It seems to run 24/7 and has done so far as I know, for at least 2+
years, but what do the experts think?
We are staying just a short walk away from the installation.
On Tuesday, 28 March 2017 14:51:37 UTC+1, Harry Bloomfield wrote:
Great technology for the 3rd world. China has been issuing grants for small farm installations. The cheapest version of this technology is nothing more than a giant polythene bag plug plastic tube going to a one ring burner.
How it adds up in this country I don't know. There is the potential to dry the slurry then burn it too.
It does however involve the usual FIT theft.
Where does the slurry, "biocrops" etc come from, how far, and what cost
is involved in doing that as opposed to doing something else with the
IOW, what are the actual economics when the FIT theft is removed?
"I love the way that Microsoft follows standards.
In much the same manner as fish follow migrating caribou."
The slurry seems to be augured into the tank, the gas collected,
pressurised, then fed to the generator system. I don't know how much
power it actually generates, but the substation and overhead outgoing
lines are quite substantial.
My guess as a past observer of the installation, is one of seeing the
slurry being brought in on carts, by tractors, obviously from other
AIUI the feed for these small-scale biodigesters is a mix of farmyard
slurry, i.e. runny cow shit, and crop residues such as stems, haulms,
stubble etc. Under normal circumstances, the slurry would be sprayed
back onto the fields, providing a modest amount of 'organic'
fertiliser for crops, and the crop waste would either be ploughed
back, also to fertilise the soil and improve its structure, or made
into silage, hay, straw or even just burnt off in the fields, although
I think that last practice is declining and may even be a thing of the
If these biogas generators are going to be widely adopted, then the
traditional uses for their feed will have to be replaced by something
else. But stuff that would otherwise have just been burnt off, is
being usefully used.
and when artificial fertilisers and soil conditioners have to be used
in their place?
"Just burnt off" is not actually so daft, which is why forest fires are
not always a bad thing. The organic content burns off, but the mineral
content does not and is available to be ploughed in. AIUI, that mineral
content is then more easily available to new growth than it would be
just from stuff rotting down.
"The idea that Bill Gates has appeared like a knight in shining armour to
lead all customers out of a mire of technological chaos neatly ignores
Stubble burning has been banned in the UK since 1993 to all intents
The runny cow shit can be produced in huge quantities which produces
storage problems , it also cannot be spread on the land at certain
times in case the nitrates it contains contaminates the water table or
watercourses so farmers are prohibited from spreading it for most of
That exasperates the storage problems so getting rid of it another way
can alleviate the problem.
On Wed, 29 Mar 2017 01:23:13 +0100, firstname.lastname@example.org wrote:
But the biogas generator won't get rid of the nitrates, which will
remain in the digester, and ultimately get spread back on the land,
according to the OP's link, so the problem of timing that spreading to
prevent nitrates contaminating the water table still exists.
Which I've just realised answers the question about finding a
replacement for the 'organic' fertiliser in farm slurry with an
inorganic one. That in fact won't be necessary if the biogas residue
is used back on the land.
The ones that I know of get most of their biogas production from maize
silage or sugar beet, one makes use of whey from a cheese making
operation. These high energy inputs are what keeps the biogas
generation stable. The slurry contains the methanogenic bugs from the
cows' rumens that produce the methane and CO2 from the "volatile
solids" in the feedstock. The thing is volatile solids is the food
value in a crop, so much of these are used up in normal digestion,
hence the crops grown especially are used.
I worked at a food waste plant that wet composted commercial waste
(still fit for human consumption), which would once have gone for pig
swill, the heat from the process pasteurised the waste which was then
spread on land. Subsequently the plant has been sold and changed to
anaerobic digestion for producing electricity, in engines and
generators the heat from which keeps the digester at blood
temperature, but in addition to the food waste it contracts local
farmers to grow 200 acres of maize for silage.
As well as the gate fee for the food waste I think the plant depends
of the FIT.
Digestate is still stored and then spread on the land, often the
solids are separated out for later application and the liquid is used
to irrigate all the time the soil is warm enough for the plants to
make use of it.
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