Re: DIG-L: Post treatment of digestates

["renertech" <renertech@xtra.co.nz>]

Gentlemen, can I buy into this debate for two cents worth.    Down here in
the Deep South  of New Zealand,  where we have  4 million people and
40,000,000 sheep,  the meat packing companies produce far more effluent than
the
cities.   Luckily, those same companies are fueled by lignite or soft brown
coal.  So, all the gut contents and other wastes from the meat processing
are mixed in with the dust from the coal pits and composted into what is
called 'Superdirt'.   There is enough activity in the meat wastes to heat up
the product, give a good fresh humus like smell to everything  and kill off
the pathogens, and the local gardening fraternity cannot get enough of it.
However,  the laws of libel preclude me from stating how much actual
fertiliser  nutrients are in the mix.    I am sure that as far as the laws
of Europe are concerned  it would be classified as humus rich material.
What it does seem to do is  to stimulate microbiological activity in the
soil.
Ken Calvert. renertech@xtra.co.nz



----- Original Message -----
From: <CAVM@aol.com>
To: <digestion@crest.org>
Sent: Sunday, April 14, 2002 2:13 AM
Subject: DIG-L: Post treatment of digestates


> You raise several significant issues in your post.
>
> Solid separation after digestion is more of a challenge than before. A
very
> fine mesh filter may be the best solution, and some will work without
> flocculants.  Take a look at the Salsnesp filter, for example.  In the USA
> you can get info from Mark Thomas of sustainablenergy@qwest.net
>
> Nitrogen is more readily available after digestion than before so it may
> become your biggest issue.  Wright-Pierce of Topsham, Maine, USA, is
working
> on various methods to remove nitrogen post-digestion.  They are probably
> ahead of the pack in this work.  You might want to contact Mike Giggey, VP
of
> Wright-Pierce, via
> MDG@Wright-Pierce.com
>
> Phosphorus is another nutrient of concern.  Alum and other simple chemical
> additions can help avoid P overloading.  Bacteria uptake and
> hyper-accumulator crops are also potential solutions.
>
> We have been working for some time to evaluate the potential of using some
of
> the post digestion solids for combustion fuel.  The heat provided cannot
only
> be used to provide some of the warmth required by the digester bacteria
but
> also to dry the separated solids post-digestion of pre-digestion.  By
> separating the solids before digestion you dramatically reduce the
required
> sized of the digester vessel but only marginally reduce the gas produced
from
> the remaining liquid.
>
> Pre-digestion separation is much simpler than post-digestion separation.
We
> recommend the Maximizer separator by Accent Stainless of British Columbia,
> Canada.  Information can be obtained via
> Bcruz92312@aol.com
>
> Pre-digestion separated solids are essentially odor free for several days.
> In the case of hog and dairy farms they can be composted into a very good
> soil amendment or dried to be a good combustion fuel.  For biosolids from
> municipal sewer systems the metal content dictates the options.  If a
> sufficient volume of solids is available electrical generation and steam
> production are options when combusted.
>
> There are other means of treatment if necessary.
>
> Cornelius A. Van Milligen
> Kentucky Enrichment Inc.
> byproduct processors
> CAVM@AOL.com
> ============================================================
> In Belgium there is a lot of chance that digestates will not be
> allowed to use on land because of the fact that they are considered
> by autorities as products rich in nutrients.  The reason is that also
> the excess of manure in Flanders, which is considered as
> nutrientrich, has to be exported out of Flanders.  In Flanders,
> normally only humusrich-nutrientpoor products wil be allowed to
> use.  Conclusion is that a digestate will have to be treated
> afterwards towards a compost or a pellet. (which is considered as
> humusrich, can be used in Flanders)
>
> Does anyone have good data on the post-treatement of digestates?
> Things that would be of big value are:
>
> Cost of solid-liquid separation, which separation equipment is
> used, which polymers and quantities are used for separation, does
> the type of inputmaterial (manure digestate or biowaste digestate
> for example) used for the biogas process influence the ease of
> separation, is digestate from slaughterhouse waste as easy to
> separate as digestate from biowaste,...
>
> Is the solid fraction easy to compost, is a lot extra structure and N-
> rich material needed to abtain good composting,...
>
> what can be done with the liquid fraction, can it be easily stripped
> from nitrogen knowing that it will contain some floating material
> which has not been removed during separation,...
>
> what is the opinion on techniques like inverse osmosis and
> ultrafiltration to treat the liquid fraction, what will the price be for
> this kind of treatments,...
>
> To resumate, every information (internetlink, report, cost
> analyse,...) that handels about post-treatement in general would be
> valuable for me.
>
> Best regards, Jan
> -------------------------------------------------------------------------
> Jan Bruneel                         | bruneelj.pih@hogeschool-wvl.be
>         |
> Hogeschool West-Vlaanderen          | Voice +32 (0)56 241211
> Departement PIH            |
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>
>
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http://www.roseworthy.adelaide.edu.au/~pharris
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http://crest.org/discussiongroups/resources/biomass/biogas/BIOGASMK.pdf
http://www.crest.org/articles/static/1/1010424940_7.html

Beginners Tour of Biogas
http://WWW.roseworthy.adelaide.edu.au/~pharris/biogas/beginners