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Teil 3 Seite 8-25
The energy required for high pressure hydrolysis is obtained through power-heat cou-
pling on the basis of the biogas produced.
Cross media effects
With the exception of the effluent, which corresponds to that of a typical waste fermenta-
tion plant in terms of composition, all other material streams are channelled into thermal
conversion. The organic component of the animal by-products, which is converted into
biogas, is incinerated in a block-type thermal power station. The fermentation remnant
that is formed during the dehydration of fermenter outflow, as well as the elementary sul-
phur that is formed during de-sulphurisation are channelled into thermal conver-
sion/disposal. The stripped ammonia is subsequently catalytically oxidised into nitrogen.
Through the discharge of the ammonia stripper, the volume of water to be transported
outwards is significantly lower compared to animal meal production.
Operational data applicability
Economics
One tonne of raw material from the animal carcass processing sector yields between
200 and 300 m³ of biogas with an average methane content of above 70%. At an electrical
efficiency rate of 38%, 610 to 780 kWh/t of electrical energy are produced. If the electricity
is fed into the network in accordance with the Renewable Energy Law, the return is € 0,06
to 0,1 per kWh. This works out to € 36,6 to 78 per tonne. The costs for a currently required
production of animal meal, including the high energy consumption involved in the drying of
animal slurry and subsequent incineration can be saved. Only the considerably lower
quantities of mechanically dehydrated fermentation remnant needs to be dried. A feasibil-
ity study shows that, in comparison to animal meal production and subsequent incinera-
tion, a cost advantage of approx. € 50 can be attained in terms of thermal high pressure
hydrolysis.
Driving force for implementation
Example plants
St. Erasmus animal carcass conversion plant (technical college plant with 1000 kg/h)
Reference literature
8.2.2 Odour
Biological wastewater treatment plants fulfil the ecological and economic demands ex-
cellently. They achieve high operation safety and plant availability and are easy to handle.
They are very suitable for the separation of odorous substances which result from the
organic and partly inorganic exhaust air components (such as nitrogen, phosphate, etc.).
According to the state-of-the-art, in many TBAs bio-filter plants are run. Given the nec-
essary dimensioning (raw gas volume flows from 50000 to more than 100000 m³/h) and
maintenance, reduction rates of 99% can be achieved. What needs to be considered,
however, is the odour of the bio-filter plant as such.