Abstract :
[en] The objective of this study is to assess the environmental impact of a fuel cell that uses gold for bipolar plates with a special focus on gold origin: could the use of secondary gold reduce the environmental impact of the fuel cell?
The inventory data for the fuel cell production are coming from a Walloon Project called HYLIFE that aims to optimize the lifetime of efficient materials for fuel cells. During this entire project, LCA has been used to help in the materials selection. The ReCiPe 2008 midpoint method has been used and the most relevant categories have been selected. The LCA is done in Simapro using ecoinvent v3.0 database. The materials selected by the project have been used to build a fuel cell prototype that is understudied here. It is composed of two bipolar plates covered with gold, a Nafion membrane, two diffusion layers (GDL). Platinum catalyst is used at anode and a platinum/cobalt catalyst is used at the cathode.
The first results underline the large contribution of gold in ecotoxicity categories, in toxicity and in freshwater eutrophication. The other categories are mostly linked to the platinum used in catalysts, except the ozone depletion that is mostly related to the Nafion membrane due to CFC emissions. A normalization is applied and underlines that the most impacting categories are those where gold has most of the impact. Therefore, two cases have been studied: an optimization of the amount of gold used by a reduction of lost during plates impregnation and the use of recycled gold from electronic materials using ecoinvent data. The first case, of course, leads to a diminution of the environmental impact in all the categories, especially those where gold contribution is high. The use of recycled gold, however, allows a reduction of the impact in some categories but also leads to an increase in some others. Indeed, even if gold is more concentrated in electronic scarps, its recovery is more difficult than in primary ores, due among others to the presence of other components such as fire retardant. Nevertheless, the use of recycled gold allows a reduction in all the categories where the gold is the major contributor in the case of the studied fuel cell, leading to an important gain for the environment with a reduction of the freshwater eutrophication and human toxicity of 60 %. The reduction in ecotoxicity categories is 50 % for freshwater and 30 % for terrestrial, therefore too small to be significant due to the large uncertainties in these categories. The largest increase is for terrestrial acidification with an increase of 15 % of the overall impact. To conclude, the use of recovery gold allows a reduction of the environmental impact of the fuel cell, especially in the categories where the gold is significant. Nevertheless, the question of secondary gold availability is not assessed by this study.
