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Total life cycle analyses may be utilized to establish the relative environmental and human health impacts of battery systems over their entire lifetime, from the production of the raw materials to the ultimate disposal of the spent battery. The three most important factors determining the total life cycle impact appear to be battery composition, battery performance, and the degree to which spent batteries are recycled after their useful lifetime. This assessment examines both rechargeable and non-rechargeable batteries, and includes lead acid, nickel cadmium, nickel metal hydride, lithium ion, carbon zinc and alkaline manganese batteries.
Battery metals such as lead, cadmium, mercury, nickel, cobalt, chromium, vanadium, lithium, manganese and zinc, as well as acidic or alkaline electrolytes, may have adverse human health and environmental effects. The specific forms of these materials as well as the relative amounts present will establish the risks associated with that particular battery system. However, the degree to which such batteries are collected and recycled after their useful life may largely mitigate any such adverse effects. Landfill or incineration disposal options are not as desirable as recycling, but the risks associated with those options are not so unacceptably high as to require the phase outs of any existing battery technologies.
Battery performance characteristics, likewise, are important in establishing the amount of potentially hazardous waste generated per unit of battery energy generated.
Rechargeable battery systems obviously enjoy a great advantage in this respect since they may be recharged and reused many times. However, other factors such as the battery voltage, ampere-hour rating, cycle life, charging efficiency and self-discharge characteristics may also be important in establishing the total amounts of hazardous waste generated per unit of battery energy and thus the total environmental impact per unit of battery energy.
Safety issues have also become more important in recent years as more active battery chemistries have been developed. In particular, the presence of corrosive electrolytes and highly ignitable or explosive battery materials under certain conditions has become an issue which the battery industry must address. At present, it appears as if improvement in the recycling rates of spent batteries will produce the most substantial decreases in the environmental and human health impacts of battery systems.
Total life cycle analysis (LCA) is increasingly being utilized to establish the relative human health and environmental impacts of many products and processes. In these analyses, the total impacts, from the production of the raw materials for the product, through its manufacture, use and ultimate disposal are established, and then usually compared to other similar products. Environmentalists and regulators have used these principles to favor the displacement of one product in the marketplace with an allegedly "more environmentally friendly" product. Very often, however, it has been found that one product may exhibit high negative LCA impacts in one area, while another product may be deficient in another area. Such appears to be the case when various battery chemistries are compared.
The components of a total life cycle analysis are generally agreed to consist of the following four basic steps:
I. Scope and Goal Definition
II. Materials and Energy Inventory
III. Environmental and Human Health Impact Assessments
The scope and goal definition (Step I) is necessary in that most life cycle analyses may be as wide or as narrow as one wishes to make them. For example, one could define a product life cycle analysis so widely as to include the production of the mining equipment used to mine the ore which produced the metal which went into the manufacture of the battery. Generally, however, these effects become normalized over so many other products as to become secondary effects of little consequence in the specific analysis of, for example, a rechargeable NiCd battery. The major area, however, which should be included, is the energy and emissions associated with the direct production of the raw materials used in the batteries. Thus, it is very important that the scope of a particular life cycle analysis be carefully defined and that comparisons between products be made on the basis of the same scope.
In the case of batteries, the following stages are considered to be the major contributors to environmental and human health impacts and would be included in a life cycle analysis:
• Battery Raw Materials Production
• Battery Production Process
• Battery Distribution and Transportation Requirements
• Battery Recharging and Maintenance (Rechargeable Batteries)
• Battery Recycling or Waste Management Option
Once these stages are established and the scope of the life cycle analysis reasonably well defined, then a complete materials and energy inventory analysis (Step II) must be performed on each of these stages to determine the overall materials and energy balances. As shown in Figure 1, the inputs of energy and materials on the left hand side for every stage in the manufacture, use and disposal of a battery are balanced by the outputs of usable products and environmental releases on the right hand side. To produce the least environmental and human health impacts, the environmental releases from all of these stages should be minimized.
