Following on from last week’s article about making the most of your batteries and keeping them out of landfill, this week we will cover off a basic overview of the recycling process for batteries.
A reminder of the type of batteries that can be recycled:
- Lead acid – exit lighting, automotive applications.
- Alkaline batteries – AA, AAA, C & D size and rectangular 6 & 9 volt batteries – remote control cars, portable radio’s etc
- Nickel Cadmium, Nickel Metal Hydride & Lithium Ion – typically rechargeable batteries for use in electronic and photographic equipment, including mobile phones, game boys etc
- Button cell – watches, hearing aids.
Battery Recycling processes:
The battery is broken apart in a hammer mill; a machine that hammers the battery into pieces.
The broken battery pieces are then placed into a vat, where the lead and heavy materials fall to the bottom and the plastic floats. At this point, the polypropylene pieces are scooped away and the liquids are drawn off, leaving the lead and heavy metals. Each of the materials goes into a different recycling “stream”.
Polypropylene pieces are washed, blown dry, and sent to a plastic recycler where the pieces are melted together into an almost liquid state. The molten plastic is put through an extruder that produces small plastic pellets of a uniform size. The pellets are sold to a manufacturer of battery cases and the process begins again.
Lead grids, lead oxide, and other lead parts are cleaned and heated within smelting furnaces. The molten melted lead is then poured into ingot moulds. After a few minutes, the impurities float to the top of the still molten lead in the ingot moulds. These impurities are scraped away and the ingots are left to cool. When the ingots are cool, they’re removed from the moulds and sent to battery manufacturers, where they’re re-melted and used in the production of new batteries.
Old battery acid can be handled in two ways:
1. The acid is neutralised with an industrial compound similar to household baking soda. Neutralisation turns the acid into water. The water is then treated, cleaned, and tested in a waste water treatment plant to be sure it meets clean water standards.
2. The acid is processed and converted to sodium sulphate, an odourless white powder that’s used in laundry detergent, glass, and textile manufacturing.
Alkaline/Zinc Carbon/Zinc Air battery recycling process
These batteries are recycled during steel making processes, where they’re placed in a molten mill furnace as a feedstock. The zinc from the batteries is fumed off into a vacuum baghouse for recovery, while the end metal product is used to make low-grade steel (i.e. rebar)
Nickel-Cadmium, Nickel Metal Hydride, and Lithium Ion battery recycling process
These batteries are recycled via a High-Temperature Metal Reclamation (HTMR) process, during which all of the high temperature metals contained within the battery feedstock (i.e. nickel, iron, cobalt, manganese, and chromium) report to the molten-metal bath within the furnace, amalgamate, then solidify during the casting operation. The low-melt metals (i.e. zinc, lithium, and cadmium) separate during the melting operation and are collected as a metal-oxide.
Lithium battery recycling process
The contents of the batteries are exposed using a shredder or a high-speed hammer depending on battery size. The contents are then submerged in caustic (basic not acidic) water. This caustic solution neutralises the electrolytes, and ferrous and non-ferrous metals are recovered. The clean scrap metal is then sold to metal recyclers. The solution is then filtered. The carbon is recovered and pressed into moist sheets of carbon cake. Some of the carbon is recycled with cobalt. The lithium in the solution (lithium hydroxide) is converted to lithium carbonate, a fine white powder. What results is technical grade lithium carbonate, which is used to make lithium ingot metal and foil for batteries. It also provides lithium metal for resale and for the manufacture of sulphur dioxide batteries.
Source for content: CMA Ecocycle