[Digestion] Digestate

Alexander Eaton alex at sistemabiobolsa.com
Tue Dec 6 06:43:44 PST 2011


Two comments from the thread:

1.  Jim, could it be that you are using digestate at extremely high
concentration, or that comes from animal waste with high levels of hormones
or other foreign materials?  We have 6 years of digestate data that shows
remarkable results with crops, and we are willing to go head to head with
chemical fertilizers in a few crops here in Mexico.  We believe strongly in
compost as well, but our lab/field results show digestate as a powerful
fertilizer, so I am curious why you do not believe that to be so.

2.  Krishna, you mention a fertilizer "free from pathogens".  This is
obvioulsy deirable, but is it 100% necessary?  In some cases I can imagine
applying fertilizers that are "greatly reduced quantities of pathogens"
(like digestate) for some types of crops at some other times.  It seems
that so many of the benefits of digestate come from the living components,
that maybe we should have some margin here.  Thoughts?

Best,

A

On Tue, Dec 6, 2011 at 12:15 AM, Anand Karve <adkarve at gmail.com> wrote:

> Dear Jim, Krishna et al.,
> soils behave differently in the tropics and in the colder regions. Because
> of wasm weather, the microbes are much more active in the tropics than in
> the colder regions. All the text books from the temperate countries talk of
> humus. Nobody mentions it in India, because our fields do not have a layer
> of humus. The top soil (i.e. the top 10 cm) is more fertile than the lower
> layers in India because the leaves, flowers and animal dung fall on the
> surface of the soil and they serve as food for the microbes in the top
> soil. As a result, the top soil has the maximum number of microbes. It is a
> well known fact that the population density of microbes in the soil is
> positively correlated with soil fertility.
> Yours
> A.D.Karve
>
> On Mon, Dec 5, 2011 at 12:38 PM, Jim McNelly <jim at composter.com> wrote:
>
>>
>>
>> On Fri, Dec 2, 2011 at 9:38 PM, Murali Krishna <bmkrishna6 at gmail.com>wrote:
>>
>>> Good day Alex,
>>>
>>> Undoubtedly the spent slurry is the best nutrient source to
>>> plants/crops, provided that necessary care is taken, and it is free from
>>> pathogens and in the available form.  "All soils have all the nutrients
>>> necessary for healthy plant growth" holds good only when  the surface top
>>> layer (12 inches) is with some flora fauna and the soil is  not overdrawn.
>>> Now a days we witness this situation only in Forest Regions.  When an ideal
>>> living conditions do exist even the small amount of macro and micro
>>> organisms would multiply and even the undigested portion of the digestate
>>> will be brought into available form by the microbes. To bring the hidden
>>> stored reserves from the bottom layers of the soils (upto 20 feet depth) we
>>> need again some species like earthworms, etc.   For all this to happen we
>>> need some carbonaceous material and which is converted into humus by macro
>>> and micro flora and fauna.  The humus is an essential link. Building soil
>>> reserves is essential so that our future generations will have something to
>>> eat .  If I am right all the magic is done in the top surface area of the
>>> soil in and around the feeder roots (even transmutation).
>>>
>>> When a human is sick we put him on drip it does not meant we will
>>> survive on drip without having balanced food to build blood and muscle,  so
>>> is the available form of nutrients.  The need of the hour is to conserve
>>> soils and build reserves that is possible with some amount of carbonaceous
>>> materials then and only  then as Dr. Karve had said microbes will take care
>>> everything.  If any system is working anywhere without carbonaceous
>>> material we can assume that there are still some reserves in the top soil
>>> and some humus.
>>>
>>> We have almost drawn out reserves and it is high time we build a
>>> deposit while drawing limited funds for day to day needs leaving behind
>>> some amount of reserve every year. This is the way our forefathers gave us
>>> richest soils!
>>>
>>> Krishna
>>>
>>>  *
>>> *
>>>
>> Krishna
>>
>> This sounds nice, but the fact is that digestate is toxic to plants. If
>> you were to take digestate and try and plant seeds in it, none would come
>> up. You have to apply digestate at least five months into the soil prior to
>> planting seeds, at modest application rates to enable soil microbes to
>> further decompose the organic matter so that plants can grow.  This means
>> apply in the fall to plant in the spring.
>>
>> You mention earthworms....  If you were to try to feed digestate to
>> earthworms, they would die within hours. As such the ASTM Earthworm Contact
>> Test would fail the anaerobically digested organic material as unstable or
>> unsuitable for unrestricted distribution.
>>
>> It is aerobically digested solids that plants like and earthworms like;
>> not anerobically digested solids. In my experience, organic matter is best
>> utilized by plants following aerobic digestion.
>>
>> Anaerobic digestion makes biogas. Aerobic digestion makes plant food.
>>
>> Your comments are correct as to the importance of organic matter in the
>> soil, but should be qualified as to whether or not these organics are
>> applied following anaerobic or aerobic digestion, and if anaerobic, then
>> with sufficient time in the soil for aerobes to convert the organics into
>> usable forms for plants.
>>
>>
>> --
>> Jim McNelly
>>
>> Renewable Carbon Management, LLC
>> 44 28th Ave N Suite J
>> Saint Cloud MN 56303
>> 320-253-5076
>>
>> www.composter.com
>>
>>
>>
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>>
>
>
> --
> ***
> Dr. A.D. Karve
> Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)
>
>
>
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> http://www.adelaide.edu.au/biogas/
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>
>
>


-- 
Alexander Eaton
Sistema Biobolsa
IRRI-Mexico
RedBioLAC

Mex cel: (55) 11522786
US cel: 970 275 4505

alex at irrimexico.org
alex at sistemabiobolsa.com

sistemabiobolsa.com
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