In carrying out life cycle analyses for battery systems, it becomes very quickly apparent that the inventory analyses for certain stages are insignificant compared to others. For example, the emissions associated with distribution and transportation of batteries and the appliances they power are spread out over so many billions of units as to be
Figure 1. Materials and Energy Inventory Analysis for Battery Systems
Figure 1. Materials and Energy Inventory Analysis for Battery Systems insignificant to the LCA of one single battery. Furthermore, sealed batteries have no emissions during normal use, and the emissions associated with the recharging of batteries depends very much upon the power generating infrastructure in a particular country. In countries dependent on high sulfur coals, the impact could be significant, but in countries with hydroelectric, nuclear, solar power or other clean energy sources, the emissions associated with recharging batteries are virtually non-existent. In any event, these emissions, even in the case of dirty fossil fuels, also appear to be so spread out over so many applications as to have little effect on an individual battery's life cycle analysis. Each one of these stages will be considered in more detail below, but it appears as if battery raw material production, battery manufacture, battery performance during use, and battery recycling or disposal as waste are the most important stages in the comparative life cycle analyses of battery systems. The emissions associated with and the energy consumed during each of these stages will establish the environmental loading resulting from each battery system, which in turn may be converted into a human health and environmental impact analysis by assuming certain impact values for each of the materials emitted and energy consumed.
A further factor particular to the evaluation of the life cycle analyses of battery systems is that their human health and environmental impacts must be normalized to the total lifetime energy output of the battery. In other words, impacts are expressed in terms of effects per kilowatt-hour of energy generated. This requirement is necessary since battery systems all differ considerably in their total lifetime energy output. Rechargeable batteries generally have higher total lifetime energy outputs than non-rechargeable batteries, and thus their environmental and human health impacts are lower. Put another way, it requires more non-rechargeable batteries to produce the same total lifetime energy as rechargeable batteries. Because the total lifetime energy of a battery system is important to its life cycle analysis, parameters such as operating voltage, ampere-hour rating, cycle life, charging efficiency and self-discharge characteristics may all become important factors in establishing a battery system's overall life cycle analysis.
Obviously, the first and most important factor in the inventory analysis stage is the overall composition of the battery system. Technically, a life cycle analysis can only be specifically performed on a specific battery composition, and there is often great variety in the compositions for batteries that nominally all belong to the same family. In addition, a rigorous life cycle analysis should consider every material in the battery, no matter how minute the environmental impacts may appear to be. The tendency in most life cycle analyses on battery systems to date has been to concentrate on the "hazardous materials" or "heavy metals" contained in those batteries while ignoring contributions which may arise from greater amounts of less high-profile substances. For example, life cycle analyses of lead acid batteries usually focus on their lead content and ignore the sulfuric acid electrolyte. Most analyses of nickel-cadmium batteries dwell on the cadmium LCA contribution while minimizing the nickel and cobalt contribution. In a rigorous analysis, the contributions of every material must be considered. Some will indeed be found to be insignificant and have little or no effect on the final total impact, but others may have suprisingly large effects.
Another factor which has yet to be properly evaluated and factored into battery life cycle analyses is the form of the material in the batteiy system itself. When evaluating the environmental and human health effects of battery materials, most analyses have assumed, for example in NiCd batteries, a single environmental impact value for nickel and all of its compounds or a single environmental impact value for cadmium and all of its compounds. Since these single values are usually derived from tests on a highly soluble species, they almost always overstate the environmental and human health impacts of the materials actually used in batteries. For example, in nickel-cadmium batteries, the relatively insoluble cadmium oxide is the compound normally used in the battery whereas the environmental and human health impact values are based on the highly soluble cadmium chloride. Thus, battery life cycle analyses usually represent the worst case scenario as far as human health and environmental impact are concerned. However, it is important to recognize the basis on which the environmental and human health impact values are assigned. In the case of zinc, for example, the surrogate compound used to derive impact values is zinc oxide which is a reasonable choice. In the case of some other metals, such as nickel and cadmium mentioned above, the impact values are based on the highly soluble species as surrogate compounds which very much overstates the relative risk. This problem has yet to be addressed in life cycle analyses of battery systems, and it is difficult to state how much it might affect them when it is addressed.
These problems not withstanding, it is possible to examine general battery families and to make some analyses of these families based on generalized or average compositions, recognizing however that individual variations within the batteiy family may be considerable. The compositions of several such generalized battery families are indicated in Table I. These chemistries vary considerably, as shown by the three sets of data presented below (Fujimoto 1999, Morrow 1998 and Gaines 1994). This wide variation in battery chemistry is one of the primary reasons why it is so difficult to draw generalized conclusions about the relative environmental and human health impacts of one family of batteries compared to another family.
