Batteries contain toxic metals and flammable chemicals that can contaminate soil and water or start fires at waste facilities. That’s the short answer. The longer answer depends on what type of battery you’re dealing with, because the rules and risks differ significantly between the standard alkaline batteries in your TV remote and the lithium-ion cells in your phone or laptop.
What’s Actually Inside a Battery
Lithium-ion batteries, the rechargeable type found in phones, laptops, power tools, and electric vehicles, contain a cocktail of metals including copper, nickel, lead, and cobalt. They also contain organic electrolytes that are both toxic and flammable. Testing by researchers at the National Institutes of Health found that defunct lithium-ion batteries exceed federal hazardous waste limits for lead, and under California’s stricter standards, they blow past limits for cobalt (by roughly 20 times), copper (by nearly 40 times), and nickel (by about 5 times).
Older rechargeable battery types like nickel-cadmium cells carry their own risks, which is why federal law (the Mercury-Containing and Rechargeable Battery Management Act) specifically targets them for recycling. Single-use alkaline batteries are the mildest of the bunch. They no longer contain mercury, which was phased out in the 1990s, and many jurisdictions do allow them in regular household trash. But rechargeable batteries of any kind are a different story entirely.
The Fire Problem
The most immediate danger of tossing batteries in the trash isn’t chemical contamination. It’s fire. When lithium-ion batteries are crushed, punctured, or compressed inside a garbage truck or at a sorting facility, they can short-circuit and ignite. The resulting fires are intense, difficult to extinguish, and increasingly common.
In 2024, publicly reported fires at waste and recycling facilities across the U.S. and Canada jumped 15% over the previous year, reaching 430 incidents. Fires at material recovery facilities and transfer stations specifically rose 20%. Lithium-ion batteries are considered the primary cause of many of these fires, and one MRF operator described the problem as far back as 2018 as an “existential threat” for the municipal recycling industry. These facilities are full of cardboard and mixed paper, so a single battery spark can turn into a building-scale blaze.
This isn’t just a risk for waste workers. Garbage truck fires caused by batteries have become routine in many cities, sometimes happening on residential streets.
What Happens in a Landfill
Batteries that survive the collection process intact and end up buried in a landfill create a slower but lasting problem. The metals inside, particularly lead, cobalt, copper, nickel, and chromium, are persistent and non-biodegradable. As battery casings corrode over time, these metals dissolve into their most toxic ionic form and can leach into surrounding soil and groundwater.
Once in the environment, heavy metals don’t break down. They accumulate in biological systems through a process called biomagnification, moving up the food chain from contaminated water to plants to animals to people. Exposure pathways include drinking contaminated water, eating food grown in contaminated soil, or direct contact. The health risks associated with chronic exposure to these metals range from kidney damage and neurological problems (lead and thallium) to respiratory issues and increased cancer risk (cobalt, nickel, and chromium).
Valuable Materials Lost Forever
Beyond the environmental damage, throwing batteries away wastes finite resources. Lithium-ion batteries contain significant quantities of cobalt, nickel, copper, and lithium, all of which are mined at considerable environmental and human cost. Professional recycling can recover these metals for reuse in new batteries, reducing the need for additional mining.
The current recovery rate tells a sobering story: worldwide, less than 1% of lithium is recovered from spent lithium-ion batteries. Much of it is lost during high-temperature recycling processes, where lithium ends up in slag and dust. Every battery that goes to a landfill instead of a recycler makes this gap worse. As demand for these metals grows with the expansion of electric vehicles and renewable energy storage, recovering them from old batteries becomes increasingly important.
What the Law Says
The EPA has determined that most lithium-ion batteries on the market today qualify as hazardous waste when disposed of, based on both their ignitability and reactivity. For businesses, the federal recommendation is to manage all used lithium batteries under “universal waste” regulations, which set rules for labeling, storage time, and where the waste can be sent. Businesses generating fewer than about 220 pounds of lithium batteries and other hazardous waste per month face reduced requirements but still can’t simply throw them in a dumpster.
For households, federal rules are actually more lenient. Under RCRA (the main federal hazardous waste law), household hazardous waste is excluded from the definition of hazardous waste as long as it isn’t mixed with non-household waste. This means that technically, under federal law, you can put household batteries in your trash. But many states have enacted stricter battery recycling laws that override this federal exemption. California, Vermont, and several other states require recycling of various battery types. Your local rules may differ significantly from the federal baseline.
How to Dispose of Batteries Safely
The type of battery determines what you need to do. Single-use alkaline batteries (AA, AAA, C, D, 9-volt) can go in household trash in most states, though recycling is still the better choice. The one exception among single-use batteries is the 9-volt: its two terminals are close together on top and can spark against metal objects or other batteries. Tape over the terminals with electrical or masking tape before disposal.
Rechargeable batteries of any kind, including lithium-ion, nickel-cadmium, and nickel-metal hydride, should never go in your regular trash or curbside recycling bin. Tape the terminals on these as well to prevent short circuits during transport. For drop-off locations, many hardware stores, electronics retailers, and home improvement chains accept rechargeable batteries at no charge. The Call2Recycle program, recommended by the EPA, maintains a searchable database of drop-off sites by zip code. Many municipal hazardous waste collection events also accept batteries of all types.
For lithium-ion batteries that are swollen, damaged, or visibly leaking, take extra precautions. Place them in a non-flammable container, ideally on sand or cat litter, and bring them to a hazardous waste facility rather than a retail drop-off. A damaged lithium battery is the type most likely to ignite, and that risk doesn’t go away just because the device stopped working.