How ALS2 Recovers Silver From Silver Oxide Button Cells
Australians toss around a staggering number of button-shaped batteries every year, often without thinking about the small but valuable silver hidden inside. From hearing aids on the kitchen bench to quartz watches left in a bedside drawer, these coin-sized cells slip into kerbside bins, e-waste skips and the battery collection buckets at hardware stores across the country. Silver oxide button cells are particularly common because they power devices that suit Australia's large and ageing population, and they tend to be replaced rather than recharged. That creates a steady, predictable stream of silver-bearing waste that recovery technologies can target.
The challenge is extracting that silver from a messy mix of household electronics, alkaline AA cells, lithium coin cells and assorted printed circuit boards, without the safety and environmental headaches that come with strong mineral acids. ALS2, developed under Ikoi S.p.A.'s acidless separation project and supported through the European Union's Horizon 2020 programme, offers a route that sidesteps aqua regia and cyanide leaching. The following sections walk through how the technology works and where it slots into compact recovery plants built for regional Australian conditions.
Why Silver Oxide Cells Matter in Mixed Waste
Silver oxide batteries look like coins but they pack a quiet metallurgical punch. A typical SR626SW cell, the kind that keeps a wristwatch running for years, contains roughly 0.3 grams of high-purity silver compressed into a zinc anode, silver oxide cathode and a potassium hydroxide electrolyte. Multiply that by the millions of cells that reach end-of-life annually across Australian households, hospitals and aged-care facilities, and the silver concentration in the urban waste stream becomes commercially interesting.
The trouble is heterogeneity. A bag of spent button cells gathered through a kerbside battery drive in Brisbane will contain silver oxide cells from watches, mercury-free alkaline button cells, lithium manganese dioxide coin cells and the occasional mercuric oxide relic from an old calculator. Mixed in with these are cracked plastic shells, paper separators, steel casings and tiny amounts of residual electrolyte. Traditional pyrometallurgical smelters, the kind that have served Broken Hill and Kalgoorlie-style operations for over a century, can handle volume but lose silver to slag and generate fumes that modern regulators dislike.
Hydrometallurgical routes using nitric acid or aqua regia dissolve silver efficiently but require acid-resistant vessels, scrubbers for nitrogen oxide emissions and careful downstream handling of acidic effluents. For a mid-sized recycler operating out of a warehouse in suburban Sydney or a regional hub near Newcastle, that infrastructure is often a deal-breaker. The ALS2 approach was engineered precisely for that scale, with reagent chemistry that prefers alkaline conditions over highly corrosive ones.
Comparing Silver Recovery Routes
Before zooming in on ALS2, it helps to recall the broader landscape of silver recovery options a recycler in Melbourne or Perth might weigh today. Each route carries different trade-offs in chemical inputs, effluent handling, yield and suitability for the messy button-cell stream that arrives at the gate. The figures below are typical operating ranges drawn from publicly available feasibility work and the project's own technical literature, not guarantees for any specific feed.
| Recovery Route | Chemical Inputs | Effluent Profile | Silver Yield | Suitability for Mixed Button Cells |
|---|---|---|---|---|
| Pyrometallurgical smelting | Coke, fluxes, oxygen | Slag, off-gas, dust | 85-92% | High volume, low selectivity |
| Aqua regia leaching | Nitric + hydrochloric acid | Acidic washwater, chloride salts | 95-99% | Strong on silver, weak on selectivity |
| Cyanide leaching | Sodium cyanide, oxygen | Cyanide tailings, treated wastewater | 90-95% | Effective but heavy regulatory load |
| ALS2 acidless separation | Alkaline leach, selective reagents | Closed-loop recirculated liquor | 92-97% | Designed for mixed button cells |
Acid-based and cyanide-based routes can hit high yields, but they also pull in heavy permitting obligations around effluent discharge, occupational exposure and community consultation. ALS2 trades a small slice of peak yield for a much friendlier permitting profile, which often matters more in a metropolitan council area than the last few percentage points of recovery efficiency.
