Environmental Assessment of Battery Systems: Critical Issues for Established and Emerging Technologies

Energy and material flows associated with portable and industrial rechargeable batteries have been quantified in a life-cycle perspective, as guidance for development of battery systems. The study included portable batteries based on nickel-cadmium, nickel-metal hydride and lithium-ion. Energy return factors and overall energy efficiencies were calculated for a stand-alone photovoltaic (PV)-battery system under different operating conditions. Eight different battery technologies for stationary energy storage were evaluated: lithium-ion (Ni), sodium-sulphur, nickel-cadmium, nickel-metal hydride, lead-acid, polysulphide-bromide, vanadium redox and zinc-bromine. In applications where batteries are difficult to collect at the end of their life, dissipative losses of toxic metals from incineration and landfills are of main concern. Indicators of global metal flows were used to assess the potential environmental impact of metals used in portable batteries. Lithium-ion and nickel-metal hydride batteries have lower impact based on indicators of anthropogenic and natural metal flows than nickel-cadmium batteries. Energy requirements during production and usage are important for battery systems where the metal losses throughout the battery life cycle are low. For a PV-battery system with a battery capacity three times higher than the daily energy output, the energy return factor is 0.64-12, depending on the battery technology and operating conditions. With a service life of 30 years, the energy payback time is 1.6-3.0 years for the PV-array and 0.55-43 years for the battery, which highlights the energy related significance of batteries and the large variation between different technologies. Some of the emerging technologies studied, e.g. lithium-ion and sodium-sulphur, show favourable performance for use in PV-battery systems, resulting in higher energy return factors and higher overall battery efficiencies than for established battery technologies. The environmental impact can be reduced by matching operating conditions and battery characteristics in a life-cycle perspective. To decrease the environmental impact of battery systems, the development of battery technologies should aim at the recycling of materials, increased service lives and higher energy densities. To decrease the environmental impact arising from the use of metals in battery systems, metals with high natural occurrence should be used and regulations implemented to decrease the need for virgin metals. To increase the overall energy efficiencies of battery systems, the development of battery technologies should aim at higher charge-discharge efficiencies and more efficient production and transport of batteries