[Gasification] Pyrolysing compost to make fuel

[Tom Reed]

Dear All:

Animal manures have been digested 3-5 times before release.  Is is so 
surprising that starch etc. generate so much more gas?

TOM REED      BEF

CAVM at aol.com wrote:

> 
>David, this is very interesting.  You say that the gas production from  mixed 
>food waste is higher than for cattle dung.  Is it significantly  higher?
> 
>We generally recommend that dry material be processed dry and wet material  
>be processed wet.  For example, dairy manure and hog manure are both  slurries 
>of various densities.  We recommend anaerobic digestion as an  energy process 
>for we slurries.  For beef manure, sawdust, and others, we  recommend 
>combustion or gasification as an energy producing process.  
> 
>In this way we do not spend valuable energy drying wet inputs nor do  we risk 
>water contamination by wetting dry inputs.  However, if we can  effectively 
>and economically produce methane from cellulose materials we might  reap 
>significant rewards.  
> 
>It is our opinion that the fermentation process of anaerobic digestion for  
>the production of methane is potentially very economical, scalable, and  
>effective in a wide variety of situations.  Most commercial digesters of  which we 
>are aware are fairly costly to build, complicated to operate and  marginally 
>effective given the energy value of the input material.  If used  for the 
>production of electricity they must be offsetting an electrical cost of  at least 
>$.075/kwh to be economical for power production alone.
> 
>Neal
>
>Neal
>
>Can I suggest you are wrong as far as anaerobic digestion  is concerned.
>
>There are biogas digesters in Sri Lanka that use very  high total solid 
>loadings of straw and these generate gas fairly  effectively. They are batch 
>digesters, cylindrical tanks made from  ferrocement, which are packed full 
>of straw and the lid is put on. Slurry  from another plant is poured in, but 
>just enough to soak the straw  through. The TS value must be 80%. The gas 
>production starts after a week  or so and follows a typical batch curve 
>(increasing to a maximum and then  steadily dropping). When the lid is 
>removed, when the gas production has  dropped to a low level, the lignin 
>remains, but the cellulose in the straw  has been digested. The straw looks 
>very similar to when it is put in, but  crumbles to a paste when it is 
>disturbed. This was described at a  conference I went to in Sri Lanka 
>several years ago, but I am not sure  where my references are to the papers 
>in which it was described. We did  visit a working unit on a local farm and 
>the owner seemed happy with the  gas produced.
>
>On a more recent visit to Mumbai, I saw the Nisargruna  process that uses 
>food residues for biogas generation. It is fed almost  entirely on 
>cellulosic materials (poorer people in India are mainly  vegetarian) and 
>gives a very good gas production, better than that from  cattle dung plants.
>
>regards,
>
>David  Fulford
>
>
> 
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