SCV Outdoor Report: Spontaneous Combustion
By Wendy Langhans
The Guiberson fire, which is now burning in Ventura County near Fillmore and Moorpark, was possibly caused by spontaneous combustion in a manure pile. I know it sounds like a bad joke, but could it possibly be true? Can spontaneous combustion actually occur? And if so, how?
It's true. Fires have been caused by spontaneous combustion of manure. There are two factors that could contribute to this and both have to do with by-products of microbial activity. One factor is explosive gases. Anyone who's ever been downwind of a cow recognizes the "rotten-eggs" smell of hydrogen sulfide. When manure decomposes under anaerobic conditions (without oxygen), explosive gases such as methane and hydrogen sulfide are produced by anaerobic bacteria. Anaerobic decomposition could occur if the manure is contained in a tank or covered pit.
The second factor is heat production, a by-product of microbial respiration, a biochemical process common to all living creatures. In a compost pile (often containing manure), biochemical respiration will raise the internal temperature to about 70-80°C (158-176°F). At some point, the microbes will die off, and additional heat-releasing chemical reactions will begin, driving the temperature even higher, to 150°C (302°F). Compost materials will ignite when the temperature reaches between 150 and 200°C (302-392°F).
To summarize, "The combination of organic materials with low moisture contents in a large unmonitored pile with limited air exchange is a prescription for spontaneous combustion." In other words, it's not a bad joke. When you have:
• Relatively dry organic materials, with a moisture content of between 20 and 45% and
• A large pile - over 10 feet high, providing heat insulation and creating anaerobic conditions,
You have the potential for spontaneous combustion.
Upcoming Outdoor Events:
Saturday, September 26, at Placerita Canyon
Family Nature Walk
September 26, 2009 (11:00 am - 12:00 pm)
An easy, 1-hour walk exploring the area's natural and cultural history.
September 26, 2009 (1:00 pm - 2:00 pm)
See, learn and ask questions about live native animals of the area.
You can listen to stories like this every Friday morning at 7:10 a.m. on "The Hike Report", brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.
For the complete MRCA hike and activity schedule and for trail maps, click here or go to www.LAMountains.com.