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June 13, 2006
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## Resolved Question

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# How much in tons of human waste (poop) is needed to produce a given amount of bio-fuel?

Sorry, I am confused. The question is, how much of human waste do I need to produce 1 KW of electrical energy?

How about garbage? How much of household garbage do I need to produce a 1KW of power?

Garbage generate methane. Methane is used to produce electricity. Using an electric generator that uses methane as energy source, how much of garbage to produce methane do I need to generate 1 KW of electric power?

4 years ago

by L. A. L.
Member since:
May 15, 2006
Total points:
11,839 (Level 6)

## Best Answer - Chosen by Voters

You have not given enough info. Somewhere in the problem you should have been given the products and means of use.

Eg how much methane is evolved per ton?...multiply that figure by the heat of combustion of CH4. Was the residue burned?...how much heat is derived from that?

Add more detail and I'll guide you through the problem.

LATER

Well, we are getting there but still do not know how much CH4 is produced. This is how to approach your problem:
The reaction, CH4 + 2O2 ---> CO2 + 2H2O
produces 50MJ/kg (megajoules/kilogram of methane) of heat.
One MJ of heat can be converted to 0.28 KWH (kilowatthours) of electricity. (This is theoretical, there is some energy loss in the generator, etc.)
So, 50MJ/kg x 0.28KWH/MJ = 14 KWH per kg of methane...or you must burn 1/14 kg of methane to get one KWH of power.
Find out how many tons of waste is needed to give off one kg of methane, then divide that figure by 14 to get tons waste needed to generate one KWH of electricity.

Is this clear? Are you given the methane produced? Questions? More info please, and back to the drawing board :-))

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