[Digestion] Multipurpose digesters?

[Duncan Martin]

Alex and all

I agree with the sentiments behind your posting.  I have a very comparable 
frustration over the lack of communication between those studying anaerobic 
digestion in digesters and the essentially similar process that goes on in 
landfills containing organic waste. I believe that has led the latter 
research community simply assuming that the same reaction mechanisms must 
apply. However my own research, which has been the subject of numerous 
publications, suggests that the process in landfills can sometimes work in a 
quite different way, albeit based on the same fundamental chemistry and 
microbiology.

However, I think you are suggesting a step too far. If I read you correctly, 
you would like to see multipurpose digesters, capable of handling a wide 
range of feedstocks. To my mind, this is an unlikely concept.  The range of 
feedstocks handled by different digesters is very wide and the different 
systems needed for handling them require substantially different design 
approaches.  The history of anaerobic digestion is littered with examples of 
plants that have failed due to an inadequate appreciation of the specific 
characteristics of the feedstocks being used.

A multipurpose plant is not impossible, of course.  However, anaerobic 
digestion has always operated to date on the margins of economic viability, 
so it would be very difficult to make the case for adding extra features to 
accommodate a variety of feedstocks. It generally makes more sense to design 
for a single feedstock the future supply of which can be more or less 
guaranteed.

By all means let us broaden our minds: I am all for more communication.

However I would be very wary of broadening our digesters. Of course, the day 
might come when rising energy prices make this a viable option. But I think 
it is still some way off.

Duncan

PS Could I repeat Paul's recent 'process' plea one one of my own:
a) Please delete any long tails of previous messages when you post a message
b) Please use an explicit title on your message

----- Original Message ----- 
From: "Alex Marshall" <MarshallAl at rpsgroup.com>
To: <digestion at listserv.repp.org>
Sent: Wednesday, June 06, 2007 5:16 PM
Subject: Re: [Digestion] Digestion Digest, Vol 12, Issue 9


> Dear Digestion Mailing List
>
> It often frustrates me that there is little integrated thinking between
> different digestion systems and industries. It seems that farmers, water
> industry and the waste industry all deal with the technology largely
> independently of each other. Why does it seem that the link up is so
> poor? The power industry in the UK is starting to wake up to the
> embedded generation potential of AD systems and may well bring a more
> rounded approach. Does anyone know of any systems that are integrated,
> handling a wider range of feedstocks or with a broader-minded approach?
>
>
> Alex Marshall - Senior Consultant
> Waste Technology Team
> RPS Planning & Development, Severn House, 1-4 Fountain Court, Woodlands
> Lane, Bradley Stoke, Bristol, BS32  4LA
>
> ( Direct dial: 01454 284480 ( Switchboard: 01454 284450   ( Mobile:
> 07810 156627
> 2 Fax: 01454 284499       * email: marshallal at rpsgroup.com
> web: www.rpsgroup.com/waste
>
>
> -----Original Message-----
> From: digestion-bounces at listserv.repp.org
>