[Gasification] Got you calculators handy??

[Art Krenzel]

Clint,

The 22 - 30 day biogas digestion period you report is the result of AD 
operators who primarily want to use the digestion process to reduce solid 
wastes such as would be the case at a waste water facility where the gas is 
flared and the facility constructed with "free" tax dollars and no focus on 
ROI.  It is used primarily a means to reduce waste volume.  This is the case 
in rural third world areas where the focus is on waste processing with 
minimal effort and getting a low cost, useable fuel.

In this new world of energy concerns, anaerobic digestion has expanded into 
a new role.  There are six to ten day operating AD processes which do the 
same amount of waste reduction
 by using two stage digestion, substraits and higher operating temperatures. 
When you are talking about reducing process capital costs, moving from a 30 
day process to a six day process is REAL progress and that is where we are 
today in large scale AD.

There are different feedstocks which require different processing times. 
Dr. Karve has presented a starch based process with eight hours of 
processing time.  This is a specialized waste stream however one that he has 
in good supply in his area.  This is not true in all areas however.

Most areas do have food wastes, manure, waste organics, etc and nature has a 
digestion process for them as well.  It just takes a bit longer to get the 
job done.  Humans can process food in their digestive tracts in about 24 
hours and recover only a fraction of the total energy in the food.  That is 
why AD can use manure as a feedstock, take a bit longer and produce more 
energy.

IMHO, I do not consider a six day processing time for AD processing of 
foodwastes, manures or waste organics to be too long to make a valuable fuel 
product and reduce waste volumes.

Art Krenzel

----- Original Message ----- 
From: "Clint LeRoy" <clint at margenergy.com>
To: <gasification at listserv.repp.org>
Sent: Saturday, March 24, 2007 8:26 AM
Subject: Re: [Gasification] Got you calculators handy??


> Dear Tom Miles
> Although Digestion is a possibility it is a slow methodology, taking
> some 22 days to complete the cycle of retrieval of the Biogas. IF you look
> to really extract the potential Ethanol carbon elements into useable 
> Ethanol
> then look to the BTL using the known practice of the Fischer Tropf 
> process.
> Add in some extra Hydrogen via steam reforming and you get a better output
> of ethanol then through distillery.
>
> Clint LeRoy
> Lead Consultant
>
>
> -----Original Message-----
> From: gasification-bounces at listserv.repp.org
> [mailto:gasification-bounces at listserv.repp.org] On Behalf Of Tom Miles
> Sent: Friday, March 23, 2007 11:24 PM
> To: 'Michael Redler'; gasification at listserv.repp.org
> Subject: Re: [Gasification] Got you calculators handy??
>
> Michael,
>
> The only use of the reference was to identify the yield of ethanol per kg 
> of
> maize which is similar to other sources. Their number is 0.371 L/kg grain
> compared with 0.406 L/kg from another source.
>
> The more interesting point is the energy that can be recovered from the
> distillers grains and solubles (DGS) via digestion.
>
> Thanks
>
> Tom
>
>
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