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Bio Gas waste


8:56 am
May 10, 2012

Buckland-pinnock Art


I enquire if anyone has had experience with waste from a bio gas digester?

Double dipping here, having already extracted what is required to produce gas, the resultant slurry is used as a low grade fertiliser completely free of any 'nasties'.

Would there be enough nutrients left to be beneficial to worms?

As it is directly sprayed onto pasture, no observations have been made as to worm activity.

Before re-inventing the wheel and doing a project directly with worms and the waste, I ask if any such work has already been done.





1:40 pm
May 10, 2012

Philip Rock


posts 84

Nope – I've no experience with it. I did just find this article entitled: The fertilizing effect of compost and biogas residues from source separated household waste.   :

I'm just speculating here but it seems to me that the anaerobic digestion process used to make bio gas will have used up most of the good stuff that worms and their aerobic microbe community would want.  From that paper it seems it would have a high nitrogen content and also be in a wet/soggy condition.  It seems it would be better directly as a plant fertilizer.  You could try a little (small-scale) test and mix the stuff with cardboard/paper/leaves etc and put some worms in there and see if they like it… and let us know how it turns out!

With organic waste it seems there is a choice to make: either composting (or vermicomposting) to generate a soil amendment or you do the anaerobic digestion to get energy in the form of bio gas. 

6:53 pm
May 25, 2012

Buckland-pinnock Art


Thank you for that Philip, – as I guessed might be the case.

The bio digester does not enhance the nitrogen content but rather utilises more of the other components to leave a stronger nitrogen presence.

The C/N ratio is way off the mark for worms without the addition of C as you suggest.

I was unable to access the link that you gave me, I will try another avenue at a later time thank you.

The query was in relation to a better use of digester product other than spraying on the paddock to get rid of it in an environmentally friendly manner.

The necessity of having to add nutrients to the slurry and/or further processing negates any advantage in proceeding further.

Many thanks,



11:39 pm
May 25, 2012

Philip Rock


posts 84

Sure thing Art- sorry abut the broken link – I couldn't access it again either!  The original link is probably buried in the cache of my office computer – but I'm away from that for the summer.  A new Google search for 'Bio gas waste and vermicomposting yields quite a few hits – like this one:  HASSAN COMPOSITE VERMICOMPOST -
  (maybe this link will work!).  It describes a project in India…but leaves out many details.  It seems the bio gas slurry could be used as a source of moisture and nitrogen to mix with carbon-rich material for worms.  It may be that "spraying it on the paddock" is your best use of the stuff.  Best of luck to you! Phil

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