Domestic Recycled PP Fibre
Figure 6.5 shows the flow of production of recycled PP fibre from domestic PP waste and its system boundary. The domestic recyclables are collected from kerbside bins every fortnight by local materials recovery facility (MRF) workers. Mixed recyclables are sorted in the MRF. The sorted plastic wastes are sent to plastic reprocessing plants, where manual and mechanical sorting is undertaken to separate out plastic bottles. Plastics are then shredded and milled into flakes, before being washed in sodium hydroxide solution at 60 °C. The PP fragments are then separated from other plastics (e.g. PET) based on density differences in a water tank. After centrifugation and drying, the PP fragments are extruded and recompounded into small granulates for future fibre production. The processing steps described here for domestic plastic waste are taken from the SimaPro databases for Australian PP reprocessing and recycling (Grant and Grant, 2011b, e), and relevant scientific publications (Arena et al. 2003; Shen et al. 2010). The MRF sorting efficiency is taken as 70%, based on a Townsville MRF plant and Perugini et al. (2005). The PP reprocessing efficiency is based on Perugini et al. (2005). The transportation and fibre production process are assumed to be same as those used for industrial recycled PP fibre.