Life-cycle methods for comparing primary and rechargeable batteries

Life-Cycle Assessment (LCA) can be used to improve the environmental performance of products throughout their life cycle. With ongoing discussions about system boundaries, appropriate data, and model limitations, LCA methods are in a constant state of evolution. This paper presents the use of a hybrid LCA approach to product environmental assessment in which two methods of analysis are combined to present the total environmental impact for two battery systems. A quantitative model for product assessment has been developed at Carnegie Mellon. The model is based on economic input-output life-cycle analysis (EIO-LCA) and has been explained in previous works. The EIO-LCA tool allows a user to quantify the direct and indirect relationships among industry sectors and the associated environmental burdens through the materials extraction and manufacturing phases. However, to study environmental effects over a product's entire life, use and end-of-life impacts must also be quantified. This is accomplished using the LCA approach in which an emissions and energy inventory is compiled and the environmental impacts are quantified. In this paper, the above hybrid LCA approach is applied to comparing the total environmental impacts of primary and rechargeable batteries. The primary (non-rechargeable) batteries mainly used in electronic products are zinc-alkaline batteries, and the most widely used consumer rechargeable batteries are nickel-cadmium. It is generally accepted that rechargeable batteries offer environmental advantages over primary batteries. We find that materials use, energy use, and emissions can be quantified over the entire product lifecycle to quantitatively show that resource use and emissions are substantially lower if a rechargeable battery can be substituted for a primary battery. However, consumer use patterns will affect the relative environmental benefits of rechargeable batteries. Noting the effect of consumer behavior also determines where uncertainties in the analysis may lie, since behavior is difficult to predict. Recycling batteries will also have associated emissions and energy use. Even accounting for the additional resource consumption and emissions for rechargeable batteries in the use and recycling phases of life, rechargeable batteries will still consume less resources over the entire life cycle when used in applications as a substitute for primary batteries. The assessment methods can also be applied to electronic products in addition to components such as batteries.