The Naked Scientists

The Naked Scientists Forum

Author Topic: Why will loose hay combust while baled hay won't?  (Read 4293 times)

Al MacDonald

  • Guest
Al MacDonald  asked the Naked Scientists:
   
Hi there, a friend of mine and I were chatting the other day and this question came up:

Why does loose hay that has been thrown into a pile have the possibility to spontaneously combust into flame but a round bale that seems to be more densely packed doesn't?

We live in Prince George BC and he spends time hunting deer on the farmers or ranchers properties in the Dawson creek area.
 
Thanks
 
Al MacDonald

What do you think?
« Last Edit: 20/01/2011 09:30:03 by _system »


 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Why will loose hay combust while baled hay won't?
« Reply #1 on: 20/01/2011 10:37:12 »
Here are notes here of spontaneous combustion.

http://www.bcg.org.au/cb_pages/images/AG1356_oct2008.pdf

This is some round bales in a field that caught fire.
http://dvmswife.blogspot.com/2010/09/round-bales-of-hay-for-sale.html

I always thought it was primarily a risk of stacking wet hay inside of a barn.  However, apparently it can also happen in the field too.

The round bales are generally baled with a harder outer shell that should help resist some weather, and a softer core.  There are ways to tarp them in the field. 

I always find it amazing that bugs can literally burn themselves up.  But, according to the notes above, it is a combination of heat resistant bugs, perhaps migrating away from the "core", and chemical processes. 

Also note,
I have also heard of biodiesel spontaneous combustion.  Usually involving vegetable oil/biodiesel, some type of wood, rags, or cellulose, and moisture.
 

Offline CZARCAR

  • Hero Member
  • *****
  • Posts: 686
    • View Profile
Why will loose hay combust while baled hay won't?
« Reply #2 on: 20/01/2011 18:24:03 »
bacteria in hay might also be a factor
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Why will loose hay combust while baled hay won't?
« Reply #3 on: 20/01/2011 18:43:13 »
I would think that bailed hay will reduce the rate at which oxygen can get to the bacteria, and it will also tend to resist combustion.
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Why will loose hay combust while baled hay won't?
« Reply #4 on: 20/01/2011 23:31:23 »
I would think that bailed hay will reduce the rate at which oxygen can get to the bacteria, and it will also tend to resist combustion.
Oxygen, of course, is the most efficient "fuel".
However, the anaerobes can do fine without it...  and produce METHANE.

One does need oxygen to progress from smouldering to open flames.
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Why will loose hay combust while baled hay won't?
« Reply #5 on: 21/01/2011 00:04:09 »
I would think that bailed hay will reduce the rate at which oxygen can get to the bacteria, and it will also tend to resist combustion.
Oxygen, of course, is the most efficient "fuel".
However, the anaerobes can do fine without it...  and produce METHANE.

One does need oxygen to progress from smouldering to open flames.

Apparently, haystack fires are caused by fermentation, which does require oxygen. I think that's probably also why compost piles have to be turned over from time to time.
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8669
  • Thanked: 42 times
    • View Profile
Why will loose hay combust while baled hay won't?
« Reply #6 on: 21/01/2011 18:21:38 »
Clifford,
converting one fuel (hay) into another (methane) doesn't generate nearly as much heat as oxidising it to CO2 and H2O.

Czarcar
the word "Bugs" is used  colloquially to refer to micro-organisms in general, particularly where you don't know what sort they are and it doesn't matter much. For examples fungi bacterial and protozoa may be involved here.

I'm pretty certain that the open access to air of a stack, rather than a bale, is the reason for the difference.



 

Offline CZARCAR

  • Hero Member
  • *****
  • Posts: 686
    • View Profile
Why will loose hay combust while baled hay won't?
« Reply #7 on: 21/01/2011 23:12:18 »
i burn sawdust 4heat & keep a pile in the cellar. called local university with concern 4 spontaneous combustion & was surprised to hear that wetter sdust  would be better able to spontaneously combust due to composting?
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Why will loose hay combust while baled hay won't?
« Reply #8 on: 22/01/2011 05:33:35 »
i burn sawdust 4heat & keep a pile in the cellar. called local university with concern 4 spontaneous combustion & was surprised to hear that wetter sdust  would be better able to spontaneously combust due to composting?

I know that making haystacks before the hay is sufficiently dry used to be a common cause of spontaneous combustion, so I would think the same could well apply to sawdust. Presumably silage does not self ignite because it is created in an environment where the intake of air is deliberately restricted.

BTW, the other nasty thing about sawdust is that if you get enough of it floating around in the air, it can produce one helluva explosion.

 

The Naked Scientists Forum

Why will loose hay combust while baled hay won't?
« Reply #8 on: 22/01/2011 05:33:35 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums