what to do with the gas?

Digester design and construction info

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ian moore
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Joined:Tue Mar 14, 2006 11:04 am
what to do with the gas?

Post by ian moore » Tue Mar 14, 2006 11:34 am

hi,
good looking site... :D

Im interested in a small scale digester for 'food waste' only
kitchen slops etc

i have played with your calculator... great!

this would suggest that some paper or sawdust/leaves would also help..

very small scale to test first 10 gallons or so. a reasonable demo model


1. say there is 1lb per day of food & .2 lb per day sawdust/leaves.
we get a 3 feet of gas per day. with about .5 gallons water added

2. how long would this take to digest... perhaps 60 or 70% of the food converted to gas?

3. how much gas is used in a burner to cook?
mmmmm... thats not very specific...
how many feet of gas does it take to boil a pint of water?
cook a meal?
fry an egg?
but any help would be great
i guess i should be looking up the definition of BTU... :D

i have a 10 gallon sealed lid container
just looking at a batch feet at first.... so i load it up
i seed it with some poo ive had in a bottle for 2 weeks...i guess!

leave it a few days... and out the tube comes some gas...

how much gas does a camping gas burner use per minute?...on medium flame?

thanks :D
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Bob
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Joined:Tue Jul 03, 2001 11:01 pm
Location:Willow, Alaska USA
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Post by Bob » Thu Mar 23, 2006 12:01 pm

Hi Ian,
this would suggest that some paper or sawdust/leaves would also help..
Yes. Often, the C/N ratio is quite low, and adding these carbon sources improves it.
how long would this take to digest... perhaps 60 or 70% of the food converted to gas?

If batch feed, including startup if all goes well, maybe 30 days. But the 2-stage digester in continuous feed mode is designed for about 12 days.
how much gas is used in a burner to cook?
A Btu is the amount of heat required to raise the temperature of one pound of water one degree F. So, if you are starting with water at room temperature (~70F) and want to raise it to 212F, that would require 212-70=142 Btu at 100% efficiency. (But you probably can't get anywhere close to that. Guessing maybe 30-40%? Dunno.)

Typical medium/small stovetop gas burners are rated at 6,500 Btu per hour at full open. The heat value of a cu ft of methane is about 900 Btu.

(Sorry for the delay in responding. I just returned from a trip out of the country -- no access to the internet...)

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