LCA case study. Part 1: cradle-to-grave environmental footprint analysis of composites and stainless steel I-beams

Purpose

I-beams for outdoor structures are traditionally made from conventional materials such as stainless steel due to its high strength and corrosive resistant properties. Alternatively, the I-beam can also be made from composite materials such as glass-reinforced plastics (GRP), which provide similar properties under a lighter weight and a lower cost condition. Nonetheless, their environmental footprint performance depends largely on activities involved during their life cycle. Therefore, the findings are presented in two parts: Part 1 and 2. This paper is about Part 1, which presents the environmental footprint for the cradle-to-grave of one linear metre I-beam that is made from two materials namely stainless steel (316) and GRP. Part 2, which will be submitted as a separate paper, has specifically analysed their environmental and economic impacts for the different cradle-to-gate scenarios and the potential carbon tax.

Materials and methods

Materials that were used to compare the environmental footprint of an I-beam are GRP and stainless steel (316). Their cradle-to-grave activities included raw material extraction, supplier transportation, manufacturing process, distribution, disposal transportation and process. Input data were based on data provided by a composites company in Australia, the Ecoinvent 2.2 and Australian data 2007 databases. The World ReCiPe midpoint and endpoint methods were used to assess the environmental footprint.

Results and discussion

The environmental footprint results for the cradle-to-grave of the I-beams are presented as a contribution percentage of the single score unit in the total and damage category levels which produced by the endpoint method. The characteristic and normalisation results were also generated for all impact categories by the midpoint method.

Conclusions

Overall, the cradle-to-grave results show that the composite I-beam produces 20 % less environmental footprint than that of the stainless steel I-beam. The human health damage category is affected the most due to the main contribution from the material stage. The cradle-to-gate results are contributed by 90 % from raw material extraction, 7 % from the manufacturing process and 3 % from the supplier transportation. In terms of the characteristic results, the composite I-beam produces less environmental impact in most of the impact categories except for the climate change, photochemical oxidant formation, terrestrial acidification, marine eutrophication, natural land transformation and fossil depletion. Therefore, the influential parameters of these impact categories are investigated further in Part 2 where the environmental footprint and economic impact are estimated for different cradle-to-gate scenarios of the I-beams.