Feel free to ask questions or post information about domestic/household size systems here.

I get a number of enquiries about converting septic systems to AD. I recall an article (a long while ago) saying it should not be done but can only see some practical problems - anyone got any further information?

Comment from DJ Fulford:
The main problem with septic tanks is that they are usually rectangular tanks made of masonry or concrete. It is very difficult to make corners gas tight, as the flat walls flex and cause cracks in the corners. It would be possible to put a flexible plastic cover over the top to collect gas, but there is a danger of forming an explosive mix with air, unless a positive pressure of biogas can be built up that stops the air leaking in.
Having been asked, as a consultant, to advise people about this, my reponse has been to recommend building a new tank that is designed as a biogas plant (using either the BSP Nepal or Deendandhu designs).

You may get some ideas from Digester Projects

Comment from P Perrin:
I am currently researching biogas and compost based heating. The info I have is that an average persons daily waste will produce no more than 1 cubic feet of gas. The better an animals digestion works, the less is in the waste to create gas from.

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