Lead- and cadmium-based batteries pose the largest environmental concerns, so much so that nickel-cadmium was banned in Europe in 2009. Attempts are being made to also ban the lead-based battery, but no suitable replacement is available as was the case by substituting nickel-cadmium with nickel-metal-hydride. For the first time, lithium-ion has been added to the list of pollutants. This chemistry was classified as only mildly toxic, but their sheer volume requires tighter scrutiny.
Lead acid paved the way to the success of recycling, and today more than 97 percent of these batteries are recycled in the USA. The automotive industry should be given credit for having organized recycling early; however, business reasons rather than environmental concerns may have been the driving force. The recycling process is simple and 70 percent of the battery’s weight is reusable lead.
Over 50 percent of the lead supply comes from recycled batteries. Other battery types are not as economical to recycle and are not being returned as readily as lead acid. Several organizations are working on programs to make the collection of all batteries convenient. Only 20 to 40 percent of batteries in mobile phones and other consumer products are currently recycled. The goal of recycling is to prevent hazardous materials from entering landfills and to utilize the retrieved materials in the fabrication of new products.Spent batteries should be removed from the household. Old primary cells are known to leak and cause damage to the surrounding area. Do not store old lead acid batteries where children play. Simply touching the lead poles can be harmful. Also, keep button cells hidden from small children as they can swallow these batteries.
Even though environmentally unfriendly, lead acid batteries continue to hold a strong market niche, especially as a starter battery. Wheeled mobility and UPS systems could not run as economically if it were not for this reliable battery. NiCd also continues to hold a critical position among rechargeable batteries as large flooded NiCds start jet airplanes and propel sightseeing boats in rivers of larger cities. Although pollution-free, these batteries are in decline.
Batteries with toxic substances will continue to be with us and there is nothing wrong in using them as long as they are being disposed of properly. Each battery chemistry has its own recycling procedure and the process begins by sorting the batteries into the correct categories.
Lead Acid: Recycling of lead acid began with the introduction of the starter battery in 1912. The process is simple and cost-effective as lead is easy to extract and can be reused multiple times. This led to many profitable businesses and the recycling of other batteries.
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In late 2013, smelters started to report an increased number of Li-ion batteries being mixed in with lead acid, especially in starter batteries. This can cause fires, leading to explosion and personal injury. The physical appearance of lead acid and Li-ion packs are similar and sorting at high volume poses a challenge. For consumers, a battery is a battery and folks are enticed to recycle all batteries, never mind the chemistry. As more lead acid are being replaced with Li-ion, the problem will only escalate. From 2010–2013, there has been a 10-fold increase in reported incidents of infiltration of Li-ion with lead acid. Please note that Li-ion is more volatile when stripped than lead acid. Presorting is done for safety reasons and not to separate hazardous material. Lead acid is benign but toxic, Li-ion is non-malignant but explosive. |
Figure 1: Lead acid are the mose recycled batteries. Recycling is profitable Source: Johnston Controls |
The Society of Automotive Engineers (SAE) and the International Electrotechnical Commission (IEC) initiate action through increased awareness, employee training, battery identification and labeling. X-ray technologies to separate batteries are being explored and “who carries the liability?” is being asked. Battery manufacturers put the responsibility on the recyclers who in turn argue that the burden and sustainability of a product must be borne by the manufacturer. The courts may become the arbitrators.
Nickel-cadmium: When NiCd batteries are disposed of carelessly, the metallic cell cylinder eventually corrode in the landfill. Cadmium dissolves and seeps into the water supply. Once contamination begins, authorities are helpless to stop the carnage. Our oceans already show traces of cadmium (along with aspirin, penicillin and antidepressants) but scientists are not certain of its origin.
Nickel-metal-hydride: Nickel and the electrolyte in NiMH are semi-toxic. If no disposal service is available in an area, individual NiMH batteries can be discarded with other household waste in small quantities; however, with 10 or more batteries, the user should consider disposal them in a secure waste landfill. The better alternative is taking the spent batteries to a neighborhood drop-off bin for recycling.
Primary Lithium: These batteries contain metallic lithium that reacts violently when in contact with moisture and must be disposed of appropriately. If thrown in a landfill in a charged state, heavy equipment operating on top could crush the cases and the exposed lithium could ignite a fire. Landfill fires are difficult to extinguish and can burn for years underground. Before recycling, apply a full discharge to consume the lithium content. Primary lithium batteries (lithium-metal) are used in military combat, as well as in watches, sensors, hearing aids and memory backup. A lithium-metal variety also serves as alkaline replacement in AAA, AA and 9V formats. Li-ion for mobile phones and laptops do not contain metallic lithium.
