[Stoves] Dung as fertilizer and fuel

[adkarve]

Dear Mr. Marshall,
1. There is no need to re-innoculate the biogas plant with methanogenic
bacteria, once a sufficiently large population of methanogens has
established itself into the biogas plant. We use dung, or water from a
septic tank, or slurry from an existing biogas plant only once, at the
beginning, as an innoculum. Afterwards we use daily only one to two kg of
starchy, sugary or cellulosic waste material as feedstock. If you used
pulped green leaves, you have to use about 5 kg. But no dung.
2. One can use dung, composts, municipal soil waste, distillery effluent,
biogas effluent etc. as a source of plant nutrients, but one must look at
their cost. The recommended dose of composted manure in agriculture is about
50 tonnes per ha. The cost of transport has increased recently due to
increased petroleum prices and therefore, farmers have stopped using these
bulky manures. Since the farmers are no loger using dung as manure, burning
it is the best solution not only of getting rid of it but also of converting
this byproduct into money.
3. Making methane from dung is unscientific, because dung is not the food of
the methanogenic bacteria. The household size dung based biogas plant,
producing daily about 500 g methane has a volume of 4 cubic meters and it
costs in India about US$350 to 400 to construct. It is thus the costliest
cooking device in India, costlier even than a microwave oven. Secondly, it
requires an input of daily 40 kg dung, which has a market value of US Cents
30, if converted into dung cakes and sold. Thus, even from the point of view
of the cost of daily expense on fuel, a dung based biogas system is the
costliest system currently available in India.
4. Organic material is applied to the soil in order to feed the soil
microbes. They degrade the soil  minerals, primarily to feed themselves, but
the minerals broken into ions by the micro-organisms also become available
to plants. When one understands this process, it is logical to feed high
calorie, noncomposted material to the soil micro-organisms rather than
feeding them with low calorie composted material. When sugars and other high
calorie material is applied to the soil, it is not the plants but the soil
microbes that feed on it and it is the microbes that make soil minerals
available to the plants. Several thousand farmers in India, including
myself, are now practicing this form of fertilising the field. I grow an
excellent crop of sugarcane, applying only 125 kg of green leaves per ha,
once every 3 months. A sugar factory has approached me recently to get this
knowhow from me.
5. I do not know why the Ethiopean soils have lost their fertility. There
are large tracts in India, where farmers grow crops totally depending upon
rain water. Because rainfall is unpredictable, this type of agriculture is a
gamble. Therefore, they do not apply any agricultural inputs to the crop.
This practice is in vogue at least for about 10,000 years and nobody has
complained about loss of fertility of the soils.
Yours
A.D.Karve
----- Original Message -----
From: jason marshall <jdmarshall at gmail.com>
To: Stoves <stoves at listserv.repp.org>
Sent: Friday, September 29, 2006 8:08 PM
Subject: [Stoves] Dung as fertilizer and fuel


> ---------- Forwarded message ----------
> From: jason marshall <jdmarshall at gmail.com>
> Date: Sep 29, 2006 7:38 AM
> Subject: Re: [Stoves] Dung as fertilizer and fuel
> To: adkarve <adkarve at pn2.vsnl.net.in>
>
>
> That can't be entirely true, can it?
>
> I mean, we know that if you put cow dung and water in a closed
> container, you continue to get methane for some time, yes?  I will
> grant you that cow dung may be very poor food for bacteria.
>
> I can see what you mean about other means of innoculating the
> bioreactor.  As I said before, I suspect that, as you say, most of the
> value of the dung is from this standpoint.  What I know of intentional
> microbial action I learned from homebrewing, and that tells me that
> your primary goal is ensuring that whatever you consider to be 'good'
> microbes overwhelm and outnumber what you consider to be 'bad'
> microbes, at all times.  To me, that means that if you want to keep
> any long-running system operating robustly, it should have a routine
> and possibly frequent reintroduction of a concentrated source of your
> 'good' bacteria.  If you're adding new dung every day (especially if
> you avoid dung from sick cows), that would most definitely accomplish
> this.  If you source it from the other sources you mention, it
> wouldn't necessarily be a one-time application.
>
> Your comment about wasted energy I thought to be the most interesting.
>   Once the methane production potential of the dung has been exhausted
> (and with it, the primary threat from dung for greenhouse gas
> production), is the rest truly wasted?  If you apply bioreactor output
> to your fields, don't the yields increase not just from the minerals
> in the dung, but also from the remaining energy?  I know, for
> instance, that the dregs from beer production (dead yeast, and
> suspeded particles from the original ingredients, which have settled
> out of solution) have been shown to cause vigorous plant growth.  The
> situation is not completely analogous, but I suspect there are some
> similarities. Yeast are eventually killed by their own effluent
> (alcohol) before they can completely consume the sugars, and we know
> that plants can and do absorb and use complex molecules from the soil,
> including sugars.  The dead microbes in the 'compost' will be broken
> down by the microbes in the soil, releasing some of that pent up
> energy back into the food chain.  That part of the chain at least is
> similar.
>
> Certainly, if I had a steady supply of non-food grade starch, or fine
> cellulose (rice husks, sawdust), I would incorporate them into my
> bioreactor without hesitation.  But am I really better off burning the
> dung, and sending all of those minerals up into the air?  Isn't
> precisely that use of animal dung one of the primary causes of topsoil
> exhaustion in Ethiopia?
>
> -Jason
>