Temperature drop and anaerobic biodigestion

Our UBAB project has not been successful so far in producing any biogas. Bikash Adhikari, chief engineer at the National Biogas Producers’ Association (NBPA) in Nepal, has visited our installation and suggested the nightly temperature drops experienced in Kathmandu’s cold season would be responsible for throwing the anaerobic bacteria into stasis. Caught between waking and sleeping, the bacteria has no opportunity to eat and multiply.

What could be done about this issue? We have one alternative:

  1. maintain the biodigester at a temperature favourable to the anaerobic bacteria;
  2. use an anaerobic bacteria that can thrive at lower temperatures.

Option 1 could be achieved by insulating the biodigester.

  • An idea is to create a green-house effect by containing the biodigester in a transparent case (creating a kind of Trombe wall around it).
  • Another idea is to create thermal mass around the biodigester, which would regulate the internal temperature. We have thought a thick-walled digester (for instance made of rammed earth) which could work at the cost of portability (and if the digester cannot be portable it probably has to be a continuous feed rather than a batch-feed).

Option 2 has come to us through a rumour that some cold-resistant anaerobic bacteria is in use in China. Unfortunately we have too little information that subject.

Let us know if you have any information that could help us complete this project.

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