Feeding a Biogas Digester (video)

Subtitles:

  • Turn off the gas-out valve
  • Fit the effluent bucket securely
  • Remove lids from the input and output pipes
  • Rinse-water, including coffee grinds and expired milk
  • This bucket is too full!
  • There’s enough here to produce about 15mins cooking gas
  • …enough to boil 1Litre of water, or make a coffee
  • An equal amount of effluent is displaced
  • Turn the gas-out valve back on
  • The biogas from this feedstock will be ready in 24 hours
  • Effluent is an excellent liquid fertiliser
  • …it’s ph neutral, and safe to use on seedlings
  • …it smells like fresh cow manure
  • I pour it in different places each day
  • It’s best to rinse everything so there’s no smells
  • This digester is capable of producing over 1 hour’s worth of biogas for cooking each day, if all kitchen scraps are ground into a slurry.
  • The collector for this system is only hobby-size; capable of storing 20mins worth of biogas. A larger collector, or more collectors could be added to this system.

What is a biogas digester?

Making a Coffee with Biogas (video)

 

6 comments on “Feeding a Biogas Digester (video)

  1. Hey, just wanted to let you know that your video is a nice “slice of life”
    showing how easy it is to put a “waste” product into multiple useful products.
    The diagram at the end is very clear and super useful in showing how the digester operates. I’ve been intending to get a digester going for some time now and your simple set up is an inspiration for action. Many thanks!
    One question: what would your strategy be for adding more barrels?
    Link the first storage barrel to a second and a second to a third in series?
    Or link the digester to each so the gas goes to all at once…?

    • Hi Seth,

      Thanks for your comments and questions. I am considering adding another collector to my system, both to collect enough gas to cook a big meal, and to demonstrate how it can be done.
      There are a couple things to consider first. One is that the digester is not designed to be under pressure – currently the only pressure is from the weight of the collector’s garbage bin. By adding additional collectors which all receive gas from the digester, each one will add the pressure of a garbage bin to the digester. If this pressure becomes too great, effluent will start spilling out the effluent-out pipe.
      Second, if all collectors are linked to the digester and cooker, you’d have to apply equal weights to each before burning, so they all release biogas evenly to the burner. I find adding one weight to my collector a tedious task I’d like to eliminate one day.
      Here’s what I’m thinking for my situation: A second collector connected only to the first, but which remains unused until a significant amount of gas has built up in the first collector, at which time a weight can be applied to the first, valves opened/closed, and gas is transferred into the second collector as storage. If cooking requires more gas than is available in the first collector, a weight can be added to the second, and the secondary gas will transfer (via the first collector’s valve system) to the cooker. This way it would be business-as-usual making my daily coffee, but I could store up gas in the second collector for a big cook-up.
      If a third or fourth collector were desired, I might connect them all to the first collector as I’ve suggested the second ought be’d. This way the digester only ever has pressure from the first collector, but the system can store a lot of gas.
      I hope that’s helpful. If I get around to doing it I’ll let you know. Likewise I’m interested in what you come up with.
      Good things

  2. hi really like the video. Could you tell me if it’s alright to use dog waste and chicken waste in the digester?

    Also what level to leave the water when starting out?

    Thanks for your time.

    Peter.

    • Hi Peter, Ive used chicken manure, and ive heard of folks using their own manure to get a digester going. Once its producing biogas you dont need to add any more manure, but you can if you like. If you’re de-worming your dog I’m not sure if the medication might upset the digester, and I’m still not sure of the potential for pathogens to persist in a digester, so if you’re uncertain about anything, just pour the effluent around ornamentals, or below a mulch layer where dogs and children wont come in contact.

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