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One man experimental humanure biogas digester and microbial fuel cell project

Discussion in 'Home Power and Microgeneration' started by [email protected], Jul 4, 2013.

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  1. Guest

    Hi all, I'm planning to make a biogas digester to connect to my mobile home's sewage out port. Hopefully this will make fertilizer, a bit of methane, and possibly electricity, as I've read that anaerobic breakdown of organic matter can run a microbial fuel cell. My main question at this point is howthe fertilizer is extracted? On all the plans I've see, the tank is buriedwith an input and output pipe going down into it. Somehow, the effluent seems to flow up and out the output pipe, but I can't for the life of me figure out how that works. It seems to defy gravity. Can anyone enlighten me? Building this will save me from trips to the dump station and use my poop for good rather than being a hazardous waste.
  2. Vaughn

    Vaughn Guest

    What you are describing doesn't sound much different from a septic tank.
    For a travel trailer with only my father living in it, I once made a
    septic system from a single buried 55-gallon drum and about 20 feet of
    drain line (sandy soil). The system worked fine for the couple years
    that it was needed. (He ultimately found a new wife who owned a condo,
    and so moved out of my yard.)

    That was done in a different time when local officials were far more
    casual about such things, so don't take the above as a suggestion. It's
    likely illegal these days and possibly a very bad idea depending on your
    soil type and groundwater situation.

    As for digesting solids, you will be surprised how efficiently a septic
    system reduces them. I have been living in this house for some 30
    years, yet we have never pumped the septic tank!

    You might hunt around for a more appropriate group that can give you
    more input. Perhaps gardeners or even survivalists.

    As for the fuel cell idea; for a thousand reasons, forget it.

  3. Guest

    Thanks for the feedback. Yes, it's similar to a septic tank, but it will produce methane and fertilizer (and electricity, though I'm curious about your reasons for a microbial fuel cell not working), without the ground water contamination problem. It will also produce heat, and larger versions can output 140 degree water.

    As for the fuel cell, it seems prototypes are cheap and easy to build. Might produce a volt or so at a few hundred mA. These are small tabletop models, so a septic tank size will likely produce a lot more.

    Anyway, my question still stands: how does the compost climb up and out theoutput pipe?
  4. mike

    mike Guest

    Please publish some links to the fuel cells that run on the gas you can
  5. Kanon Kubose

    Kanon Kubose Guest

  6. Kanon Kubose

    Kanon Kubose Guest

    Ok, I think I figured it out.

    1. In biogas digesters where an upside down floating drum is used, the output level will be close to the level inside the tank.

    2. In digesters where the methane is under pressure, the pressure will pushthe effluent upwards to some extent. I'm sure this is where know-how comesin to determine just how much. Also note that the input pipe must be long enough so that this pressure doesn't push the manure out of it as well.

    3. When new manure is put in, this will raise the level inside the tank which can push the effluent out the output pipe if its height is correct as in#1 and #2 above.
  7. mike

    mike Guest

  8. Kanon Kubose

    Kanon Kubose Guest

    I'll be excited if I get anything at all. It's just an initial, uninformed proof of concept type of thing for me at this point, and I'm only doing it because it's so simple and yet so fun--electricity from poop! Mostly, I'm doing it for the compost and the need to get rid of my waste. The methane too is just for fun, though I hear there are off-grid houses that get all their cooking fuel from their methane producing compost pile. Some people alsoharvest the heat and get 140 degree water.

    As for the pumps, zero. It'll be gravity fed. Approximately the same amountof fertilizer (4-6 weeks of fermentation) comes out the other end when newblack water from the trailer enters the input. Do it right, and it's safe for using on food crops, but I wouldn't do it with this prototype since I'mnot planning to carefully monitor the carbon nitrogen ratio, the temperature, etc. Good for flowers, though.

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