[Digestion] Biogas plant at Zoo

Thu Jun 27 23:07:15 CDT 2013

Alexander,

I believe Dr. Karve might be referring to using dehydrated dung as a
feedstock for heating water. Or, perhaps he is referring to biomass
gasification.

Regardless, I think it is important to measure total energy of a given
system. In the case of AD, it's hard to measure the positive effect the
nutrient slurry has on biomass production. Surely that fertilizer provides
some measure of growth for plants, trees, and/or crops. Can this be
measured? If so, I would venture a guess that the total positive effect of
AD would outweigh burning dehydrated dung.

Let me illustrate. 

Suppose that the nutrient effluent was used to grow cattails (Typha
Latifolia) in a shallow pond. Cattails spread in the rhizome layer, forming
large interconnected stands. Routine harvesting of a small amount of roots -
preferably at the same rate of propagation - would yield a very starchy
feedstock to use WITH dung, as a blend.

Nutritional value per 100 g (3.5 oz)

Energy = 106 kJ (25 kcal)

Carbohydrates = 5.14 g

Sugars = 0.22 g

This is just speculation on my part, but I would think that a system such as
this might be surprisingly efficient. Cattails are far more starchy and
prolific than, say, potatoes. Additionally, the bagasse could be used as
fodder (more future dung), and/or used for compost.

Troy

From: Digestion [mailto:digestion-bounces at lists.bioenergylists.org] On
Behalf Of Alexander Eaton
Sent: Thursday, June 27, 2013 7:58 PM
To: For Discussion of Anaerobic Digestion
Subject: Re: [Digestion] Biogas plant at Zoo

Dr. Karve,

You have held this stance in many past posts, comparing starch to waste, and
arguing waste as not an ideal feedstock for AD.  I have always thought that
your point is valid, but a bit academic and missing the fact that AD systems
can be seen as an extension of the animal digestive system, treating waste
further and extracting energy that has not been used.  Clearly starch
creates more gas, but the questions posed here is not about choosing starch
or animal dung for a digester, it is about whether a zoo would be wise to
consider a digester to treat animal waste and recover energy.  Is dedicating
space and time at a zoo to dehydrating animal dung and then developing a
system to burn it and recover the energy really a better alternative than an
AD system?  From an energy and process balance, can you explain a system
that would perform better than a digester in this context?  

Best, 

A

On Thu, Jun 27, 2013 at 2:28 PM, Anand Karve <adkarve at gmail.com> wrote:

Dear Rabin,

all animals, including humans, function as live biogas plants. The fecal
matter represents slurry coming out of a biogas plant. Using animal dung as
feedstock in a biogas plant is a highly inefficient way of producing biogas.
You get about 800 litres biogas from just 1 kg starch. To get the same
amount of biogas from cattle dung, you need 40 kg of it. One gets much more
energy from dung if it can be dehydrated and burned directly
Yours

A.D.Karve

On Wed, Jun 26, 2013 at 11:35 AM, Rabin Shrestha <rshrestha at winrock.org.np>
wrote:

Hello,

Will it be a good idea to install biogas plant at zoo to manage and generate
energy from the animal waste in the zoo???

Regards,

Rabin

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for more information about digestion, see
Beginner's Guide to Biogas
http://www.adelaide.edu.au/biogas/
and the Biogas Wiki http://biogas.wikispaces.com/

-- 
***
Dr. A.D. Karve
Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)

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for more information about digestion, see
Beginner's Guide to Biogas
http://www.adelaide.edu.au/biogas/
and the Biogas Wiki http://biogas.wikispaces.com/

-- 
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
www.irrimexico.org
www.redbiolac.org

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