Life Cycle Assessment Process
Functional Unit and Scenario Formulations
Following the international standards, including ISO14040: 2006—Principles and framework (ISO14040 2006), and ISO14044: 2006—Requirements and guidelines (ISO14044 2006), LCA addresses the environmental aspects and potential environmental impacts throughout a product’s life cycle from raw material acquisition through production, use, end-of-life treatment, recycling and final disposal.
The FU yields 40 kg of PP fibres and 364 kg of SRM, necessary to achieve the same degree of reinforcing in 100 mm thick concrete footpaths of area 10 m x 10 m. According to AS 3600-2009 (AS 2009) for 100 m2 of concrete footpath (100 mm thick) reinforced with Class L SRM, seven sheets of SL82 SRM (6 m x 2.4 m) are needed. The SL82 SRM consists of 7.6 mm steel bars at 200 mm spacing in both directions (Fig. 6.1c). One SRM sheet weighs 52 kg. Alternatively,
4 kg/m3 of PP fibres by volume (equivalent to 4 kg PP fibre per cubic meter of concrete) are found to be able to produce equivalent reinforcing effects to that of the SRM (Cengiz and Turanli 2004). The PP fibres (Fig. 6.1a, b) have a thickness of 0.7 mm, a width of 1.5 mm and a length of 47 mm.
The study set out herein was carried out to compare four scenarios with equal reinforcing effects in 100 m2 of concrete footpath:
Scenario a: Production of seven SL82 SRM (364 kg of total weight) using electric arc furnaces and basic oxygen furnace.
Fig. 6.1 Virgin PP fibre (a), 100% recycled PP fibre (b), and SL 82 SRM (c)
Scenario b: Virgin PP fibre production. 40 kg of virgin PP fibre produced from 42 kg of virgin raw materials using traditional extrusion process. 2 kg of waste produced during the fibre production is landfilled.
Scenario c: Industrial recycled PP fibre (100% recycled fibre), which refers to mechanically recycling industrial PP waste into recycled PP fibre. In order to get 40 kg of recycled PP fibre, 46.5 kg of industrial PP waste is collected (taking into account manufacturing efficiency provided by Martogg Group and Danbar Plastic). During the processing of 46.5 kg of industrial waste, 6.5 kg of processing waste is landfilled.
Scenario d: Domestic recycled PP fibre (100% recycled fibre), which is produced from mechanically recycling domestic PP waste into PP fibre. Taking into account manufacturing efficiency according to the research of Chilton et al. (2010), Perugini et al. (2005), Arena et al. (2003), SimaPro 8.0 Australian LCA databases (Grant and Grant 2011b, e) and on-site investigation, 68 kg of domestic plastic waste needs to be collected to obtain 40 kg of recycled PP fibre, 28 kg of waste produced during processing is considered to be landfilled.