtha. Montell Geelong extrudes propylene from both gasoil and naphtha. The mass allocation splitting PP production across these three plants is 19, 44 and 37%, respectively. The virgin fibre production process from virgin PP granulates is assumed to be the same as the production of recycled PP fibres.
Industrial Recycled PP Fibre
A diagram of the processes required in the production of industrial recycled PP fibre is shown in Fig. 6.4. The industrial PP waste are first compacted and then transported to a PP reprocessing plant by rigid trucks. The transport distance is on average 75 km. The collected industrial PP waste are shredded and recompounded in the PP reprocessing plant. The efficiency of both shredding and recompounding processes, as obtained directly from the reprocessing plant, is around 95%. The machine generates about 800 kg of the recycled material per hour, and the energy consumption on the reclaim line is roughly 280 kWh. The processed PP granulates are then transported about 55 km to a collection centre, and finally transported a further 100 km to a fibre production plant. The processing and transportation data were collected from the manager of the PP reprocessing plant (Martogg Group, Australia).
For the plastic fibre manufacturing process, an on-site investigation was carried out. The manufacturing process considered in this study includes PP granulates extrusion, PP fibre drawing and stabilisation, and fibre cutting and packing. In this process, the plastic granulates are vacuumed into an extruder, and then stretched and stabilised in ovens at 110-170 °C. The fibres are then cut into a length of 30-70 mm and packed. The majority of waste is generated during the cutting
Fig. 6.3 Flow sheet of the production of virgin PP fibre in traditional methods and the system boundary
process (approximately 5%). The electricity consumption in the PP fibre manufacturing process is obtained through actual electricity bills from the plastic processing plant data. According to the data, 1445 kWh are used to produce one tonne of PP fibres. Figure 6.4 also shows the system boundary of the LCA study for the recycled PP fibre. Information was collected from on-site investigation of Danbar Plastic, and communication with the managers of Martogg Group and Danbar
Fig. 6.4 Flow sheet of the production of recycled PP fibre from pre-consumer industrial PP wastes and the system boundary
Plastic. The environmental impacts of production of industrial recycled PP fibre were obtained by including this collected data within SimaPro 8.0 (LCS 2014). The calculations are based on Australian databases (Grant 2011a, b, 2012; Grant and Grant, 2011c) and Australian Indicator Set V3.00 method (SimaPro 2010).
Fig. 6.5 Flow sheet of the production of recycled PP fibre from municipal PP wastes and the system boundary