How to take care of button cells so we don’t all end up paying

Caring for the environment often involves making logical assessments about the impact an individual can have ¬– and then doing the right thing anyway. Does it still make sense to cycle to work in the rain the day after your neighbour brought home a brand-new SUV? Does it still make sense to put solar panels on the roof when so much energy went into making the microchips in their power control circuitry? If I usually recycle the big things, does it matter if I sometimes don’t recycle the small things?

Given the scale of the environmental challenge we face, perhaps it makes sense just to say, “We should do it anyway”, and leave logic out of the equation. And we are getting better at recycling the big things, such as plastic and glass bottles, paper, electrical goods, and food waste. But what about the little things, like batteries?

The European Commission certainly thinks recycling batteries is important. Back in 2006 it mandated their recycling and so today, many supermarkets, drug stores, and recycling centres have battery collection points. Some municipalities will take batteries during weekly rubbish collections. There’s more work to do, though. According to a recent study, of the 239,000 tonnes of batteries sold across the European Economic Area and Switzerland in 2018, only 47.4% were collected for recycling that year (ii).

The Commission went further in March 2020 (iii) when it adopted a circular economy action plan that sets a target for battery recycling of at least 60% by 2030 (iv). The plan says that the collection rate for batteries should rise to 65% in 2025 and 70% in 2030 . It also says that batteries must be recycled using processes that recover high proportions of the cobalt, lithium, nickel, and lead in them.

But what about watch batteries, also known as button cells? They’re often seen as too small to bother with, and are usually handled by professionals, such as jewellers and specialist repairers, who may feel they need a financial incentive to make the effort. Well, it turns out recycling them does matter.

Until 20 years ago, silver oxide watch batteries contained mercury, a toxin that, if allowed to escape into the environment, could end up in the human food chain. Mercury poisoning can damage nerves and vital organs such as the brain. Mercury can also pass through a pregnant woman’s placenta and into the foetus, causing congenital health issues for the baby. Clearly, these batteries need responsible handling throughout their entire lifecycle.

Despite the level of concern about mercury in button cells, it took until 2004 for Sony to announce the first mercury-free silver oxide batteries. A year later, mass production began at a Murata facility in Japan. The mercury-free button cells provide a similarly high charge capacity and power output as mercury-based cells, which enabled the Commission to ban the use of mercury in batteries in 2015.

The new cells are easier to recycle than mercury-based cells and, because they contain a tiny amount of silver, may offer recyclers a financial incentive for handling them.

Silver oxide batteries use silver oxide as the positive electrode (cathode), zinc as the negative electrode (anode), plus sodium hydroxide or potassium hydroxide as an alkaline electrolyte.

Once the battery case is removed, the contents are treated using one of two processes. In pyrometallurgical processing, the battery’s contents are put in a furnace to recover the precious metals. The alternative hydro-metallurgical processes dissolve the battery in acids. Both approaches are fast, expensive and emit toxic gases and chemicals (v). Pyrometallurgical processing also uses a lot of energy.

More eco-friendly processes are in development. For example, bioleaching uses micro-organisms to recover metals (vi). Another process, which uses sulphuric acid to both leach materials out of the battery directly and to enable electro-extraction, has shown promising results in feasibility studies (vii).

In any case, though, you’ll still have to save up at least 2.5kg of batteries to make it worthwhile (viii) to have them recycled at a specialist centre.

This is where jewellers and watch repairers come in, since they are in an ideal position to gather button cells easily and in sufficient volume to make it worthwhile to have them recycled. Usually, battery recycling services offer full traceability of the materials involved, as well as legal documentation that enables users to show they have recycled the cells in a responsible way.

So, is it worth sweating the small stuff, while also focusing on the big stuff? Given the challenges the environment faces and the example of the humble coin cell, absolutely.

i Directive 2006/66/EC of the European Parliament and of the Council of 6 September 2006 on batteries and accumulators and waste batteries and accumulators and repealing Directive 91/157/EEC, OJ L 266, 26.9.2006, p. 1
ii https://www.epbaeurope.net/assets/resources/Report-on-the-portable-battery-collection-rates-Short-Update-Mar-20-final-1.1.pdf
iii https://environment.ec.europa.eu/strategy/circular-economy-action-plan_en
iv https://ec.europa.eu/commission/presscorner/detail/en/ip_20_2312
v https://www.sciencedirect.com/science/article/abs/pii/S0959652612006282
vi https://www.sciencedirect.com/science/article/abs/pii/S0045653521006652
vii https://pubs.acs.org/doi/abs/10.1021/acssuschemeng.0c04701
viii https://www.archenterprises.com/silver-oxide-batteries.html