G'day All,
As a generalisation Westerners tend to have "tunnel vision", so only concentrate on one thing (I know this does not apply to all members of this group!). This is from my observations and I don't have too much experience in other cultures for comparison. I think it really results from our "reductionist" approach, or maybe the approach is a result of this limitation. As a result some people see AD as "biogas", some as "Carbon", some as "waste disposal", some as "pathogen reduction" and some as "fertiliser". What we really need to do is see anaerobic digestion as all of the above and as part of a larger system. This involves a move away from the typical Western "linear" approach (of extract, use, discard) to a more cyclic approach (we have a Reuse, Recycle, Reduce slogan going around, sometimes with a 4th R that I can't remember). I know some areas have been doing this for centuries, and even Westerners used to be better at it (before coal and oil!). Happy digesting, HOOROO Mr. Paul Harris, Room S116b, Waite Main Building Faculty of Sciences, The University of Adelaide, Waite Campus, PMB 1, Glen Osmond SA 5064 Ph : +61 8 8303 7880 Fax : +61 8 8303 4386 mailto:[email protected] http://www.adelaide.edu.au/directory/paul.harris CRICOS Provider Number 00123M This email message is intended only for the addressee(s) and contains information that may be confidential and/or copyright. If you are not the intended recipient please notify the sender by reply email and immediately delete this email. Use, disclosure or reproduction of this email by anyone other than the intended recipient(s) is strictly prohibited. No representation is made that this email or any attachments are free of viruses. Virus scanning is recommended and is the responsibility of the recipient. From: [email protected] [mailto:[email protected]] On Behalf Of P M Allison Sent: Thursday, 18 November 2010 6:06 PM To: digestion Subject: [Digestion] Re Digestate as fertilizer The use of digestate for crop fertilizers, is to me the very best option. The material contains all the nutrients required by plant-life as it is made up of the very same ingredients. Laboratory analysis of the spent material confirms this. A very similar substance is derived from vermiculture. The main problem with spent digestate is the fiber content. This will create nozzle lock-up on any spray delivery system. Fiber is not digested by anaerobes or worms. If the digestate is splayed too thick it will smother soil and emerging plants. The simple solution is to vibro filter the fiber and undigested material from the slurry. The solid matter is ideal for pelletizing and broadcast delivery. The resultant liquid component is a colloidal nutrient complex containing the same ingredients as the original material but in plant ready form. This liquid does contain particulate matter which can clog nozzles. My solution to this is to centrifuge the liquid and trap out the sedimentary material leaving a purely colloidal substance. This can be used as a foliar fertilizer when diluted with water as the substance is too rich to be used neat. The trapped debris is a rich nutrient mud, primordial ooze so to speak. This is also rich in nutrient and the finest of carbon flocs. An ideal binder for pelletizing the solid matter initially extracted. By the way, the carbon flocs are the same as those used carbon-fiber production. Biogas is a wonderful bonus to the system, but should not be the be-all and end-all of the process. The spent material is the sort of substance which will make sustainable agriculture a much better option than what chemical farming will ever do. The crop improves, the soil improves, the soil biology improves, soil moisture holding capacity improves, soil carbon increases. Remember, it's the dark matter which differentiates soil from being just lifeless dirt. Regards, Peter.
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