[Digestion] Sugar feedstock

Tony Dovey td at tiscali.co.za
Thu Feb 7 00:21:28 CST 2013


Re: [Digestion] Sugar feedstockHi David

Thank you for the quick response and the info.

Regards

TD

From: David Fulford 
Sent: Wednesday, February 06, 2013 10:06 AM
To: Tony Dovey 
Cc: digestion at lists.bioenergylists.org 
Subject: Re: [Digestion] Sugar feedstock

Hello Tony,

When I was running a laboratory digester at Reading University, I wanted to make it as automatic as possible. I used dissolved sugar as a "base" feed, as it could be fed as a solution through a valve controlled by a timer. I did add small amounts of fertiliser to make sure the C:N ratio was correct - between 10:1 and 30:1. (I used ammonium sulphate, a BIG mistake, as the digester generated hydrogen sulphide; ammonium nitrate is better). At low rates of feed the digester ran very well. 

A student also ran some tests on molasses as a feed material for a digester. When we tried to increase the loading rate, the digester went sour: too many fatty acids were generated. Acid generation works much faster than methane generation, so the feed rate must match the methane rate. Sugar digests fairly rapidly, as it is readily available to the microbes. Sugar is therefore a good additive for other feed material. 

So, a biogas system runs very well on sugar, but nitrogen needs to be added and the feed rate needs to be limited. There are models for designing the right size of plant (see http://biogas.wikispaces.com/ which has links to Paul Harris's model). Increase the sugar feed rate slowly until the gas production rate does not increase at the same rate as the feed rate, then reduce the feed rate slightly and keep it at that level. 

-- 
Best regards,
David
  mailto:davidf at kingdombio.com

Wednesday, February 6, 2013, 6:35:26 AM, you wrote:


     Hi there.
       
      I have read with keen interest about the Indian sugar/starch digester being punted by ARTI.
       
      We have access to between 200 –300kg sugar sweepings a month and am very keen to build a floating drum type digester.
       
      Does anyone have any practical experience of using stock standard sugar as a feedstock?
       
      Regards
       
      TD
       
       

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Kingdom Bioenergy Ltd, www.kingdombio.com, davidf at kindombio.com
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