low/ ambient temperature

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pjeter schornstein
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low/ ambient temperature

Hey all!

I have build a 60 liter barrel biodigester in my house in Germany mainly to learn and prepare for building a bigger one in the future.

It's been a month and there is still no gas production. I figured the temp is too low (20 Celsius). I am not sure if I should continue waiting. I covered it with rockwool but when I put a thermometer through the feeding tube it is still 20 degrees.

I thought perhaps I should start over. mix the manure with warm water and then wrap in insolation.

Another option I thought is an electric blanket with low walt and a timer. I know it's now optimal but it is mainly for educational reasons.

What would you suggest I should do?

Thank you!

Nick Chase
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Hey Pjeter,

Hey Pjeter,

60 litre can be heated easily with PEX tubes - running a hot water circle through the digester. You can also use Heat Lace Tapes (used to heat water pipes). BUT: insulation is key, otherwise you will lose heat too fast.

Is your digester inside or outside. Is it housed, for example in a green house?

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pjeter schornstein
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Hey Nick thanks for the quick

Hey Nick thanks for the quick answer!

heating it with water might be complicated because it's very far from the tap..

It is inside the house in a small corner I could close down like a cabinet. I thought I probably should start again because in an attempt to warm it up I kept adding warm water and I'm afraid it's too diluted by now (please correct me if I'm wrong on those point's since I'm not sure...). After that I thought to isolate the cabinet and the digester with rockwool slabs and mix the initial dung with warm water so it could stay warm for a while then just sometimes when needed.

Do you thin that might work?

Nick Chase
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yes, that might work. And yes

yes, that might work. And yes, probably diluted too much. Depends on your starting ratio.
With colder temperature production rate drops. I would give it another 2 weeks and when there is still no gas production start over.

I still suggest heat lace tapes https://www.conrad.de/de/Search.html?search=heizkabel&searchType=CAMPAIG... to be put inside. As your digester is insulated and the size is 60liter you are able to use that kind of heating.

And yes: using hot water while feeding in a 50/50 ratio makes sense. Your digester is 60l, with an hydrolic retention time of 30 days you have to feed 2 liter as day. 1 L food 1L warm water.

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pjeter schornstein
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Ah. Couldn't find it before

Ah. Couldn't find it before but good to know there is such thing, though much higher then my budget at the moment...

thought also about adding some mud from duck pond http://solarcities.eu/content/where-can-one-get-psychrophilic-microbes-c...

Don't know if it might make much difference though..

1 litter of food from kitchen waste might be a lot. What could happen if I underfed it?

I wrote down (can't remember where from) that 100 litter digester would need 500 gram daily + 2 litter water but I guess it'll be too diluted? 

Nick Chase
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100 Liters with a HRT of 30

100 Liters with a HRT of 30 days = 3,333 Liter = 1,6L food + 1,6L water. yes, too diluted probably.
Duck mud might help. I have no direct comparison or study material about pyschrophilics vs. mesophilics.

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pjeter schornstein
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Thanks a lot Nick.

Thanks a lot Nick.

For the future, what about under feeding- would it make less gass or couse problems?

Nick Chase
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under feeding, haven't done

under feeding, haven't done that yet. Mathematically your HRT changes, it gets longer, hence less gas production per day. Afaik under feeding is not that much of a problem.

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Jeff Stout
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low temperature.

   I have a 30 liter digester that I'm practicing with and I use a service light that is directed towards the bottom of the container and shielded for best results and a thermostat to turn the light on and off. My container is insulated to R30+- and I maintain around 95 degrees +- 3 degrees. My first thermostat failed and the temps were at 104 deg. and I could not believe the gas moving through the bubbler trap, replaced stat and carried on. My substrate is horse manure and ocassional algae and when I orginally started I filled a 5 gallon pail with manure and set out of way with a vented lid for 4 months and it was ready to go when I need some for my educational digester...