TENHUNEN@finujo.bitnet (04/18/89)
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*HEAT RECOVERY COMPOSTING PLANT IN AN INTEGRATED PRODUCTION*
*OF COMPOST, EARTHWORMS, FISH BREED, GREENHOUSE, AND OUTDOOR*
*CULTURES: a demonstration project of VJ-Komposteringssystem*
*AJ, sponsored by EC. Part III: Eel production - Anaerobic*
*filter - Water hyacinth greenhouse *
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3.3
Eel production
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A recirculated modular fish production plant for the farming
of eel at 25 degrees Centigrade will be delivered by Skive
Aal A/S. The fish basins are insulated units with automatic
oxygen and temperature control. The heat energy needed,
calculated as ca. 3.8 tons of oil equivalent per year, will
be supplied by the CH plant. Annual eel production has been
calculated as 50 - 100 tons.
The water from the eel production will be aerated and recir-
culated after purification. Part of the water will be cle-
aned in a water hyacinth greenhouse for reuse, and the
latter part will be used for irrigation of the area with
outdoor production of vegetables.
Influence of the feedstuff composition on the growth rate of
eel will be tested. Feeding trials will be carried out by
the use of living earthworms alone, by dry fodder alone, and
the mixed feeding of living earthworms and dry fodder. Dry
fodder consumption will be about 1,5 kilograms per kilogram
of eel growth. Due to the lower dry matter content, the
earthworm biomass consumption will be about 4,5 kilograms
per kilogram of eel growth. The sludge, about 5 cubic
metres per day, will be sedimented in a separate sedimenta-
tion unit and used for biogas production in an anaerobic
filter.
3.4
The anaerobic filter
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Anaerobic filter will be suited very well for the treatment
of the liquid fraction of the slurry and the sludge formed
in eel production, due to their high content of easily bio-
degradable organics. The efficiency of an anaerobic filter
in the BOD5 (biochemical oxygen demand in 5 days) removal --
60 - 70 percent -- is good. The size of the anaerobic
filter will be about 5 cubic metres, and it will be capable
to produce biogas with an annual energy content of approxi-
mately 15 tons of oil equivalent per year.
3.5
The water hyacinth greenhouse
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Water hyacinths must be kept in greenhouses due to their
temperature needs of 25 degrees Centigrade. The main fea-
tures of the water hyacinth greenhouse are:
1) Water hyacinths can take up nutrients directly from the
water.
2) Water hyacinths will evaporate lots of water.
The productivity of water hyacinth is extremely high - some
20 times more efficient than with normal agricultural plants
- and due to this, the features mentioned above are highly
efficient.
The water hyacinth greenhouse will be divided into two
parts:
1) A part where the wastewater from eel production will be
cleaned, mainly for ammonia. The treated water can later be
recycled to the eel basins.
2) A part where the water in the slurry treated in the anae-
robic filter will be let to evaporate.
The exhaust air from the CH plant - with excess heat and
carbon dioxide - will be used for the heating and stimula-
tion of the greenhouse.
Harvested water hyacinths will be tested as a feedstuff for
different animals, and they wil also be used for anaerobic
digestion.
3.6
The biogasified slurry
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The slurry treated in the anaerobic filter will be returned
back to the farmer who will use it as a fertiliser during
the growth season.
ADDITIONAL INFORMATION:
Agr. Eng. Per Thostrup
BioPlan environmental consultants
Fanoevej 5 B
DK-8800 Viborg
DENMARK
Tel. (Int.) + 45-86-613833
Fax (Int.) + 45-86-626836