Underground fires induced by disposed Li-ion battery in peatland and landfill

Battery-induced fires have become an increasing concern, posing significant environmental and safety risks. This work investigates the smoldering ignition of underground fire in peatland and landfill by disposed Lithium-ion batteries. Both internal and external short circuits of the 18650 cylindrical battery cell are triggered to initiate an in-depth fire of typical landfill soil waste with various moisture contents. Results show that a minimum state of charge (SOC) of 50 % is required for a single-battery thermal runaway to initiate a smoldering fire in the dry waste, which increases with waste moisture. About 18 ± 5 % of battery energy is transferred to the waste within 6–10 min as effective heating for smoldering ignition. For external short circuits, the major ignition source is the Joule heating of the external resistor, not the heating from the battery itself. The propensity of ignition is controlled by both heating intensity and duration, so it varies with the battery SOC and external resistance. A fully charged cell (internal resistance of 35 mΩ) requires a minimum external resistance of 60 mΩ to ignite the dry waste. If the moisture of waste reaches 30 % or above, a single cell cannot initiate a smoldering fire, regardless of external or internal short circuits in current test setups. This work reveals a possible mechanism of landfill fires induced by disposed battery failure and thermal runaway, highlights fire safety issue of disposed batteries, and supports wildfire prevention and suppression strategies for landfills.