[permaculture-oceania] biodigesters

[James Sprunt]

Hi all,

Yes, the biodigestors, or biogas as they are usually
referred to in India,
are a very common part of life in India, especially in
the villages. Some
people have had them for nearly 20 years predominantly
using fresh cow dung
but there are those that use human sewage. Quite
simple mechanisms.

James

-----Original Message-----
From: permaculture-oceania-bounces at lists.cat.org.au
[mailto:permaculture-oceania-bounces at lists.cat.org.au]
On Behalf Of adam f
Sent: Friday, 29 September 2006 11:20 AM
To: permaculture-oceania
Subject: [permaculture-oceania] biodigesters (was An
Inconenient Truth -More
Ways Than One)


I agree with Tom that biodigesters will be an import
part of an energy 
mix.  

Tom, I don't know if they're as well known here as you
think, and 
probably need a champion such as yourself to help
build demonstration 
sites people can see, and work on promoting them in
and out of 
permaculture circles.  (Perhaps working with Ceres
Cafe, who were really 
interested -- we should talk again!)  In person I've
appreciated your 
positive enthusiasm, and I think that approach will
win more converts. 

The way I think about it, biodigesters might offer the
evolution of 
composting, on the farm or community scale.  This is
an enormous thing 
in itself. 

For those that don't know, biodigesters are a way of
anaerobically 
fermenting animal / human / food wastes in a tank
which produces compost 
and a mixture of gases including methane, useful as a
cooking fuel. (And 
Tom thinks an automobile fuel - but I'm yet to be
totally convinced on 
it's scale/convenience).  There are over a million
biodigesters in India 
and China.  But as far as I'm aware, still no small
scale community ones 
in Australia.  (There are a few big ones attached to
industrial 
piggeries.)  They don't really suit the backyard /
home toilet scale 
because you need a fair bit biomass to get a
worthwhile amount of gas.

There's some background and an audio presentation
about them here by 
Melbourne-based biodigester builder Dr Lu Aye: 
<http://greeningtheapocalypse.com/index.php?option=com_content&task=blogcate
gory&id=0&Itemid=28>

Biodigesters appeal to one of the core principles I
learnt from 
permaculture (capture and store energy ... and try to
slow down and 
utilise that energy in as many ways possible).

So why might they be an evolution over composting?

When we compost, we are taking a relatively high
energy quality material 
such as manure or food scraps -- too high energy to
apply directly to 
plants, too 'hot' -- and waiting for microorganisms
and chemical 
reactions to break it down into a lower energy source
which plants can 
handle.  So actually a whole lot of potential energy
is wasted in 
composting.  This is actually evident in the heat
being produced by our 
hot piles.  Biodigesters capture some of that
otherwise lost energy in 
the form of methane, and you still get good compost at
the end.   By 
analogy that's akin to moving water from a hilltop
spring across a water 
wheel on it's way down, rather than letting it flow
directly to the 
bottom of the hill under-utilised.

Adam Fenderson in Melbourne



Tom Duncan wrote:
<snip>
> Please someone prove me wrong - I would love to know
of any projects 
> in Australia that have a biodigester working
efficiently.  How much 
> money has been spent on permaculture education in
Australia? My 
> estimates that if you take all the PDCs done in
Australia, and total 
> that, and then look at if just a small percentage of
that money had 
> been put into developing biodigester technology by
the permaculture 
> community and feeding back trials info then we would
have a rich body 
> of info - but I believe one of the stumbling blocks
to this has been 
> the whole focus of doing compost toilets. worm
farming, mulching etc, 
> eclipsing biodigesters from the design vision.
Perhaps permaculturists 
> have been moddle coddling themselves from the hard
reality that the 
> only sustainble energy source is from our own
wastes, and that 
> composting toilets,worm farming and mulching doesn't
have to eclipse 
> biodigesters as part of the system? And believeing
that solar and wind 
> will be their saviour? ...
...
> Why has permaculture consistently ignored
biodigesters? When your shit 
> goes into the compost toilet, it releases methane -
surely there would 
> be a better transformation pathway for it than going
straight to the 
> compost stage?
>

</snip>
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