[Digestion] Ideal pH and temperature

[frank]

Warren and gas people,

Does ammonia mixed in with the gas a problem? perhaps reducing the BTU's 
or corrosion? It seems if we raise the pH we get ammonia in the gas and 
if we lower it we get CO2 in the gas.
When you suggest adding lime or ash (both to raise the pH) that would 
reduce the CO2 concentration in the air- is that what you are trying to 
do? But then off goes the ammonia into the air...

Does the ammonia and CO2 need be scrubbed out before the gas can be used 
- say in a generator?

Thanks
Frank




Warren Weisman wrote:

>My two cents---based on experience instead of books---
>
>Ideal pH balance for anaerobic digestion is a little
>on the alkaline side, between pH 7.0-8.5. 
>
>Couple rules of thumb... if no flammable biogas is
>present after a few days 3-5, but you're getting good
>CO2 activity, use lime or ash to adjust the pH
>balance. 
>
>Also, a red or yellow flame generally means
>over-acidity. Remove some old material and inlet some
>fresh stuff. A nice blue flame means happy
>micro-organisms. 
>
>Ideal temperature for AD is same as for us 99 F or 37
>C. It will make biogas at temperatures lower than
>this, but production will fall off drastically. Higher
>temperature, thermophillic digestion, is unstable and
>will not produce more biogas to offset the energy
>needed to heat the digesters. General rule of thumb,
>don't let your digester get too hot to be
>uncomfortable to touch. Shade it from the sun if
>necessary. 
>
>Warren Weisman
>USA
>
>
>
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>

-- 
Frank Shields
Soil Control Lab
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