Lithium-ion: Li-ion is reasonably harmless but spent packs should be disposed of properly. This is done less to retrieve valuable metals, as is the case with lead acid, than for environmental reasons, especially with the growing volume used in consumer products. Li-ion contains harmful elements that are at the toxicity level of electronic devices.
With the increasing use of Li-ion, the European Commission report named “Towards the Battery of the future” delivers warnings because of the large number of batteries that will meet end-of-life. In Europe, Li-ion cannot be landfilled because of toxicity and danger of explosion, nor can they be incinerated as the ashes are also toxic in landfill. Of concern is cobalt and agents that bind electrode materials together.
The report no longer brands lead acid as the most toxic battery. Lead acid is the only battery that can be recycled profitably. With almost 100% of lead acid being recycled, the focus shifts to Li-ion because of growing volume and value of retrievable materials.
According to an ATZ report (2018), the 33kWh Li-ion traction battery of the BMW i3 electric vehicle contains 2kg (4.4 lb) cobalt, 6kg (13 lb) lithium, 12kg (26 lb) manganese, 12kg (26 lb) nickel and 35kg (77 lb) graphite. Not all retrieved materials may reach battery-grade quality when recycled but the gained resources can be used for less demanding purposes. Lithium is also used as a lubricant.
Progress is being made and Duesenfeld GmbH demonstrates an innovative method that uses 70% less energy to recycle lithium-ion batteries that with traditional smelting furnaces. Figure 1 illustrates the recycling plant for electric vehicle batteries in Germany.
The recycling process of Li-ion batteries normally begins with deactivation involving a full discharge to remove the stored energy and prevent a surprise thermal event. The electrolyte can also be frozen to prevent electrochemical reactions during the crushing process. Duesenfeld patented a process that evaporates and recovers the organic solvents of the electrolyte in a vacuum by condensation. This process is said to not produce toxic exhaust gases. In Figure 2, technicians disassemble EV batteries for recycling.
The following steps are divided into mechanical, pyrometallurgical and hydrometallurgical treatments. Mechanical involves crushing the battery cells; pyrometallurgical extracts the metals by thermal treatment; and hydrometallurgy involves aqueous processes.
Once disassembled, sorting separates copper foil, aluminum foil, separator and the coating materials. Nickel, cobalt and copper can be recycled from the cast, but lithium and aluminum remain in the slag. A hydrometallurgical process is necessary to recover lithium. This includes leaching, extraction, crystallization, and precipitation from a liquid solution. Hydrometallurgical treatment is used to recover pure metals, e.g. lithium, gleaned from separated coating materials after mechanical processes or from slag in pyrometallurgical processes.
Umicore in Belgium uses a furnace to melt the batteries directly to recover 95% of cobalt, nickel and copper. After the furnace, Umicore uses a special gas washing process to clean the toxic incineration products from the fluorine containing exhaust gases.
To reduce the dangers of fire incidents during the recycling process, smaller recyclers incinerate lithium-ion batteries externally in special waste treatment facilities before doing mechanical separation.
Duesenfeld in Germany discharges the batteries, crushes them in inert atmosphere, evaporates and re-condenses the organic solvents of the electrolyte and separates the electrode coating material from the rest. The metals are then leached from the former active materials. The graphite is filtered and regained, after which lithium-carbonate, nickel-sulfate, cobalt-sulfate and manganese-sulfate are produced. This recycling process yields more metals than with the Umicore thermal method. The CO2 footprint is also reduced while saving energy and lowering the formation of hazardous gases.
Alkaline: After lowering the mercury content in alkaline batteries in 1996, many territories now allow disposing these batteries as regular domestic trash; however, California considers all batteries hazardous waste. In Europe, lead acid, NiCd, mercury containing batteries, unsorted collections of multiple battery types, and battery electrolytes are considered hazardous waste. All others can pass as non-hazardous. Most stores selling batteries are also required to take back spent batteries. Alkaline batteries contain the reusable materials of zinc and manganese but the retrieval process is a liability. Efforts are made to increase the recycling of alkaline cells from the low 4 percent in 2015 to 40 percent in 2025.
