The end use of lead-acid batteries is dominated by use in the automotive and other transportation (i.e. forklift trucks) industries. Each car battery contains around 12kg of lead, and with an estimated 1.4bn cars currently in the world that is over 16.8Mt of lead in circulation which will be able to be recycled in the future, and, with the average lifecycle of a car battery is 3-4 years the future is not too distant.

Uninterruptable Power Source (UPS) applications is another large user of lead-acid batteries. In systems such as back-up generators batteries spend most of their time idle. When they are used the UPS must discharge its batteries very rapidly and at a high current until the generators come online. When power is restored, the UPS recharges the batteries, then enter another extended waiting period. Lead-acid batteries are well suited to this type of intermittent use.

Recycling Process

Almost 100% of material in an ULAB can be recycled and infinitely reused with no degradation or loss of future performance. Schemes have also been implemented to make it financially rewarding to recycle ULABs giving them an extremely high recycling rate of over 90% in many countries.

The recycling of lead acid batteries involves two main steps: breaking and separation, and secondary lead refining.

The first step of the recycling process is battery breaking, literally breaking open the batteries in a hammermill and extracting and sorting the component parts including lead paste, metallic plates and connectors, polypropylene and other plastics, and acid electrolyte.

The lead, in the form of lead metal and paste, from the breaking and separation process, is refined in a secondary lead smelting process, that produces lead in bullion form.

The sulfuric acid can be converted to sodium sulphate which is commonly used in fertilisers and laundry detergents and the plastic polypropylene container is output as pellets for reuse in new battery containers and other plastic products.

In the recycling process there is less than 3% of the battery which is not able to be recycled and is sent to the landfill.

Benefits of Battery Recycling

Recycling keeps more than 130 million lead-acid batteries out of landfills each year. Approximately 80% of a lead-acid battery consists of recycled materials, which include lead and plastic components. The major benefits of recycling ULABs include; ensuring unsafe and environmentally damaging materials are properly handled and do not enter the environment. Recovering expensive metals and materials which also helps to ensure a consistent supply and helps to drive down the cost of new batteries.

Risks/Hazards

Recycling of ULABs is not only vital for supporting the future supply, but also for environmental reasons. Lead is high toxic, there are currently no known levels of lead exposure that are considered safe. If any lead enters the atmosphere it can lead to huge consequences to both the environment and health leading to birth defects, delayed development, neurological problems and even death.

Lead-acid batteries are covered under the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and Their Disposal is an international treaty that was designed to reduce the movements of hazardous waste between nations, and specifically to prevent transfer of hazardous waste from developed to less developed countries. The Convention entered into force in May 1992. This sets out guidelines to improve recycling of old batteries and protect human health and the environment.

Future Recycling Growth

Lead-acid batteries will play an essential part in the global transition to green energy sources. With ambitious global targets to achieve the 2015 Paris Agreement of limiting global warming to well below 2C, preferably to 1.5C, compared to pre-industrial levels, new low carbon emitting and green energy solutions are booming. With countries such as India, who are developing rapidly, having much later net-zero targets than the rest of the world, lead usage is predicted to continue to grow.

In traditional internal combustion engine (ICE) vehicles lead-acid batteries are used as a starting battery. The application is called starting, lighting, and ignition (SLI). Although the growth of electric modes of transportation will eventually result in fewer ICE vehicles, production of low-cost gasoline and diesel-powered cars in places such as India and Asia will keep demand high for decades to come.

In electric vehicles (EVs) lithium-ion batteries are the batteries of choice to power the traction motors, however, many continue to use lead-acid batteries to power the microprocessors that start up the system, and, to operate lighting and audio, and entertainment systems. The low voltage lead-acid battery is typically kept charged using a DC to DC converter which converts the high-voltage (typically 300-600V) from the lithium-ion battery pack to the low-voltage (12V) that maintains the charge of the lead-acid battery.

In intermittent renewables energy source like wind and solar an energy storage system is required to make them effective. This is because of the need to store the electricity when it is produced (i.e. when the wind is blowing or the sun is shining) as the supply is not guaranteed. The low cost of lead-acid batteries makes them a popular choice to store renewable energy for both small-scale home use and grid-scale industrial use.

 Lead-acid is frequently used in off-grid applications such as isolated microgrids, particularly where upfront costs can be a barrier. There is work being done to replace these batteries with zinc-ion or lithium-ion but the low-cost and high availability/reliability of lead-acid batteries mean they will still be used for years to come.