Energy storage systems can play a vital role in the implementation of a sustainable energy grid by allowing the wide scale implementation of fluctuating renewable energy sources like wind and solar. Therefore it is expected that in the coming years, the total amount of energy storage systems will drastically increase. Analysing the sustainability of these storage systems before widespread implementation is therefore of great importance. In this thesis such a life cycle assessment has been conducted to assess the environmental sustainability of one type of energy storage system: the Organic Redox Flow Battery produced by the Baliht research group.