In North America, Retriev Technologies, formerly Toxco, and the Rechargeable Battery Recycling Corporation (RBRC) collect spent batteries and recycle them. While Retriev has its own recycling facilities, RBRC is in charge of collecting batteries and sending them to recycling organizations. Retriev in Trail, British Columbia, claims to be the only company in the world that recycles large lithium batteries. They receive spent batteries from oil drilling in Nigeria, Indonesia and other places. They also recycle retired lithium batteries from the Minuteman missile silos and tons of Li-ion from war efforts. Other divisions at Retriev recycle nickel-cadmium, nickel-metal-hydride, lead, mercury, alkaline and more.
Europe and Asia are also active in recycling spent batteries. Among other recycling companies, Sony and Sumitomo Metal in Japan and Umicore in Belgium have developed technology to retrieve cobalt and other precious metals from spent lithium ion batteries.
Umicore uses an ultra-high temperature (UHT) processes to recycle Li-ion and NiMH batteries. Spent packs are dismantled and melted in an UHT furnace. The derbies are separated into metal alloy containing copper, cobalt and nickel, and slag, a stony waste containing rare earth metals. Slag can be further processed to recover lithium, but producing battery-grade lithium is not yet economical and the slag is used for construction. Methods are being developed to extract lithium for reprocessing into lithium carbonate for Li-ion production. With an anticipated 10-fold growth in the use of Li-ion batteries between 2020 and 2030, the reuse of lithium could become economical so the metals end up in battery production again much like lead for lead acid batteries.
Recycling Process
Recycling starts by sorting batteries into chemistries. Collection centers place lead acid, nickel-cadmium, nickel-metal-hydride and lithium ion into designated drums, sacks or boxes. Battery recyclers claim that recycling can be made profitable if a steady stream of batteries, sorted by chemistry, is made available.
The recycling process begins by removing the combustible material, such as plastics and insulation, with a gas-fired thermal oxidizer. Polluting particles created by the burning process are eliminated by the plant’s scrubber before release into the atmosphere. This leaves the clean and naked cells with metal content.
The cells are then chopped into small pieces and heated until the metal liquefies. Non-metallic substances are burned off, leaving a black slag on top that a slag arm removes. The alloys settle according to weight and are skimmed off like cream from raw milk while still in liquid form.
Cadmium is relatively light and vaporizes at high temperatures. In a process that appears like a pan of water boiling over, a fan blows the cadmium vapor into a large tube that is cooled with water mist. The vapors condense to produce cadmium that is 99.95 percent pure.
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, 24kg) or “hogs” (2,000 pounds, 746kg). Other battery recyclers use nuggets (7 pound, 3.17kg). The pigs, hogs and nuggets are shipped to metal recovery plants where they are used to produce nickel, chromium and iron for stainless steel and other high-end products.
To reduce the possibility of a reactive event during crushing, some recyclers use a liquid solution or freeze lithium-based batteries with liquid nitrogen; however, mixing Li-ion starter batteries with the common lead acid type still remains a problem as a charged Li-ion is far more explosive than lead acid.
Battery recycling is energy intensive. Reports reveal that it takes 6 to 10 times more energy to reclaim metals from some recycled batteries than from mining. The exception is the lead acid battery, from which lead can be extracted easily and reused without elaborate processes. To some extent, nickel from NiMH can also be recovered economically if available in large quantities.
New recycling methods are being developed that retrieve the metals by electrolysis, also knowns as chemical recycling. The process is said to be more cost effective and produces higher yields with less pollutants than traditional smelting. One such alternative to recycle lead acid batteries has been developed by Aqua Metals. This technology has the potential of revolutionizing traditional melting methods. An electrochemical process separates the lead by breaking down metals into nanoscopic sizes particles that are dispersed in water to create a hydro-collodial metal. The process is called AquaRefining. Technical issues are delaying full implementation at this time.
Each country sets its own rules and adds tariffs to the purchase price of a new battery to make recycling feasible. In North America, some recycling plants invoice by weight and the rates vary according to chemistry. While NiMH yields a fairly good return with nickel, the spent NiCd battery is less in demand because of soft cadmium prices. Due to poor metal retrieval value, Li-ion commands a higher recycling fee than most other battery types.
Recycling Li-ion batteries is not yet profitable must be government subsidized. There is an incentive to recover costly cobalt. No recycling technology exists today that is capable of producing pure enough lithium for a second use in batteries. Lithium for batteries is mined; second hand lithium is used for lubricants, glass, ceramics and other applications.
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