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Before the invention of batteries, electricity could only be used when it was directly connected to a source. Batteries convert chemical energy into electrical energy by creating a flow of electrons between the anode and cathode through an electrolyte. This process powers everything from cell phones to emergency medical equipment.
Battery chemistry varies by type, but most contain hazardous metals such as cadmium, lead, mercury, nickel, and lithium, along with electrolytes. When discarded in landfills, the metal casing corrodes and leaches toxic substances into soil, groundwater, and ultimately the ocean. Lithium, in particular, can ignite underground fires that release hazardous gases, as documented by Battery University.
Exposure to the heavy metals in batteries poses serious health risks. The Agency for Toxic Substances & Disease Registry lists cadmium and nickel as carcinogens, lead as a cause of birth defects and neurological damage, and mercury as a potent neurotoxin. Although mercury has been banned from batteries since 1996, trace amounts can still be present in manufacturing by‑products.
Rechargeable batteries contain dangerous heavy metals and should always be recycled. Most new smartphones come with a prepaid return envelope so you can send the old device back for proper disposal. National programs like Call2Recycle accept used rechargeable batteries. Car batteries (lead‑acid) can be dropped off at local or state hazardous‑waste facilities, or many automotive supply stores will forward them to certified recyclers.
Single‑use alkaline batteries no longer contain mercury, thanks to the 1996 federal ban, so they can be placed in the trash. However, recycling them still reduces landfill burden and recovers valuable materials. Municipal recycling programs often accept them, and bulk recyclers such as Big Green Box provide convenient drop‑off points.
