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horsepoop for heat?

Discussion in 'Home Power and Microgeneration' started by G M D, Aug 2, 2005.

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  1. G M D

    G M D Guest

    I have been floating the idea around of running pipes thru my manure pile
    and grabbing the heat from it. This is just a wild (one of many) thought
    that I had. I was thinking a closed water system that runs water thru the
    poop and back into the henhouse. I am thinking a small low flow waterpump
    (something i can run from my batts and solar cell). has anyone ever tried
    this or is this another crazy thought?

    Thanx in advance.

    Gerry in Nova Scota
  2. Guest

    It's not crazy. Composting makes about 10 Btu/lb of heat, like wood burning,
    based on dry weight, and with enough temperature (eg 130 F) and oxygen
    (10% min?) and moisture (50% by weight) and the right mix (25:1 C/N ratio),
    it can disappear at a rate of 15% per day.

    Keeping the temp up requires a large pile, eg m^3 min. O2 requires turning
    or aeration with a blower, moisture might come from a soaker hose with a
    humidistat, and horse manure and bedding straw be close to the right mix.

    That said, it takes a lot of pipe surface to extract heat efficiently from
    a manure pile, and how do we replace the compost with fresh manure without
    disturbing the pipes?

    I've thought about heating greenhouses with compost inside large cylinders
    made from rings of used tires, but the greenhouses are not very near the
    horses, and moving the manure and compost isn't easy. Circulating a little
    warm moist air between the cylinders and the greenhouses seems easier than
    using pipes, with condensation inside the greenhouses and desirable CO2
    enrichment. Anna Edey mixed chickens and compost and greenhouses, with a
    compost air filter to keep the chickens healthier...

  3. Guest

    ...Composting makes about 10 Btu/lb of heat, like wood burning,

    Oops. That's 10K Btu/lb.
    And 1 m^3.
    Especially if the compost pile is aerated with a small blower...
    100 cfm of 90 F air with 80% RH can move about 100(90-50) = 4K Btu/h
    of sensible heat into a 50 F greenhouse, as well as about 10 lb/h of
    water vapor, which can release about 10K Btu/h as it condenses.

  4. Nog

    Nog Guest

    So what causes the heat in a poop bile or compost pile? Can science capture
    the process and use it artifically to make heat? Why can't the chemical or
    biological reaction be duplicated and applied commercially?
  5. Guest

    These would be aerobes.

  6. daestrom

    daestrom Guest

    'aerobic digestion' is done with microbes that are open to air, while
    'anaerobic digestion' is done by microbes that die in air. Septic digesters
    and such usually use 'anaerobic' microbes. They give off methane as a
    byproduct. (swamp gas is another example of anaerobic digestion). Aerobic
    digestion requires lots of fresh air. This gives of CO2 as a byproduct.
    Secondary treatment in a modern sewage plant is a good example.

    A compost pile is probably aerobic since it is occasionally 'turned'. But
    manure could be either, depending on how well it is aerated and how 'wet' it
    is. But regardless, the point about not cooling it too far is valid either

  7. El Kabong

    El Kabong Guest

    Very interesting.

    I've often wondered if farmers could build a silo-shaped structure
    underground adjacent to their barns and feed their barn cleaners into it via
    an auger of some type. Heated water could be scavenged by pipes coiled
    through the concrete circumference, methane could be acquired off the top of
    the contents and liquefied waste could be processed into fertilizer. The
    methane could be used to generate electricity or run farm equipment.

    To do any significant good it would have to be a very large structure. Also,
    it would require 'anaerobic digestion' to function and airtight seals would
    be an obvious problem that someone smarter than me would have to figure out.
    Has anyone ever heard of such a system being tried?

  8. Guest

    Anaerobic digestion is very slow, compared to aerobic, so methane generators
    produce little heat. "Manure hot dogs" in South America have manure and water
    inside a polyethylene film duct in a trench, with horizontal sticks on top
    near the ends to squish down the duct and make airseals. People shovel manure
    in one end and remove digested manure from the other, and methane collects
    in a long bubble above the sticks in the middle.

    In a cold climate, the trench might run east and west to collect solar heat
    in wintertime, with some insulation below the film and and an extra layer of
    film above it and a low reflective wall on the shady side.

  9. El Kabong

    El Kabong Guest

    Thanks, Nick, for the enlightening response. I had never heard of "Manure
    hot dogs". That's funny. How do they use the products of this process?

    I still wonder, if the manure was stored in a vertical column (silo shaped)
    and completely underground and under self-generated pressure (there's that
    problem with the seals again), wouldn't the heat be able to propagate itself
    to a useful level since atmospheric influences would be minimized? Or, then
    again, maybe the problem of sealing the chamber would go away if the process
    became aerobic, with air pumped to the bottom of the stack and methane
    pumped off the top? (That means provision of power to the pump--an external
    energy source being required.)

    Thanks again.

  10. Guest

    They use the methane for cooking, drawing it off with a tube in the bubble.
    Again, methane generation is slow, with very little heat production.
    Aerobic digestion is much faster, with lots of heat. I don't think you
    can do both at the same time, altho one local sewage treatment plant
    generates methane in a big tank with a floating lid and burns the
    methane under the same tank to make the reaction go faster.

    You might enjoy visiting a few local sewage treatment plants. Operators
    often welcome people who (rarely) walk in and ask for a tour. Try to
    avoid acting like a sewage terrorist :)

  11. El Kabong

    El Kabong Guest

    Good idea. I'll try to act like I'm there because I love sewage!

  12. No problem,horsemanure steambike ( could roll your
    manure piles.
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