[Digestion] Digestate

[Jim McNelly]

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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