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After trying and failing batch domestic anaerobic digestion in Kathmandu at its coldest (December, January), a biogas expert observed our system and explained the bacteria could not operate because of temperature fluctuations--which would throw the anaerobic bacteria back into stasis every evening when the temperature would drop.

A rumor reached us about an anaerobic bacteria (used in China?) which is cold resistant.

Inoculating a bio-digester with a different bacteria is more appealing than re-designing a complete system with insulation.

Unfortunately we have had no details regarding this bacteria. Would you have more information about any cold-resistant anaerobic bacteria? Which one is it exactly? How can it be found, grown and used?

  • finally got around to find the source on the psychotrophiles from cold lakes ... – mart Feb 6 '13 at 10:30
  • also this could be a question for the biology SE – mart Feb 8 '13 at 14:59
  • Is the purpose to just dispose of waste, or to generate fuel. If waste, then can you use an aerobic bug instead? If fuel, can you insulate the tank and/or use some of the fuel to heat it? – Sherwood Botsford Mar 21 at 21:59
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The bacteria in the muck in cold lakes that produce swamp gas live at cooler temperatures ~0-20 °C. Here's an account of the gathering of psychotrophiles from lakes near Mount Everest.

Note that you will still want to avoid temperature swings - insulate fermenters. Also, the retention times needed at lower temps are far longer. With long retention times in a cont. process, the right bacteria will remain in the vessel by themselves. In a batch process, you need to "seed" the fermenter with biologically active material from the last batch. Mind that whith slower methanogenesis, acid build-up is higher can - you may want to aim for lower OLR.

However, from what you have written I'm not entirely sure that psychotrophiliacs would solve your problem.

A typical retention time for psychotrophilic process would be 70-80 days, I did not (yet) find good OLR guidances. 3-5kg/m³d is a good guideline for continuos processes, for a batch process I would aim for a lower loading rate.

I would strongly suggest trying with a lower ratio of substrate to dung, using a lot of digested material as a seed for the next batch, and slowly adding more substrate. You need to "train" your bacteria.

What else did you try? Did you measure pH? Could there be poisons in the substrate (antibiotics, heavy metals (Cu), strong nitrogen loads (>7g/kg))? How long did you wait? I saw you added dung (good) did you mix it? What's the estimated OLR? Did you measure solid and organic solids content?

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