Table I. Various Nominal Compositions of Battery Families
Nominal Composition, Weight Percent
Lead Acid* Nickel-Cadmium* Nickel Metal Hydride (ABS)* Nickel Metal Hydride (AB2)*
65Pb - 25H2S04 30Fe - 30Ni - 15Cd 45Ni - 10Mg/Al - 9Ce - 4Co 39Ni - 6V - 6Zr - 3Cr - 3Ti - 2.5Co
Nickel-Cadmium** Nickel Metal Hydride** Lithium-Ion**
32.5Fe - 17.5NÍ - 22.5Cd - 3Co 42.5NÍ- 17.5Fe - 7.5Co - 12.5 Rare Earths 22.5Fe - 17.5CO - 7.5A1 - 7.5Cu - 3Li
Lead Acid*** Nickel-Cadmium(PBE)* * * Nickel-Cadmium(FNC)* * * Nickel Metal Hydride(AB5)*** Nickel Metal Hydride(AB2)***
69Pb - 22H2SO4 14Fe - 26Ni - 18Cd 15Fe - 31Ni - 22Cd 44Fe - 29Ni - 5 Rare Earths - 2Co - 1 Mn 44Fe - 24Ni - 7V - 3Zr - 2Cr- ITi
The above data and data from other sources show some interesting trends in battery compositions over time. For example, the older NiCd batteries, which are the ones being collected and recycled now, tend to exhibit lower cadmium and cobalt values than the newer generations of NiCd batteries. There are also distinct differences in nickel and cadmium contents between industrial and consumer batteries. The battery industry generally agrees that consumer NiCds being collected today for recycling contained an average of 15% Cd. Industrial NiCds, on the other hand, may show a much wider variation, and levels from 7% Cd to 24% Cd have been noted in some industrial NiCds.
Interestingly enough, a "Li-ion" battery actually contains very little lithium, and should more properly be designated an Fe-Co-Al-Cu-Li battery. These examples, however, should be sufficient to demonstrate that using nominal compositions for battery life cycle analyses may introduce large factors of uncertainty into such analyses, and the compositional basis for any battery's LCA must be stated as part of the analysis results.
The first analysis which obviously must be performed is to establish the emissions produced and the energy consumed during the production of the raw materials used for battery production. In the case of the metals utilized for the electrode materials in most batteries, the mining, smelting, and refining of the base metal, and their subsequent conversion into the specific form of the material utilized in the battery are the processes which must be addressed. Direct emissions of metals from the mining, smelting and refining of battery metals such as lead, cadmium, nickel, cobalt, zinc, manganese and many other metals are generally well-controlled and are subject to stringent regulation today. Metal emissions from the primary nonferrous smelters have diminished
Figure 2. Sources of Human Cadmium Exposure (Van Assche 1998) (the sources listed are arranged clockwise from: fertilizers, 42%)
Figure 2. Sources of Human Cadmium Exposure (Van Assche 1998) (the sources listed are arranged clockwise from: fertilizers, 42%)
considerably in the past twenty years as demonstrated by Canada's ARET (Accelerated Reduction and Elimination of Toxics) Program and the U.S. Environmental Protection Agency's TRI (Toxics Release Inventory) and 33/50 Programs. In addition, studies on the sources of human cadmium exposure, for example, indicate that only 6.3% of all human cadmium exposure comes from nonferrous smelting, principally zinc, lead and copper, and that only 2.5% arises from cadmium applications such as NiCd batteries. This data is shown graphically in Figure 2 and is based on studies in Europe (Van Assche 1998, Van Assche and Ciarletta 1992). Thus, it is clear that primary metals production processes do not contribute significantly to the environmental impact of the battery systems.
A second environmental impact from the production of nonferrous battery metals arises because of the relative amount of energy utilized to produce a given quantity of the metal. In this case, the amount of energy necessary to produce a metric tonne may be related to the amount of greenhouse gases produced to create that energy. However, again, this may be too simplistic a view in that the amounts of greenhouse gases depend very much upon the types of fossil fuels used, air pollution control devices in place, and the nature of the energy producing combustion mechanisms. The energy consumed in the primary metal production of five common battery metals is summarized in Table II (Schuckert 1997).
From an energy consumption standpoint, metals with low melting temperatures such as lead and cadmium, require less energy to produce, and thus have a lower environmental impact with respect to the generation of greenhouse gases. Metals which are produced by electrolytic processes or have high melting temperatures require higher energy inputs to produce and thus have higher environmental impacts with respect to greenhouse gases.
Table II. Energy Consumed in Primary Metal Production
Manganese Nickel Lead Zinc/Cadmium
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