In Japan refuse-derived fuel (RDF) pellets are used as fuel in energy plants. Garbage is processed and converted into uniform pellets. These may spontaneously combust under certain circumstances.
Conditions for spontaneous combustin of RDF pellets:
(1) The pellets contain a high number of bacteria.
(2) The pellets are exposed to moisture.
(3) Under the right conditions the bacteria will proliferate and ferment the pellet contents, with generation of heat and a combustable gas (hydrogen, methane, other).
(4) The storage facility is poorly ventilated, with accumulation of the gases.
(5) If the mass becomes hot enough or if there is an ignition source, then combustion can take place with fire and/or explosion.
Prevention:
(1) Keep the pellets dry.
(2) Make sure that the storage facility is well-ventilated.
(3) Use temperature probes to monitor temperature of the pellets.
(4) Use gas sensors to detect high concentrations of combustible gas.
(5) Presence of a fire suppression system.
