If rotting vegetation produces sulfer, could it reach a point at which it would be combusitble?

Answer 1

There's more to self-heating and spontaneous combustion than sulfur. Sulfur isn't really "produced" by decomposing vegetable matter; it's already present in amino acids and other components of the cell, and its composition is unlikely to change substantially during decomposition. It'll remain present as organic compounds.

However, as has already been noted, decomposing vegetable matter can produce methane (CH4), which is quite flammable and very useful as a cooking gas. Other gases are produced in smaller amounts.

With respect to spontaneous combustion, under some circumstances it is possible for sufficient heat to build up such that flame may break out. Spontaneous combustion (SC) may occur when there is sufficient moisture to encourage bacterial and fungal growth, and there is enough physical bulk to allow the pile to insulate. Most common are hay bale fires, in which some amount of moisture is either introduced to cut and baled hay, or hay is mown and baled with too much moisture (i.e., the hay is not allowed to cure in the field before baling). At some point, enough heat is generated that the bacteria and fungi are killed, and oxidative processes take over; under the right conditions, the heat generated catalyzes further heat production, and eventually open flame if there is a path to open air so the fire can "breathe."

Insidious, and now (fortunately) quite uncommon due to improvements in storage and handling of organic products.

Answer 2

As long as the composting mass meets the four requirements for combustion, it's possible.

Fuel, oxygen, temperature and the ability for the nuclear reaction that takes place during combustion. These are all requirements for fire to start and maintain itself.

In a compost heap, there is an abundance of fuel, oxygen and nuclear reaction potential. The only thing missing is temperature. Sulfur has a flash point of 405 degrees Fahrenheit.

I've never heard of a compost heap getting anywhere near that temperature. Therefore, I can't think of any natural way in which rotting vegetation would spontaneously combust.

Answer 3

Yes. Marsh gas is another name for methane, which is combustible. Hydrogen sulphide is also combustible, and also produced from rotting vegetation. Here in Southland, NZ, we've got big coal seams which also contain methane gas, which must have been produced by this process when the coal vegetation rotted, millions of years ago.