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Another important consideration for recycling is the toxicity and reactivity of materials. Because EV batteries are large, heavy, operate at high voltages, and frequently contain toxic, corrosive, or reactive materials, health and safety issues must be considered when handling them and may present limits on how to recycle them as well. These issues are all manageable as long as careful planning is done in advance. Most battery maintenance will be performed by trained personnel while the system is in the vehicle, and replacement batteries will most likely only be available through auto dealers or specialty shops. The control provided by the need to use trained installers and the significant cost of the battery means that virtually all batteries will be returned for recycling at end-of-life. A training package to address accident scenarios, including a video, has been prepared for emergency response personnel [11]. This kind of safety information will become more available as the number and types of EVs proliferate.

Chemical hazards broadly fall into two categories: 1) physical and health hazards from exposure to these materials during battery handling and dismantlement, and 2) environmental hazards from disposal. If these materials are considered hazardous waste because they are listed by the EPA or categorized as characteristic wastes, then they can only be disposed of in specially designated landfill facilities. Characteristic wastes are classes of materials that are identified as exhibiting leachability, flammability, and corrosivity/reactivity. This adds to the cost and could justify further expenditures to reclaim or recycle these materials even if they are not inherently valuable. An assessment of the health impacts from reclamation of automotive batteries was completed for the California EPA, and a report was issued in 1999 [12]. This study compares the relative impact of recycling nine different types of EV batteries in terms of cancer, toxicity, and ecotoxicological potential. The methodology is semiquantitative and was based on the protocol developed by the Office of Environmental Health Hazard Assessment, a division of the California EPA.

Table 2 shows the health and environmental impact score that was developed for each battery constituent. Antimony, arsenic, cadmium, lead, and nickel are the five materials with the highest scores (i.e., the most negative impacts). A health/hazard score for each battery type was then determined by multiplying the constituent score by the estimated amount of emissions to the air and a battery life factor in terms of grams per mile of battery pack usage. The scores were then totaled for each battery type and recycling process as described in Reference 12. These health/hazard scores are primarily determined by the human health impacts. A log-scale graph of the normalized health/hazard scores is shown in Figure 8 for different battery types and recycling processes.

Generally, the health/hazard score is highest for batteries containing significant amounts of materials with a high health impact or that are potentially emitted in large amounts by the recycling process. The advanced battery chemistries such as Ni/MH and Li-ion appear to offer improvement over conventional battery systems because they incorporate less hazardous materials and may use hydrometallurgical rather than pyrometallurgical or smelting processes for recycling.

A closer examination of hazardous waste characteristics of battery materials does reveal differences between battery chemistries. The toxicity of conventional battery materials such as lead, antimony and cadmium are well known, and therefore they are usually recovered as much as possible rather than disposing of them. Strict emission controls are required to prevent their release into the air or water. The problems with advanced battery systems in this regard are not quite so severe, but there still may be reactive, corrosive, or toxic materials present that must be dealt with during the recycling process.

Both Ni/MH and Li-ion batteries do contain hazardous materials. Nickel/metal hydride battery packs, of course, contain nickel, which is a suspected carcinogen in some forms. However, the only hazardous material in a Ni/MH battery, as defined by federal regulations, is the potassium hydroxide (KOH)-based electrolyte (corrosive). The only characteristic hazard of any consequence for the electrode materials in these batteries is toxicity. The hazard level is determined by a test called the toxicity characteristic

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