The concern is actually true.
Landfill fires are usually caused by discarded batteries, be they alkaline, Nickel Cadmium (NiCd), Nickel Metal Hydride (NIMH), or Lithium Ion ( Li-ion ). All off these batteries are commonly tossed in the trash by the end user. Fires are also started from petroleum distillate soaked shop rags, or similar material, spontaneously combusting. The third usual cause is fire started by green, mulched, organic matter which ignites when in a large enough concentration to reach temperature while fermenting.
A landfill not from from me averages 2 landfill fires per year. The fire crews have a bad time extinguishing those fires.