This is news story from Nashville: May 7, 2001 Investigators believe spontaneous combustion sparked a fire that destroyed a Nashville mulch company over the weekend. Flames could be seen for miles as tons of mulch went up in smoke yesterday. Dozens of firefighters worked for seven hours to bring the blaze under control. At one point flames and smoke became so intense three firefighters were treated for heat exhaustion. Investigators say mulch is mixed with fly ash, which is coal dust and that can ignite spontaneously. They recommend if you have mulch in your garden you periodically wet it down to prevent it from igniting in the same manner. This appears to be the Black/Midnight mulch that caught fire. Just thought I'd pass this along.