Digester Effiency

Discussion in 'Renewable Energy' started by Somerset Farmer, Nov 8, 2018 at 7:51 PM.

  1. Somerset Farmer

    Location:
    West Somerset
    I am now surrounded by crops grown for a digester, fodder beet, maize, and ryecorn(cut wholecrop) and I was thinking how much energy each of these crops produce an acre/year. There appears to be huge machinery costs in both growing and haulage before these crops even reach the digester (which is 10 miles away) and then the digestate has to be hauled back again. Can it ever be economic if this energy is paid for with the wholesale price of electricity or gas ?
     
  2. Don't know about economic but it certainly isn't green energy.
     
  3. thesilentone

    thesilentone Member

    There is a sustainability criteria to ensure it is green energy.
     
    Will Wilson likes this.
  4. I assume that's a joke.
     
  5. thesilentone

    thesilentone Member

  6. Somerset Farmer

    Location:
    West Somerset
  7. thesilentone

    thesilentone Member

    We need to break down into two areas, one being the field and crops grown = yield in tons/per/hectare.

    We then calculate the Biogas potential per ton,followed by the utilisation of the Biogas.

    Grass, maize and whole crop have a similar output of gas per ton, with Beet and Rye (whole) giving less due to the reduced DM level.

    This can be offset by the yield per hectare, so of course as your question suggests, the real figure is m3 biogas/hectare then cost per ton (which is why maize is so popular)

    Once we have produced biogas, we can use it to produce electricity, heat or methane which can be sent to the gas grid. We also produce digestate that returns the nutrient to whence it came.

    There are many references on the internet to gas yield/ton, kwhr production/m3 biogas and the benefits of digestate, I'll let you enjoy the research.
     
  8. Suffolk Serf

    Suffolk Serf Member

    Location:
    Bury/Thetford
    Easy answer. One I know is 2.25 MW/h gas to grid. Uses about 3000 acres of Maize and rye.
    Nearby is a 13MWh solar farm occupying 55 acres, but being solar probably averages 3 or so.
     
  9. thesilentone

    thesilentone Member

    Different efficiency levels for each technology, however Biogas is far and away the most efficient.
     
    Will Wilson likes this.

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