[Digestion] Digestate as fertilizer.

[Douglas Renk]

Hello "Gordon" :)
 
I'm curious to see Peter's response to your question.
 
Over and above the nutritional value of the digestate versus cost of separation and application, let's hope health and productivity of soil as a natural resource converts to monetary value. Soil's ability to sequester carbon is an ecological service that has been monetized. 
 
http://www.scribd.com/doc/49240018/lbfb-en 
 
I think as agricultural or bioprocess engineers, we are by nature, conditioned to think circularly. Therefore the total cost of an agricultural model should include all costs (which should include preservation of land, fertility and resources) to function as closely to a successful market model as possible.

 
All the best,
Doug Renk

--- On Wed, 6/29/11, Randy Mott <randymott at ceeres.eu> wrote:


From: Randy Mott <randymott at ceeres.eu>
Subject: Re: [Digestion] Digestate as fertilizer.
To: "'For Discussion of Anaerobic Digestion'" <digestion at lists.bioenergylists.org>
Date: Wednesday, June 29, 2011, 2:05 AM






Okay. My nickname is the Gordon Gecko of biogas: cost per ton? Value of separate constituents per ton? 
 
Randy Mott 
CEERES 
  


From: digestion-bounces at lists.bioenergylists.org [mailto:digestion-bounces at lists.bioenergylists.org] On Behalf Of Peter Allison
Sent: Wednesday, June 29, 2011 4:31 AM
To: digestion
Subject: Re: [Digestion] Digestate as fertilizer.
  

Hi All,

With regard to utilizing digestate as a crop fertilizer, it is often stated the slurry is spread on fields with the inherent problem of biological toxicity and crusting of surface applications.

I believe this process is an incomplete and basically a cheap and nasty means of disposing a potentially valuable resource.

The addition of a 1.5% potassium hydroxide solution of  to the spent digestate enables a disassociation of the solid fraction from the colloidal material. When the un-reacted and fibrous remains are filtered from the treated mix and the resultant fluid is allowed to settle, colloidal concentrate or fulvic acid will be found in the top fraction, humic acid in the lower portion and carbon rich nutrient at the bottom. 

The increased pH also enables a stabilization of biological activity within the fluids until dilution with water.

These fractions are the most valuable components of the AD process. The bio-gas is a bonus.

The fulvic acid is a supreme foliar fertilizer, the humic acid is best suited to soil applications and the carbon mud is an excellent binder for a wide range of solid crop fertilizer inclusions such as rock-dust, blood and bone, etc, before pelletizing for broadcast operations.

We are desperately looking for sustainable solutions to chemical based crop fertilizers. Most agriculturalists are aware of the folly of NPK reliance. 

AD, like the composting of organic waste materials provides all of the nutritional requirements for every form of plant-life.

Recycling of crop nutrients via AD has the ability to negate the detrimental effects of chemical agriculture, repair degraded soils, help resolve salinity problems, increase nutritional food values of crops, increase soil moisture holding capacity and put an end to the contamination of precious waterways. 

Simply dumping spent digestate on fields is a lazy and mindless means for disposal.

Don't waste waste.

Regards,

Peter.  
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