why does hay self combust?

[Marilyn]

Why does hay self combust? I don't understand?

 

[_jetset_]

I think it's more haylage when it gets warm in the plastic wrapper... The centre gets hotter and hotter and then... boom!

 

[Marilyn]

I've got a hay stack (about 5 bales high) and it's this years, cool as a cool thing (i've just put my arm in it) and although it's in the garage at the mo (until lean to outside up and running) it has been in a barn for a good few weeks now...will it be ok?

 

[H's mum]

It's the fermentation process which causes the "heating" - sometimes it can combust - sometimes when you open haylage you can feel it quite warm inside - Also when feeds are known as "heating" feeds - it's not because they make the horse "hot" necessarily - but it's referring to the same fermentation process which goes on in the digestive tract which is "heating" - (It also can make horses "hot" headed though!)
Hope this explains it ok?
Kate x

 

[Marilyn]

is my hay going to go up?!

 

[_jetset_]

I think there should be some ventilation where there is a lot of hay, that's why people have them in open fronted barns. Can you leave your garage door open?

 

[Marilyn]

The door has been open in the day and there's a window open. It's double garage that's only half full so there's plenty of air moving around it...it's 100 bales

 

[Santa_Claus]

Hay will catch on fire if it has not fully dried out when baled and then is stored without adequate ventilation. It is rare but it can happen.

 

[allijudd]

Santa is right,
So long as the hay was baled dry there should be no problem. But if there is any green in the crop ( i mean really green fresh grass) there is a risk it could go up. But that said, if it has been in store for a few weeks now you will be ok. Also you would know if the stack was getting hot because it would be smelling very musty and when you put your arm in, it would be very hot.
But from what you have said it will be fine, it is very rare for hay to self ignite and usually only in years when the hay was made in showery weather and was baled in a hurry ahead of the rain.
Best of luck

 

[Marilyn]

Thanks you lot, that puts my mind at rest...we're getting it organised to be moved, it smells divine, it not hot and it not green.

Thanks,

 

[Fransurrey]

Hay isn't purely hay, it will also contain soil bacteria. When these respire, they produce excess energy, which is released as heat. Most metabolic processes take place in water, and bacteria need some moisture to metabolise (or they undergo what are called heat-shock processes, where metabolism 'shuts down'). Thus, the more moisture in the hay or haylage, the more bacterial respiration. If the heat cannot dissipate in the air, it will build up and you risk combustion.

So, new hay needs to be stacked with circulating air for two reasons: 1) to allow it to dry out further 2) to allow any heat generated to dissipate.

Although haylage is obviously more moist, it's less of a problem as it is tightly sealed and therefore most of the respiration is anaerobic (without oxygen). This generates less heat, as the process is not as energy efficient.

Here endeth the lesson, lol! Sorry, Biochemist in me coming out...