Life cycle assessment of a plastic air intake manifold

Nowadays, some engine components subjected to mechanical stress and high temperature are made of thermoplastic materials. The air intake manifold (AIM) is one of these parts. In the past, AIM was made of aluminium or magnesium alloy, while today, engine manufacturers prefer to use lighter materials such as nylon reinforced with glass fibre. The scope of this work is to assess from an environmental point of view the adoption of two alternative thermoplastic materials (polyamide reinforced with 30 % of glass fibre and polypropylene reinforced with 35 % of glass fibre) for the construction of a Magneti Marelli^® AIM and the introduction in the production stage of new additional design solutions (scraps recycling and brass inserts elimination). The outcome of the paper would contribute both to establish a baseline for comparison with other composite AIMs and to improve the knowledge of materials and manufacturing technologies related to the product.

The study has been performed applying the LCA methods as described in the ISO standards 14040 and 14044. The life cycle inventory (LCI) captures the whole AIM life-cycle (LC) subdivided in four stages: materials supply, production, use and end-of-life (EoL). For the LCI data collection, primary data have been provided by the AIM manufacturer, while available databases have been used as source for secondary data. Unlike previous LCAs regarding AIM, the environmental profile is assessed through a broader range of life cycle impact assessment (LCIA) impact categories as provided by the CML 2001 framework in its November 2010 release.

The results show that for both the polyamide composite and the polypropylene composite, the AIM the most influential LC stages are use and materials supply. Such outcome is due to the considerable quantity of fuel consumed during the whole LC and the energy/resources consumption involved by the raw materials extraction and production processes. The substitution of polyamide composite with polypropylene composite reduces the potential environmental impacts for all the categories and for each stage of the AIM LC. Contribution analysis by LC stage of potential environmental impact evidences that the change of material involves a remarkable increase of the use stage quota with no notable mutation of production and EoL contributions. The introduction of scraps recycling and brass inserts elimination entails no significant impact reduction for all the categories with the only exception of abiotic depletion potential (ADP_e).

The substitution of polyamide composite with polypropylene composite involves considerable reduction of the AIM LC impact, while the introduction of scraps recycling and brass inserts elimination entails negligible effects.