Fwd: [GreenYes] Fire in pile !

[Gary Liss <gary@garyliss.com>]

I thought Jim McNelly's answer to the Composting Council listserve below
was great on this, for people who are not subscribed to that
listserve.

From: Jim McNelly <jim@composter.com> 
Subject: Re: [USCC] FIRE IN PILE 
Date: Mon, 09 Sep 2002 17:39:21 -0500 

At 08:46 PM 9/6/2002 -0300, you wrote:
Does anybody can me help? 

I work with composting since 1995 and I use the method of static piles
with forced aeration. 
The sludge and wood chips proportions are calculated for the total mass
to be composting it reaches with humidity of 60% and relationship C/N
30/1. 

Greetings Kátia G.
Beltrame

I will offer my suggestions point by point, but these are only thoughts
as it is hard to be definitive without being at your location. One
initial question is how much of your carbon and moisture are
"available" vs how much is tied up in the woody mass, not
available to the composting reaction. I have seen high moisture piles
that are too dry because the moisture is locked in the chip. I have also
seen piles that were too wet, even thought though the wood chips were
dried leading to a false "available" moisture reading.

The fans are connected the timers that call and they turn off in regular
intervals of time in way to supply the amount of necessary air for the
maintenance of levels of oxygen enough to maintain conditions aerobics.

It is my understanding that the "on and off" cycles of
blowers using Beltsville aeration systems were designed to replace oxygen
that was depleted, usually within one half hour. Continuous air can also
provide sufficient oxygen without timers. Blowers were turned on and off
to save electricity, especially as the blowers were often sized to the
mass of the pile being oxygenated. Are you actually measuring oxygen
inside the pile or just guessing based upon the mass and the size of the
blower? I suspect that you may have an anaerobic pile, if not in all of
the pile, in most of it.


One of the piles was with average of
very low temperature, for that I interrupted the aeration for 24 hours
and then I began again to supply the air inside of the pile
(400m3ar/hour/t dry matter). 


How did you sample your temperature? Was the sample point
representative of the pile? I have seen supposedly cool piles around 40C
that were actually overheating inside, up over 70C. Remember, heat is the
enemy of composting and a pile over 65C is a pile that is not under
control. Heat is a by-product of decomposition, not a cause of it. Heat
must be removed to help promote optimum decomposition rates.

One fatal flaw I noticed with forced aeration systems in the 1980s was
that the flow of air was based upon the capacity of the blower, not upon
the actual flow of air through the pile. I saw odorous piles with plenty
of "theoretical" air, but little actual air due to back
pressure problems. I first noticed this problem when I put a piece of
paper up to the intake duct of a blower and it did not provide even
enough suction to hold the paper! No air was moving through the blower. I
would look at the aeration system to ensure that the air exhaust ports
are not clogged with compost, filled with condensate, or collapsed. Many
blowers simply have too little pressure, only around 1 or even two inches
of water column. Typically, pressure over four to eight inches is needed
to force air through a pile. This often requires a larger blower and
consequently an air manifold rather than air to a single pile from a
single blower. I suspect that your pile had insufficient air.

After about 20 minutes of aeration
the pile caught fire and the aeration tube melted. 

There are many causes of a fire in a pile including too high, over
3 meters which causes compaction and the retention of methane, alcohols,
and other undesired flammable byproducts. The spark to ignite the fire
has been suspected to be pieces of metal such as nails or baling wire,
which can act like a battery and spark when they touch other pieces of
metal. When agitated or infused with oxygen, the mostly woody pile can
begin to burn. Typically a pile that burns is too dry, too high, too hot,
and is lacking in oxygen.

We choked the fire of the surface,
we began to disassemble the headboard of the pile and we noticed that all
your interior had burned and we didn't find the aeration tube that,
probably, it melted. 
I end that the oxygen inside of the pile provoked the fire, that was
favored by the grass bed. 
Can anybody explain scientifically because that happened? 
I never saw similar in all those years. 

I would suggest a more thorough initial mixing to avoid wet and
dry areas, and helping to ensure blending of carbon and nitrogen
materials. Then keep the piles smaller, around 2 to 2.5 meters. , keeping
the base of the windrow to less than 7 meters.

Finally, spread the air more evenly through the pile using more pipe and
a 200 cm coarse wood chip base. I believe that air should flow through
the mass at locations of at least every .5 meters, often requiring a
diffusing manifold to ensure pressure equalization. Get a air velocity
tester and actually measure air flow, making sure that you are not
experiencing channelling and losing air through only one area of the
pile.

In the systems I design, I provide for air sensing in each composting
zone and appropriate air flow regulation as well as temperature feedback
and high rates of air, typically 10 times that of oxygenation, to keep a
pile from overheating.

I hope some of this helps.

Jim~ McNelly
The Compost Man
jim@composter.com
Http://www.composter.com

> From: "Moacir Beltrame" <moacir@bioland.com.br>
> Date: Fri, 13 Sep 2002 18:44:03 -0300
>
> Does anybody can me help?  
>   
> I work with composting since 1995 and I use the method of static piles with forced aeration.  
> The sludge and wood chips proportions are calculated for the total mass to be composting it reaches with humidity of 60% and relationship C/N 30/1.  
> The fans are connected the timers that call and they turn off in regular intervals of time in way to supply the amount of necessary air for the maintenance of levels of oxygen enough to maintain conditions aerobics.  
> One of the piles was with average of very low temperature, for that I interrupted the aeration for 24 hours and then I began again to supply the air inside of the pile (400m3ar/hour/t dry matter).   
> After about 20 minutes of aeration the pile caught fire and the aeration tube melted.  
> We choked the fire of the surface, we began to disassemble the headboard of the pile and we noticed that all your interior had burned and we didn't find the aeration tube that,  probably, it melted.  
> I end that the oxygen inside of the pile provoked the fire, that was favored by the grass bed.  
> Can anybody explain scientifically because what happened ?  
> I never saw similar in all those years.  
>
> I apologize for my English and I thank if somebody to be able to help me.
>
> Katia G. Beltrame
> Piracicaba/Brazil
> moacir@bioland.com.br       



>

Gary Liss

916-652-7850

Fax: 916-652-0485