Inside the Acidless Separation Process
ALS2 stands for the project's acidless separation line and is built around a multi-stage aqueous chemistry that does not rely on concentrated mineral acids. Crushed button cells first pass through a size-reduction step that liberates the cathode material from steel casings. A gentle alkaline leach then mobilises zinc from spent anodes while leaving silver oxide largely intact, because silver oxide is far less soluble in alkaline media than in acidic ones.
The silver-bearing fraction is then routed to a selective precipitation stage, where a reagent mix tuned through the Horizon 2020 research programme pulls silver out of solution as a clean silver chloride or directly as metallic silver, depending on downstream needs. A polishing step recovers residual precious metal from the pregnant liquor, lifting overall yield into the range shown above. Every reagent in the chain is recirculated within closed loops, which keeps wastewater volumes low and sidesteps the heavy-metal neutralisation burden that drags down the economics of acid-based plants.
The closed-loop architecture matters because Australian regulators, both state and federal, have tightened the rules around e-waste processing under product stewardship obligations. A recycler who can show that their silver recovery line operates without fuming nitric acid baths or cyanide stripping columns has an easier time getting planning approval in a metropolitan council area. That alone can shave months off a project timeline.
Compact Plant Footprint and Modular Scaling
ALS2 was designed for compact precious-metals recovery plants, the kind that fit inside a 20-foot shipping container or a corner of an existing transfer station in regional South Australia. Modularity is the philosophy, with each stage packaged as a skid-mounted unit that can be added or removed as feed volumes change. A small operation might start with a single cell-crushing module and a precipitation skid, while a larger hub near Adelaide or Geelong could add an electrolytic refining cell and an X-ray fluorescence analyser for in-process assay.
Energy draw is modest, mostly for agitation, pumping and gentle heating of the alkaline leach, which keeps operating costs compatible with Australia's industrial electricity tariffs. There is no furnace running at 1,200 degrees Celsius, no oxygen lance and no acid regeneration plant. For a business evaluating the technology, that translates into a leaner capex envelope and fewer occupational health obligations around fume extraction and PPE for acid handling.
Another practical advantage is the technology's tolerance for feed variability. Silver oxide cells from European watch brands differ from cells made in Chinese factories, and alkaline button cells from Japanese makers behave differently under leach conditions. ALS2's reagent profile was developed across a wide range of button-cell chemistries, which gives operators the flexibility to accept whatever arrives at the dock without expensive feed-blending campaigns. For a regional recycler in Perth or Townsville, that flexibility is often the difference between a viable business case and a stranded asset.
Australia's E-Waste Reality and the Silver Opportunity
Australia produces roughly 20 kilograms of e-waste per person each year, putting it near the top of OECD rankings and well ahead of many European countries. The National Television and Computer Recycling Scheme captures larger items, while button cells slip through informal channels including the battery bins at Bunnings, Officeworks collection points, council hard-rubbish pickups and dedicated drop-off days run by organisations such as MobileMuster. The volumes gathered through these schemes are growing, and the silver concentration in button cells makes them an attractive target for a localised recovery loop.
Silver is also quietly important to Australia's energy transition. The country leads the world in rooftop solar penetration, and silver paste sits at the heart of every crystalline silicon panel. Recovering silver from spent button cells and feeding it back into the photovoltaic supply chain closes a loop that resonates with national net-zero commitments and with state-based circular-economy roadmaps in Victoria, New South Wales and Western Australia.
There is a cultural angle too. Australians talk about "doing the right thing" with waste, and the phrase pops up regularly in council communications, school science competitions and the signage at local transfer stations. A silver recovery line that demonstrably avoids aqua regia and cyanide speaks directly to that instinct, and gives recyclers a story to tell when they engage with local media, schools and community workshops.
If you operate a recycling facility in Australia and want to explore how ALS2 can plug into your existing e-waste line, the project team welcomes enquiries through the contact page of the ALS2Project website. Technical briefings, sample feed evaluations and feasibility scoping are available for processors weighing a move away from acid-based refining toward a cleaner, modular silver recovery workflow. Reach out today to see how an acidless separation line could fit your operation and help you build a credible silver recovery story for your local community.