Simplified LCA of Nilar NiMH battery pack (EC 10Ah, 144V) - Report within the Grön BoStad Stockholm project

This subproject has been carried out within the framework of the Grön BoStad Stockholm project, funded by the European Regional Development Fund.

The report includes a life cycle assessment (LCA) study of a Nilar Nickel-metal hydride battery pack (EC 10Ah, 144V) carried out by IVL Environmental Research Institute on behalf of Nilar AB. The goal of this project is to provide knowledge of the environmental strengths and weaknesses of the Nilar NiMH battery pack from a cradle to gate perspective. The material composition of the battery was provided by Nilar.

The study is made on a Nilar EC 144V battery pack, which can store up to 1.44 kWh of energy. The functional unit is 1 kWh of stored energy which corresponds to 0.7 battery packs.

For the cradle to gate approach, the gate is the Nilar production site i.e. when the battery pack is ready to be delivered to customers. The cradle means the production of fuels, electricity, raw materials and extraction of natural resources. It also covers relevant transportation. The actual production of the battery at Nilar as well as the production of components by suppliers are however omitted since the process is assessed to have a minor impact.

This study is simplified, only based on an inventory of the bill of materials provided by Nilar AB i.e. kg of materials such as metals and different polymers. Data applied for the materials are based on generic database data mostly representing EU averages. The data applied for production of raw materials has been extracted from thinkstep/GaBi databases and EcoInvent database.

Data gaps and assumptions regarding key materials in this study will affect the result since these materials correspond to high percentages of the total battery weight. Production of compounds such as rare metals can also have a high environmental impact in their extraction and production phases. Due to lack of data for production of one of the rare metals it has been approximated as equal to production of a close neighbour in the periodic system. For one substance within the electrolyte, a similar compound was used as an approximation.

Transportation of materials has been included on a rough level. For materials produced in China or Asia a long-distance sea transport from Shanghai to Europe has been applied, while for all other materials an assumption of 1000 km truck has been assumed. These are fair assumptions since the total impact from transportation is small in relation to the production of the materials. Also, electricity use from the production phase has been excluded since it was assessed to be small in relation to the total impact.

The impact categories used in the study are Global warming potential (Climate change), Acidification potential, Eutrophication potential, Photochemical ozone creation potential and Abiotic resource depletion potential (ADP) elements. Categories used for LCA-results are Renewable and Non-renewable energy resources.

  The production of one of the rare metals was approximated with production of a close neighbour in the periodic system. The share of the metal is very low, but the data applied corresponds to a very high impact resulting in a contribution to the total climate change. This is the most uncertain assumption made in this study and has a significant effect on the final result.

The negative electrode corresponds to the highest share of the total climate change impact with 47% followed by the positive electrode with 24% and contact plate/case with 18%. For abiotic resource depletion potential, the negative electrode corresponds to the highest share of total impact with 71% of the total followed by the positive electrode with 23%.