Materials Management and Recycling for Nickel-Cadmium Batteries

Rechargeable battery use is expected to continue growing with the increasing prevalence of portable electronics, appliances, and tools. Nickel-cadmium batteries (NiCds) are widely used in these applications and represent a large volume of toxic materials in common use. While the management of lead-acid batteries is well-established, that of NiCds is in the formative stage. This thesis considers the relationship between material flows of lead, cadmium, and nickel used in batteries. Battery materials, characteristics, and recycling technologies for NiCd, nickel metal-hydride, and lithium-based batteries are considered. The definition of an environmentally friendly battery is developed, as are substitution models. Life cycle emissions for NiCds are characterized, focusing on materials management during recycling. A materials mass balance of a facility recycling NiCds is constructed. Using publicly-available information, it is difficult to account for all outputs of the metals studied. The life cycle energy use of NiCds is estimated. Manufacturing batteries using some recycled materials instead of all virgin materials uses about half the energy. Economic issues are presented, and potential costs and revenues for recycling facilities are estimated. The potential net revenue from NiCd recycling depends on current metal prices. The consumer NiCd recycling rate is estimated, and a standardized equation for calculating the total NiCd recycling rate is proposed. NiCd processing facilities are modeled using distillation software, and an example tutorial is developed. Battery regulations and initiatives are summarized for the U.S. and other countries. U.S. legislation has encouraged the development of a nationwide collection system for NiCds. In Europe bans on the use of cadmium are being considered, although other battery types also use toxic and hazardous materials. When the total life cycle emissions, energy, and waste generation for each battery type are considered, allowing niche battery markets to develop and promoting recycling for all battery types may be more environmentally friendly than simply banning specific battery types. This thesis provides a basis for continuing evaluation of NiCds and for the analysis of emerging rechargeable battery technologies which have not been comprehensively studied.

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Author Rebecca Lankey
Institution Carnegie Mellon University
Advisor Francis C. McMichael
Expected graduation 1998