15.7 Battery Recycling
Even though the emphasis in battery research has shifted away from NiCd to newer technologies, the NiCd battery continues to be one of the most used rechargeable batteries. Over 75 million NiCd batteries were sold in the US during the year 2000. Market reports indicate that the demand of NiCd batteries is expected to rise six percent per year until 2003. The demand for other chemistries, such as the NiMH and Li-ion family, is rising at a more rapid pace. Where will the mountains of batteries go when spent? The answer is recycling.
The lead acid battery has led the way in recycling. The automotive industry should be given credit in organizing ways to dispose of spent car batteries. In the USA, 98 percent of all lead acid batteries are recycled. Compared to aluminum cans (65 percent), newspaper (59 percent) and glass bottles (37 percent), lead acid batteries are reclaimed very efficiently, due in part to legislation.
Only one in six households in North America recycle rechargeable batteries. Teaching the public to bring these batteries to a recycling center is a challenging task. Homeowners have the lowest return ratios, but this should improve once more recycling repositories become available and better environmental awareness is emphasized.
Careless disposal of the NiCd is very hazardous to the environment. If used in landfills, the cadmium will eventually dissolve itself and the toxic substance will seep into the water supply, causing serious health problems. Our oceans are already beginning to show traces of cadmium (along with aspirin, penicillin and antidepressants) but the source of the contamination is unknown.
Although NiMH batteries are considered environmentally friendly, this chemistry is also being recycled. The main derivative is nickel, which is considered semi-toxic. NiMH also contains an electrolyte that, in large amounts, is hazardous to the environment.
If no disposal service is available in an area, individual NiMH batteries can be discarded with other household wastes. If ten or more batteries are accumulated, the user should consider disposing the batteries in a secure waste landfill.
Lithium (metal) batteries contain no toxic metals, however, there is the possibility of fire if metallic lithium is exposed to moisture while the cells are corroding. Most lithium batteries are non-rechargeable and are used by defense organizations. For proper disposal, these batteries must be fully discharged in order to consume all the metallic lithium content. Li-ion batteries do not contain metallic lithium and the disposal problem does not exist. Most lithium systems, however, contain toxic and flammable electrolyte.
In 1994, the Rechargeable Battery Recycling Corporation (RBRC) was founded to promote the recycling of rechargeable batteries in North America. RBRC is a non-profit organization that collects batteries from consumers and businesses and sends them to Inmetco and Toxco for recycling. Inmetco specializes in recycling NiCd, but also accepts NiMH and lead-based batteries. Toxco, focuses on lithium metal and Li-ion system. Currently only intended to recycle NiCd batteries, RBRC will expand the program to include also NiMH, Li-ion and SLA batteries.
Programs to recycle spent batteries have been in place in Europe and Asia for many years. Sony and Sumitomo Metal in Japan have developed a technology to recycle cobalt and other precious metals from Li-ion batteries. The rest of Asia is progressing at a slower rate. Some movements in recycling spent batteries are starting in Taiwan and China, but no significant infrastructure exists.
Battery recycling plants require batteries to be sorted according to chemistries. Some sorting is done prior to the battery arriving at the recycling plants. NiCd, NiMH, Li-ion and lead acid are often placed in designated boxes at the collection point.
Sorting batteries adds to the cost of recycling. The average consumer does not know the chemistry of the batteries they are using. For most, a battery is a battery.
If a steady stream of batteries, sorted by chemistry, were available at no charge, recycling would be feasible with little cost to the user. The logistics of collection, transportation and labor to sort the batteries make recycling expensive.
The recycling process starts by removing the combustible material, such as plastics and insulation using a gas fired thermal oxidizer. Gases from the thermal oxidizer are sent to the plant’s scrubber where they are neutralized to remove pollutants. The process leaves the clean, naked cells which contain valuable metal content.
The cells are then chopped into small pieces, which are then heated until the metal liquefies. Non-metallic substances are burned off; leaving a black slag on top that is removed with a slag arm. The different alloys settle according to their weights and are skimmed off like cream from raw milk.
Cadmium is relatively light and vaporizes easily at high temperatures. In a process that appears like a pan boiling over, a fan blows the cadmium vapor into a large tube, which is cooled with water mist. This causes the vapors to condense. A 99.95 percent purity level of cadmium can be achieved using this method.
Some recyclers do not separate the metals on site but pour the liquid metals directly into what the industry refers to as ‘pigs’ (65 pounds) or ‘hogs’ (2000 pounds). The pigs and hogs are then shipped to metal recovery plants. Here, the material is used to produce nickel, chromium and iron re-melt alloy for the manufacturing of stainless steel and other high end products.
Current battery recycling methods requires a high amount of energy. It takes six to ten times the amount of energy to reclaim metals from recycled batteries than it would through other means. A new process is being explored, which may be more energy and cost effective. One method is dissolving the batteries with a reagent solution. The spent reagent is recycled without forming any atmospheric, liquid or solid wastes.
Who pays for the recycling of batteries? Participating countries impose their own rules in making recycling feasible. In North America, some recycling plants bill on weight. The rates vary according to chemistry. Systems that yield high metal retrieval rates are priced lower than those which produce less valuable metals. The highest recycling fees apply to NiCd and Li-ion batteries because the demand for cadmium is low and Li-ion batteries contain little in the way of retrievable metal. The recycling cost of alkaline is 33 percent lower than that of NiCd and Li-ion because the alkaline cell contains valuable iron. The NiMH battery yields the best return. Recycling NiMH produces enough nickel to pay for the process.
Not all countries base the cost of recycling on the battery chemistry; some put it on tonnage alone. The cost of recycling batteries is about $1,000 to $2,000US per ton. Europe hopes to achieve a cost per ton of $300US. Ideally, this would include transportation, however, moving the goods is expected to double the overall cost. For this reason, Europe sets up several smaller processing locations in strategic geographic locations.
Significant subsidies are sill required from manufacturers, agencies and governments to support the battery recycling programs. These subsidies are in the form of a tax added to each manufactured cell. RBRC is financed by such a scheme.
<p class="Standout"><span class="warning">Caution</span>: Under no circumstances should batteries be incinerated as this can cause them to explode.</p> <p class="Standout"><span class="warning">Important:</span> In case of rupture, leaking electrolyte or any other cause of exposure to the electrolyte, flush with water immediately. If eye exposure occurs, flush with water for 15 minutes and consult a physician immediately.</p></blockquote><p align="center"><font size="2"><a href="/guides/electronics/bpw/c15_07"><< Previous page</a> <a href="/guides/electronics/bpw/00_toc">INDEX</a> <a href="/guides/electronics/bpw/c16_01">Next page >></a></font></p>