How to Identify Relevant Parameters for the Recycling of Ni-MH Batteries to Decrease Their Environmental Impacts?

International audienceMetal recovery is a key stake for the European Union. Indeed, some materials have a high economic importance and are associated with a high risk of supply. That is the reason why a European Commission has undergone a study about environmental impacts, strategic and industrial importance, supply and geopolitical risks associated with a list of materials. Twenty-seven raw materials have finally been identified as critical. They are registered in the Report on critical raw materials for the EU [1]. Actions are being taken to preserve these materials. Recycling of Nickel Metal Hydrure batteries (NiMH) can be an interesting track to recover some of them. NiMH batteries are made of different materials: nickel, cobalt, iron, manganese and rare earths such as cerium and lanthanide. Rare earths and cobalt are listed in the European report as critical metals. These batteries can be an interesting deposit of metals. Indeed, they are used for a wide range of applications such as portable hand held electric power tools, hybrid vehicles, AA and AAA batteries. Amongst all the batteries, their market share is around 3%, which represent a large amount of materials. So far, processes of metals recovery have not been sufficiently efficient and have had high environmental impacts. As a consequence, more efficient processes are developed in the laboratories. In order to estimate the environmental reliability of such an approach, it can be interesting to have an idea of the impact of recycling on the overall environmental impacts of the NiMH batteries. This is the subject of this paper: how can recycling affect environmental impacts of the batteries ? To answer this question, it is first necessary to have an overview of the environmental impacts of a battery on its whole lifecycle. Thus, a literature review of Life Cycle Assessments of NiMH batteries have been realized. The idea to identify the main hypothesis that were considered in terms of functional unit, system boundaries and impact categories. Then, the most impacting stages will be identified. Finally, a focus will be made on the end of life. The goal of this part is to evaluate the environmental impacts, the potential benefits and the key parameters: collection rate and ratio between the different options (landfill, incineration and recycling). The first results show that NiMH batteries have an important environmental impact that can be counterbalanced by their efficient recycling. These benefits depends on the collection rate of the batteries. In the context of the development of new process of recycling, it will be interesting to compare the influence of the collection rate on the environmental impacts in regards to the influence of environmental improvement of processes. [1] Communication from the Commission to the European Parliament, The Council, the European Economic and Social Committee and the Committee of the regions on the 2017 list of Critical Raw Materials for the EU, COM/2017/0490 final, available on http://eur-lex.europa.eu/legal-content/EN/ALL/?uri=COM:2017:0490:FI